Benefit of Implantable Cardioverter-Defibrillators in Patients with Catecholaminergic Polymorphic Ventricular Tachycardia - Reply

In Reply: We thank Maass and Cox for their comment on our work,1 and for stimulating the discussion on the role of implantable cardioverter-defibrillators (ICDs) in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT). In our cohort, we did not observe an excess of crude mortality rates in ICD carriers (0.15 per 100 person-years) compared with noncarriers (0.56 per 100 person-years; P = .38). Considering that in this relatively young population, the dominant contributor to mortality is sudden cardiac death, we assessed the likelihood of survival at the occurrence of the first life-threatening arrhythmic event (LTAE; composite of sudden cardiac death, aborted cardiac arrest, or hemodynamically nontolerated sustained ventricular tachycardia), a previously validated hard end point.2,3 Our data show that patients without an ICD were 25-fold more likely to die at the occurrence of the first LTAE compared with ICD carriers, supporting the conclusion that ICD confers a survival benefit in high-risk patients with CPVT.1 However, when discussing the benefits and drawbacks of ICD, mortality should not be the only factor considered, since patients without an ICD may survive an out-of-hospital cardiac arrest with neurological disability secondary to anoxic brain injury, as in the case of 2 of 6 patients without an ICD who survived a cardiac arrest in our cohort. We agree with the authors that appropriate ICD shocks are not always necessary, especially on self-terminating arrhythmias. We acknowledge that a typographic mistake occurred during the editing of the article, and the sentence cited by the authors regarding the episodes terminated by the ICD should read, “Overall, all 15 episodes of VF [ventricular fibrillation] were successfully interrupted, while only 3 of 6 episodes (50%) of hemodynamically unstable, polymorphic fast VT [ventricular tachycardia] were terminated (P < .001).”4 We thank the authors for giving us the opportunity to clarify that the majority of ICD shocks on LTAE occurred on ventricular fibrillation, which are known to not cease spontaneously. This is also explained by our long-standing collaboration with Maurizio Gasparini, MD, which led to us to adopt into our clinical practice ICD programming with a long detection to deliver a shock only on ventricular fibrillation, a strategy demonstrated to reduce the rate of both appropriate and inappropriate shocks without differences in mortality.5 Regarding the 3 of 6 shocks (50%) on polymorphic VT that failed to terminate the arrhythmia, this is not surprising, since it is known that substrate (and arrhythmia mechanism) is a potent predictor of shock efficacy.6 Lastly, neither flecainide nor verapamil nor left cardiac sympathetic denervation have been demonstrated to reduce mortality in patients with CPVT at the time of the publication of this work. Considering that the practice of modern medicine should be based on the best evidence available, at the present time, these therapies cannot represent an alternative for ICD.