Abstract
BACKGROUND
The impact of age on outcomes in cardiogenic shock (CS) is poorly described in the pre-hospital setting. We assessed the impact of age on outcomes of patients treated by emergency medical services (EMS).
METHODS
This population-based cohort study included consecutive adult patients with CS transported to hospital by EMS. Successfully linked patients were stratified into tertiles by age (18-63, 64-77, and > 77 years). Predictors of 30-day mortality were assessed through regression analyses. The primary outcome was 30-day all-cause mortality.
RESULTS
A total of 3523 patients with CS were successfully linked to state health records. The average age was 68 ± 16 years and 1398 (40%) were female. Older patients were more likely to have comorbidities including pre-existing coronary artery disease, hypertension, dyslipidemia, diabetes mellitus, and cerebrovascular disease. The incidence of CS was significantly greater with increasing age (incidence rate per 100,000 person years 6.47 [95% CI: 6.1-6.8] in age 18-63 years, 34.34 [32.4-36.4] in age 64-77 years, 74.87 [70.6-79.3] in age > 77 years, P < 0.001). There was a step-wise increase in the rate of 30-day mortality with increasing age tertile. After adjustment, compared to the lowest age tertile, patients aged > 77 years had increased risk of 30-day mortality (adjusted hazard ratio = 2.26 [95% CI: 1.96-2.60]). Older patients were less likely to receive inpatient coronary angiography.
CONCLUSION
Older patients with EMS-treated CS have significantly higher rates of short-term mortality. The reduced rates of invasive interventions in older patients underscore the need for further development of systems of care to improve outcomes for this patient group.
Cardiogenic shock (CS) is characterized by end-organ hypoperfusion that can result in severe multi-organ dysfunction.[1, 2] Despite contemporary resuscitative and reperfusion therapies in acute myocardial infarction complicated by cardiogenic shock (AMI-CS), this condition continues to be associated with a high risk of significant morbidity and mortality.[3] In AMI-CS, advanced age has been shown to be an independent predictor of mortality.[4-6] However, previous studies have demonstrated that older patients with AMI-CS are less likely to be treated with invasive coronary therapies, despite earlier revascularization being associated with lower mortality compared with those receiving late or medical therapy alone.[7, 8] These data suggest that the excess risk of mortality experienced by older patients with AMI-CS could be partially explained by variations in clinical care. Using a large Australian emergency medical services (EMS) database, which has been linked to health service medical records and state death index data, we aimed to define the impact of age on treatment and clinical outcomes in patients with CS who received pre-hospital care through EMS.
METHODS
This population-based cohort study included consecutive adult patients attended by EMS presenting with cardiogenic shock between January 1, 2015 and June 30, 2019 in Victoria. Within Victoria, approximately 70% of the population live in the greater Melbourne metropolitan region and the remaining population within semiurban and rural areas. Paramedic electronic patient care record data were linked to the Victorian Emergency Minimum Dataset (VEMD), the Victorian Admitted Episodes Dataset (VAED), Victorian Ambulance Cardiac Arrest Registry (VACAR), and the Victorian Death Index (VDI).[9, 10] The VEMD, VAED and VDI contain state-wide administrative and clinical data relating to emergency department presentations and hospital admissions. A detailed description of the linkage processes and methodologies employed has been previously described and is provided in Supplemental Methods (see Appendix 1).[11, 12] This study was conducted in accordance with the Declaration of Helsinki and ethics approval for the data linkage, in addition to this specific analysis, was granted by the Monash University Human Research Ethics Committee (approval number 11681).
Study Setting
Ambulance Victoria is the sole provider of EMS in the state of Victoria, Australia. Access to EMS is provided through a single nationwide telephone number (i.e., Triple Zero ‘000’). The EMS is funded primarily through the Victorian State Government, with a proportion of funding generated through membership subscription and transport fees.[10] The EMS system provides a 2-tiered response to medical emergencies in the community: (1) approximately 4,500 advanced life support paramedics that are capable of laryngeal mask airway insertion and medication administration (i.e., analgesics, bronchodilators, aspirin and thrombolysis); and (2) approximately 450 intensive care paramedics capable of endotracheal intubation and a wider scope of medications (including intravenous epinephrine infusions and antiarrhythmics).[11] At the conclusion of each case, paramedics complete an electronic patient care record that captures patient and case details, pre-existing comorbidities, as well as any pre-hospital management. Data from these records are uploaded to and stored within a secure clinical data warehouse.
