The Food & Drug Administration is probing reports that certain types of lower-power external defibrillators failed to deliver enough of a jolt to revive patients suffering attacks of atrial fibrillation and ventricular arrhythmia.
The federal safety watchdog said it’s examining 14 reports that biphasic defibrillators delivering 200 Joules or less failed to resuscitate patients, when subsequent treatment with defibs delivering 360 Joules “resulted in immediate defibrillation/cardioversion.”
Biphasic defibrillators deliver current across the chest in two directions, sending an initial shock to the heart in one direction followed by another in the reverse direction. The devices calibrate the amount of time needed to deliver the current by measuring electrical resistance (impedance) across the chest.
FDA said most of the device failure reports, received since 2006, involved patients with atrial defibrillation, but at least one instance also involved ventricular arrhythmia. Its analysis of the cases doesn’t warrant any changes to clinical practice, and it noted that the success of defibrillators is dependent on a number of factors including patients’ body types and the type of irregular heartbeat they’re suffering from.
And because there’s virtually no data on the optimal level and method of delivering energy during defibrillation treatment for various types of arrhythmia, it will be difficult to weigh whether the reported failures were the result of faulty or underpowered devices.
The lone randomized trial the FDA reported finding, a 2007 study published in Cardiology, addressed heart attacks. That trial compared treatment with a series of fixed, 150-Joule shocks and escalating jolts of 200, 300 and 360 Joules:
“Although escalating energy levels resulted in a greater proportion of successful cardioversion/defibrillation for patients requiring multiple shocks (primarily in those patients in ventricular fibrillation rather than those in ventricular tachycardia), there were no detectable differences in clinical outcomes (survival to 1 hour, to 24 hours or to discharge),” according to the agency.
1t wants to hear from any healthcare providers who’ve experienced similar incidents, through its MedWatch program.