A new method to investigate the response to the morphology discrimination algorithm in patients with ICD

Background: Inappropriate therapy for supraventricular tachyarrhythmia is still a major problem in implantable carchoverter defibrillators (ICD). The morphology discrimination algorithm compares the morphology of a tachycardia electrogram with a stored template on a beat-to-beat basis. However, algorithm responders could not yet be identified prior to the occurrence of first tachycardia episodes. We analyzed whether rapid atrial pacing and/or exercise testing can be used for identification of responders and compared the results with ICD detected tachycardia. Methods. 22 patients ( 16 male, 61 +/- 14 years) with dual-chamber lCDs have been enrolled. Patients Underwent a standardized bicycle exercise testing and an atrial pacing protocol. For both tests, morphology match scores of 8 consecutive beats were analyzed for each 10-bpm-step increment above sinus rhythm. patients were categorized as responders, if morphology match was >= 90% tested heart rates. During follow-up, ICD stored episodes with morphology discrimination activated were evaluated. Results: There were no significant differences between morphology match (85 +/- 29% vs. 84 +/- 27%) and linear regression slope B (-0.19 +/- 0.87 vs. -0.20 +/- 0.48) during exercise testing and atrial pacing. 16 patients (73%) were classified as responders. During follow-up (739 +/- 338 days) 121 sustained supraventricular (m=88) and venticular tachycardia (73%) were detected in 10 patients (45%). Specificity for tachycardia discrimination was 78% overall, 100% in responders and 22% in non-responders. Conclusion: Exercise testing and atrial pacing were equally suitable for identification of patients who seem to respond to the morphology discrimination algorithm with a high specificity for ventricular tachycardia discrimination. Thus, morphology match tests are suggested to optimize tachycardia discrimination and to reduce inadequate therapies. (c) 2006 Elsevier Ireland Ltd. All rights reserved.