Exploring the mechanisms of yoga-based cardiac rehabilitation in heart failure via assessment of endothelial function, genomics and arterial health (Yoga-EndOmics): a study protocol

Abstract

Introduction

Heart failure (HF) remains a major global health challenge, particularly in low-resource settings where access to comprehensive cardiac rehabilitation (CR) is limited. Yoga, a culturally contextualised mind-body intervention, holds promise as an adjunctive therapy in CR. The Yoga-EndOmics study aims to evaluate the effects of Yoga-based cardiac rehabilitation (Yoga-CaRe) on gene expression, endothelial function, vascular biomarkers and clinical outcomes in systolic HF, providing mechanistic insights into its potential integration into conventional cardiac rehabilitation.

Methods and analysis

This is a prospective, randomised, open-label, blinded-endpoint (PROBE) mechanistic trial enrolling 78 patients with HF with reduced ejection fraction (HFrEF). Participants will be randomised in a 1:1 ratio to receive either a structured Yoga-CaRe intervention or enhanced standard care for 3 months. The Yoga-CaRe group will attend 20 supervised sessions with guided home practice involving tailored asanas, pranayama and meditation. Primary outcomes are changes in endothelial-dependent flow-mediated dilation (FMD) and functional exercise capacity at 3 months. Secondary outcomes include changes in arterial compliance and stiffness, circulating biomarkers of endothelial dysfunction, oxidative stress and inflammation, and immediate changes in global gene expression profiles in peripheral blood mononuclear cells following the Yoga-CaRe intervention. Data will be analysed using analysis of covariance (ANCOVA) for between-group comparisons and significant analysis of microarray (SAM) for global gene expression profiles.

Ethics and dissemination

The study has received ethical clearance from the Institutional Ethics Committee of the SDM College of Medical Sciences and Hospital, India (SDMIEC/2025/1072) and is registered with the Clinical Trials Registry of India. Findings will be disseminated through peer-reviewed journals, scientific conferences and stakeholder engagement platforms to inform future integrative strategies in HF management.

Trial registration number

CTRI/2023/12/060758

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• This is a prospective, randomised, open-label, blinded-endpoint (PROBE) mechanistic trial design, enhancing methodological rigour.

• The study uses comprehensive and validated gold-standard techniques to assess endothelial function, arterial stiffness and central blood pressure.

• Integration of molecular (gene expression and DNA methylation) and physiological assessments provides a multidimensional evaluation of mechanistic pathways.

• Standardised Yoga-CaRe sessions with supervised and home-based components may improve intervention fidelity.

• Participant adherence to home-based yoga practice may vary and could influence consistency in outcomes

Introduction

Heart failure (HF) is a progressive clinical syndrome characterised by impaired ventricular filling or ejection of blood, resulting from structural or functional abnormalities of the heart. The global burden of HF is increasing, with a particularly sharp rise in India, driven by the growing prevalence of risk factors such as obesity, hypertension, insulin resistance and type 2 diabetes. In India, the annual incidence of HF is estimated to range from 0.5 to 1.7 cases per 1000 individuals, translating to approximately 492 000 to 1.8 million new cases each year.¹ Despite advancements in medical therapy, HF remains associated with significant morbidity, poor quality of life (QoL), frequent hospitalisations and a 5-year mortality rate approaching 65%.²

HF is commonly classified based on left ventricular ejection fraction (EF) into three categories: heart failure with reduced ejection fraction (HFrEF; EF<40%), mid-range ejection fraction (HFmrEF; EF 41–49%) and preserved ejection fraction (HFpEF; EF≥50%). It is also categorised into systolic and diastolic HF. Systolic HF is marked by impaired myocardial contractility, whereas diastolic HF is characterised by increased ventricular stiffness and impaired relaxation. These classifications represent distinct phenotypes with differing demographic patterns, comorbidities and therapeutic responses, underscoring the heterogeneity of HF and the need for individualised treatment approaches.³

Cardiac rehabilitation (CR) is a Class I guideline-recommended intervention for patients with heart failure (HF), aimed at restoring physical, psychological and social well-being following cardiovascular events.^{4 5} Yoga, a holistic mind-body practice rooted in Indian tradition, addresses multiple domains of rehabilitation, including physical activity, stress management and lifestyle modification.⁶ The yoga-based cardiac rehabilitation (Yoga-CaRe) study, a multi-centre randomised controlled trial (RCT), demonstrated that yoga-based CR is a safe and effective approach for promoting recovery to pre-infarct functional status and improving quality of life (QoL) in patients following acute myocardial infarction.⁷ Additional clinical studies have reported favourable effects of yoga-based interventions on cardiovascular risk factors, functional capacity and psychological well-being.⁸,¹⁰ A meta-analysis by Pullen et al further supported the role of yoga in enhancing exercise tolerance and QoL among HF patients.¹¹ However, a large, high-quality RCT specifically evaluating the impact of Yoga-CaRe in Indian patients with HF is still lacking. Moreover, the mechanistic pathways underlying the observed benefits of yoga in this population remain poorly understood.

