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 cardioverter 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 ICDs 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% of 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 (n = 88) and ventricular tachycardia (n = 33) 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.