Management of Ventricular Arrhythmias in ARVD/C
Abstract & Commentary
By John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville. Dr. DiMarco is a consultant for Novartis, and does research for Medtronic and Guidant.
Source: Dalal D, et al. Long-term efficacy of catheter ablation of ventricular tachycardia in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy. J Am Coll Cardiol 2007;50:432-440.
Dalal and his colleagues describe data from the Johns Hopkins Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy (ARVD/C) registry concerning the efficacy of catheter ablation for ventricular tachycardia (VT) in this condition. Data were collected from multiple electrophysiology laboratories participating in the registry. The authors identified 24 registry participants who met the task force definition of ARVD/C and who had undergone one or more attempts at radiofrequency ablation for recurrent ventricular tachycardia. The mean age at first procedure was 36 + 9 years and 46% of the patients were male. ICD implantation was performed in 5 (21%) of the patients before their first catheter ablation procedure, in 14 (58%) of the patients after one or more ablations, and 5 (21%) of the patients never received an ICD. Thirteen of the 14 patients underwent more than one ablation procedure because of recurrent VT after the initial ablation. More than 1 distinct VT morphology was induced during 77% of the procedures. VT mapping was performed using 3-dimensional mapping during 10 of the procedures and traditional entrainment or activation sequence maps were used in the others. Ablation procedures were either considered completely successful if there was no inducible VT after ablation (22 of 48 procedures , 46%), partially successful if the clinical VT was suppressed but other VT's could still be induced (15 of 48 procedures, 31%), and a procedural failure if the clinical VT was still inducible (11 of 48 procedures, 23%). There was one major complication related to an ablation procedure. One patient who was undergoing his third ablation attempt developed an unstable VT and then became severely hypotensive. Resuscitation was unsuccessful. There were no mechanical complications of the procedure.
During long-term follow-up, time to recurrence after each ablation attempt was calculated. The mean time to recurrence after each ablation was 8 + 10 months and VT recurred after 40 of the 47 (85%) ablations. Only one patient had a single RF ablation procedure that proved successful both short- and long-term. The cumulative VT recurrence for each survival after a single radiofrequency ablation procedure was 75% at 1.5 months, 50% at 5 months, and 25% at 14 months of follow-up. The cumulative incidence of VT recurrence after a single procedure was 64%, 75% and 91% at the end of 1, 2, and 3 years. Of interest, there was no significant difference in the VT recurrence rate based upon the presumed acute success of the procedure. There was also no difference in success rates related to whether or not 3-dimensional mapping was used to guide ablation.
The authors conclude that catheter ablation of VT in patients with ARVD/C is at best a palliative procedure designed to reduce the frequency of VT episodes. Further studies to refine techniques for ablating arrhythmias in this difficult condition need to be developed.
These data from the ARVD/C registry should be useful to cardiologists and electrophysiologists who care for patients with ARVD/C. This condition is caused by mutations in the genes that code a number of desmosomal proteins. Alterations in the structure of these proteins results in poor cell-to-cell adhesion and fibro-fatty degeneration in multiple areas of the right ventricle. These changes are progressive over time and frequently result in sustained and potentially life-threatening ventricular arrhythmias. Progression can occur at varying rates that are impossible to predict when the patient is first identified. Many patients with ARVD/C have frequent arrhythmias that are drug unresponsive and the frequent episodes of VT make ICD therapy problematic. This paper illustrates that ablation therapy also has significant limitations in patients with gradually progressive changes in the myocardial substrate for arrhythmia. However, despite the low overall success rate reported here, ablation can still be a useful adjunct in these patients as a way to decrease the frequency of ICD therapies. The operator and patient, however, should recognize that ablation is likely to provide only short-term palliation rather than a long-term solution to the problem.