Evaluation of morphology discrimination for ventricular tachycardia diagnosis in implantable cardioverter-defibrillators Dominic A.M.J. Theuns, PhD,* Maximo Rivero-Ayerza, MD,* Dick M. Goedhart, PhD, † Ronald van der Perk, BSc,* Luc J. Jordaens, MD, PhD* *From the Department of Cardiology, Erasmus MC, Rotterdam, The Netherlands, and † Department of Statistics, Cardialysis, Rotterdam, The Netherlands. BACKGROUND To reduce inappropriate therapy from implantable cardioverter-defibrillators (ICDs), electrogram morphology dis- crimination has been developed to improve arrhythmia discrimi- nation without compromising device safety. OBJECTIVES The purpose of this study was to determine the accuracy of the morphology discrimination algorithm for detecting ventricular tachycardia (VT). METHODS Stored electrograms of 795 tachyarrhythmias from 106 patients with a St. Jude Medical ICD (51 single-chamber and 55 dual-chamber) were analyzed by the investigators. The data were analyzed for morphology discrimination alone, sudden onset and stability, and morphology discrimination in combination with sud- den onset and stability. Data were corrected for multiple episodes within a patient with the generalized estimating equation method. RESULTS Using the nominal template match of 60%, morphology discrimination alone provided sensitivity and specificity of 78% and 95% for single-chamber ICDs and 63% and 92% for dual- chamber ICDs, respectively. Based on the receiver operator char- acteristic curve, the optimal-match percent threshold was 80% to 85% but at the expense of specificity. Morphology discrimination combined with sudden onset and stability increased sensitivity to 98% with specificity of 86% in single-chamber devices. In dual- chamber devices, the loss in sensitivity is compensated by rate branch analysis, yielding a sensitivity of 98%. CONCLUSION Arrhythmia discrimination based on electrogram morphology has the potential to reject atrial tachyarrhythmias. However, there is a risk for underdetection of ventricular tachy- arrhythmias if arrhythmia discrimination is primarily based on morphology. To guarantee patient safety in single-chamber de- vices, the morphology discrimination algorithm must be pro- grammed in combination with established detection algorithms. In dual-chamber devices, loss of sensitivity is compensated by the V  A rate branch. KEYWORDS Implantable cardioverter-defibrillator; Arrhythmia; Ventricular tachycardia; Morphology; Electrogram (Heart Rhythm 2006;3:1332–1338) © 2006 Heart Rhythm Society. All rights reserved. Introduction Accurate discrimination of tachyarrhythmias is a challenge in implantable cardioverter-defibrillator (ICD) therapy. In- appropriate therapy for supraventricular tachyarrhythmias (SVTs) is the most common adverse event in defibrillator patients. 1–4 To reduce inappropriate device interventions, interval-based discriminators such as “sudden onset” and “stability” were developed. Activation of these discriminators can reduce inappropriate therapy. 5,6 Recently, morphology- based algorithms have been introduced for further improve- ment of tachyarrhythmia discrimination. 7–10 Morphology- based algorithms focus on the premise that the ventricular electrogram changes during ventricular tachycardia (VT) compared with the supraventricular baseline rhythm. A ma- jor concern of discrimination algorithms is the potential risk for underdetection of ventricular tachyarrhythmias. The ex- tent to which the addition of morphology discrimination affects the sensitivity and specificity of appropriate detec- tion of ventricular tachyarrhythmias is unknown. The purpose of the present study was to determine the performance of morphology discrimination alone and in combination with interval-based discriminators in the ap- propriate detection ventricular tachyarrhythmias. Methods Patient population The study population consisted of 106 patients who under- went initial ICD implantation for established indications. All patients received a device incorporating a morphology- based discrimination algorithm (St. Jude Medical, Sylmar, CA, USA). Fifty-five patients received a dual-chamber ICD (model Atlas DR-241 and DR-243) and 51 patients received a single-chamber ICD (model Atlas VR-199 and VR-193). For ventricular sensing, defibrillation leads with dedicated bipolar sensing were used in 98% of patients. Two patients (2%) were implanted with a defibrillation lead that provided integrated sensing. Morphology discrimination algorithm and programming The morphology discrimination algorithm is based on the comparison of each ventricular complex during tachycardia Address reprint requests and correspondence: Dr. Dominic A.M.J. Theuns, Department of Electrophysiology, Bd416, Erasmus MC, Dr. Molewaterplein 40, 3015 GD Rotterdam, The Netherlands. E-mail address: d.theuns@erasmusmc.nl. (Received April 24, 2006; accepted June 28, 2006.) 1547-5271/$ -see front matter © 2006 Heart Rhythm Society. All rights reserved. doi:10.1016/j.hrthm.2006.06.034