Whether an individual survives a cardiac arrest may depend, at least in part, on which emergency medical services agency shows up, a new study suggests.

Researchers found a wide variation in cardiac arrest survival rates depending on which EMS agency provided initial treatment, according to the study published September 26 in JAMA Cardiology.¹

In fact, the odds of surviving to hospital discharge could vary by more than 50 percent for two similar patients treated by two randomly selected EMS agencies.

“We found large outcome variations between EMS agencies that come after a cardiac arrest even after adjusting for many factors,” said lead author Masashi Okubo, MD, instructor of emergency medicine at the University of Pittsburgh.

The study did not reveal why some EMS agencies did better than others, however. “We need to determine in future research what are the underlying factors,” Dr. Okubo said in a phone interview.

Dr. Okubo and colleagues analyzed data from the Resuscitation Outcomes Consortium, a multi-center registry that tracks what happens to patients who experience a cardiac arrest outside the hospital. Patients seen at one of 10 sites in North America after initially being treated by EMS from 2011 to 2015 were included in the analysis.

Altogether, the researchers studied 43,656 patients treated by 112 EMS agencies. When they looked at how many patients survived long enough to be discharged from the hospital, variations among different agencies were quite large: the worst performing agency had 0 survivors out of 36 patients treated, or 0 percent, as compared to 66 survivors out of 228 patients treated, or nearly 30 percent, for the best-performing agency.

The pattern was similar when it came to recovery of function by the time a patient was discharged from the hospital. The worst performing agency in this category had favorable functional recovery in 0 out of 87 patients, or 0 percent, while the best had favorable functional recovery in 11 out of 54 patients, or 20 percent.

“These findings suggest there may be important differences in the quality of resuscitation efforts among different EMS agencies,” Gregg Fonarow, MD, professor of cardiovascular medicine and science at the David Geffen School of Medicine at the University of California, Los Angeles, and co-director of the UCLA Preventive Cardiology Program, said in an email.

Also, he pointed out, “More layperson interventions such as timely CPR [cardiopulmonary resuscitation] and more EMS personnel responding to cardiac arrest patients were associated with better outcomes. These findings suggest that dissemination of best practices and use of formal quality improvement programs by community-based EMS agencies may help to improve quality and outcomes in cardiac arrest.”