CHICAGO, IL—A large-scale, multifaceted strategy involving the community and emergency medical services (EMS) failed to improve survival after out-of-hospital cardiac arrest when compared with usual care, the RACE-CARS trial shows.
Carolina Malta Hansen, MD, PhD (Copenhagen University Medical Services, Denmark), who led the study, said that despite performing a large, high-quality trial that engaged large segments of the community in emergency response, “survival remained low and unchanged.”
Although they didn’t move the survival needle, researchers did see some positive signs. An exploratory analysis showed 33% higher adjusted odds of receiving bystander CPR in year 4 with the intervention compared with usual care. Moreover, roughly 200,000 people across North Carolina were trained in bystander CPR, with nearly 20,000 trained in a single day as part of a world-record attempt.
“In light of the apparent improvement in CPR in the last year of the trial, further evaluation of a longer and more intense intervention is warranted,” said Hansen.
In the US, more than 350,000 people have an out-of-hospital cardiac arrest every year. Survival, both in the US and around the globe, is less than 10%. According to data from the US Cardiac Arrest Registry to Enhance Survival (CARES), roughly 40% of people receive bystander CPR and less than 5% receive defibrillation.
It takes time to change culture and infrastructure across communities.
Carolina Malta Hansen
Brahmajee Nallamothu, MD (University of Michigan School of Medicine, Ann Arbor), who wasn’t involved in the study, praised the study investigators, calling RACE-CARS an enormous achievement in a complex area of care. He also noted that North Carolina is a leader in statewide, quality-improvement initiatives in resuscitation care. Still, the absence of benefit with the intervention raises important questions about the best way to impact survival rates in out-of-hospital cardiac arrest.
“It’s wonderful to train 20,000 individuals in a single day, but I think we still struggle with the best way to train individuals so that they have a sustained ability to understand and utilize the tool when the situation arises in an emergency,” he said. “That’s an area that’s still complicated and unknown.”
Although the trials were very different, Nallamothu compared RACE-CARS to ZEUS and Lp(a)HORIZON, two large intervention studies with investigational therapies. In those, treatment with ziltivekimab and pelacarsen reduced inflammatory markers and Lp(a), respectively, but neither had any impact on cardiovascular outcomes. In RACE-CARS, rates of bystander CPR increased over time, but there was still no impact on survival.
“We need randomized trials in spaces like [bystander CPR and cardiac arrest] more than ever,” said Nallamothu. “Otherwise, we run into the danger of merely saying we’re checking off boxes, but those boxes are not translating into important patient outcomes. There’s enormous amounts of resources poured into communities improving cardiac arrest care and knowing how to do that in best possible way is essential.”
Survival No Different with Intervention
RACE-CARS was a registry-based, cluster randomized trial in North Carolina. Counties participating in the study were grouped into clusters based on the local EMS system. The counties had a population of 8.5 million people and included rural and urban communities.
For the intervention, 911 operators were trained to improve rapid recognition of cardiac arrest with priority dispatch of EMS and first responders. The 911 operators were also trained to rapidly give CPR instructions to bystanders on the line. The next component involved comprehensive outreach to train people in hands-only CPR and to use an automated external defibrillator (AED). The goal of the outreach was to train 10% of the cluster population. The last component involved optimizing the first-responder response, such as intervening early with CPR and AEDs before EMS arrival.
In all, 57 clusters, with 62 participating counties, were randomized to the intervention or usual care. During the 4-year study period, 33,570 out-of-hospital cardiac arrests were documented in CARES. After excluding arrests witnessed by EMS or those that occurred in nursing homes or healthcare facilities, 22,459 (median age 64 years; 36.7% female) were included in the primary analysis. Of these, 85.3% occurred in a private setting, 50.4% were witnessed, and 23.4% of arrested patients had a shockable rhythm.
Over the 4-year assessment period, survival to hospital discharge with good neurologic outcome was 9.0% in the intervention group compared with 9.4% in the usual-care arm (adjusted odds ratio 0.97; 95% CI 0.75-1.26).
There was no significant difference in the rates of bystander CPR between the two randomized arms: 44.8% vs 42.3% in the intervention and usual-care groups, respectively. Similarly, there was no difference in the percentage of defibrillation performed by a bystander/first responder before EMS arrival: 13.5% vs 15.3% in the intervention and usual-care groups, respectively.
More People Need CPR Training
While researchers aimed to train 10% of the population in clusters randomized to the intervention, cumulative CPR training reached only 4.8% of the population. There was also considerable heterogeneity across counties, with some training less than 3% of the population.
“What we saw was that we trained almost 5% of the population, and that’s when we started to see a difference in the delivery of bystander CPR, but obviously that’s not enough,” said Hansen. “We have evidence from other countries, like in Denmark where I live, where 80% of the population is trained and 75% of patients receive bystander CPR. So, I definitely think we need to go further.”
Only 50% of cardiac arrests are witnessed by a bystander.
Christine Albert
Christine Albert, MD (Brigham and Women’s Hospital, Boston, MA), the discussant following the late-breaking clinical trial presentation, pointed out that the penetration of CPR training might not have been sufficient. However, even if 10% of the population is trained, there might be a limit to what these types of community-based interventions can achieve.
“We’re really going up against something that’s very difficult,” said Albert. “Only 50% of cardiac arrests are witnessed by a bystander. You can’t get CPR and you can’t get defibrillation if you’re not witnessed. The majority of cardiac arrests occur in homes and private settings.”
Still, Albert stressed that RACE-CARS should not discourage continued investment in CPR education, community-based initiatives to optimize delivery of CPR, and the pursuit of other technology.
In Denmark, Hansen said, survival after out-of-hospital cardiac arrest is roughly 16%. “That was not done in 2 years,” said Hansen. “It’s work over 25 years. It takes time to change culture and infrastructure across communities.”
Next steps, said Hansen, will involve digging into their data to better understand how the intervention was delivered to communities and whether that can be improved. They are also looking at different ways to deliver CPR education to whole communities, as well as starting early in schools.
Source:
Hansen CM, Krychtiuk KA, Starks MA, et al. Community and EMS interventions to improve in after cardiac arrest. N Engl J Med. Published online November 8, 2026.
Disclosures:
Hansen reports research grants from TrygFonden, Laerdal Foundation, Helsefonden, and Novo Nordisk Foundation.