Study Definitions
Shock was defined as sustained hypotension (systolic blood pressure < 90 mmHg sustained for greater than 30 min) or EMS-administered intravenous epinephrine. Exclusion criteria included: known traumatic etiology; for palliative treatment only; ambulance attendances for transfers between hospitals; transfer to a private hospital emergency department; died at scene or during transport to hospital; and age < 18 years. Final diagnosis was defined according to International Classification of Diseases (ICD) as the VAED primary diagnosis if discharged from hospital or the VEMD primary diagnosis if discharged from the emergency department. Patients were included in the primary analysis if they survived transport to a public hospital and had a successful linkage to VAED or VEMD. Patients were defined as having cardiogenic shock based on their hospital primary ICD-10-AM discharge diagnosis. Further details relating to the specific ICD diagnostic codes utilized to classify shock etiology are described in the Supplementary Methods. Patients were stratified into tertiles according to age (18-63, 64-77, and > 77 years).
Outcomes
The primary outcome was 30-day all-cause mortality. Secondary outcomes included incidence of cardiogenic shock, rates of inpatient coronary angiography and percutaneous coronary intervention (PCI), length of hospitalization and discharge destination.
Statistical Methods
Incidence per 100,000 person-years was calculated using mid-year age-sex-specific population estimates available from the Australian Bureau of Statistics using the total number of patients meeting the study’s inclusion criteria. 95% confidence intervals (CIs) were derived with the assumption that the observed number of episodes followed a Poisson distribution. Continuous variables are presented as medians and interquartile ranges or mean and standard deviation (as appropriate). Categorical variables are presented as frequencies and percentages. All tests were 2-tailed and assessed at the 5% significance level. Comparisons of continuous variables were performed using unpaired t-tests and one-way analysis of variance (ANOVA) for normally distributed data and the Mann-Whitney U or Kruskal-Wallis for skewed data. Differences in proportions were assessed using the Chi square test and Fisher Exact. Association between clinically relevant pre-hospital covariates and 30-day mortality were assessed using a mixed effect parametric survival model based on a Weibull distribution with the inclusion of region of the event (local government area) as a random effect to account for potential clustering. To assess the impact of age on 30-day mortality, using the same parametric model, a restricted cubic spline was generated, fitting the model with 5-knots. Variables included in the model were as follows; age tertile, female gender, initial systolic blood pressure and heart rate, pre-hospital cardiac arrest, pre-hospital intubation, ST-elevation myocardial infarction (STEMI), non-st-elevation myocardial infarction (NSTEMI) and pre-hospital epinephrine administration. A logistic regression analysis was also performed to assess for factors associated with inpatient coronary angiography. Unadjusted Kaplan-Meier survival analysis was performed to assess risk of death in the 30-day follow-up period. Sensitivity analyses were performed to assess age-related differences with the exclusion of patients who sustained out-of-hospital cardiac arrest. Statistical analyses were conducted using Stata version 16.1 for Windows (College Station, Texas, USA).
RESULTS
Baseline Characteristics and EMS Interventions
Between January 1, 2015 and June 30, 2019, there were 2,857,760 calls made for EMS, resulting in 2,485,311 ambulance attendances for any reason (see Appendix 2 for cohort derivation). Of those that required ambulance attendance, 3523 patients were successfully linked and met the inclusion criteria for cardiogenic shock. Baseline cohort characteristics are summarized in Table 1. The mean age of patients transported to hospital with cardiogenic shock was 68 ± 16 years (P < 0.001). Female patients comprised 40% (n = 1,398) of this cohort (P < 0.001). Patients in the 64-77 and > 77 years of age tertiles were more likely to have pre-existing medical comorbidities such as hypertension, dyslipidemia, diabetes mellitus, pre-existing coronary artery disease and vascular disease compared to those < 64 years. Younger patients were more likely to have sustained pre-hospital cardiac arrest (30% in 18-63 years) compared to those > 77 years (20%), P < 0.001. Cardiac arrest determined by primary hospital diagnosis was the predominant cause of cardiogenic shock in all patients (42%, n = 1463) and was proportionally higher in younger patients (53% in age 18-63 years, 45% in age 64-77 years) than older patients (26%), P < 0.001. STEMI as cause of shock was higher in younger patients than older patients (17% in age 18-63 years, 15% in age 64-77 years, 12% in age > 77 years, P = 0.002), whereas NSTEMI was more prevalent in older patients (2.5% in age 18-63 years vs. 6.9% in age > 64 years, P < 0.001). Initial systolic blood pressures did not differ significantly between the age tertiles, while initial heart rate was lower in older patients than younger patients (110.8 ± 51.5 beats/min in age 18-63 years, 96.6 ± 45.6 beats/min in age 64-77 years, 86.9 ± 43.6 beats/min in age > 77 years, P < 0.001). Younger patients were more likely to be intubated prior to arrival in hospital than older patients (47% in age 18-63 years vs. 23% in age > 77 years, P < 0.001).
