Wide Variation in Cardiac Arrest Survival by EMS Agency

September 28, 2018

The odds of survival could differ by more than 50% for any two otherwise similar patients with out-of-hospital cardiac arrest treated by different emergency medical services (EMS) agencies in North America, a new study suggests.

"The variation in outcomes that we saw in this study is quite remarkable, and the variation was still there even after adjusting for all the measurable factors," senior author Clifton Callaway, MD, University of Pittsburgh School of Medicine, Pennsylvania, commented to Medscape Medical News.

"Even when comparing similar patients with similar EMS arrival times, same shockable rhythm status, same number of epinephrine administrations, same number of bystander CPR [cardiopulmonary resuscitation], etc, we still found a large variation in survival between different EMS agencies."

Callaway suggested that there must be factors to account for this variation that weren't picked up in this study.

"So what we want to do next is go back and look qualitatively at those agencies with the best survival results and see what they are doing differently to the others — what are their best practices.

"Our data don't tell us what these are, but we can hypothesize that some agencies have a better culture — they work better as a team, making all the steps involved in resuscitation work together smoothly, maybe because of better leadership, good management leading to a motivated team," he said.

"We often find that when we take good care of the providers, we get better results, so we're going to try and analyze that, which will involve interviewing personnel and really taking a deep detailed dive in to their practices."

The bulk of survival rates in this study were between 6% and 20%, he noted.

"If we can learn what those at the 20% level are doing differently and get most of the agencies in the bottom half of the survival outcomes up to rates in the top half, that would double survival after out-of-hospital cardiac arrest," Callaway said.

With 300,000 or so such events treated by paramedics every year in the United States, "that could translate into an additional 30,000 people surviving. That's an exciting thought."

The study was published online in JAMA Cardiology on September 26.

In the article, the authors note that survival after out-of-hospital cardiac arrest varies across geographic regions, and understanding the relative contributing factors to this variation may reveal modifiable targets to refine performance and improve patient outcomes.

To investigate differences in EMS factors that may contribute to variation in outcomes after out-of-hospital cardiac arrest, the researchers analyzed data from the Resuscitation Outcomes Consortium (ROC) Epistry-Cardiac Arrest, a database of prospectively identified consecutive patients with out-of-hospital cardiac arrest from 10 regional coordinating sites across North America, with detailed patient-level and EMS agency-level data.

The database included 43,656 patients with out-of-hospital cardiac arrest treated by 112 EMS agencies in the United States and Canada.

Results showed there were large variations in all outcomes measured, which persisted despite adjustment for patient-level and EMS agency–level factors known to be associated with outcome.

Table. Variation in Outcomes Across Different EMS Agencies

Outcome Range (%) Unadjusted Median Odds Ratio Adjusted Median Odds Ratio
Survival to hospital discharge 0 - 28.9 1.43 1.56
Return of spontaneous circulation on emergency department arrival 9 - 57.1 1.52 1.50
Favorable functional outcome 0 - 20.4 1.54 1.53


Callaway explained that a median odds ratio of 1.5 means that if two agencies were picked at random from the 112 included in the study, the odds of survival would be 50% higher in one than the other.

"The EMS agencies included were all good, solid agencies who had the wherewithal to join a research network and take part in randomized controlled trials. So this study was not weighed down by marginal EMS agencies or those that had not been in business for very long," he commented to Medscape Medical News.

"The real value of this study is that we used one of the richest datasets available which had information on many factors that could affect outcome — such as time to get to the patient, how many people were present, how much CPR had been given before EMS arrived, and in many cases we actually had recordings of the EMS giving chest compressions, so were able to comprehensively adjust for these variables," he said. "But despite this, we still saw large, unexplained variations in survival and other outcomes."

The researchers note that in a previous study from the United Kingdom, the crude survival to hospital discharge after out-of-hospital cardiac arrest ranged from 2.2% to 12.0% between different ambulance services. The variation persisted after adjustment for presumed causative mechanisms of illness, witnessed collapse, and initial rhythm.

They add that the current findings confirm and expand these observations on EMS agencies, "including functional outcome and multiple health care settings with a robust statistical approach, accounting for known confounders and clustering of patients within EMS agencies."

The ROC is supported by the National Heart, Lung and Blood Institute in partnership with the National Institute of Neurological Disorders and Stroke, the US Army Medical Research and Material Command, the Canadian Institutes of Health Research – Institute of Circulatory and Respiratory Health, Defense Research and Development Canada, the Heart and Stroke Foundation of Canada, and the American Heart Association. Dr Callaway reported receiving grants from the National Heart, Lung, and Blood Institute during the conduct of the study.

JAMA Cardiol. Published online September 26, 2018. Full text

For more Medscape Neurology news, join us on Facebook and Twitter.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.