[Inadequate therapeutic effects of implantable cardioverter/defibrillators: etiology, therapy and prevention].

With the increasing number of implantable cardioverter-defibrillator (ICD) implantations in patients with sustained ventricular tachyarrhythmias, there is a growing interest in typical complications associated with this therapy. We analyzed the reasons and the incidence of inadequate therapy deliveries in 100 patients with epicardial (n = 27) or transvenous (n = 73) ICDs during a follow-up period of 10 +/- 8 months. A total of 21 of 100 patients received inadequate therapies. The most common reason was sinus tachycardia in eleven patients. Additional unnecessary shocks were avoided by reprogramming and application of beta-blockers. Lead failures caused the erroneous detection and defibrillation of ventricular fibrillation without any preceding clinical symptoms in four patients with an epicardial and in one patient with a transvenous ICD. All patients underwent successful surgical revision of their system. Atrial fibrillation with rapid ventricular response triggered inadequate shocks in four patients. Following digoxin administration no patient had additional inadequate shocks. In one patient non-sustained tachycardias caused unnecessary defibrillations. These results demonstrate that inadequate defibrillations are a common complication in patients after ICD-placement. The performance of x-ray, stress testing, and Holter monitoring on a regular basis may facilitate early diagnosis of possible reasons for unnecessary therapy deliveries. The improvement of detection and memory functions in future ICD-generations appears to be mandatory as well.