Long-term Arrhythmia Variability after Monomorphic Ventricular Tachycardia in Patients with an Implantable Cardioverter Defibrillator

Background: Arrhythmia burden in patients receiving an implantable cardioverter defibrillator (ICD) after monomorphic ventricular tachycardia (mVT) is higher than in patients with other indications. We investigated the long-term arrhythmia profile in this subset of patients. Methods: Fifty-two patients with an ICD implanted after mVT were followed up for at least 3 months. The cycle lengths (CLs) of the tachycardias recovered from the device memory were compared with the CL of the index arrhythmia. Morphological analysis of the intracardiac electrograms was performed and the response to antitachycardia pacing (ATP) was also assessed. Results: A total of 833 mVT episodes with intracardiac electrograms occurred during the follow-up (3-58 months; mean: 30.3 months) in 41 of the 52 patients analyzed. mVTs with different CLs as compared with the index mVT were found in 26 (50.0%), and at least two different mVT morphologies were observed in 28 (53.8%) patients. Multiple mVT morphologies were predictive of lower ATP efficacy (95.6%, 85.0%, and 70.3% in the patients with 1, 2, and 3 or more mVT morphologies, respectively; P < 0.0001) and a higher shock burden (4.2%, 19.3%, and 24.7% in the patients with 1, 2, and 3 or more mVT morphologies, respectively; P < 0.0001). Conclusion: A high mVT burden was demonstrated with marked variability of the arrhythmias as concerns both CL and morphology in patients with an ICD implanted for mVT. Multiple mVT morphologies during the follow-up were predictive of lower ATP efficacy and a higher shock burden. (PACE 2011; 34:1185-1191)