Chronotropic incompetence as a risk predictor in children and young adults with catecholaminergic polymorphic ventricular tachycardia.

Abstract

Risk stratification tools for catecholaminergic polymorphic ventricular tachycardia (CPVT) are limited. The exercise stress test (EST) is the most important diagnostic and prognostic test. We aimed to determine whether heart rate (HR) and blood pressure (BP) response during EST were associated with the risk of arrhythmias. We studied the association between HR and BP response and ventricular arrhythmia burden on EST in 20 CPVT patients. HR reserve values <80% and ≤62% were used to define chronotropic incompetence (CI) off and on therapy, respectively. Symptoms and ventricular arrhythmia score (VAS) in all patients with respect to CI and BP during index EST off therapy and on maximal therapy were compared. CI in CPVT patients off therapy was associated with a worse VAS during EST (P = .046). Patients with CI also more frequently presented with syncope and/or cardiac arrest compared to patients with a normal chronotropic response (P = .008). Once on therapy, patients with CI had similar VAS compared to patients without CI (P = .50), suggesting that treatment attenuates risk related to CI. Patients with CI also had a lower peak systolic BP (P = .041) which persisted on maximal therapy (P = .033). Untreated CPVT patients with CI have more ventricular arrhythmias than those without CI. This may serve as a simple disease prognosticator that can be modified by antiarrhythmic therapy. A mechanistic link between CI and arrhythmia susceptibility remains unknown. Larger studies are needed to confirm and establish the mechanism of these findings.