Table 1. Baseline characteristics of cohort.
| All N = 3523 |
18-63 years N = 1199 (34%) |
64-77 years N = 1164 (33%) |
> 77 years N = 1160 (33%) |
P-value | |
| Data are presented as mean ± SD or n (%). *Determined by Victorian Ambulance Cardiac Arrest Registry (VACAR) linkage; † shock aetiology determined by hospital primary ICD discharge diagnosis derived through linkage with VEMD and VAED datasets; ‡ arrhythmia included hospital primary discharge diagnoses of complete heart block, atrial tachyarrhythmias, and ventricular arrhythmias. COPD: chronic obstructive airways disease; ICD: international classification of diseases; NSTEMI: non-ST elevation myocardial infarction; STEMI: ST elevation myocardial infarction; SVT: supraventricular tachycardia. | |||||
| Mean age | 68.4 ± 16 | 50.1 ± 10.6 | 70.9 ± 4 | 84.9 ± 4.9 | < 0.001 |
| Female | 1,398 (40%) | 435 (36%) | 409 (35%) | 554 (48%) | < 0.001 |
| Hypertension | 1309 (41%) | 262 (26%) | 517 (48%) | 530 (48%) | < 0.001 |
| Dyslipidemia | 826 (26%) | 160 (16%) | 344 (32%) | 322 (29%) | < 0.001 |
| Diabetes mellitus | 702 (22%) | 186 (19%) | 274 (25%) | 242 (22%) | 0.001 |
| Pre-existing coronary artery disease | 827 (26%) | 154 (16%) | 311 (29%) | 362 (33%) | < 0.001 |
| Pre-existing heart failure | 435 (14%) | 51 (5.1%) | 144 (13%) | 240 (22%) | < 0.001 |
| Chronic kidney disease | 222 (7%) | 58 (5.8%) | 64 (5.9%) | 100 (9.1%) | 0.004 |
| Peripheral vascular disease | 52 (1.6%) | 6 (0.6%) | 23 (2.1%) | 23 (2.1%) | 0.008 |
| Cerebral vascular disease | 234 (7.4%) | 40 (4%) | 79 (7.3%) | 115 (10%) | < 0.001 |
| COPD | 319 (10%) | 57 (5.7%) | 159 (15%) | 103 (9.3%) | < 0.001 |
| Pre-hospital cardiac arrest* | 905 (26%) | 365 (30%) | 314 (27%) | 226 (20%) | < 0.001 |
| Shock aetiology† | |||||
| STEMI | 505 (14%) | 198 (17%) | 173 (15%) | 134 (12%) | 0.002 |
| NSTEMI | 190 (5.4%) | 30 (2.5%) | 71 (6.1%) | 89 (7.7%) | < 0.001 |
| Decompensated heart failure | 257 (7.3%) | 66 (5.5%) | 69 (14.9%) | 122 (11%) | < 0.001 |
| Cardiac arrest | 1463 (42%) | 639 (53%) | 528 (45%) | 296 (26%) | < 0.001 |
| Arrhythmias‡ | 947 (27%) | 334 (28%) | 313 (27%) | 300 (26%) | < 0.001 |
| Mean initial systolic blood pressure, mmHg | 85.5 ± 29.6 | 86.2 ± 29.1 | 87.9 ± 32.7 | 83.2 ± 27.3 | 0.011 |
| Mean initial heart rate, beats/min | 97.7 ± 27.9 | 110.8 ± 51.5 | 96.6 ± 45.6 | 86.9 ± 43.6 | < 0.001 |
| Pre-hospital intubation | 1307 (37%) | 558 (47%) | 484 (42%) | 265 (23%) | < 0.001 |
| Pre-hospital epinephrine infusion commenced | 1880 (53%) | 678 (57%) | 694 (60%) | 508 (44%) | < 0.001 |
The incidence of cardiogenic shock per 100,000 person years significantly increased with age (see Table 2 and Figure 1). Incidence in age > 77 years was 11.6-fold higher than that of age 18-63 years (6.47 [95% CI: 6.1-6.8], 34.34 [32.4-36.4] in age 64-77 years, 74.87 [70.6-79.3] in age > 77 years, P < 0.001). Overall, males were almost twice as likely to develop cardiogenic shock than women of the same age.
