INADEQUATE THERAPY DELIVERY BY IMPLANTABL E CARDIOVERTER-DEFIBRILLATORS - REASONS, THERAPY AND PREVENTION

With the increasing number of implantable cardioverter-defibrillator ( ICD) implantations in patients with sustained ventricular tachyarrhyth mias, there is a growing interest in typical complications associated with this therapy. We analyzed the reasons and the incidence of inadeq uate therapy deliveries in 100 patients with epicardial (n = 27) or tr ansvenous (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 unn ecessary shocks were avoided by reprogramming and application of beta- blockers. Lead failures caused the erroneous detection and defibrillat ion of ventricular fibrillation without any preceding clinical symptom s in four patients with an epicardial and in one patient with a transv enous ICD. All patients underwent successful surgical revision of thei r system. Atrial fibrillation with rapid ventricular response triggere d inadequate shocks in four patients. Following digoxin administration no patient had additional inadequate shocks. In one patient non-susta ined tachycardias caused unnecessary defibrillations. These results de monstrate that inadequate defibrillations are a common complication in patients after ICD-placement. The performance of x-ray, stress testin g, and Holter monitoring on a regular basis may facilitate early diagn osis of possible reasons for unnecessary therapy deliveries. The impro vement of detection and memory functions in future ICD-generations app ears to be mandatory as well.