Endothelial dysfunction (ED) is a central pathophysiological mechanism in heart failure, characterised by reduced nitric oxide bioavailability, increased oxidative stress, inflammation and altered gene expression profiles.¹²,¹⁴ ED contributes to adverse vascular remodelling, progression of atherosclerosis and increased arterial stiffness—factors that exacerbate cardiovascular deterioration. Emerging evidence suggests that yoga may improve endothelial function and antioxidant capacity in individuals with cardiovascular disease, including those recovering from myocardial infarction.^{14 15} A systematic review and meta-analysis by Patil et al reported significant improvements in flow-mediated dilation (FMD), a gold-standard, non-invasive marker of endothelial function, following yoga-based interventions. However, the impact of yoga on endothelial function in heart failure populations remains underexplored.

In post-myocardial infarction patients, the Yoga-CaRe programme has shown promise in modulating biomarkers associated with inflammation, oxidative stress and endothelial function. A randomised controlled trial assessing Yoga-CaRe demonstrated significant reductions in levels of asymmetric dimethylarginine (ADMA), endothelin-1 (ET-1) and intercellular adhesion molecule-1 (ICAM-1), alongside increases in total antioxidant capacity (TAOC). These biomarker shifts suggest that yoga-based rehabilitation may enhance vascular health and bolster antioxidant defenses, indicating beneficial effects on molecular pathways relevant to cardiovascular recovery.¹⁶

Arterial stiffness, particularly aortic stiffness, is recognised as an independent predictor of cardiovascular morbidity and mortality.¹⁷,¹⁹ It increases central systolic blood pressure and cardiac afterload, thereby accelerating HF progression.^{20 21} Previous studies have demonstrated that yoga can reduce arterial stiffness in both normotensive and hypertensive populations^{14 21}; however, its role in modulating central arterial pressure and improving vascular health in patients with HF remains unclear.

This Yoga-EndOmics study seeks to address critical knowledge gaps by investigating the mechanistic effects of a structured Yoga-CaRe programme on endothelial function, gene expression, oxidative stress and arterial stiffness in patients with systolic heart failure (HFrEF). The primary aim of the Yoga-EndOmics study is to investigate the effects of a structured Yoga-Based Cardiac Rehabilitation (Yoga-CaRe) programme on endothelial function, arterial health and molecular markers to explore the underlying mechanism of heart health in patients with HFrEF or systolic HF.

The objectives are: (a) to evaluate whether Yoga-CaRe improves endothelial function through enhanced endothelium-dependent vasodilation after 3 months of intervention, (b) to assess rapid changes in global gene expression profiles in peripheral blood mononuclear cells immediately following Yoga-CaRe training of 7 days, (c) to determine the effects of Yoga-CaRe on endothelial-related gene expression, DNA methylation, central blood pressure, arterial stiffness, oxidative stress and inflammatory biomarkers at 3 months and (d) to explore whether Yoga-CaRe–induced improvements in vascular function and associated molecular changes correlate with clinical outcomes in HF. These insights may help establish a mechanistic rationale for incorporating yoga into standard cardiac rehabilitation strategies for HF management.

Methods and analysis

Design

This study adopts a Prospective Randomised Open-label Blinded Endpoint Mechanistic Study (PROBE) design to evaluate the impact of a Yoga-CaRe on HF patients rigorously.

Study setting

The study will be conducted at a tertiary care centre equipped for advanced cardiovascular diagnostics and rehabilitation.

Study timeline

Participant recruitment began in January 2025, and the study is expected to be completed by February 2026, including data collection and follow-up

Sample size determination

The sample size for the primary endpoint (FMD change) was calculated based on previous yoga-based intervention studies reporting significant improvement in FMD among cardiac patients. Specifically, Patil et al¹⁸ and Christa et al¹⁵ demonstrated mean FMD improvements of 2.5–3.0% with SD+3.5%. To detect a minimum difference of 2.5% in FMD between groups with 80% power and a two-sided α=0.05, 62 participants (31 per group) were required. Accounting for 20% attrition, we plan to recruit 78 participants (39 per group). For gene expression profiling, 24 participants (12 per arm) provide adequate power (80%) to detect differential expression (≥1.5 fold) using Significance Analysis of Microarrays (SAM) with FDR<0.05, as supported by prior mechanistic yoga studies with similar sample sizes.

