Cardiac rehabilitation for older adults: current evidence and future potential

Abstract

Introduction:

Growth of the older adult demographic has resulted in an increased number of older patients with cardiovascular disease (CVD) in combination with comorbid diseases and geriatric syndromes. Cardiac rehabilitation (CR) is utilized to promote recovery and improve outcomes, but remains underutilized, particularly by older adults. CR provides an opportunity to address the distinctive needs of older adults, with focus on CVD as well as geriatric domains that often dominate management and outcomes.

Areas covered:

Utility of CR for CVD in older adults as well as pertinent geriatric syndromes (e.g., multimorbidity, frailty, polypharmacy, cognitive decline, psychosocial stress, and diminished function) that affect CVD management.

Expert opinion:

Mounting data substantiate the importance of CR as part of recovery for older adults with CVD. The application of CR as a standard therapy is especially important as the combination of CVD and geriatric syndromes catalyzes functional decline and can trigger progressive clinical deterioration and dependency. While benefits of CR for older adults with CVD are already evident, further reengineering of CR is necessary to better address the needs of older candidates who may be frail, especially as remote and hybrid formats of CR are becoming more widespread.

1. Introduction

Cardiac rehabilitation (CR) is a multidisciplinary secondary prevention program for adults with cardiovascular disease (CVD). When CR was initially developed in the 1960s, it primarily targeted middle-aged men recovering from acute myocardial infarctions (AMI) [1]. In contrast, contemporary CR patients are now more likely to include older men and women with eligibility including AMI as well as other types of CVDs [2]. Among older adults, CVD is also more likely to occur in a context of age-related complexities, including the likelihood that multiple types of CVDs and non-CVDs will occur in aggregate, with related issues of polypharmacy, frailty, and other challenges. While there is conceptual rationale for CR to comprehensively address the idiosyncratic needs of older adults with CVD, in fact, the referral and adherence to CR falls sharply among older patients. Recent data show that only approximately 25% of Medicare beneficiaries who qualify for CR participate, and only approximately 27% completed the program [3]. This review highlights the utility of CR for older adults with CVD and opportunities for better utilization.

2. Background

2.1. Demographics and CVD Prevalence

Advances in medicine have resulted in the prolongation of the average lifespan, such that life expectancy in the United States is projected to increase from 70 years in 1960 to 85 years by the year 2060. In addition, by 2030 the baby boomer generation is expected to surpass the threshold of 65 years of age, accounting for almost 25% of the total population. Similar growth of the older demographic is prevalent throughout much of the world, placing a significant burden on healthcare systems. Prevalence of CVD increases with age along with the progression of long-established cardiovascular risk factors such as hypertension, hypercholesterolemia, hyperglycemia, and reduced physical activity [4]. Furthermore, aging itself is an independent risk factor for CVD as increased oxidative stress, inflammation and intrinsic age-related subcellular changes, markers inherent to the pathophysiology of CVD, intertwine with the biology of aging [2]. The prevalence of CVD, inclusive of hypertension, is reported to be approximately 77% in males and 78% in females in those 60–79 years of age and reaches up to 89% in males and 91% in females in those 80 years or older [5]. When CVD occurs in a context of advanced age, it is typically associated with geriatric syndromes that exacerbate CVD itself, management complexity, as well as risks for functional decline, poor quality of life, and the development of disabilities. CR is an intervention that has the potential to address these challenges [6–10].

2.2. Broader Rationale and Format for Cardiac Rehabilitation

Cardiac rehabilitation is a secondary prevention program that aims to promote sustained recovery after an acute CVD event. It has evolved over decades from its original design as what was exclusively an exercise-training program, into what is now a multifaceted program that addresses physical activity, risk reduction and wellness behaviors [11]. In contemporary CR, tailored exercise prescriptions are still utilized to improve physical activity, offsetting the effects of acute hospital-related deconditioning as well as widespread patterns of chronic sedentariness. Risk reduction is accomplished after a medical assessment that clarifies modifiable CVD risk factors such as hypertension, hyperlipidemia, diabetes mellitus, tobacco, and obesity. Finally, education and counselling are incorporated to instill and sustain life-long healthy behaviors [12–14]. Traditional models of CR services start during the acute hospitalization as phase I CR, with early ambulation, education, and referral to outpatient CR. However, phase I has become harder to sustain as hospitalization lengths of stay have generally shortened. Outpatient or phase II CR has traditionally been organized as a center-based program with group sessions occurring three times a week for 12 weeks. While there is strong value associated with face-to-face center-based CR in respect to safety, adherence, and guidance, it is also associated with many logistical barriers that frequently limit utilization. Emerging alternative models, such as remote CR and hybrid programs, that combine center-based and remote treatment have been evolving to make CR more accessible, especially for those who prefer not to attend center-based programs, and/or who reside in geographical locations where center-based CR is inaccessible [15]*.

Eligibility criteria for CR have also expanded significantly, allowing for the inclusion of a wider variety of conditions. It is now recommended by the American College of Cardiology (ACC) and American Heart Association (AHA) following acute coronary syndrome, percutaneous coronary intervention (PCI), coronary artery bypass graft (CABG), valvular replacement and/or repair, and heart or heart-lung transplantation, and for patients with stable angina, peripheral vascular disease (PVD), and stable chronic heart failure (HF) with reduced ejection fraction (HFrEF) [16–21]. There is emerging evidence that supports the extending criteria further to include CR for patients with heart failure with preserved ejection fraction (HFpEF) and preoperative rehabilitation, particularly for older frail patients.

Rationale for CR was originally premised on mortality and morbidity benefits for patients with coronary artery disease (CAD) [22–25]. Its value was mostly attributed to surveillance for patients as progress was initiated for patients who tended to be relatively unstable after myocardial infarctions associated with residual ischemia, arrhythmia, and heart failure. However, even as CVD interventions and pharmacological therapeutics have vastly improved over the decades since CR originated, CR outcomes remain independently associated with continued reductions of CVD mortality and reduced hospitalization, [26,27] as well as improvements in physical capacity, self-efficacy, quality of life, independence, and falls [28–30]. Hammill, et al. also demonstrated a CR dose effect with data that showed a linear relationship between the number of CR sessions attended and long-term benefits; participants who attended 36 sessions had a 47% lower risk of death and a 31% lower risk of MI compared to those who attended only one session [31]. A more recent study by Beatty and colleagues assessed Veterans’ participation in CR after PCI and mortality benefit across the Veteran Affairs (VA) facilities between 2007–2011 with a median follow-up of six years. Veterans who attended ≥ one CR session had a 33% lower mortality rate than all nonparticipants (hazard ratio 0.67; p<0.001) and a 26% mortality reduction as compared to propensity-matched nonparticipants (hazard ration 0.74; p<0.001). Similar to Hammill’s study, participants in Beatty’s analysis who attended more CR sessions had lower mortality rate. Those who attended ≥36 sessions had the lowest rate (hazard ratio 0.47; p<0.00) [32]. Critics to such dose effect, however, call attention to the implicit selection bias pertaining to those who are most likely to attend 36 sessions, including a more robust baseline capacity, better social support, greater financial means, fewer comorbidities, and less disease severity – thus making them more conducive to improved morbidity and mortality [33].

3. Distinctive Age-Related Clinical Complexities that become more common among older adults with CVD

Table I summarizes age-related healthcare challenges that complicate the management of older cardiac patients, which are also described below [34]*.

Table I.

