Introduction: Repair of Tetralogy of Fallot up until recent decades involved aggressive resection and annular enlargement through a right ventriculotomy. This resulted in ventricular scarring and pulmonary incompetence, with an increased risk of ventricular tachyarrhythmia and sudden death in young adulthood. Following the NICE guidelines, implantation of ICDs as primary prevention in patients with repaired Tetralogy is ever increasing. This study aims to determine the rate of appropriate and inappropriate discharges, the success rate of ICD therapy and the impact of ICD implantation on the use of anti-arrhythmic medication in this population of patients. Materials and Methods: This is a retrospective review of patients with repaired Tetralogy of Fallot (n = 18) and pulmonary stenosis (n = 2) with implantable cardioverter defibrillators managed at our tertiary centre. Patients were identified from our outpatient database, their notes and charts were examined and details regarding indication for ICD implantation, device specifications and complications following implantation were collected. Data was also collected on the incidence of appropriate and inappropriate therapies and the success rate of ICD therapy along with the impact of implantation on the usage of anti-arrhythmic medication in these patients. Results: Of the 20 patients, 18 had previous repair of Tetralogy of Fallot and 2 had pulmonary valvotomy and infundibular resection for pulmonary stenosis between 1969 and 1989. 70% (n = 14) of these patients required reoperation with 10 patients having pulmonary valve replacements (PVR), 3 having redo infundibular resections and 1 requiring aortic valve replacement. At the time of consideration for ICD implantation 80% had moderate to severe pulmonary incompetence and 60% had more than mild right ventricular dilatation on echocardiography. Indications for ICD implantation were symptomatic ventricular tachycardia requiring cardioversion (n = 8), ventricular tachycardia on 24 hr tape/Reveal or electrophysiological study (n = 8), ventricular fibrillation (VF)/pulseless ventricular tachycardia (VT) (n = 2) and syncope with an abnormal EPS other than VT (n = 2, high grade ventricular ectopics, sinus node dysfunction).The median age at implantation was 22 years (16.4–43 years). All our patients had dual chamber devices implanted with either dual (n = 13) or single coil (n = 6) ventricular leads. GEM3 AT (n = 5), Marquis DR (n = 8) and Maximo DR (n = 7) generators (Medtronic Inc.) were implanted in sub pectoral position and both anti-tachycardia pacing and cardioversion modes were programmed as part of individualised VT and VF protocols. Early post procedural complications included atrial lead displacement (n = 1) and pneumothorax requiring drainage (n = 1).During a median follow up of 1.6 years (0.03– 4.5 years) several episodes of inappropriate therapies were noted in 6 patients (30%) especially early after implantation. This was found to be mainly due to atrial tachyarrhythmia, double counting of T waves or inaccurate interpretation of varying PR intervals as AV dyssynchrony which were effectively dealt with by changes in device programming. There were 33 episodes of inappropriate anti-tachycardia pacing (ATP) in 4 patients and 19 episodes of inappropriate cardioversion in 5 patients. Appropriate ATP was instituted in 4 patients (25%) with successful termination of all 20 episodes (100% success rate) of ventricular tachycardia. One patient required cardioversion with successful termination of VF. One patient (5%) with troublesome tachyarrhythmia died suddenly of unknown cause, 10 months after AICD implantation having had no detections or therapies on his device.Prior to ICD implantation 8 patients were on amiodarone therapy. At the time of last follow up after AICD implantation all patients were established on anti-arrhythmic agents and of these 6 patients were on amiodarone with the others being effectively managed on beta-blockers and/or flecainide.Late complications of ICD implantation included lead failure in 1 patient requiring replacement 3.3 years after implantation and generator replacement in a patient who was pacemaker dependent a year after implantation due to an advisory issued by the manufacturer regarding the risk of sudden battery depletion. Conclusions: In our study we found a rate of 0.6 appropriate and 1.4 inappropriate therapies (0.9 episodes of inappropriate ATP and 0.5 episodes of inappropriate cardioversion) per patient-year of follow up following ICD implantation which is in keeping with published literature. The mortality in our study group was 5% which is acceptable given the high risk population. Implantation of an ICD allowed switching over from amiodarone to less toxic anti arrhythmic therapy in a proportion of patients. Anti-tachycardia pacing was very successful in terminating tachyarrhythmia in our population with 100% success in terminating ventricular tachycardia.
Successful termination of ventricular tachycardia with intrinsic anti-tachycardia pacing