Selection criteria

Inclusion criteria: for the study, include male and female patients aged 18 years and above, diagnosed with heart failure with reduced ejection fraction (HFrEF) according to the European Society of Cardiology (ESC) guidelines. Eligible participants must be classified as New York Heart Association (NYHA) functional Class II/III, have an ejection fraction (EF) of less than 40%, and be physically capable of participating in a cardiac rehabilitation (CR) programme.

Exclusion criteria: include the presence of comorbid conditions that significantly limit physical activity, recent major cardiovascular procedures, or planned elective cardiovascular interventions or hospitalisations within the next 3 months. Patients with heart failure secondary to a significant correctable or reversible cause, such as primary valvular disease or congenital heart defects amenable to correction, will also be excluded. Additional exclusion criteria include current participation in other clinical trials or engagement in regular yoga or structured exercise training (more than once per week at moderate-to-vigorous intensity) within the past 6 weeks.

Randomisation and allocation: Participants will be randomly assigned in a 1:1 ratio to either the Yoga-CaRe group or the control group using a computer-generated randomisation system, with stratification based on age and gender.

Intervention: Participants will be randomly assigned to either the Yoga-CaRe intervention group or the control group. Those in the Yoga-CaRe group will undergo 20 supervised yoga sessions over 3 months, supplemented by guided daily home practice. The sessions will incorporate a combination of asanas (physical postures), pranayama (breathing techniques) and dhyana (meditation), specifically adapted to suit the functional capacity and clinical needs of patients with heart failure (details provided in the online supplemental material tables 1-4).

The intervention will be delivered by a qualified Yoga Physician holding a Bachelor of Naturopathy and Yogic Sciences (BNYS) degree, with clinical experience in yoga-based cardiac rehabilitation. All instructors will undergo a 2-day centralised training workshop led by senior faculty from the Yoga-CaRe development team to ensure uniform delivery, safety monitoring and adherence to standardised protocols. A detailed standard operating manual (SOP) outlining session content, progression guidelines and safety procedures will be used to maintain inter-instructor consistency. The training emphasised safety precautions for patients with HF, session sequencing, posture modifications and adverse event management.

Adherence monitoring and participant engagement

Study Group: Attendance at supervised sessions of Yoga CaRe training will be recorded by the study staff. For home-based practice, participants will maintain a daily yoga diary documenting duration, frequency and components of practice. Adherence and participant well-being will be reinforced through regular follow-up phone calls, intermittent online classes and access to audio-video instructional materials to facilitate correct and consistent home practice. Home practice frequency will be objectively verified using video/photo logs (optional) or periodic demonstration during follow-up visits. Adherence will be considered satisfactory if participants complete at least 75% of the prescribed sessions. Random compliance checks and review of participant logs will be conducted periodically to ensure fidelity.

The control group will receive enhanced standard care consisting of educational sessions on heart-healthy living, medication adherence and stress management, without any structured yoga component. Participants in the control arm will receive enhanced standard care comprising three structured educational sessions delivered over a three-month period (approximately one session every month). Each session will last 45–60 minutes and will cover key aspects of CR, including (a) understanding heart failure and its management, (b) medication adherence and side-effect monitoring, (c) dietary and salt restriction guidance, (d) safe physical activity and energy conservation, (e) stress reduction and sleep hygiene and (f) recognising early warning signs and appropriate health-seeking behaviour.

All sessions will be conducted by qualified health science professionals who are part of the clinical trial team and trained in delivering standardised patient education for CR research. These facilitators possess a relevant background, with at least 2 years of experience in patient education or cardiovascular care. The educational content and delivery structure have been standardised using a detailed intervention manual to ensure uniformity across sessions. Participants will also receive printed educational materials summarising key points from the session, and attendance will be recorded to monitor engagement and adherence

Outcome measures

Primary outcomes: There are two primary outcomes of the study. The first primary outcome will be a change in FMD and the second is a 6-minute walk test (6MWT) at 3 months from baseline. The study designates FMD as the principal primary endpoint with the highest analytical priority, while 6MWT is treated as a second primary clinical endpoint.