Geriatric Syndromes and Associated Medical Challenges and the Potential of Cardiac Rehabilitation

Geriatric Syndromes	Medical Care Challenges	Cardiac Rehabilitation Benefits
Multimorbidity	Multimorbidity increases risk of impaired function and rehospitalization Multiple subspeciality providers complicate care coordination Commonly leads to polypharmacy	CR provides opportunity to determine primary goals of care, initiate consultations, and establish integrated management CR provides opportunity to better understand symptoms and to establish better coordination of care
Frailty	Frailty is associated with CVD, and both contribute to functional decline Decreased physical activity leads to sarcopenia, weakness, increased risk of falls, and disabilities Frailty increases susceptibility to adverse outcomes	CR provides opportunity to improve exercise capacity, reduce frailty, and reduce CVD risk factors CR provides opportunity to promote nutrition
Polypharmacy	Drug-drug interaction (e.g., Warfarin-amiodarone, NSAID-Anticoagulation etc.) Increases risks of adverse drug events (e.g., orthostatic hypotension with diuretic or vasoactive medications, GI bleeding with antiplatelets and/or anticoagulation) Undercuts medication adherence	CR provides opportunity for comprehensive medication reconciliation and medication adjustments especially in programs that integrate a pharmacist. CR provides opportunity for deprescribing potentially inappropriate medications CR provides opportunity to reinforce adherence to medical therapy
Cognitive Impairment	Impaired cognition adversely affects adherence to medical therapy Impaired cognitive function is associated with poor self-efficacy and increased adverse health outcomes	CR provides opportunity for exercise and risk reduction to possible improve cognitive function. CR provides a structure that positively impacts ability to perform ADLs and IADLs
Psychosocial	Depression and anxiety are associated with diminished physical activity, exacerbating functional decline. Depression is associated with poor adherence to medical therapy Social isolation and loneliness are associated with poor self-care	Exercise improves mood and anxiety CR addresses medical concerns, provides counselling and improves self-efficacy CR provides an opportunity for socialization and improves physical functioning to promote participation in social opportunities outside of CR
Post-acute hospitalization syndrome	Hospitalization is associated with poor sleep and nutrition, acute deconditioning, and worsening of sarcopenia, cognitive function (delirium), and depression Medication adjustments during hospitalization can lead to confusion	CR augments recovery as patients benefit from monitoring and support as they initiate exercise CR provides opportunity to manage medications, reduce risk factors, and overcome deficiencies in nutrition.
Sensory Impairment (Vision and Hearing)	Increases risk of fall Adversely affect medication adherence	CR provides guidance to establish routines and contingencies that account for sensory impairments
Urinary Incontinence	Diuretics worsen incontinence and increases likelihood that many patients will be non-adherent or more reclusive	CR provides guidance to reduce incontinence (e.g., timing of medications) and regain self-efficacy in spite of incontinence

Abbreviations:GI = gastrointestinal; NSAIDs =non-steroidal ant-inflammatory drugs.

3.1. Multimorbidity

As defined by the National Institute for Health Research (NIHR), the term multimorbidity can be used to refer to the co-existence of two or more chronic conditions. These may include a physical non-communicable disease of long duration, a mental health condition of long duration, or an infectious disease of long duration [35]. In older adults, CVD tends to occur in this manner as part of a cluster of concurrent CVDs and non-CVDs. In an analysis of Medicare beneficiaries with CVD, it was found that almost 70% of this population had greater than two chronic conditions. Among those with heart failure, 60% were found to have three or more chronic conditions [36]. Management for an incident CVD event is generally more challenging amidst concurrent medical challenges. Multimorbidity is associated with accelerated aging and frailty, premature mortality, increased hospitalization, disabilities, and poor quality of life [37–40]. It has also been linked to a higher risk of being sedentary and exhibiting poorer baseline functional status, which results in diminished reserve if illness or hospitalization occurs [41,42]. Non-medical comorbidities such as self-reported health status, impaired activities of daily living, and cognitive function are also relevant, as these add to mounting mortality and morbidity risks [43]. Furthermore, multimorbidity is commonly associated with an added sense of burden that stems from cumulative disease, incapacity, symptoms, and treatment burden. As the number of chronic conditions increases, the risk of mental health conditions also tends to increase, often compounding the morbid effects of the primary diseases. The latter is often exacerbated by both lifestyle- and treatment-specific factors [44].

3.2. Frailty

Frailty is a geriatric syndrome that categorizes older adults based on their physiological reserve as opposed to chronological age. It entails decreased physiological reserve and resilience in conjunction with increased vulnerability to stressors [45–47]. Frailty is a dynamic state in which a person can move from a state of pre-frailty to robustness and vice versa [48]*. The prevalence of frailty increases with age especially among patients with CVD [49,50]. Adults who are frail are more likely to suffer from CVD, have a worse prognosis, and experience a poorer tolerance of therapy [51]*. Most older adults with CVD have some degree of frailty at the time of hospitalization, and acute hospitalization further accelerates the problem, thereby increasing the risks of diminished independence, disabilities, nursing home placement, poor quality of life and increased mortality [52–58].

The measurement of frailty remains controversial, as there is no single standardized assessment method of evaluating this syndrome [59]. Frailty can be measured as an index of cumulative clinical deficits and can also be defined in respect to physical attributes. Physical frailty is commonly assessed as a phenotype of weakening, weight loss, slowing, exhaustion, and reduced physical activity, and to correlating performance measures such as gait speed, timed up and go (TUG), and tandem stand. Performance measures and additional tools to evaluate frailty are summarized in Table (2) [9,59].

Table 2.A.

Physical Frailty Assessment and Screening Tools Commonly Used in CVD

Measurement Tool	Description	Utilization	Limitation
Fried Criteria[45]	Consists of 5 components: Slowness- 5-m gait speed Weakness- handgrip strength measured by hand dynamometer Exhaustion- self reported (tool or scale?) Low physical activity measured by Minnesota Leisure Time Activity Questionnaire (Men <383 kcal/week, Women <270 kcal/week) Weight loss of ≧ 10 lb Score: 0 robust, 1–2 pre-frail, ≧ 3 frail	Well established criteria for physical frailty	Accurate assessment of exhaustion and low physical activity are patient-reported and can be unreliable. Weight loss patients with HF can be difficult to assess
Essential Frailty Toolset (EFT)	Consists of 4 items with a composite score of 5 Five chair rises without using arms (1 point if ≧15s, 2 points if unable) Cognitive function measured by MMSE (1 point if < 24) Hemoglobin (1 point if < 13 g/dl in men and <12 g/dl in women) Serum albumen (1 point if <3.5 g/dl) Score: 0 robust, 1–2 prefrail, ≧ 3 frail	Validated for risk assessment with biological and functional components Compared to other frailty assessments, EFT demonstrated to be the strongest predictor for mortality and disability after TAVR and SAVR [95]
Short Physical Performance Battery (SPPB)[96]	Multidomain physical assessment of lower extremity function and mobility that includes 3 physical tests, each score from 0–4, composite score 12. Five-meter gait speed (endurance) Five chair rises (strength) Tandem stand for ≧ 10 s (balance) Score: 10–12 robust, 9–7 prefrail, ≦ 6 severe frailty	Functional metric that is often used as a measure for physical frailty which has been extended to patients with CVD Highly predictive of outcomes (mortality, disability) in many clinical applications [97–99]	Ceiling Effect that limits its utility in adults with relatively greater functional capacity.
Clinical Frailty Scale (CFS)[100,101]	Judgment-based tool to screen for frailty. Consists of 9 categories based on an individual’s level of wellness and fitness. Very fit— robust, active, exercises regularly. Fit— without active disease symptoms but less fit, active occasionally. Managing Well— medical conditions are well controlled, but not regularly active beyond routine walking. Very Mild Frailty— not dependent in ADLs, but has disease symptoms that limit activities, complain of fatigue and slowness. Mild Frailty— move evident slowing (not sure what this means), needs help with IADL (finance, transportation, heavy housework, meal preparation, medications). Moderate Frailty—needs help with all outside activities and most ADLs, often has problems with stairs, needs assistance with bathing and dressing. Severe Frailty— completely dependent for personal care caused by physical or cognitive impairment, but not at high risk of dying within 6 months. Very Severe Frailty— completely dependent for personal care and approaching end of life. Terminally Ill— approaching end of life with a life expectancy of <6 months.	Screening tool for frailty	Susceptible to interobserver variability
Edmonton Frail Scale (EFS)[102]	Multidomain scale consists of 10 domains with a cumulative score of 17. Two domains are assessed by performance-based tools: Clock test for cognitive function, TUG for balance and mobility. The other 8 domains are functional independence, burden of medical illness and quality of life, health attitude, social support, medication use, nutrition, mood, and continence. Score: ≧12 frail; 0–5 robust, 6–7 Vulnerable, 8–9 Mild frailty, 10–11 Moderate frailty, 12–17 Severe frailty	Rapid screening tool
Gait Speed	5-m or 4-meter gait speed Slow: <0.83 m/s (>6s) Very slow: <0.65 m/s (>7.7 s) Extremely slow: <0.50 m/s (>10 s)	Functional metric that is often used as a measure for physical frailty which has been extended to patients with CVD Correlates with Fried scale and independent predictor of health outcomes.[103–105]	Although convenient, single performance assessments have diminished specificity.

