Appropriate Therapies and Life Saving Interventions

Once an ICD is implanted, it appears that many (if not most) ARVC/D patients experience an appropriate ICD intervention (either antitachycardia pacing or defibrillation shock). In the series already mentioned, a high incidence of appropriate ICD interventions was encountered. Overall, between 48% and 78% of patients received appropriate ICD interventions during the mean follow-up period of 2-7 years after implantation [10-15] (Table 20.1). Many of these patients experienced multiple shocks during this period, and VT storm was not infrequently encountered. In the largest series to date, the rate of appropriate interventions was 15% per year [10]. Appropriate intervention rates were similar in patients presenting with VT, unexplained syncope, or cardiac arrest, although the latter group experienced slightly more events during follow-up (Fig. 20.3). An important observation is that patients with hemodynamically well-tolerated VT had significantly longer event-free survival than those with hemodynamic compromise during VT, unexplained syncope, or cardiac arrest. None of the asymptomatic patients implanted because of a family history of SCD experienced any appropriate ICD interventions, regardless of the results at EPS.

One method employed to assess the benefits of the ICD in observational series has been proposed by the Muenster group and compares the actual patient

  1. 20.3 • Analysis of appropriate ICD interventions experienced by a 132-patient cohort with ARVC/D and an ICD: these Kaplan-Meier curves depict freedom from any appropriate ICD interventions for different patient subgroups (with ARVC/D) stratified for clinical presentation. From [10] with permission from Lippincott Williams & Wilkins
  2. 20.3 • Analysis of appropriate ICD interventions experienced by a 132-patient cohort with ARVC/D and an ICD: these Kaplan-Meier curves depict freedom from any appropriate ICD interventions for different patient subgroups (with ARVC/D) stratified for clinical presentation. From [10] with permission from Lippincott Williams & Wilkins survival rates with projected freedom of fast VT/VF >240 bpm (used as a surrogate for aborted SCD) [14]. This is achieved by device interrogation and analysis of ICD interventions in response to either VF or flutter during follow-up. When comparing actual patient survival rates with projected SCD-free survival rates in this manner, it becomes apparent that there is a significant improvement in survival. In the large series reported by Corrado et al. [10], 24% of patients had one or more episodes of either VF, ventricular flutter, or both, that were successfully recognized and treated by their device, and that would otherwise likely have been fatal. These interventions were therefore deemed to be life-saving. In this pop ulation, actual total patient survival rates were 96%, compared with a 72% VF/flutter-free survival rate at 36 months (Fig. 20.4). The largest single-center experience was published by Wichter et al. [14] and provides the longest follow-up period (mean 80±43 months) reported to date. This group found an estimated survival benefit of 23%, 32%, and 35% after 1,3, and 7 years of follow-up. Event-free survival in that cohort appeared to plateau after about 5 years after the ICD was implanted, suggesting that the greatest benefit may be observed earlier in the course after ICD implantation [14,17] (Fig. 20.5). These results were confirmed by other series reporting similar rates of life-saving ICD interventions (30%-50%
  1. 20.4 • Survival data from 132 patients with ARVC/D with implanted defibrillators. This Kaplan-Meier analysis compares actual patient survival with survival free of ventricular fibrillation/flutter that in all likelihood would have been fatal in the absence of an appropriate ICD intervention. Divergence between lines reflects the estimated survival benefit conferred by ICD therapy in these patients. At 36 months,actual total patient survival was 96%, compared with 72% VF/flutter-free survival.The general population estimated survival rate was 99.5% when matched for age,gender,and ethnicity.From [10] with permission from Lippincott Williams & Wilkins
  2. 20.4 • Survival data from 132 patients with ARVC/D with implanted defibrillators. This Kaplan-Meier analysis compares actual patient survival with survival free of ventricular fibrillation/flutter that in all likelihood would have been fatal in the absence of an appropriate ICD intervention. Divergence between lines reflects the estimated survival benefit conferred by ICD therapy in these patients. At 36 months,actual total patient survival was 96%, compared with 72% VF/flutter-free survival.The general population estimated survival rate was 99.5% when matched for age,gender,and ethnicity.From [10] with permission from Lippincott Williams & Wilkins
  1. 20.5 • Mortality and recurrence of VT or VF during follow-up (80 ±43 months) after ICD implantation in ARVC/D. Kaplan-Meier curves depict event-free survival for all-cause mor-tality,fast VT/VF (>240 bpm),and VT/VF at any rate. The difference between all-cause mortality and fast VT/VF indicates the potential survival benefit from ICD therapy in this cohort. From [14] with permission from Lippincott Williams & Wilkins
  2. 20.5 • Mortality and recurrence of VT or VF during follow-up (80 ±43 months) after ICD implantation in ARVC/D. Kaplan-Meier curves depict event-free survival for all-cause mor-tality,fast VT/VF (>240 bpm),and VT/VF at any rate. The difference between all-cause mortality and fast VT/VF indicates the potential survival benefit from ICD therapy in this cohort. From [14] with permission from Lippincott Williams & Wilkins ofpatients over the course of follow-up) [11,12,15], although in some cases slightly more permissive definitions were applied to arrive to this determination.

Time of first appropriate ICD therapy may yield further insight into the potential for ICD to improve outcomes. From published data, it appears that most patients received their first appropriate therapy in 4 months to 3 years after ICD implantation (Table 20.1). In a homogeneous cohort of ARVC/D patients compared with controls, it was observed that time to first ICD discharge for VT >240 bpm was similar to the time of death of the control group, confirming this concept of"hypothetical death" [14,15].

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