Secondary outcomes, including arterial compliance, arterial stiffness and circulating biomarkers of endothelial dysfunction, oxidative stress and inflammation, will be analysed at 3 months from baseline with appropriate control for multiplicity using the Bonferroni correction. Immediate changes in global gene expression profiles on day 7 will also be examined as secondary outcomes.

Study Protocol

Eligible patients will be screened for inclusion in the study based on predefined criteria. A comprehensive medical history, including prior medication use, demographic information and relevant personal history, will be recorded. This will be followed by a clinical examination, relevant investigations and measurement of baseline parameters such as brachial blood pressure and heart rate. After confirming eligibility, baseline data will be collected, and participants will be randomised and allocated to their respective study arms. Participants in the intervention group will receive the Yoga-CaRe programme, while those in the control group will receive enhanced standard care, including structured educational sessions on heart-healthy living (figures1 2).

Figure 1. Study Flow Chart (Objective 2).

Figure 2. Study flow chart (Objectives 1,3-4).

Method of Data Collection

The following parameters will be systematically assessed to evaluate the functional, vascular, molecular and biochemical outcomes of the Yoga-CaRe intervention in patients with systolic heart failure:

1. Functional exercise capacity: Functional exercise capacity will be evaluated using the 6MWT, a standardised and validated tool in HF populations. Participants will be instructed to walk along a predefined corridor for 6 min, and the total distance covered in metres will be recorded. The test will be performed under clinical supervision, following established guidelines, with pre-test and post-test measurements of blood pressure, heart rate, oxygen saturation and perceived exertion.²²

2. Systolic and diastolic function of the heart: A comprehensive echocardiographic assessment will be conducted to evaluate both systolic and diastolic function. Measurements will include left ventricular ejection fraction (LVEF), left ventricular end-diastolic and end-systolic volumes, E/A ratio and E/e’ ratio using two-dimensional, M-mode and Doppler imaging techniques, as per the American Society of Echocardiography guidelines.²³

3. Assessment of endothelial function: Endothelial function will be comprehensively evaluated through multiple complementary methods. Flow-mediated dilatation (FMD) of the brachial artery, a gold-standard non-invasive technique, will be performed using high-resolution ultrasound before and after transient forearm occlusion; the percentage change in artery diameter will indicate endothelial-dependent vasodilation.²⁴ Carotid Intima-Media Thickness (CIMT) will be measured by B-mode ultrasonography to assess subclinical atherosclerosis, serving as an indirect marker of endothelial dysfunction and vascular ageing.²⁵ Additionally, circulating biomarkers of endothelial function will be quantified: Endothelin-1 (ET-1) levels will be measured using a commercially available ELISA kit, while total nitric oxide concentration (NOx) will be determined through the Griess reaction, reflecting nitric oxide bioavailability and vascular tone.²⁶

4. Gene Expression Profiling: RNA will be extracted from peripheral blood mononuclear cells (PBMCs) using the Qiagen RNeasy Mini Kit. RNA integrity will be verified using the Agilent 2100 Bioanalyser (RIN≥7.0). Microarray-based global gene expression profiling will be performed using the Agilent SurePrint G3 Human Gene Expression 8×60K platform. Processed and normalised gene expression data will be deposited in the Gene Expression Omnibus (GEO) repository on publication, ensuring open access in compliance with FAIR data principles. These additions appear in the “Gene Expression Profiling” subsection. Real-time quantitative reverse transcription PCR (qRT-PCR) will be used to measure mRNA levels of key endothelial and inflammatory genes, including eNOS, ET-1, TNF-α, NADPH oxidase, MMP, Ang-1, VCAM and ICAM.

5. Assessment of global gene expression will be conducted using Significance Analysis of Microarrays (SAM) to identify differentially expressed genes immediately following the intervention. SAM provides a robust statistical framework that controls the false discovery rate, allowing for reliable detection of significant changes in gene expression. This method offers valuable insights into the rapid molecular responses and early physiological adaptations induced by Yoga-CaRe.

6. DNA methylation analysis: DNA methylation will be assessed to evaluate epigenetic modulation associated with the Yoga-CaRe intervention. Locus-specific quantitative methylation analysis will be performed using PCR-based pyrosequencing. Global DNA methylation levels will be estimated by analysing the methylation status of ALU and LINE-1 repetitive elements, which are commonly used surrogates for overall genomic methylation and have been linked to cardiovascular risk and biological ageing.