Abbreviations: AVR = aortic valve replacement, CGA = Comprehension Geriatric Assessment, CVD = cardiovascular disease, HF = heart failure, MMSE = Mini-Mental Status Examination, SAVR = surgical aortic valve replacement, TAVR = transcutaneous aortic valve replacement, TUG = Timed Get Up and Go.

Sarcopenia, defined as the loss of skeletal muscle mass (atrophy) and strength (dynapenia), is primarily an age-related process that can contribute to the development of frailty and resulting compromise of physical function [60]. It has been estimated that older adults experience a decrease in muscle mass by approximately 6% per decade after mid-life, with individual variations in the rate at which muscle is lost and the age at which this process begins [61]. Two attributes of frailty are weakening and slowing, which can be directly impacted by the sarcopenia. Janssen and colleagues found that the likelihood of having a physical disability was almost 80% higher in older adults diagnosed with severe sarcopenia when compared to those without sarcopena [62]. Older adults with sarcopenia experience higher rates of recurrent falls, poorer HRQOL, and disability [63,64].

3.3. Polypharmacy

Polypharmacy involves the administration of multiple medications, generally defined as an individual who is taking ≥ 5 medications [65]. It is particularly common among older patients with CVD and multimorbibity as multiple clinicians tend to address a single disease such that the polypharmacy results [66]. Polypharmacy is associated with an increased risk of orthostatic hypotension, falls, bleeding, confusion, hospitalization, disability, drug interactions (between drugs and or by one drug exacerbating a different disease) and other adverse drug events, as well as mortality [67–70]. Age-related changes in pharmacodynamics and pharmacokinetics further potentiate the risk of adverse drug-drug and drug-disease events [71]. Additionally, polypharmacy in older adults contributes to medication non-adherence. It was noted that medication adherence for chronic cardiac conditions declines up to almost 40% by 2 years [72]. Medication non-adherence has been associated with poor quality of life, and increased risk of hospitalization and mortality [72].

3.4. Cognitive Decline

Aging and CVD are both independent risk factors for cognitive impairment, resulting in a high prevalence of cognitive impairment among older adults with CVD [73]. Approximately 35% of individuals with CAD and up to 80% of individuals with HF experience issues with cognitive impairment, with increased incidence also associated with acute hospitalization [74,75]. In patients with CAD and HF, those with cognitive impairment have poorer medication adherence and self-care, increased mortality, and higher rates of 30-day rehospitalizations [76–78]. Even community-dwelling adults are likely to incur subtle declines in executive cognitive function despite having preserved memory capacity. Non-adherence to medical therapy is associated with an increased risk for re-hospitalization and the worsening of CVD, factors that can often then exacerbate cognitive decline.

3.5. Psychosocial

Depression is highly prevalent among older adults and is two to three times more likely to occur in individuals with CVD [79,80]. Older adults are inherently predisposed to depression due to age-related functional decline, frailty, poor nutrition, sarcopenia, fatigue, and decreased self-efficacy [81,82]. In patients with HF, depression has been associated with reduced exercise adherence and cardiovascular fitness, often undermining self-care and compounding cognitive impairment and overall risks [83]. The effects from cardiac medications (e.g., beta blockers), recurrent hospitalizations, and CVD symptoms such as dyspnea, chest pain, and dizziness, can contribute to isolation and loneliness, further increasing the risk for depression and premature mortality [84–87]. Similarly, approximately half of individuals who suffer an acute cardiac event experience anxiety and often self-limit physical activity due to fear, predisposing to increased risks of social isolation, loneliness and poor recovery [88].

3.6. Functional Decline

Functional decline is a common clinical issue faced by older adults as a component of the aging process. Whereas “function capacity” is commonly conceptualized as abstract concepts of cardiorespiratory fitness (usually as peak oxygen consumption [VO₂] as measured by a stress test) by cardiologists, for many older adults, it is more meaningfully considered in terms of the capacity to perform activities of daily living (ADLs [eating, bathing, mobility, etc.]) or instrumental activities of daily living (IADLs [grocery shopping, household chores, paying bills, etc.]) [89–92]. Among older adults, deficits in ADLs can be severely exacerbated by CVD and even CVD therapeutics (e.g., hospitalizations, medications, and stress). Activity-limiting symptoms associated with ADL can become much harder to tolerate, with associated tendencies of sedentariness. Inactivity exacerbates risks for sarcopenia that compound the likelihood of frailty, falls, and disability [93]. Hospitalizations related to CVD commonly accelerate loss of function and increase susceptibility to disability even when the initial treatment of CVD is successful [94].

4. Potential of CR to address Geriatric Complexities of care

The potential benefits of tailoring CR to address individual geriatric needs as well as cardiovascular outcomes will be delineated further below.

4.1. CR and Multimorbidity

Cardiac rehabilitation provides an opportunity to address the incident CVD event in the context of overall disease, allowing for a better understanding of symptoms, alignment of care, and optimization of medication regimens. The safety and feasibility of CR specifically oriented to multimorbidity was demonstrated by Barker and colleagues in two pilot randomized control trials. The trials evaluated “multimorbidity rehabilitation” compared to usual care and “multimorbidity rehabilitation” compared to single-disease rehabilitation [112,113]. The multimorbidity rehabilitation and single-disease rehabilitation contained similar exercise training components, the main difference was the education. Multimorbidity rehabilitation participants received a novel education session that was directed to foster skills in disease self-management [113], an intervention that has been shown to improve patients self-efficacy, clinical outcomes and reduce cost [114]. Although this study was not powered to evaluate functional outcomes or the benefits of education, it demonstrated that multimorbidity rehabilitation programs can be implemented successfully. Additional research is needed to determine the most efficacious components for this type of program.

4.2. CR and Frailty:

While older adults who are frail are less likely to participate in CR, the fact remains that among those who do attend, many benefit disproportionately, particularly in regard to their potential for vital functional gains. A study conducted by Kehler and colleagues examined the relationship between a 12-week CR program and the gradient of frailty experienced by patients. Frailty was measured using the 25-item accumulation of deficits frailty index (range 0–1; higher values indicate greater frailty). Higher frailty levels were associated with an increased occurrence of participant drop-out, but patients with higher frailty who completed the program exhibited the most improvement in their frailty levels from a mean of 0.34 (95% CI, 0.32–0.35) to 0.26 (95% CI, 0.25–0.28), P < 0.001[115]*. These findings are consistent with previous observational studies [48,116,117]. Baldasseroni and colleagues assessed the effect of a four-week exercise-based CR program on exercise tolerance (peak VO₂ and 6-minute walk distance [6MWD] and muscle strength [peak torque]). A total of 160 participants (mean age 80 ± 4 years) were included in this study, all of whom had suffered a recent acute coronary event or surgical cardiac intervention. The study showed that lower baseline physical performance was associated with greater improvement in all 3 indexes, peak VO2, 6MWD, and peak torque [116]. Lutz and colleagues retrospectively compared the effect of a phase II CR program on physical function among 243 older patients with CVD (age ranging from 45 to 92) based on their frailty (frail, intermediate-frail, and non-frail) by Fried criteria [48]*. Function indices were assessed using the physical frailty measures of gait speed, TUG, grip strength, and 6MWD. Frail patients demonstrated significant improvement in TUG as compared to non-frail and intermediate-frail patients (P = .007) and had the highest percentage of improvement in 6MWD from their baseline [48]*.

