Out-of-Hospital Cardiac Arrest: Impact on Long-term Survival

Out-of-hospital cardiac arrest (OHCA) is a leading cause of mortality in adults worldwide, with approximately 10% of patients with OHCA surviving to hospital discharge and only 8.2% surviving with good functional status.^1,2 Coordinated, timely intervention is paramount, requiring accurate recognition, cardiopulmonary resuscitation (CPR), and defibrillation to maximize the chances of a positive outcome.²

While improving initial survival is a primary focus, there has been increased interest in longer-term outcomes for surviving patients, as evident by the recent updates to the European post-resuscitation care guidelines.³ Previously identified prognostic indicators for long-term survival include younger age, administration of bystander CPR, appropriate diastolic function, functional status at the time of discharge, initial cardiac arrest rhythm, and post-cardiac arrest care at a tertiary referral hospital.⁴ While substantial data concerning short-term (1-year) survival rates are available, statistics regarding survival beyond 1 year are lacking.

With this in mind, Simon A. Amacher, MD, and his colleagues from the University of Basel, in Switzerland, recently conducted a systematic review and meta-analysis. The primary analysis of the study, which was published in JAMA Cardiology, was long-term survival after hospital discharge or 30 days after OHCA, with long-term survival defined as more than 12 months. A secondary analysis evaluated long-term survival after hospital admission.

How the studies were chosen

Eligible clinical studies for the meta-analysis included prospective, retrospective, and interventional studies. Ultimately, 38 studies were included in the final qualitative and quantitative analysis, with 21 (11,800 patients) used for the Kaplan-Meier-based meta-analysis and 33 (16,933 patients) used for the aggregate data meta-analysis.

Twenty studies originated from Europe, 8 from North America, 6 from Asia, and 4 from Australia. Sample sizes ranged from 35 to 3449 for the Kaplan-Meier-based meta-analysis and from 16 to 3449 for the aggregate data meta-analysis; none of the studies included patients with COVID-19.

Low risk of bias was identified with 13 studies, and moderate risk of bias with 21 studies, due to select subgroups of patients with OHCA. A high risk of bias was identified with 4 studies, which included only patients 65 years or older, only patients with idiopathic ventricular fibrillation, or only unexplained cardiac arrests.

A total of 1992 deaths occurred among 8175 patients over a total observation time of 44,515 person-years, with a mean survival time of 5.4 years (standard deviation [SD] 3.8 years) and a median survival time of 5.0 years (interquartile range [IQR] 2.3 to 7.9 years). Survival rates decreased over time:

• 8% (95% CI 81.9% to 83.7%) at 3 years
• 0% (95% CI 75.9% to 78.0%) at 5 years
• 9% (95% CI 62.3% to 65.4%) at 10 years
• 5% (95% CI 54.8% to 60.1%) at 15 years

‘These patients were essentially dead’

“A 10-year survival rate around 64% is quite remarkable,” says Christopher Granger, MD, a cardiologist and professor of medicine at Duke University School of Medicine, in Durham, N.C. “These patients were essentially dead and then brought back to life. This should reinforce the importance of optimizing care for this high-risk population because, if they do survive that first period, they have a good chance of surviving for many years.”

Long-term survival based on the presence or absence of shockable initial rhythm was evaluable in 1111 patients from 2 studies. A significant advantage to long-term survival was observed in patients with a shockable initial rhythm versus those without (HR 0.30, 95% CI 0.23 to 0.39; P<.001). Specifically, patients with a shockable rhythm had a mean survival time of 5.2 years (SD 2.6 years) and a 5-year survival rate of 83.2% (95% CI 80.3% to 85.7%), compared to 3.9 years (SD 3.0 years) and 52.8% (95% CI 44.9% to 60.2%) for those without.

Dr. Granger, who wasn’t part of the current study, noted the importance of shockable initial rhythm and the need for rapid identification and care of OHCA patients. “The way to increase the proportion of those with shockable rhythm is to administer care more rapidly,” he says. “If a patient is experiencing ventricular tachycardia or fibrillation, that rhythm tends to degrade to asystole if there is a time delay.”

A deeper dive into the data

Long-term survival after hospital or intensive care unit (ICU) admission was evaluated in a total of 3385 patients from 6 studies, with a maximum follow-up time of 11 years. Death occurred in 2150 patients over a total observation period of 5753 person-years. The mean survival time was 1.7 years (SD 2.5 years), and the median was 0.1 years (IQR 0.0 to 3.0 years), with a 5-year survival rate of 32.6% (95% CI 30.8% to 34.4%) and a 10-year survival rate of 28.2% (95% CI 25.7% to 30.7%).

“The interesting, and often unappreciated, population are those surviving up to 5 years after hospital admissions,” Dr. Granger notes. “I suspect if you asked a resident caring for these patients, they would think it’s a lot lower, and the reality would be encouraging.”

A total of 15,599 patients from 30 studies were eligible for an overall survival analysis after hospital discharge, which revealed high overall heterogeneity (I² = 99%; P<.001), especially between follow-up durations of >1 to 3 years, >3 to 5 years, and >5 years (P=.04). Proportions of survivors based on follow-up duration varied across studies, with rates of 0.22 to 0.92 for >1 to 3 years, 0.49 to 0.99 for >3 to 5 years, and 0.50 to 0.76 for >5 years.

What are the implications of the study?

Patients with OHCA have a significantly lower long-term survival outlook compared with age- and sex-matched cohorts or an unselected overall population, as do those who experience nonshockable rhythm or hospital or ICU admission. However, it should be noted that patients with OHCA often carry a high burden of pre-arrest comorbidities; analyses of long-term survival compared to patients with similar comorbidities are therefore recommended.

In-hospital mortality remains high in OHCA patients, approximately 50% to 60%. Yet despite this, long-term survival data of patients surviving the index hospitalization are comparable to those for general ICU patients, including patients with ST-elevation myocardial infarction (STEMI).

“There’s not much long-term survival data out there, but again, this reinforces that if the patient survives OHCA then they likely have many more years ahead of them,” says Dr. Granger.

Both the study authors and Dr. Granger also mentioned the need for rapid intervention in this high-risk population. “The area with the greatest need for further research is how to improve bystander CPR and defibrillation, the interventions we know improve survival outcomes,” Dr. Granger says. “The problem is only 40% of people receive bystander CPR and 20% receive defibrillation before EMS arrives.”

New horizons in community interventions

An ongoing randomized trial from the Duke Clinical Research Institute entitled RACE-CARS (RAndomized Cluster Evaluation of Cardiac ARrest Systems; https://racecarstrial.org), of which Dr. Granger is the principal investigator of the Clinical Coordinating Center Team, aims to test implementation of community interventions to improve survival in cardiac arrest patients.

“In North Carolina, 50% of first responders arrive without an automated external defibrillator [AED] when a patient is experiencing OHCA,” Dr. Granger says, emphasizing the need for community involvement with wider CPR education and easy access to AED devices.

“It’s not easy but is so important, and I think we can save a lot more lives,” he concludes. “If you can have 10 or 15 more years, as highlighted by this study, it emphasizes the importance of these approaches to ensure long-term survival.”

Published: June 15, 2022