NHLBI stops enrollment in study on resuscitation methods for cardiac arrest

A large, multicenter clinical trial comparing different resuscitation strategies, as well as the use of an impedence threshold device, has stopped enrollment, based on findings that all strategies were equally effective.

The National Heart, Lung and Blood Institute (NHLBI), the study’s lead sponsor, and the independent monitoring board stopped enrollment based on the Oct. 23 recommendation of the Data and Safety Monitoring Board (DSMB) that sufficient data had been gathered and continuing recruitment was unlikely to change the overall outcomes of the study.

The trial is called ROC PRIMED (Resuscitation Outcomes Consortium: Pre-hospital Resuscitation using an IMpedance valve and Early versus Delayed).

One strategy in the study compared different durations (30-90 seconds vs. three minutes) of manual cardiopulmonary resuscitation (CPR) by EMS providers before they assessed whether defibrillation was needed. Another strategy tested the potential benefits and risks of an investigational impedence threshold device (ITD), which helps maintain pressure in the chest during CPR.

For patients randomly assigned to the Analyze Early group, EMS providers were instructed to perform CPR until they were able to analyze the patient's heart rhythm (approximately 30 to 90 seconds). Patients in the Analyze Later group received CPR for at least three minutes before their heart rhythm was analyzed. When indicated, defibrillation was provided. Based on current study data, both timing strategies were equally effective, according to the Resuscitation Outcomes Consortium (ROC).

Some smaller studies have suggested that longer periods of CPR before defibrillation might increase survival, while other studies have suggested that more immediate defibrillation -- when the patient is treated within two minutes after the start of cardiac arrest -- might be better.

“The ROC PRIMED study answers a long-standing question in the EMS community over whether it is better to defibrillate earlier or later when trying to resuscitate a patient,” said Ian Stiell, MD, professor and chair of the department of emergency medicine at the University of Ottawa and a principal investigator for the ROC PRIMED Analyze Early vs. Later protocol. “Both techniques appear to be equally beneficial."

ROC, the largest clinical research network to study pre-hospital treatments for sudden cardiac arrest in the U.S. and Canada, found that the impedance threshold device (ITD) did not significantly improve or worsen survival rates for cardiac arrest patients.

To test the ITD strategy, patients were randomly assigned to receive standard CPR from participating EMS providers either with an ITD or with a sham ITD.

"While the ITD is based on a sound physiologic principle, in this study it did not appear to improve survival rates for adults in cardiac arrest outside of the hospital," said ROC principal investigator Tom Aufderheide, MD, a professor of emergency medicine at the Medical College of Wisconsin in Milwaukee.

After reviewing data on approximately 11,500 study participants, DSMB recommended enrollment cease. The DSMB had no safety concerns of any of the interventions tested, and NHLBI accepted the recommendations immediately.

The researchers will continue to monitor study participants who agree to follow-up visits for up to six months. They will analyze and publish the final data in the coming months.

"This study provides important evidence to help inform first responders and other healthcare providers… We will continue to search for new ways to save lives in the precious few moments after cardiac arrest – and evaluate the benefits and risks of commonly used practices," said Susan Shurin, MD, deputy director of the NHLBI.