Frailty and preoperative functional capacity are strong predictors for procedural outcomes, particularly in older adults undergoing cardiovascular interventions. Lower functional capacity and a high level of frailty are associated with increased mortality, length of stay, and disability [95,99,103,118,119]. There has been a rising interest in preoperative rehabilitation (prehabilitation) for patients awaiting an elective surgery to maximize functional capacity, improve nutrition, and address modifiable risk factors (e.g. smoking, obesity, alcohol cessation, etc.) with the goal of improving postoperative outcomes. Sawatzky and colleagues conducted the first pilot randomized controlled trial of the safety and efficacy of prehabilitation for patients awaiting elective CABG [120]. Fifteen participants completed the study, seven received standard of care and eight participated in prehabilitation, with all participants undergoing cardiac stress testing prior to initiation of exercise training. All participants were noted to have a significant low baseline functional capacity. Prehabilitation included exercise training, education and counseling, and stress management. Exercise training consisted of aerobic exercise (85% of their baseline maximum oxygen consumption) for 60 minutes a day, twice weekly until surgery. The prehabilitation group exhibited significant improvements in their 6MWD and gait speed pre-operatively and 3 months post-operatively, whereas no changes were noted in the standard of care group. Prehabilitation significantly enhanced the enrollment in CR program post-operatively (100% of the pre-rehabilitation as compared to 43% off standard of care P<0.05) and there were no reported adverse events. This remains a novel approach and not yet a standard of care, however, it holds remarkable promise in improving candidacy of frail older adults for interventions by improving outcomes and clinical benefits. Future research is needed to determine optimal intervention components for older adults as well as safety and efficacy.

4.3. CR and Polypharmacy

Cardiac rehabilitation provides an opportunity to address polypharmacy, assess medication adherence and tolerance, and optimize therapy, particularly if a pharmacist with appropriate expertise is integrated as part of the CR caregiver team [121]. Polypharmacy can be addressed through medication reconciliation, reviewing drug-drug interactions, discussing goals of medical therapy, effectively communicating with a patient’s cardiologist or primary care physician, and considering the deprescription of inappropriate medications [122]. Deprescribing, either by discontinuing harmful medications or decreasing the dose of medications to lessen side-effects (e.g., orthostatic hypotension with vasoactive medications, fatigue with BB), requires regular monitoring and assessment of individuals’ response to the changes. Cardiac rehabilitation provides longitudinal hemodynamic monitoring and assessments, making it a well-suited clinical platform for deprescription.

Medication tolerance and adherence are other factors that are particularly important for older adults with polypharmacy that can be addressed by CR. Poor health literacy, lack of self-efficacy, cognitive impairment, and complexity and/or intolerance of medical therapy are all factors for medication non-adherence and are more pronounced in the older adult population [123–127]. Doll and colleagues demonstrated that CR provides an opportunity to build a longitudinal relationship with patients that permits close monitoring of medication tolerability, and enhanced compliance with secondary prevention medication regimens [128].

4.4. CR and Cognitive function

Cardiac rehabilitation has been shown to positively impact cognitive function for older adults with CVD by improving both self-care and cognitive abilities [129]. CR provides a structured platform that improves physical function, nutrition, depressive symptoms, psychological well-being, and medication compliance,[52,130–134] providing individuals with the foundational tools to be more successful in managing their ADLs and IADLs independently [135]. Improvement in cognitive domains have also been noted after completing CR.

In a systematic review that investigated the effects of CR on cognitive impairment in patients with CVD, CR was found to positively impact attention, executive function, and memory domains, with the language domain remaining at baseline [129]. Additional studies have demonstrated the significant impact structured aerobic exercise programs can have on the improvement of executive functioning in older adults in the inpatient and outpatient settings.[136,137] Although the optimal regimen of exercise to improve cognitive function with CR is not defined, aerobic and resistance exercise of at least moderate intensity are supported by published literature [138]. Notably, studies supporting exercise for cognitive benefits were conducted in supervised settings, both inpatient and outpatient. Strategies to implement CR for cognitive benefits safely and effectively as part of remote-based models remains an area of ongoing research.

4.5. CR and Psychosocial Challenges

Cardiac rehabilitation has the potential to improve nutrition, sleep hygiene, and socialization, and also provide education and counselling that can help to alleviate anxiety and depression [139]. Cardiac rehabilitation also improves physical function, which contributes to improved self-efficacy and reduced depression [48,140,141]. In addition, functional gains enable older adults to increase daily activity, contributing to a reduction in social isolation and loneliness. Lavie and colleagues found that in older adults with CAD, CR exercise training reduced the rates of depression, as well as anxiety and hostility [139]. In a recent study targeting older adults with HF, the use of a tailored, multidomain exercise program demonstrated improvements in depression, self-perception of health status, and overall quality of life [52,134]. Although this was not a CR program, it still highlights the value of multidomain exercise training (balance, strength, mobility and endurance) for older adults with CVD and psychosocial difficulties.

4.6. CR for function

Whereas as traditional exercise training and physical activity is usually limited to aerobic modalities, many older adults with CVD are often too functionally compromised to initiate or sustain aerobic activity. Emphasis on resistance training (RT) provides a vital foundation from which aerobic training can eventually become more feasible. A combination of aerobic and resistance exercise training is currently recommended by the European and North American guidelines, and it is the cornerstone for exercise training in contemporary CR, with benefits including improved function overall (including dimensions of strength, aerobic and balance) [13,142]. Yamamoto et al. conducted a meta-analysis of RCTs that compared the effect of RT with either usual care or aerobic training among middle-age and older adult patients with CAD. They showed that both age groups had more significant improvements in upper and lower body muscle strength and exercise capacity (peak VO₂ and exercise time) with RT compared to usual care or aerobic training. Importantly, older patients also had significant improvements in mobility with RT, which was not evident in the middle-age or control group [143]. The benefits of RT with aerobic exercise were mirrored by another meta-analysis that focused on patients with heart failure with reduced ejection fraction (HFrEF), which additionally noted enhancements in HRQOL when RT was included [144].

Sarcopenia and balance are risk factors for loss of mobility and physical function, and exercise training components of CR can cater to these contributors of function [131]. The optimal therapy for sarcopenia remains unclear, but there is strong evidence to support strength training and nutrition as benefits for adults with aggregate CVD [131]. Muscle strength improvement is mainly driven by RT and combining this with aerobic exercise further enhances not only muscle strength, but muscle quality as well [145–147]. Muscle quality corresponds to improved strength independent of change in muscle mass and is an important factor in older adults maintaining physical functioning.

Balance is a second factor that may negatively impact an older adult’s mobility and physical function in addition to increasing their risk of falls. Multiple factors contribute to the high prevalence of balance impairment in older adults, including age-associated neurovestibular impairment, sarcopenia, frailty, autonomic dysfunction, neuropathy, visual and cognitive impairment, and musculoskeletal disorders [148–150]. The addition of balance training exercises to CR improves patient outcomes. Busch and colleagues investigated a CR program for older adults post CABG that incorporated the addition of balance training to resistance and aerobic exercise. Relatively greater improvements in 6MWD (67.3 ± 49.0 m vs 41.9 ± 51.7 m; P- 0.003), workload (maximum power), and TUG were noted in the intervention group as compared to the control [151]. Highlight the value of balance training to better restore function, moderate falls and anxiety, and maintain independence.

