NHLBI stops enrollment in study on resuscitation methods for cardiac arrest

Different CPR durations found equally successful; CPR device does not add benefit

Enrollment has ended early in a large, multicenter clinical trial comparing two distinct resuscitation strategies delivered by emergency medical service (EMS) providers to increase blood flow during cardiac arrest. The study's independent monitoring board and the National Heart, Lung, and Blood Institute (NHLBI), the lead sponsor of the study, stopped enrollment based on preliminary data suggesting that neither strategy significantly improved survival. One strategy compared different durations of manual cardiopulmonary resuscitation (CPR) by EMS providers before they assessed whether defibrillation was needed, and the other strategy tested the potential benefits and risks of an investigational device to maintain pressure in the chest during CPR.

After reviewing data on approximately 11,500 study participants, the study's Data and Safety Monitoring Board (DSMB) recommended on Oct. 23 that the NHLBI stop enrollment because sufficient data had been gathered, and continuing recruitment was unlikely to change the overall outcomes of the study. The board had no concerns about the safety of any of the interventions tested, and NHLBI accepted the DSMB recommendations on the same day. 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. The NHLBI is part of the National Institutes of Health.

"Survival rates for patients who suffer cardiac arrest before reaching a medical facility are tragically low," said Susan Shurin, M.D., deputy director of the NHLBI, who oversees clinical trials supported by NHLBI and accepted the DSMB recommendation. "This study provides important evidence to help inform first responders and other health care providers on safe and effective life-saving treatment options. 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."

The Resuscitation Outcomes Consortium (ROC), the largest clinical research network to study prehospital treatments for cardiac arrest in the United States and Canada, tested both resuscitation strategies as part of the Prehospital Resuscitation using an IMpedance valve and Early versus Delayed (ROC PRIMED) clinical trial. An impedance valve, also called an impedance threshold device (ITD), is a small, hard plastic device about the size of a fist that is attached to the face mask or breathing tube during CPR administered by EMS providers. The device is designed to improve circulation by enhancing changes in pressures within the chest during CPR. Researchers found that ITD use did not significantly improve or worsen survival rates for cardiac arrest patients.

The early versus delayed strategy compared two currently used timing strategies of assessing the heart's rhythm in relation to when CPR is started by EMS providers. The heart rhythm assessment is done to determine whether defibrillation to restore the heart to its normal rhythm is needed. The study compared patient survival rates after EMS providers performed at least 30 seconds of CPR before assessing the need for defibrillation with delivering three minutes of CPR before the assessment. Based on current study data, both timing strategies were equally effective.