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12.10.2013

NIH Workshop Report Urges New Focus on Pulseless Electrical Activity

Led by the Miller School’s Robert J. Myerburg, M.D., a dozen experts in sudden cardiac arrest have issued a major report on pulseless electrical activity aimed at improving the dismal survival rate among the increasing number of people who suffer this mechanism of cardiac arrest that does not respond to defibrillation.

Published online in advance of print in Circulation, the official journal of the American Heart Association, the report, “Pulseless Electrical Activity – Definition, Causes, Mechanisms, Management, and Research Priorities for the Next Decade,” summarizes the findings of a June 2012 workshop the National Heart, Lung and Blood Institute convened to identify the current knowledge, scientific gaps and research priorities for predicting, preventing, and managing the condition that has emerged as a more frequent mechanism for sudden cardiac arrest than ventricular fibrillation (VF) or other ventricular tachyarrhythmias (VT).

Both kinds of heart rhythm disturbances can be corrected by a shock from a defibrillator. But pulseless electrical activity (PEA), which is characterized by an organized heart rhythm that produces no pulse, cannot. The interventions for PEA include CPR, certain medications, and reversing respiratory, fluid and electrolyte disturbances, when appropriate, but few people survive an episode. According to data from the Resuscitation Outcomes Consortium, only 8 percent of people hospitalized for PEA survive until discharge, compared with more than 30 percent for VT/VF arrests.

“If you go back 20 or 30 years, the overwhelming majority of cardiac arrests were due to shockable rhythms. What’s changed is that the shockable rhythms are now the minority and PEAs and other forms of non-shockable cardiac arrests the majority,” explained Myerburg, the American Heart Association Chair in Cardiovascular Research, who co-chaired the workshop and coordinated the report with Henry Halperin, M.D., a cardiologist at Johns Hopkins University School of Medicine.

“We’re not sure why,” continued Myerburg, who is also professor of medicine and physiology. “It could be from the medications people are taking or the increase in implantable defibrillators. But we do know that, as preventive and therapeutic interventions for shockable rhythms were developing, PEA did not get much attention. Given that PEA is growing in magnitude and we don’t know much about how to predict or prevent it, nor do we have specific treatment for it, PEA must receive greater attention.”

As the report notes, there isn’t even a single unifying definition for PEA, which once was known as electromechanical dissociation.

“The common denominator is the presence of spontaneous organized cardiac electrical activity, in the absence of blood flow sufficient to maintain consciousness, and absence of a rapid spontaneous return of adequate organ perfusion and consciousness,” the authors wrote. “The latter qualifier excludes transient losses of blood flow, such as vasovagal syncope, that have clinical implications different from true PEA. Therefore, the Workshop participants defined PEA as a syndrome characterized by absence of a palpable pulse in an unconscious patient with organized electrical activity other than ventricular tachyarrhythmia on ECG.”

Among their top recommendations, the authors suggest that the NHLBI support different tiers of clinical research to better ensure success at finding preventive and therapeutic interventions for PEA. “Generally, the NIH supports large clinical studies with sufficient power to test hypotheses,” Myerburg said. “But for something like this, where we know so little, we should conduct smaller clinical studies in addition to larger ones — not to test hypotheses, but to generate testable hypotheses. It’s a good investment when we don’t much about the physiology of a problem.”

Also participating in the workshop and contributing to the paper were experts in sudden cardiac arrest from Johns Hopkins Medical Institutions, the National Heart, Lung, and Blood Institute, Cedars-Sinai Heart Institute in Los Angeles, the University of Calgary and University of Toronto in Canada, UCLA Harbor Medical Center, Virginia Commonwealth University Medical Center, the University of Alabama at Birmingham, and the Krannert Institute of Cardiology at Indiana University.

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