The use of CR as a means to address functional decline amidst geriatric complexities has become an important area of research. The recently published REHAB-HF trial randomized older adults with acute decompensated heart failure into tailored multidomain physical rehabilitation or usual care. Almost all patients (97%) at baseline were frail or pre-frail and had significant functional impairments. In this trial, a physical therapy (PT)- based exercise intervention focused on four physical domains (strength, balance, mobility, and endurance) and was initiated during hospitalization or soon after discharge, occurring three times a week for 12 weeks. The multidomain exercise intervention resulted in significant improvements in SPPB (mean difference between intervention and control 1.5; P < 0.001) at 3 months follow-up and a lower rate of all cause rehospitalization at 6 months for the intervention group [52]. This study demonstrated the advantages of a multidomain assessment approach for frail and functionally impaired adults with CVD, with a tailored, progressive exercise intervention. REHAB-HF highlighted the utility of PT as a core aspect of recovery, especially as the protocol relied on a one-on-one therapist to patient training method. This constitutes a shift in staffing design from traditional CR and represents an area in which more research is anticipated.

Modified Application of Cardiac Rehabilitation for Older Adults (MACRO) is an ongoing trial that is assessing the utility of a coaching intervention to reinforce the utility of CR to meet the needs of older adults with CVD (NCT03922529). The goal of this study is to integrate geriatric risk assessment, personalize approaches to CR.

5. Safety of Cardiac Rehabilitation

Older adults with functional impairment or limited functional capacity are already at a high risk of fall and injury, which is only aggravated as functional decline progresses. Exercise training is a safe and valuable intervention for older adults A study that assessed the safety and benefits of early ambulation after aortic valve surgery among octogenarians showed that early ambulation was not only safe (i.e., no increased risk for adverse outcome) but also resulted in a significant reduction in the incidence of post-operative delirium, a shorter hospital stay and a higher likelihood of direct discharge to home - 95% of patients who received early ambulation as compared to 47% of patients that didn’t get mobilized early (P value 0.001) [152]. The misperception that frail older adults are “too unfit for rehabilitation” has significantly inhibited many patients who would probably benefit. Multiple studies have demonstrated that the frailest patients have witnessed the most benefits of rehabilitation with significant improvements in functional capacity and quality of life - a coveted outcome for many older adults with CVD [48,115–117].

Older adults who are relatively more fit and accustomed to exercise also benefit from CR as CVD events may undercut confidence or threaten clinical stability such that prior patterns of activity are no longer sustainable or safe. Supervised exercise provides importance guidance, feedback and education.

Nonetheless, studies demonstrating the safety of CR have entailed supervised exercise training, with benefits of study personnel to ensure proper form, breathing and intensity. The safety of remote-based CR is relatively less certain.

6. Factors for Underutilization of Cardiac Rehabilitation

Despite the above-mentioned benefits of CR, there is a significant gap in its utilization, as only 20–60% of eligible patients get referred [3,32,153–156], of which only 20%−30% end up participating and actually complete the program [157–160]. These numbers are remarkably low especially in relation to predictions that that 25,000 lives could be prolonged, 180,000 hospitalizations avoided, and even more lives could be improved in the United States if CR participation increased from 20% to 70% [161]*.

Across healthcare systems and participants, multiple factors have been identified to influence referral and enrollment to CR. Epidemiological studies have shown that older adults, patients with multiple comorbidities or low socioeconomic status, females, uninsured, ethnic minorities, and those relying on Medicare are among the lowest participants in CR [3,155,160,162–166]. While each of these populations may possess individual-specific barriers for enrollment in CR, the referral rates also remain low. Physicians’ perception of the perceived benefits is one of the most important factors that influence referral and patients’ participation in CR [167]. In a study that assessed physicians’ judgment and attitude toward CR referral, many physicians did not feel compelled to refer their female patients or older adults to CR with the belief that they are less likely to benefit [168,169]. A Study by Retchey and colleagues noted that among Medicare beneficiaries, patients who qualified for CR tended to be older and with multiple comorbidities, and those patients had the lowest rate of referral [3].

Referral rates to CR also vary remarkably across its indications. Patients with CAD who undergo CABG are more likely to be referred to CR than patients who receive PCI or get treated medically [32,155,158].

Notably, many older adults who receive PCI rather than CABG are particularly likely to have comorbidities, frailty, and decreased functional status that led to the decision of PCI over surgical intervention. Cardiac rehabilitation in such patients is a crucial component for their recovery.

Referral rates are even lower in patients with HF (10–12%) compared to CAD patients [170]. In a cross-sectional study of 106 patients aged 65 years and older admitted with heart failure, 72% reported interest in enrolling in CR; however, only 21% were referred on discharge [171].

Valvular disorders represent an additional cohort of patients that underutilize CR. CR is well established and strongly recommended for patients after surgical aortic valve replacement (SAVR), but with relative referral gap after transcatheter aortic valve replacement (TAVR) [172,173]. Similar to patients who undergo CABG, patients undergoing TAVR treatment are more likely to have multimorbid conditions and be of advanced age, disability, and frailty [174–178]. While TAVR improves cardiac performance [179–181], it does not completely reverse deficits in exercise capacity and function that have usually evolved over decades [182]. Residual impairment in functional capacity or disability after TAVR are predictors for poor outcome and increased mortality [183–185]. Mounting evidence highlights the safety and efficacy of CR in improving functional capacity, exercise tolerance, and health-related quality of life after TAVR [177,186–188]. A systematic review and meta-analysis of observational studies comparing the safety and outcomes of exercise-based CR in patients post-TAVR and SAVR revealed that 2–3 weeks of combined endurance, resistance, and/or respiratory muscle training is safe and significantly improved 6MWD and functional independence (Barthel Index [BI]) in both patient populations [173]. Work by Pressler and colleagues further demonstrated the benefits of CR following TAVR, conducting a RCT comparing exercise-based CR versus usual care, with participants experiencing significant improvements in peak VO₂, muscle strength, quality of life, and symptoms burden after eight weeks of endurance and resistance exercise [189]. The long-term follow-up of this pilot study (SPORT-TAVI) at 24 ± 6 months showed that the intervention group retained significant improvements in submaximal exercise capacity (VO₂ at anaerobic threshold) (95% CI 0.8–4.6; P 0.008) and a trend toward increased longevity was also noted.

7. Gap in Enrollment and Adherence

Automated referral to CR alone can help increase referral but it does not necessarily correlate to optimal enrollment [157,190,191]; approximately only one-third of referred patients ultimately get enrolled. Recommendation by a healthcare professional is often the most influential factor for enrollment, underscoring that perceived benefits of CR among cardiac clinicians implicitly affect referral their patients utilization of the program [192,193]. Enrollment is additionally impacted by a number of individual-specific factors such as fear of physical activity (kinesiophobia) after acute CV event, lack of self-efficacy, depression, anxiety, low health literacy, and difficulties in accessibility - many of which are prominent among older adults after a CVD event [194–196]. Kinesiophobia has been observed in 20% of patients with CAD [196]. It is commonly related to negative beliefs and attitudes toward physical activity, fear of injury, lack of knowledge of the perceived benefits of physical activity, and poor education and counseling by healthcare professionals [194,197]. Older adults with low self-efficacy, reduced functional capacity, weakness, recurrent falls, and frailty are more likely to avoid CR due to the fear of sustaining injury while exercising or feeling ashamed of their physical deficits. Tailoring CR to address geriatric specific concerns can help mitigate these barriers.

Limited access to CR programs is another major factor that negatively impacts enrollment and adherence in CR, with both lack of transportation and limited scheduling options both impeding participation. A significant number of older adults do not drive and depend on others for transportation, which compounds the logistical challenges. Moreover, caregiver responsibilities, especially for older women, tend to undercut the capacity to attend center-based programs. Multimorbidity can pose additional challenges, as chronic disease management usually entails frequent clinician visits, such that CR becomes less of a priority, particularly if it was not strongly recommended by their physician.

