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Shocks for AF, ventricular rhythms increased risk of death

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Heart Rhythm Society 32nd Annual Scientific Sessions

SAN FRANCISCO – Among patients with an implantable cardioverter defibrillator or cardiac resynchronization therapy-defibrillator, those who received shocks for atrial fibrillation and ventricular rhythms had a significantly greater likelihood of death compared with those who did not receive a shock, according to data presented here.

“The overall findings suggest that the increased risk of death after inappropriate shock is related to the underlying arrhythmia and the associated disease process with it as opposed to a adverse effect from the shock itself,” said Brian Powell, MD, electrophysiologist at the Mayo Clinic, Rochester, Minn., and the study’s primary investigator, in an interview with Cardiology Today.

In the study, all ICD and cardiac resynchronization therapy-defibrillator (CRT-D) patients (n=3,809) involved were enrolled in the Latitude remote monitoring system (Boston Scientific) through January 1, 2010. A group of seven electrophysiologists adjudicated the first shock episode rhythms for these patients and matched them to patients without a shock (n=3,630).

During a mean follow-up of 25 ± 17 months after the first shock, 36% experienced a shock as the result of sustained monomorphic ventricular tachycardia (SMVT), 18% resulted from atrial fibrillation/flutter, 17% from sinus tachycardia/supraventricular tachycardia (SVT), 5% from noise/artifact/oversensing, and 1% from non-sustained ventricular tachycardia (NSVT).

Overall, mortality in the shock group was significantly higher compared with the no shock group for ventricular fibrillation/polymorphic ventricular tachycardia (PMVT; HR=2.10, P<.0001), SMVT (HR=1.65; P<.0001), SMVT and PMVT (HR=2.77; P<.0001) and AF (HR=1.61; P=0.003). No difference in mortality was reported among those who received a shock for sinus tachycardia/SVT (HR=0.97; P=0.86) or noise/artifact/oversensing (HR=0.91; P=0.76) when compared with those who did not experience a shock.

As a result of these findings, Powell said that electrophysiologists can have some reassurance that the shock itself may not affect the patient’s survival. “This is something that electrophysiologists have been concerned about based on previous studies,” he said. “This is the first study that is large enough to look at the subgroups within the inappropriate shock category to see what exactly is driving that increased risk of death among patients who receive inappropriate shocks. It appears that AF and its associated comorbidities account for the increased risk of death after an inappropriate shock.” – by Brian Ellis

Disclosure: Dr. Powell reports that he has received consulting fees from Boston Scientific in the 12 months preceding initiation of this research. Several other investigators involved in the trial also report receiving funding from Boston Scientific as well as St. Jude Medical, Medtronic and Biotronik.

For more information:

• Powell B. LB 01. Presented at: Heart Rhythm Society 32nd Annual Scientific Sessions; May 4-7, 2011; San Francisco.

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