INAPPROPRIATE ICD-THERAPIES - INCIDENCE, CAUSES, RISK-FACTORS AND PREVENTION

Patients with implantable cardioverter defibrillators (ICD) often suff er inappropriate ICD-therapies. The incidence, causes and risk factors of ICD-therapies for a rhythm other than ventricular tachyarrhythmias (VT) were determined retrospectively in 462 consecutive patients (pts ). Inappropriate ICD-therapies were identified based on stored R-R int ervals and/or electrograms. Eighty-two pts (18%) had inappropriate ICD -therapies. Actuarial rates for inappropriate ICD-therapies were 13%, 20%, 24% and 29% at 1, 2, 3 and 4 years after ICD-implantation, respec tively. Atrial fibrillation with rapid ventricular response was the mo st common cause (34 pts, 39%). In 26 pts (30%), sinus tachycardia trig gered inappropriate ICD-therapies, in 21 pts (24%) oversensing, mostly due to fractures and insulation failures of the leads, in three pts a trial flutter, in two pts non-sustained VT, in one pt supraventricular tachycardia and in another pt T-wave double sensing caused inappropri ate ICD-therapies. In order to prevent recurrences of inappropriate IC D-therapies due to atrial fibrillation or sinus tachycardia, a rate st ability (n = 19) or onset (n = 15) criterion was programmed, 41 pts ad ditionally received betablocking agents and/or digoxin. In pts with ov ersensing an operative revision of lead system was performed. During f urther follow-up (15 +/- 13 months), 15 pts had recurrences of inappro priate ICD-therapies (eight pts due to atrial fibrillation, three due to sinus tachycardia and four due to oversensing). On multivariate ana lysis (Cox regression), history of atrial fibrillation, maximum heart rate during exercise and low cut-off rate for VT-detection were predic tors of inappropriate ICD-therapies. Thus, inappropriate ICD-therapies are frequent, especially in the first year after implantation. Additi onal detection criteria, betablocking agents and/or digoxin prevent re currences in most patients. In patients with a history of atrial fibri llation, high heart rate during exercise or a low cut-off rate for VT- detection, activation of additional detection criteria should be consi dered directly after ICD-implantation.