The low referral and utilization of CR suggest that innovative strategies are needed. The Million Hearts Initiative in collaboration with American Association of Cardiovascular and Pulmonary Rehabilitation (AACVPR) developed a change package which provides strategies that target systems change, improve awareness, and increase referral and enrollment [198]. In 2018, the ACC/AHA published a report on clinical performance and quality measures that provides practitioners and healthcare institutions who deliver CVD services with tools to measure the quality of care provided, aimed to enhance the utilization of CR. The clinical performance measures track the rate of referral for qualifying patients prior to discharge from the inpatient setting, qualifying patients from the outpatient setting, claims-based enrollment, time to enrollment, and patient adherence [199]. Strategies that have enhanced referral and enrollment include automatic referral at discharge for patients with a qualifying diagnosis, having a case manager to track referrals and assist with enrollment, initiating post-hospitalization clinic visits to initiate CR referral, and comprehensive patient education with integrated CR endorsement [32,190,193]. The combination of automatic referral and patient education was noted to achieve 85% referral and 73% enrollment rates [190].

8. New Models of Care for Cardiac Rehabilitation

Traditional CR started as a center-based monitored exercise training. Patients usually attend 3 times per week for 12 weeks. While such face-to-face care provides the benefit of monitored exercise and associated opportunities to optimize safety, clinician-patient bonding, and patient confidence, many eligible patients are not able to access it. Patients often reside in rural areas, lack transportation, have scheduling limitations that limit participation, or are too functionally impaired to be able to mobilize. New models of care are beginning to address these challenges in an effort to achieve the national target of 70% enrollment to CR. Remote-CR (previously referred to as home-based CR [HBCR]) and hybrid CR (combined CBCR and HBCR) have emerged as alternative models with growing evidence supporting their safety and efficacy [200]. Although barriers such as caretaking responsibilities, work schedule conflicts, lack of full or partial insurance coverage, and lack of knowledge and/or appreciation for CR remain, integration of a CR liaison into newer models has been cited as a method to counteract these challenges [201]. Nonetheless, the ability of these programs to also address geriatric domains of multimorbidity, frailty, cognitive impairments, and other complexities remains an additional area of concern.

8.1. Remote-Based Model (Opportunities and challenges)

While almost all CR programs address the five core components of CR, wide variations in the protocol and mode of delivery between different remote-CR programs have been reported in the literature [15,202,203]. There has been a variation in the number and frequency of sessions, duration of each session, and the mean by how exercise training is delivered and monitored. Remote-CR can be offered as a synchronous supervised or an asynchronous/self-directed rehabilitation. Some programs may utilize digital health such as smartphone, web-based, or email/SMS in delivering remote-CR [203–207]. The Veterans Affairs (VA) Office of Rural Health HBCR is an example of a simple yet effective remote-CR program [208]. The program was established at one center in 2010, and now over 30 US Veterans Administratin (VA) centers have adopted it. It is delivered by a CR specialist who contacts the patients by phone or video once per week for 12 weeks, addressing CR’s core components and assessing progress after an initial in-center assessment. Patients are provided with simple exercise equipment such as rubber bands and pedometers and receive individualized exercise prescription and progressed based on the weekly reported metrics [208].

Irrespective of the mode of delivery, CR programs have persistently improved health outcomes [209]. Multiple studies have demonstrated the safety of remote-CR in low-to-moderate risk adult cardiac patients with equivalent efficacy to CBCR; however, older adults and females were significantly underrepresented in these studies [15,200,207,210–212]. Using routine clinical data from the National Audit Cardiac Rehabilitation (NACR), Harrison and colleagues evaluated the physical fitness outcome across different modes of delivery of CR (traditional supervised versus self-directed) across a 5-year period. The study showed that physical fitness significantly improves after completing CR irrespective of the mode of delivery [209]. The NACR data demonstrated that a larger proportion of self-directed CR participants were older adults or females, but these populations remain underrepresented in RCTs pertaining to CR [200,209].

Remote-CR has many advantages over CBCR. Adherence was noted to be better in patients enrolled in remote-CR as compared to CBCR [211], and remote-based CR has the advantage of longer maintenance of physical activity and healthy lifestyle behaviors [213]. It has been found that participants completing exercise programs within their home versus a facility exhibit increased consistency in participation over a longer duration of time [214]. The improved adherence and sustained health behaviors are likely the influencing factors for the observed lower rate of hospitalization in patients attending remote-CR compared to CBCR at 6-year follow-up in the RCT by Smith and colleagues [213].

Despite its benefits, there are still challenges that limit the implementation of remote CR. A lack of consensus regarding optimal components of delivery contributes to the absence of a standardized delivery model. Without this, it is difficult to maintain consistency in the facilitation of remote CR programs or determine the components that offer the most efficacious outcomes. The safety of participants, particularly frail older adults, is an additional challenge. The burden of various geriatric syndromes such as neuromotor impairments, sensory impairments (vision and hearing), cognition and poor management of chronic diseases (hypertension, diabetes, etc.) can lead to a higher risk of adverse events such as falls, and completing an exercise program without direct supervision may not be safe. Participants may also simply not have the space or equipment within their home environment to complete the proposed exercises. Reimbursement structures are an additional factor that have limited the application and feasibility of remote CR until recently, as the Centers for Medicare and Medicaid Services, as well as some third-party insurance companies, were not reimbursing for remote CR until the COVID-19 pandemic. This has broadened opportunities to conduct research pertaining to outcomes for remote CR and mobilized initiatives to further leverage the utilization of this modality. Despite challenges to remote CR, technology offers the potential to counteract these issues with interventions such as remote monitoring systems. Additional research is needed to demonstrate the efficacy and logistical use of these interventions.

8.2. Integrating technology to Advance Accessibility to Cardiac Rehabilitation (Mobile Health)

Mobile health (mHealth) has gained significant attention in recent years with the rapid evolution of technology. The World Health organization defined mHealth as the “medical and public health practice supported by mobile devices, such as mobile phones, patient monitoring devices, personal digital assistants (PDAs) and other wireless devices”. This definition has since expanded to include the utilization of mobile applications, social media, and location tracking for disease diagnosis, prevention, and management [215]. This emerging approach has the potential to significantly improve the management of chronic conditions relevant to older adults, as many of mHealth applications have been utilized in the management of CVD to track dynamic measures, including blood pressure, heart rate, and cardiac rhythm. Evidence to support its implementation remains limited, but several small studies have demonstrated promising outcomes and support the potential safety and effectiveness of smartphone-based CR [206,216]*. The current literature evaluating the use of mHealth for CR has focused primarily on younger cohorts, however, the use of mHealth to address other CVD domains among older adults has demonstrated a compelling signal of benefit on health outcomes [216]*. In addition, an on-going NIA funded study is evaluating mobile health CR (mHealth-CR) in improving functional capacity after IHD specifically for older adults (≥70 years), Rehabilitation at Home Using Mobile Health in Older Adults After Hospitalization for Ischemic Heart Disease (RESILIENT) (NCT03978130).

Challenges specific to the geriatric population must be identified and addressed in order to ensure successful adoption of mHealth. Accessibility to a digital device and the ability to navigate digital devices are two factors that may influence utilization. Geriatric syndromes can act as barriers, including sensory limitations (vision or hearing), cognitive impairments, or movement disorders (e.g., Parkinson’s Disease) with increased risks of injury or ineffective care. Identifying challenges specific to the geriatric population allows for opportunities to adapt technology and therapeutic approaches advance.

