Abstract 2690: Efficacy and Safety of Implantable Cardioverter-Defibrillator Therapy in Long QT Syndrome Patients
Background. This study aimed to evaluated the efficacy and safety of implantable cardioverter-defibrillators (ICDs) in long QT syndrome (LQTS) patients.
Methods and Results. We prospectively enrolled 191 LQTS pts (32+/-18 years) who received an ICD at the discretion of their cardiologists. Indications for ICD therapy included aborted cardiac arrest in 64 (secondary), prior syncope in 109, and 18 considered at high risk without prior LQTS symptoms. Appropriate ICD therapy occurred in 28/191 patients (15%): 13 had prior aborted cardiac arrest, 14 had a history of syncope, and 1 had no prior symptoms. Patients with appropriate shocks had longer QTc than those without shocks (525+/-66 ms vs. 502+/-60 ms; p=0.06). Kaplan-Meier analysis revealed appropriate life-saving therapy at a rate of 3% per year in those with symptoms prior to ICD implant (Fig⇓.). In 69 pts, LQTS genotype was known: 27 LQT1, 34 LQT2, and 8 LQT3. Among them, 1 (4%) LQT1 (missed beta-blockers), 8 (24%) LQT2 (on beta-blockers), and none of LQT3 patients received ICD therapies (p<0.05). In 23 pts, 36 inappropriate therapies occurred: 22 due to inappropriate sensing (T wave oversensing particularly when QTc>500ms), 11 due to lead/generator malfunction, and 3 for sinus tachycardia.
Conclusions. LQTS patients with prior history of aborted cardiac arrest and prior syncope have a 3% per year risk of ventricular tachyarrhythmias requiring ICD shocks. LQT2 patients have high risk of recurrent arrhythmias despite beta-blocker treatment. High rate of inappropriate shocks for T-wave oversensing requires improvement of ICD algorithms to eliminate these unwanted episodes.