Table 2. Incidence of cardiogenic shock per 100,000 person years.
| 18-63 years | 64-77 years | > 77 years | P-trend | ||||||
| Incidence* | 95% CI | Incidence | 95% CI | Incidence | 95% CI | ||||
| *Incidence per 100,000 person years; 95% CI derived assuming poisson distribution. P-trend calculated using Cochran-Armitage test. | |||||||||
| All | 6.47 | 6.1-6.8 | 34.34 | 32.4-36.4 | 74.87 | 70.6-79.3 | < 0.001 | ||
| Male | 8.30 | 7.7-8.9 | 46.31 | 42.8-49.5 | 91.59 | 84.4-99.2 | < 0.001 | ||
| Female | 4.66 | 4.2-5.1 | 23.25 | 21.1-25.6 | 62.41 | 57.3-67.8 | < 0.001 | ||
Figure 1.
Incidence of cardiogenic shock per 100,000 person years.
Outcomes
Primary outcome
Of the 3523 patients in this study, 1481 patients (42%) died within 30 days of presentation (Table 3). 30-day mortality rate was highest in age tertile > 77 years and lowest in 18-63 years (38% in age 18-63 years, 42% in age 64-77 years, 47% in age > 77 years, P < 0.001).
Table 3. Outcomes and inpatient interventions.
| All N = 3523 |
18-63 years N = 1199 |
64-77 years N = 1164 |
> 77 years N = 1160 |
P-value | |
| Data are presented as n (%). | |||||
| 30-day mortality | 1481 (42%) | 451 (38%) | 485 (42%) | 545 (47%) | < 0.001 |
| Death within 24 h of ambulance arrival | 501 (14%) | 143 (12%) | 142 (12%) | 216 (19%) | < 0.001 |
| Inpatient admission length of stay, days | 6.1 ± 7.8 | 6.6 ± 8.2 | 6.5 ± 8.6 | 5.3 ± 6.4 | < 0.001 |
| Coronary angiogram | 975 (28%) | 435 (36%) | 368 (32%) | 172 (15%) | < 0.001 |
| Percutaneous coronary intervention | 493 (14%) | 235 (20%) | 191 (16%) | 67 (5.8%) | < 0.001 |
| Requirement for mechanical ventilation | 1145 (33%) | 510 (43%) | 436 (38%) | 199 (17%) | < 0.001 |
| Requirement for dialysis | 199 (5.6%) | 91 (7.6%) | 78 (6.7%) | 30 (2.6%) | < 0.001 |
Predictors for 30-day mortality are summarized in Table 4. The greatest predictor for 30-day mortality was pre-hospital cardiac arrest (HR = 3.99 [95% CI: 3.09-5.17], P < 0.001). Older age was an independent predictor of 30-day mortality (HR = 1.34 [1.17-1.53], P < 0.001 for age 64-77 years [compared with age 18-63 years]; HR = 2.26 [1.96-2.60], P < 0.001 for age >77 years [compared with age 18-63 years]). STEMI, NSTEMI and requirement for intubation were also associated with an increased risk of 30-day mortality (HR = 1.82 [1.54-2.16], P < 0.001; HR = 1.78 [1.43-2.22], P < 0.001; HR = 2.36 [1.87-2.98], P < 0.001, respectively). Inpatient coronary angiography (irrespective of whether PCI was performed) was associated with significantly reduced risk of 30-day mortality (HR = 0.33 [0.28-0.38], P < 0.001). Female gender and administration of epinephrine infusion were not predictive of mortality in this study. Unadjusted Kaplan-Meier survival analysis was performed, demonstrating increased risk of death throughout the 30-day follow-up period with increasing age tertiles, log-rank < 0.001 (Figure 2). The cubic spline depicted in Figure 3, demonstrated a marked increase in adjusted risk of 30-day mortality in those aged ≥ 70 years.
