(Reuters Health) - Whether you survive a cardiac arrest may depend, at least in part, on which emergency medical services agency shows up to treat you, 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 in JAMA Cardiology.

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 Dr. Masashi Okubo, an 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,” Okubo said in a phone interview.

Cardiac arrest “is the abrupt loss of heart function, and if appropriate steps are not taken immediately it most often is fatal,” explained Dr. Gregg Fonarow, a 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. “Each year in the United states more than 350,000 cardiac arrests occur outside the hospital setting.”

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,” Fonarow 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.”

Can anything be done in the meantime?

Yes, said Fonarow, who was not involved in the new research. “When performed promptly and properly, CPR can markedly improve the chance of survival for someone having an out-of-hospital cardiac arrest,” he explained. “The best advice that might save lives of loved ones if a cardiac arrest occurs is to learn CPR. Anyone can and everyone should learn CPR. The American Heart Association offers a variety of online and in person classes to efficiently and effectively teach CPR.”

SOURCE: bit.ly/2Ijlxja JAMA Cardiology, online September 26, 2018.