UNIQUE SENSING ERRORS IN 3RD-GENERATION IMPLANTABLE CARDIOVERTER-DEFIBRILLATORS

Objectives. Third-generation cardioverter-defibrillators appear to be susceptible to unique sensing errors. This study was performed to dete rmine the incidence and types of sensing errors in combination therapy implantable devices. Background. One of the advantages offered by thi rd-generation implantable cardioverter-defibrillators is the combinati on of bradycardia and antitachycardia pacing and cardioversion-defibri llation capabilities in a single device. The potential for unique sens ing errors, those caused by the conflicts presented by combining brady cardia and tachycardia sensing and therapy algorithms in the same devi ce, has not been previously addressed. Methods. To determine the incid ence of important sensing errors, 61 patients with a combination thera py device (Cadence [Ventritex] and PCD [Medtronic]) were studied for a 25-month period. In addition to surface electrocardiographic recordin gs during implantation and routine device testing, real-time and store d electrograms recorded from the rate-sensing leads (Cadence) and real -time marker channel recordings (PCD) were reviewed to diagnose sensin g errors that resulted in symptoms, device inefficacy or delivery of i nappropriate therapy. After recognition, specific reprogramming steps were performed in an attempt to avoid recurrent sensing errors. Result s. A total of 13 sensing errors were diagnosed in 12 patients (19.7%); the incidence was similar in both devices. Five distinct categories o f sensing errors were identified. After device reprogramming, only one recurrent error occurred in 98 patient-months of follow-up. Conclusio ns. Important sensing errors occur in approximately 20% of patients wi th third-generation combination therapy cardioverter-defibrillators. P rompt diagnosis of sensing errors can lead to specific reprogramming s teps to avoid recurrent errors.