Table 4. Hazard ratio for 30-day mortality.
| Variable | Hazard ratio | 95% CI | P-value |
| Mixed effects model for 30-day mortality using Weibull distribution with LGA in which case occurred as a mixed effect. LGA: local government area; NSTEMI: non-ST elevation myocardial infarction; STEMI: ST elevation myocardial infarction. | |||
| Age 64-77 yrs (compared with age 18-63 yrs) | 1.34 | 1.17-1.53 | < 0.001 |
| Age > 77 yrs (compared with age 18-63 yrs) | 2.26 | 1.96-2.60 | < 0.001 |
| Female | 1.08 | 0.97-1.21 | 0.18 |
| Initial systolic blood pressure, mmHg | 1.0 | 1.0-1.0 | < 0.001 |
| Initial pulse rate, beats/min | 1.0 | 1.0-1.0 | < 0.001 |
| Pre-hospital cardiac arrest | 3.99 | 3.09-5.17 | < 0.001 |
| STEMI | 1.82 | 1.54-2.16 | < 0.001 |
| NSTEMI | 1.78 | 1.43-2.22 | < 0.001 |
| Inpatient coronary angiography | 0.33 | 0.28-0.38 | < 0.001 |
| Pre-hospital intubation | 2.36 | 1.87-2.98 | < 0.001 |
| Pre-hospital epinephrine infusion commenced | 0.85 | 0.71-1.03 | 0.093 |
Figure 2.
Kaplan-Meier survival curves for cardiogenic shock according to age.
Figure 3.
Association between age and 30-day mortality.
aHR are estimated from a model with age fitted as a restricted cubic spline, adjusted for clinical characteristics and diagnosis with local government area of ambulance attendance included as a random effect. aHR is in comparison to 40 years of age as the reference. aHR: adjusted hazard ratio.
Secondary outcomes
Of 3,523 patients included in this study, 501 patients (14%) died within 24 hours of ambulance arrival at scene. A greater proportion of patients in age tertile > 77 years died within 24 h compared with the younger age tertiles (12%, n = 143 of aged 18-63 years; 12%, n = 142 of aged 64-77 years; 19%, n = 216 of aged > 77 years, P < 0.001, respectively) (Table 3).
Less than a third of patients (28%), underwent inpatient coronary angiogram (P < 0.001) and only 14% (n = 493) received PCI (P < 0.001) (Table 3). A greater proportion of younger patients received invasive coronary intervention than older patients (36% of age 18-63 years received coronary angiogram vs. 15% in age > 77 years, P < 0.001). Predictors of inpatient coronary angiography are summarized in Table 5. Older age and female gender were negatively associated with receiving inpatient coronary angiography (OR = 0.78 [0.63-0.97], P = 0.02 for age 64-77 years [compared with age 18-63 years]; OR = 0.35 [0.27-0.45], P < 0.001 for age > 77 [compared with age 18-63 years]; OR = 0.50 [0.41-0.61], P < 0.001 for female gender). STEMI was the strongest predictor of inpatient coronary angiography (OR = 22.24 [16.66-29.68], P < 0.001). Requirement for commencement of pre-hospital epinephrine infusion, NSTEMI and pre-hospital cardiac arrest were also associated with coronary angiography (OR = 3.70 [2.81-4.88], P < 0.001; OR = 3.02 [2.04-4.48], P < 0.001; OR = 2.31 [1.56-3.41], P < 0.001, respectively). Initial systolic blood pressure, pulse rate and requirement for intubation were not reliable predictors.
