Morphology discrimination: A beat-to-beat algorithm for the discriminationof ventricular from supraventricular tachycardia by implantable cardioverter defibrillators

Inappropriate therapy of SM by ICDs remains a major clinical problem despit e enhanced detection criteria like "sudden onset" and "rate stability" in t hird-generation devices. Electrogram morphology discrimination offers an ad ditional approach to improve discrimination of supraventricular tachycardia (SVT)from ventricular tachycardia (VT). In a prospective, multicenter stud y, patients received an ICD with a beat-to-beat algorithm for morphological analysis of the intracardiac electrogram (Morphology Discrimination, MD). A nominal programming for standard enhancement criteria and morphology disc rimination was required at implant. Electrogram storage of tachycardia epis odes irrespective of delivery of therapy was used to assess sensitivity and specificity of the morphology algorithm alone and in combination with esta blished detection criteria. During a 12 6 6-month follow-up, 886 episodes o f device stored electrograms from 82 of 256 patients were evaluated. At nom inal settings, th e MD algorithm correctly identified 423 of 551 episodes a s VT resulting in sensitivity of 77%. The classification of SVT was met in 239 of 335 episodes resulting in specificity of 71%. In combination with su dden onset, sensitivity increased to 99.5% at the expense of specificity (4 8%). In conclusion, SVT-VT discrimination based on morphological analysis a lone results in limited sensitivity and specificity. Programming the monito r mode allows individual assessment of the performance of this detection en hancement feature during clinical follow-up without compromising device saf ety. Only in patients with documented efficacy of morphology discrimination should this feature be subsequently activated.