9. Effect of COVID-19 Pandemic on CR

The coronavirus 2019 (COVID-19) pandemic led to significant interruptions in non-urgent cardiac care, including CR programs. At the start of the pandemic, almost all CR services ceased with the exception of the few previously established remote-based CR programs [208,217,218]. Social distancing resulted in a significant reduction in physical activity, increased isolation, and a shift to a more sedentary lifestyle among a significant portion of the population, and older adults in particular [219]. Geriatric syndromes predispose older adults to isolation and physical inactivity and the pandemic exacerbates these issues, with worsened frailty, social isolation, loneliness, anxiety and cognitive impairment among the geriatric population [220,221].

The COVID-19 pandemic has highlighted the need for new modes of delivery for CR and has catalyzed changes in the way CR is offered. The exponential utilization of remote-CR since the onset of COVID-19 has been reinforced by changes in payment models that support this form of CR. Additionally, the pandemic prompted the Million Hearts initiative to plan ‘think tanks’ that have established innovative strategic plans for new models of care like hybrid CR, HBCR, or community-based CRT [222]. Although remote CR remains in its early stages, the potential to build a more fiscally feasible, sustainable, and individualized approach to CR offers promise for improved accessibility and effectiveness.

10. Conclusion

Cardiac rehabilitation is a secondary prevention program for adults with CVD that has evolved from being exclusively focused on exercise-training, into a multifaceted program that addresses physical activity, risk reduction and wellness behaviors. The burgeoning population of older adults constitutes a particular challenge to the healthcare system and providers due to the increased complexity of health issues associated with age. Cardiovascular disease is the leading cause of mortality worldwide and older adults are disproportionately affected. Cardiac rehabilitation can be leveraged to improve CVD and functional outcomes (physical and cognitive) for older adults, but this program remains underutilized due to many barriers in referrals and enrollment. Physical limitations further exacerbated by geriatric syndromes pose additional challenges to participation in CR. Cumulative data substantiate the importance of CR in the recovery for older adults, and new research is mounting to reinforce accessibility, safety and value of this vital component of care.

11. Expert Opinion

Cardiac rehabilitation (CR) has evolved over the past half-century to stay synchronized with ever-changing cardiovascular disease therapeutics, yet contemporary CR remains paradoxically underutilized. This is particularly consequential as older adults are intrinsically susceptible to CVD as well as to age-related clinical complexities for which CR is conceptually well-suited, but infrequently applied. In this manuscript we have highlighted some of the mounting evidence that supports increased CR utilization for older adults for indications for CR that are already approved by Center for Medicare (CMS). In this section we suggest additional indications for CR that are especially germane to older adults but which are not yet CMS approved. Cardiac rehabilitation for patients with Heart Failure with Preserved Ejection Fraction (HFpEF), CR after hospitalization for acute decompensated heart failure (ADHF), and CR for patients with HF in post-acute care are all examples of clinical challenges that increase among older adults, and for which conceptual benefits of CR are especially compelling as potential enhancements of care, but for which CR is not yet endorsed by most healthcare insurers. Evidence suggesting the value of CR for these novel applications is presented, with the expectation that a tipping point towards widespread implementation may eventually arrive.

11.1. Heart Failure with Preserved Ejection Fraction

Heart failure (HF) with preserved ejection fraction (HFpEF) is the predominant type of HF among older adults, particularly older females, with a 1% incremental increase in its incidence annually [223,224]. Chronic exercise intolerance is the dominant morbidity in HFpEF patients, and it is influenced by cardiac and non-cardiac factors that affect their functional capacity, leading to sedentariness and poor quality of life [225]*. Moreover, despite the advances in medical therapies, HFpEF patients continue to have a high rate of recurrent hospitalizations and disabilities. Unlike HFrEF, most randomized controlled trial’s (RCT) of pharmacological therapies for HFpEF have not achieved mortality or hospitalization benefits. Thus, alternative interventions are being sought to improve HFpEF outcomes [225]*. Among these interventions is exercise training. Considerable literature has consistently shown that exercise-based CR improves functional capacity and quality of life in patients with HFpEF, even in frail older adults [226,227]. Peripheral benefits of exercise training are among the mechanisms of benefit. Nonetheless, the evidence of its impact on mortality and hospitalization has been inconsistent. Lack of mortality and hospitalization benefits may be attributable to the fact that most studies were exercise-based CR alone rather than multi-component comprehensive CR. A recent retrospective study in Japan evaluated the effect of comprehensive CR on frail older HFpEF patients. In this analysis, CR resulted in a significant reduction in all-cause mortality and heart failure (HF) rehospitalization in addition to the significant improvement in functional capacity and quality of life [228]. The Rehabilitation EnAblement in CHronic HF (REACH-HF) program is a novel comprehensive home-based self-management rehabilitation developed in the UK as an alternative to traditional CR for HF patients and their caregivers with a goal to improve self-management and quality of life. Initial data from 50 randomized patients shows a trend toward improvements in quality of life and decreased cardiac-related hospitalizations, in addition to an improvement in caregiver burden and mental health [229].

The fact that HFpEF is not approved by CMS and most other insurers in US has been attributed to the fact that approval of HF for CR was largely based on A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION), a large trial which only enrolled patients with heart failure with reduced ejection fraction (HFrEF) [230].

The recently published REHAB-HF, a multicenter, randomized controlled trial by Kitzman and colleagues, has the potential to broaden CR HF indications to include HFpEF [52]*. This study randomized multimorbid, older HF patients, of whom over half had HFpEF, to tailored exercise-based rehabilitation versus usual care. Though reduced mortality and rehospitalization did not reach a significant difference, tailored rehabilitation significantly improved physical function regardless of the ejection fraction [134]. Notably, this intervention was exclusively exercise-based rehabilitation, and other components of comprehensive CR were not part of the intervention. Thus, a large-scale, multicenter RCT to evaluate the impact of comprehensive CR on prognostic factors for patients with HFpEF is warranted to fill the gap and provide the support needed for the approval of CR for HFpEF.

11.2. Cardiac Rehabilitation after Acute Decompensated Heart Failure

Hospitalization with acute decompensated HF carries a significant burden on patients and healthcare systems; almost 25% of Medicare patients with ADHF get re-hospitalized within 30 days of discharge [231]. Moreover, acute hospitalizations for older adults with ADHF are associated with prolonged bed rest, malnutrition, and poor sleep leading to significant deconditioning, worsening sarcopenia, and loss of function. It was noted that 30%−50% of hospitalized older adults with CVD develop a new disability by discharge, and 40% of those who did not recover, died within the first year from discharge. Thus, the first month after hospital discharge is a critical period for recovery [232]. Nonetheless, based largely on the protocol used in HF-ACTION, current clinical guidelines recommend referral to CR only after 6 weeks from an ADHF hospitalization. This omits the potential benefits of CR during the critical period of recovery when it seems likely patients would benefit from CR.

Conceptually, CR earlier after ADHF is a powerful tool to catalyze recovery. Specific geriatric needs that could be addressed include functional deficits strength, balance, mobility, and endurance) arising from disease and deconditioning as well as the complexities of multimorbidity, frailty, polypharmacy, and cognitive impairments [52,233]. In a small, randomized, controlled trial that randomized patients who had been hospitalized with cardiogenic pulmonary edema to exercise training or usual care, exercise training was found to be safe and resulted in significant improvements in functional capacity and quality of life [234]. In REHAB-HF, almost all patients (97%) at baseline were frail or pre-frail and had significant functional impairments. Exercise rehabilitation was initiated soon after hospitalization and resulted in significant improvements in SPPB (the mean difference between intervention and control 1.5; P < 0.001) at three months follow-up [52]*. Due to the fact that Rehab-HF was solely focused on exercise training interventions, it can be postulated that additional benefits might also be derived from education, counseling, medications management, and psychosocial support if included as a component of multidomain comprehensive CR.