Table 5. Predictors of inpatient coronary angiography.
| Variable | Odds ratio | 95% CI | P-value |
| NSTEMI: non-ST elevation myocardial infarction; STEMI: ST elevation myocardial infarction. | |||
| Age 64-77 yrs (compared with age 18-63 yrs) | 0.78 | 0.63-0.97 | 0.02 |
| Age > 77 yrs (compared with age 18-63 yrs) | 0.35 | 0.27-0.45 | < 0.001 |
| Female | 0.50 | 0.41-0.61 | < 0.001 |
| Initial systolic blood pressure, mmHg | 1.0 | 1.0-1.0 | 0.65 |
| Initial pulse rate, beats/min | 1.0 | 1.0-1.0 | 0.26 |
| Pre-hospital cardiac arrest | 2.31 | 1.56-3.41 | < 0.001 |
| STEMI | 22.24 | 16.66-29.68 | < 0.001 |
| NSTEMI | 3.02 | 2.04-4.48 | < 0.001 |
| Requirement for intubation | 0.93 | 0.65-1.34 | 0.70 |
| Pre-hospital epinephrine infusion commenced | 3.70 | 2.81-4.88 | < 0.001 |
Younger patients were also more likely to receive mechanical ventilation than older patients (43% in age 18-63 years vs. 17% in age > 77 years, P < 0.001) and other invasive interventions such as dialysis (7.6% in age 18-63 years vs. 2.6% in age > 77 years, P < 0.001) (see Table 3). Younger patients were more likely to be admitted to the intensive care unit (23% in age 18-63 years, 21% in age 64-77 years, 12% in age > 77 years, P < 0.001). Patients aged > 77 years had the shortest inpatient length of stay (6.6 ± 8.2 days in age 18-63 years, 6.5 ± 8.6 in age 64-77years, 5.3 ± 6.4 in age > 77 years, P < 0.001) (see Table 3).
Sensitivity analyses were performed, and age-related differences persisted when study patients who sustained out-of-hospital cardiac arrest were excluded from analyses (see Appendix 3 and Appendix 4).
DISCUSSION
In this cohort of 3523 patients with cardiogenic shock, we observed that older age was associated with the following: a higher incidence of pre-hospital CS; death within 24-h of ambulance arrival and 30-day mortality; and lower rates of invasive interventions including inpatient coronary angiography. In multivariable analysis of risk factors for 30-day mortality, increased age remained a strong predictor, even after adjustment for cardiac arrest, intubation and presentation with AMI. Receiving inpatient coronary angiography was protective.
Previous studies have demonstrated age as an independent predictor of mortality in CS.[4-6, 13-16] Kanwar, et al.,[17] in a retrospective observational study of 1412 CS patients using the Cardiogenic Shock Work Group Registry, showed that increasing age quintile was associated with 1.47 times the odds of in-hospital mortality (aOR = 1.47, 95% CI: 1.20-1.79). In AMI-CS, age, initial systolic blood pressure, evidence of congestive cardiac failure and requirement of mechanical circulatory support have been well-described as independent predictors of 30-day mortality.[14, 18, 19] We demonstrated an increased adjusted risk of 30-day mortality in those aged ≥ 70 years, as shown in the cubic spline by visual assessment (Figure 3). Our study’s findings are consistent with these data, demonstrating the powerful adverse prognostic impact of older age in patients with CS.
Elderly patients are less likely to receive invasive interventions when they present with CS.[7, 20-22] Dauerman and colleagues in the multi-center GRACE registry found 33% of patients aged ≥ 75 years received revascularization in CS secondary to AMI, compared to 50% in those aged < 75 years (P < 0.001).[21] These findings are consistent with those presented in our study, which also demonstrated significantly lower rates of coronary intervention in older patients. This variation in treatment provision may be partially explained by older patients with CS having a greater burden of comorbidities, including previous myocardial infarction requiring surgical or percutaneous coronary intervention, congestive heart failure, diabetes mellitus, peripheral vascular disease and more complex coronary anatomy.[5, 7, 15, 17, 23-25] Despite the well-described benefits of emergent revascularization in CS, it appears that elderly patients may be under treated.[19] The reasons for these differences are likely multifactorial, including underlying comorbidities, frailty, predilection for medication-induced adverse effects, and operator hesitancy to undertake high risk procedures with increased risk of adverse outcomes and perceived short life expectancy, and thus a decision for conservative management.[8, 25-27] The greater adverse outcomes and mortality in elderly patients have previously been demonstrated to also be related to a higher prevalence of more severe cardiogenic shock (as classified by the Society for Cardiovascular Angiography and Interventions (SCIA)) and increased burden of pre-existing significant coronary artery disease.[17, 27, 28] Older age has been demonstrated to be associated with higher mortality in each SCAI shock stage.[28] Furthermore, admission to centres with intensive cardiac care units have been associated with lower mortality and greater rates of revascularization in elderly patients.[29-31] This represents another treatment disparity in older patients that may contribute to poor outcomes.
