Indication for ICDs in Arrhythmogenic RV Cardiomyopathy Patients

Abstract & Commentary

By John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville

Source: Bhonsale A, et al. Incidence and predictors of implantable cardioverter-defibrillator therapy in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy undergoing implantable cardioverter-defibrillator implantation for primary prevention. J Am Coll Cardiol 2011;58:1485-1496.

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is an uncommon condition with a wide spectrum of possible clinical presentations. Implantable defibrillators (ICDs) are standard therapy for treating ARVD/C patients who present with sustained ventricular tachycardia (VT) or cardiac arrest. In this paper, Bhonsale and his colleagues at Johns Hopkins report data on ICD utilization among the ARVD/C registry patients who received their devices for primary prevention of sudden death.

The Johns Hopkins ARVD/C registry is a prospective longitudinal study that enrolls patients who meet the clinical criteria for ARVD/C established and revised by an ARVD/C Task Force in 2010. The criteria include major and minor criteria describing functional and structural alterations, changes is right ventricular tissue characteristics, repolarization abnormalities on scalar ECG, arrhythmias, and family history. A "definite" diagnosis of ARVD/C is made if the subject has 2 major or 1 major and 2 minor criterion. A "borderline" diagnosis is made if the subject has 1 major and 1 minor or 3 minor criterion. A "possible" diagnosis is made if the subject has only 1 major or 2 minor criterion.

This study includes 84 patients who received an ICD for primary prevention between 1995 and 2010. Data from ICD shocks were collected, analyzed, and classified as appropriate or inappropriate. There were 70 patients with a definite diagnosis and 14 patients with a probable diagnosis of ARVD/C. The mean patient age at presentation was 32 years and the group had approximately equal numbers of men and women. There were 54 patients who were independently identified and 34 identified by screening of family members of known ARVD/C patients. Desmosomal mutations related to ARVD/C were identified in 36 of 63 (57%) of patients who underwent testing. Electrophysiologic studies (EPS) were performed in 72 patients and inducible sustained ventricular tachyarrhythmia were observed in 40 (56%).

During a mean follow-up of 4.7 years, 40 of 84 (48%) patients received one or more (median 5.5) appropriate ICD therapies. ICD shocks were commonly associated with exercise (63% of first shocks). VT storm was observed in 16 (19%) patients. Prior to receiving initial therapy, only three patients were being treated with an antiarrhythmic drug, but 36% were receiving a beta-adrenergic blocker. Predictors of appropriate ICD therapy included symptoms prior to presentation, proband status (higher risk if the patient was independently identified), and higher PVC and nonsustained VT presence on Holter monitoring. Induction of VT at EPS had a positive-predictive value of 65% and a negative-predictive value of 75% for appropriate ICD therapy. ICD-related complications including infection, pocket hematoma, lead dislodgment, subclavian vein occlusion, lead fracture, and malfunction need for revision were noted in 20 (24%) patients. Inappropriate ICD shocks for sinus tachycardia, supraventricular arrhythmias, or lead malfunction were experienced by 20 (24%) patients.

The authors propose that patients with ARVD/C can be risk stratified using four factors: proband status, PVC frequency (≥ 1000 in 24 hours), nonsustained VT, and VT induction at EPS. Risk increases in a stepwise fashion in patients with two to four of these risk factors. Patients with only one or zero risk factors can be spared ICD therapy with its costs and potential for complications.

Commentary

Prescription of an ICD for primary prevention in a patient with ARVD/C is often difficult. In ARVD/C, a serious or fatal arrhythmia may be the first presenting major symptom. On the other hand, intervening with an ICD implant too early or in low-risk patients subjects these patients to risks for repeat procedures, infection, device malfunction, and inappropriate shocks. Effective risk stratification of ARVD/C patients therefore is quite important. In this paper, we see that findings at EPS and on Holter monitoring and proband status can be used to identify patients with a higher likelihood to benefit from a primary prevention ICD implant. Unfortunately, the data presented here constitute only the first step. We don't know anything about the reproducibility of the Holter and EPS findings on either a day-to-day or long-term basis as the disease progresses. Will it be necessary to rescreen patients periodically if their initial evaluation suggests a relatively low risk?

ARVD/C is an uncommon disorder and it is unlikely that definitive, randomized trials of therapy in these patients will ever be conducted. In the absence of data from randomized trials, registry data such as in this important paper, will likely provide the best guide to treating individual patients.