Optimal Programming of Implantable Cardiac-Defibrillators

Implantable cardioverter-defibrillators (ICDs) reduce sudden cardiac death risk and improve survival in patients with a history of life-threatening arrhythmia or cardiac arrest (secondary prevention) and in high-risk patients without such a history (primary prevention).1–3 Patients with ICDs, however, may receive unnecessary shocks, which have been associated with proarrhythmia, anxiety, depression, poor quality of life, and possibly increased mortality.4–8 In contrast to drug therapy, in which a limited number of parameters (such as dose) are adjustable, hundreds of programmable parameters affect device therapy delivery. Moreover, selection of nonnominal parameter settings (ie, changing the out-of-the-box factory default settings) reduces morbidity and mortality compared with nominal settings in many clinical situations because of publication and regulatory delays.4,9,10 Thus, optimization of programming to prevent unnecessary shocks is paramount to minimize morbidity and mortality and is dependent on clinician proactivity. Delivery of ICD therapy for rhythms other than ventricular tachycardia (VT) or ventricular fibrillation (VF) is termed inappropriate therapy . It may result from inappropriate detection of supraventricular tachycardia (SVT) such as atrial fibrillation (AF) or sinus tachycardia or from oversensing of physiological (eg, T wave) or nonphysiological (eg, lead fracture noise) signals. Inappropriate shocks have been reported in 16% to 18% of ICD recipients and constitute 30% to 50% of all shocks.11–13 Although therapy delivered for a ventricular tachyarrhythmia is considered appropriate, a growing body of evidence has shown that programming antitachycardia pacing (ATP) or delaying shocks to permit nonsustained episodes to terminate significantly reduces the frequency of shock delivery. Koneru et al14 have used the term unnecessary shocks to refer to inappropriate shocks delivered for rhythms other than VT/VF and to include shocks delivered for VT that would have responded to ATP or terminated spontaneously if given time. Optimal programming minimizes unnecessary shocks. A …