7. Assessment of arterial health: Arterial health will be evaluated using ARTSENS Plus, a validated non-invasive device that employs automated algorithms for comprehensive vascular assessment.⁹ Key parameters measured will include carotid-to-femoral pulse wave velocity (cfPWV), which reflects central arterial stiffness, carotid arterial compliance (cAC) that indicates the elasticity of the common carotid artery, and local carotid pulse wave velocity (PWVβ), providing site-specific measurements of carotid arterial stiffness. This integrated assessment offers valuable insights into vascular function and cardiovascular risk.

8. Central arterial pressure: Central blood pressure indices will be measured using the ARTSENS device and will include carotid systolic pressure, carotid diastolic pressure and carotid pulse pressure. These parameters offer important insights into central haemodynamic load, reflecting the stress imposed on the cardiovascular system and contributing to the understanding of vascular health and disease risk.²⁷

9. Oxidative stress and inflammatory markers: Plasma levels of biomarkers of oxidative stress and inflammation will be measured using ELISA-based assays. Oxidative stress biomarkers include oxidised low-density lipoprotein (Ox-LDL), superoxide dismutase (SOD) and total antioxidant capacity (TAOC). The inflammatory biomarkers include tumour necrosis factor-alpha (TNF-α) and high-sensitivity C-reactive protein (hs-CRP). These markers offer important insights into the redox balance and systemic inflammatory status in patients with HF, helping to elucidate the biochemical pathways involved in disease progression and response to intervention.

10. Other biochemical investigations: Fasting blood glucose and a comprehensive lipid profile, including total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL) and triglycerides, will be measured using standardised enzymatic colourimetric assays in a certified laboratory. These assessments will provide essential metabolic and cardiovascular risk data to complement the study’s clinical and molecular evaluations.

Data Analysis

Quantitative data will be analysed using SPSS (version 20). Descriptive statistics will summarise baseline characteristics: categorical variables will be presented as frequencies and percentages, while continuous variables will be expressed as means with standard deviations (±SD) or medians with IQRs, depending on data distribution. Between-group comparisons will be conducted using analysis of covariance (ANCOVA). Within-group changes from baseline to post-intervention will be assessed using parametric or non-parametric tests based on data normality. Significance analysis of microarrays (SAM) with false discovery rate (FDR) adjustment will be employed to identify differentially expressed genes following the intervention. Correlation and multivariable regression analyses will be performed to explore associations between clinical outcomes and vascular or molecular parameters. A two-tailed p value<0.05 will be considered statistically significant.

Ethics and dissemination

The study was approved by the Institutional Ethics Committee of the SDM College of Medical Sciences and Hospital, India (SDMIEC/2025/1072) (sdmiec@sdmucmsh.edu.in) and is registered with the Clinical Trials Registry of India (CTRI) under the registration number CTRI/2023/12/060758. A Data and Safety Monitoring Board (DSMB) established for this project will closely monitor the study to ensure participant safety and uphold research integrity. Informed consent will be obtained voluntarily from each participant after initial screening, ensuring they fully understand the nature, procedures, risks and benefits of the study. To protect participant privacy, strict confidentiality protocols will be followed, with access to research data limited to the Principal Investigator (PI) and Co-Principal Investigator (Co-PI).

Safety monitoring and discontinuation criteria

Even though Yoga-CaRe offers potential benefits, there are possible risks, including fluctuations in blood pressure, abnormal heart rhythms and chest discomfort. Incorrect postures may lead to muscle strains, joint pain or falls, and rapid breathing techniques could occasionally result in dizziness. Therefore, all sessions will be conducted under supervision at the HF Care Centre to ensure safety. These considerations underscore the need for careful supervision and appropriate guidance during the intervention. Given the potential risk of haemodynamic fluctuations during yoga practice in patients with HF, participant safety will be continuously monitored throughout supervised sessions.

Heart rate, blood pressure and oxygen saturation will be recorded before, during (mid-session) and immediately after each supervised yoga session. Any significant deviations, defined as systolic blood pressure >180 mmHg, diastolic blood pressure >110 mmHg, heart rate <50 or >120 beats/min and oxygen saturation <90%, or the onset of symptoms such as chest pain, dizziness or severe dyspnoea, will lead to immediate discontinuation of the session and prompt medical evaluation by the study physician.

Participants experiencing sustained haemodynamic instability, arrhythmia or any serious adverse event deemed related to the intervention will be withdrawn from the study after consultation with the principal investigator and Data Safety Monitoring Board (DSMB). A predefined adverse event reporting protocol will be followed, and all events will be recorded and reviewed periodically by the DSMB to ensure participant safety and data integrity.