A considerable body of data exists about the efficacy of ICD therapy in patients diagnosed with ARVC/D. While no prospective randomized trials of ARVC/D have compared ICD therapy with antiarrhythmic drug treatment, catheter ablation of VT, or no therapy, the available clinical data supports the use of ICDs in ARVC/D. Forty percent of ARVD patients have appropriate ICD therapy if they have spontaneous or induced VT with hemodynamic compromise or unexplained syncope . Despite this high frequency of appropriate ICD intervention, the actual patient survival over time is 96% , supporting the role of ICD in prolonging survival in this patient population. The best data currently available relating to the efficacy of ICD therapy in ARVC/D patients come from several recent series of ARVC/D patients who received ICDs and were subsequently followed clinically over a variable period of time [10-15]. Data from these series are summarized in Table 20.1 and published in a review by Wichter et al. . Cumulatively, 303 patients with ARVC/D who underwent ICD implantation at several centers worldwide are represented. The majority of ICD implants were performed for: secondary prevention (after episodes of resuscitated cardiac arrest, documented sustained VT, or syncope) or primary prevention (inducibility of VT during electrophysiologic study, family history of SCD in first degree relatives).
Intermediate and long-term outcomes may be analyzed from these data, thereby providing some insight into the efficacy of ICDs in this patient population. The majority of these series focused on clinical outcomes, complications (related to both initial implantation of the device as well as long-term integrity of the systems used), and frequency and timing of appropriate and inappropriate therapies delivered by the ICD. In several of these series, some attempt was made to identify clinical variables predictive of ICD utilization, VT/VF, and death. Although all patients were diagnosed with ARVC/D on the basis of certain major and minor diagnostic criteria stipulated by the international Task Force criteria  and were therefore relatively heterogeneous, one study identified a genetically homogeneous population with ARVC/D specific to eleven Newfoundland families (ARVD5, involving region 3p25 on the short arm of chromosome 3) . The latter group may shed additional light on familial ARVC/D, and may in time provide insight into the value of genetic screening as a tool to identify asymptomatic relatives for the purposes of risk stratification .
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