Is inappropriate therapy a resolved issue with current implantable cardioverter defibrillators?

Patients with an implantable cardioverter defibrillator (ICD) can undergo inappropriate therapies if electrical activity not originating in the ventricle is wrongly recognized as ventricular by the device. Inappropriate therapy can be the result of detection of supraventricular tachycardias or over-sensing of other artifacts by the device. Enhanced detection criteria in third-generation ICD have been implemented to recognize fast supraventricular arrhythmias. Analysis of the use of these criteria in patients with an ICD has shown that arrhythmias detected in the ventricular tachycardia zone are frequently supraventricular (193 supraventricular of 690 tachycardia episodes in 23 of 59 patients). Use of sudden onset was very effective in detecting sinus tachycardia (65 of 67 episodes) and stability was very useful in detecting atrial fibrillation (31 of 32 episodes). However, sensitivity in detecting ventricular tachycardia was only 90% (451 of 497 episodes). Application of the sustained, rate duration criteria allowed appropriate treatment of all ventricular tachycardia episodes, increasing sensitivity to 100%; however, specificity in appropriate nontreatment of supraventricular episodes decreased from 96% to 83%. Subsequent analysis of different algorithms showed that sudden onset >9% and stability <40 msec was the algorithm with the best specificity and sensitivity. mming sudden onset and stability detection criteria with a sustained, rate duration safety net for triggering tachycardia therapy results in appropriate device management in most patients with supraventricular and relatively slow ventricular tachycardia.