Early revascularization has been associated with reduced mortality in elderly patients presenting with CS due to ACS.[5, 7, 8, 25, 32, 33] An analysis of the SHOCK Trial Registry demonstrated that older patients who received early revascularization had lower in-hospital and 60-day mortality than those who received late or no revascularization, and early revascularization in older patients is associated with improved survival (relative risk = 0.46, 95% CI: 0.28-0.75, P = 0.002).[7] Furthermore, previous studies have demonstrated high rates of PCI success can be achieved in patients ≥ 75 years (80%-92%) with establishment of TIMI grade 2-3 flow,[7, 24, 32, 34] although the incidence of TIMI 3 flow decreased with older age.[35] In the SHOCK Trial Registry, in-hospital mortality rate was not significantly different between patients ≥ 75 years (n = 39) and < 75 years (n = 178) receiving PCI (49% vs. 47%).[7] These findings suggest that the lack of coronary intervention performed in elderly patients with CS, in our study and multiple others, may be contributory to the excess mortality observed in this patient group.
Recent observational studies across multiple sites have demonstrated a survival benefit when CS is managed using a standardized, multidisciplinary team-based approach with focus on an early invasive treatment strategy.[22, 36-41] The prospective National Cardiogenic Shock Initiative’s initial 171 patients with CS showed an overall survival to hospital discharge of 72%, when utilizing this approach.[37] Investigators from the INOVA Heart and Vascular Institute demonstrated 30-day post discharge survival of 77% with implementation of the shock team, compared to previous survival of 47% (P < 0.001).[38] Similarly, the Utah Cardiac Recovery Shock Team evaluated the outcome of 123 patients with CS managed with a standardized, comprehensive multidisciplinary assessment.[41] In that study, an in-hospital survival increase of 13% was achieved compared with standard care (P = 0.041), as was a reduction in 30-day all-cause mortality (aHR = 0.61 [95% CI: 0.41-0.93]).[41] Of note, the above-mentioned studies[37-39, 41] included a younger cohort of patients with a mean age of 55-64 years, the oldest patient noted in the INOVA Heart and Vascular Institute of 65.8 years.[38] Thus, there is an ongoing paucity of data regarding the standardized management of elderly patients presenting with CS and the findings from these studies should therefore be treated as hypothesis generating.
Study Limitations
The current study has several limitations. First, it is a retrospective cohort study, which likely has multiple unmeasured confounders that may influence survival and the likelihood of undergoing invasive coronary procedures. Second, the study only includes patients with shock diagnosed in the pre-hospital setting by EMS which may influence its generalizability with patients who develop CS in-hospital. Furthermore, patients who were unsuccessfully linked with VAED and VEMD on presentation were excluded from this study, thus the incidence of cardiogenic shock is likely to be underestimated.[12] Lastly, we acknowledge the limited data relating to the severity of cardiogenic shock, as classified by the SCAI criteria,[28] severity of pre-existing coronary artery disease, and other age-related variables including frailty, malnutrition and pre-existing cognitive impairment. These factors may further assist in the prognostication of CS in the elderly patient cohort.
Conclusion
In this contemporary study, older patients with pre-hospital CS had increased rates of 30-day mortality and significantly lower rates of coronary angiography. These findings warrant further investigations to assess if standardized CS management algorithms may improve outcomes for older patients.
DISCOSURE
SUPPLEMENTARY DATA
Supplementary data to this article can be found online.
Acknowledgments
The authors would like to thank Ambulance Victoria’s paramedics and acknowledge the Victorian Department of Health as the source of VAED and VEMD data for this study, the Victorian Department of Justice and Community Safety as the source of Victorian Death Index data and the Centre for Victorian Data Linkage (Victorian Department of Health) for the provision of data linkage.
Contributor Information
Karen Smith, Email: karen.smith@ambulance.vic.gov.au.
Dion Stub, Email: d.stub@alfred.org.au.
References
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