11.3. Cardiac Rehabilitation for Atrial Fibrillation (AF)

Atrial fibrillation (AF) is the most common arrhythmias, and its incidence increases with age. The estimated lifetime risk for AF after the age of 40 years is 1 in 4 [235]. AF carries a significant burden; it increases mortality and hospitalization, predisposes to heart failure, stroke, and cognitive impairment. Additionally, older adults with AF were found to have accelerated functional decline, lower exercise capacity, and poor quality of life even if they were asymptomatic [236]. This burden is anticipated to grow with the burgeoning aging population, making primary and secondary prevention for AF particularly important. AF management aims to control symptoms, prevent associated complications, and improve quality of life through rhythm or rate control, anticoagulation, and risk factors modification (weight loss, sleep apnea, BP control). Even though CR programs are well-suited to address both medical therapies and risk factors and moderate physical activity is recommended as part of managing CVD risk factors, they have not yet been in the AF prevention and management guidelines [237]. Limited clinical evidence and controversy on the safety of exercise in patients with arrhythmias are likely accounting for the lack of recommendations [238–241]. Strenuous physical activity and high-intensity endurance training have been associated with an increase in the incidence of AF [238,242]. However, a growing body of literature supports that moderate-intensity exercises are inversely associated with the risk of AF and in-fact have a positive impact on AF and decrease its burden [239,243–245] for those treated with ablative procedures as well as those who are treated medically. Risom and colleagues randomized 210 patients with AF treated with catheter ablation to 6 months of comprehensive multidisciplinary CR intervention or usual care. At 12 months follow-up, those who were randomized to CR had a higher mean VO₂ peak compared to usual care group; 25.82 mL/kg/min vs 22.43 mL/kg/min, P= 0.003, and lower proportion of high level of anxiety; 12% vs 24%, P=0.004 [246]. Among non-ablation studies, a small RCT of 49 patients with permanent AF and mean age 70 years, showed that 12-week exercise training significantly improved functional capacity, 6MWD, QoL, and decreased resting pulse rate [247]. Existing evidence highlights the valuable potential utilization of CR for AF, particularly for older adults who have permanent AF and are less likely to maintain sinus rhythm and/or tolerate antiarrhythmics or ablation. Putative benefits are both physiologic (e.g., greater parasympathetic tone that may in some instances restore sinus rhythm and/or slow heart responses) and emotional as adults grow more accustomed to their own exercise responses. Unfortunately, the utilization of CR for AF has been limited by insufficient evidence and a lack of insurance reimbursement. The data regarding the risk of hospitalization, mortality, and mental health vary between studies. Additionally, even though there was no reported safety concern, only a few studies reported adverse events as part of their outcomes. Thus, there is a need for large and multicenter RCTs to fill those knowledge gaps.

11.4. Cardiac Rehabilitation for Post-Acute Care

The use of CR for older adults in post-acute care is another opportunity to improve care. Older adults hospitalized with acute cardiac events have a higher likelihood of being frail, suffering from multiple comorbidities, and experiencing a longer length of stay, which puts them at an increased risk of requiring admission to a skilled nursing facility (SNF) [248,249]. In a study of Medicare beneficiaries, 25% of patients hospitalized with HF, 30% of myocardial infarction, 11% of coronary artery bypass surgery, and 20% of valve surgery were discharged to a SNF [248]. Older patients with CVD discharged to SNF have higher 30-day hospital readmission rates [250]. Incorporating the elements of CR (exercise and education) during subacute rehabilitation has been recommended by the American Association of Cardiovascular and Pulmonary Rehabilitation (AACVPR) [251]. However, these recommendations have not been widely implemented. Limitations associated impeding application include lack of suitable finances, organization, and the resources to deliver CR care [252]. Podlogar and colleagues suggested strategies to increase CR as part of post-acute care include 1. early identification of patients’ physical and emotional goals; 2. purposeful and relevant disease-specific educational initiatives focused on medication adherence, dietary modifications, self-monitoring of exercise intolerance; and 3. exercise tolerance testing to guide exercise prescription, integration of consistent monitoring and management of exercise-related symptoms. Nonetheless, the feasibility and efficacy of CR in post-acute care settings remain an area where additional research is needed [253].

11.5. Conclusion

Overall, there is much conceptual rationale for CR to address CVD in older adults, but CR still needs to be reengineered to better provide geriatric premised care. Cumulative data support the importance of CR as part of recovery for CVD among older adults, but more research is needed in respect to underlying biological value, process of care, and optimal implementation strategies. Given the prevailing demographics of an aging population and the inherent risks of complex CVD, such research seems highly worthwhile.

Table 2.B.

Functional Assessment Tools that are Commonly Used in Cardiac Rehabilitation

Measurement Tool	Description	Utilization	Limitation
6MWT[106]	Measures the distance a patient can walk on a flat, hard surface over 6 minutes. Patients are asked to walk as fast as possible back and forth along a fixed path (usually 25 meters) for six minutes. Assistive devices (cane, walker) can be used while performing the test. Individuals are allowed to rest if needed, however, the clock is not stopped.	Assesses endurance and submaximal aerobic capacity. Widely utilized to assess the effect of an intervention and as an outcome measure. Is especially useful to discriminate differences in function if SPPB is ≧10. Can be an index for a patient’s ability to perform ADLs.	Its utility diminishes in severely frail or deconditioned individuals with significant weakness. While 6MWT is a measure of brisk walking, it does not correlate to cardiopulmonary exercise testing assessments.
400-m Walk Test	Measures the individual’s ability to walk 400-m at a usual pace within 15 minutes without assistance or sitting.	Assesses mobility. Serves as an index of disability Is especially useful to discriminate differences in function if SPPB is ≧10.	Not an assessment for aerobic capacity
TUG Test[107]	Measures the time it takes an individual to rise from a chair, walk 3-m, turn around, and return to a seated position. Normal 8–12 seconds depending on age.[108] The mean (95% confidence intervals) for each age group: 60–69 years, 8.1 (7.1–9.0) seconds 70–79 years, 9.2 (8.2–10.2) seconds 80–89 years, 11.3 (10.0–12.7) seconds	Single assessment for strength (raise from chair), mobility (3-m walk), and balance (turn around) Provides perspective on fall risk [109]
Grip Strength	Measured by single hand dynamometer. Individuals are asked to squeeze the dynamometer as hard and as long as they can. Repeat the trial on each hand, alternating. The score is the average of 3 trials from both hands [110].	Assesses upper body strength Correlates with other strength tests that measure upper- and lower-body strength (1RM testing) Strongly correlation with physical function and disability.[89]*
Barthel Index (BI)[111]	Measures the ability to perform 10 ADLs, each scored according to the amount of time or assistance needed (range from completely dependent to completely independent). ADLs include feeding, transferring from chair to bed and back, grooming, toileting, bathing, dressing, bowel and bladder continence, walking or propelling a wheelchair, and climbing stairs up and down. Score from 0–100, higher scores indicate better function.	Metric of independence and disability

Abbreviations: 1RM = 1-repetition maximum, 6MWT = 6-minute walk test, ADL = activity of daily living, SPPB = Short Physical Performance Battery, TUG = Timed Up and Go

Article highlights:

• The needs of older adults with CVD is increasing germane to CR as the population of older adults continues to grow.

• Cardiovascular disease in older adults tends to be associated with geriatric syndromes that add to the complexity of care.

• Cumulative data substantiate the benefits and importance of CR in recovery for older adults, but many older adults with CVD are often too functionally or cognitively compromised to initiate or sustain the aerobic activity required.

• Reengineering CR to address geriatric syndromes and overcome strength and balance deficits in older frailer adults is needed, with goals to better enable older adults to participate and maintain independence.

• The utilization of CR falls sharply with age. Barriers to referral as well as enrollment must be addressed in order to enhance the use of this program.

• New models of care, such as remote CR, offer the opportunity to increase access as well as effectiveness of CR, but refinements are needed to best enable remote CR to be safe and effective for the wide range of eligible older adults, including those who are frail, sedentary, and fearful.