In a new trial, two new programs for delivering implantable cardioverter–defibrillator therapy resulted in fewer inappropriate interventions (shocks or antitachycardia pacing) and an unexpected reduction in mortality. Improved programming could benefit patients with ICDs.
The implantable cardioverter-defibrillator (ICD) is highly effective in reducing mortality among patients at risk for fatal arrhythmias, but inappropriate ICD activations are frequent, with potential adverse effects.
• How common are inappropriate ICD activations?
Inappropriate ICD activations, which are typically caused by supraventricular tachyarrhythmias, are frequent, despite sophisticated device-related detection algorithms that are designed to differentiate supraventricular from ventricular tachyarrhythmias; such activations have potentially life-threatening side effects. Inappropriate device-delivered therapy, defined as therapy delivered for nonventricular tachyarrhythmias, affects 8 to 40% of patients with ICDs.
• How are conventional ICDs programmed?
Conventional ICD programming typically treats ventricular tachyarrhythmias at a heart rate of 170 beats per minute or higher.
Morning Report Questions
Q: What were the results of this study, which compared conventional ICD programming to high-rate or delayed therapy?
A: The study, published in this week’s edition of the Journal, compared conventional ICD programming to high-rate therapy (with a 2.5-second delay before the initiation of therapy at a heart rate greater than or equal to 200 beats per minute) or delayed therapy (with a 60-second delay at 170 to 199 beats per minute, a 12-second delay at 200 to 249 beats per minute, and a 2.5-second delay at greater than or equal to 250 beats per minute). In the Kaplan-Meier estimates of all-cause mortality, the conventional-treatment group had a significantly higher cumulative mortality during follow-up than did the high-rate and delayed-therapy groups. Inappropriate shock energy was reduced in the high-rate and delayed-therapy groups by 77% (P=0.01) and 54% (P=0.03), respectively. The total appropriate shock energy was similar in the three treatment groups (P=0.48). The frequency of syncope was similar in all three treatment groups.
Q: What was the most common rhythm associated with inappropriate antitachycardia pacing and inappropriate shock in this study?
A: First occurrences of inappropriate antitachycardia pacing were most frequent with regular supraventricular tachyarrhythmia (73%) and atrial fibrillation (19%), and first occurrences of inappropriate shocks were also most frequent with these arrhythmias (55% and 36%, respectively).