(P072) DIAGNOSTIC UTILITY OF HOLTER MONITORING IN CATECHOLAMINERGIC POLYMORPHIC VENTRICULAR TACHYCARDIA

Background: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare genetic arrhythmia predisposing to a high risk of sudden death during periods of adrenergic stress. The diagnosis hinges on the exercise stress test, which induces progressive polymorphic and bidirectional ventricular arrhythmias in affected patients. Genetic testing usually identifies a missense variant in the cardiac ryanodine receptor (RyR2). When arrhythmia symptoms are reported by patients, it is also common to perform a Holter monitor, which may identify ventricular arrhythmias. The scope and nature of ventricular arrhythmias during Holter monitoring to identify CPVT patients has not been assessed. To address this uncertainty, we sought to compare the characteristics of PVCs in CPVT patients to healthy controls during Holter monitoring.

METHODS AND RESULTS: In this retrospective study of the National Hearts in Rhythm Organization (HiRO) registry, we analyzed 94 24-hour Holter recordings from 55 healthy controls (genotype and phenotype negative) and 39 CPVT-affected patients (RyR2 variant positive, and CPVT phenotype positive). No patients were on CPVT therapy during the recordings. We used the Borg cardiorespiratory intensity scale to correlate heart rate during Holter monitoring with the level of exertion. A cut-off of 76% of maximal heart rate was defined to separate periods of adrenergic and non-adrenergic stress. Mean PVCs during the two separated episodes were plotted on a boxplot and compared using the nonparametric Anderson-Darling K-Sample test across both populations. Within periods of “low” activity, the mean PVC count between healthy controls and CPVT-affected patients did not differ. However, during periods of “high” activity, the mean PVC was significantly higher in CPVT-affected patients compared to control (p=0.041).

Conclusion: The Holter monitor may have diagnostic utility in CPVT when PVCs occur during periods of elevated heart rate. However, a high burden of PVCs during rest (i.e. ambient PVCs) largely precludes a diagnosis of CPVT. If patients with CPVT are not under adrenergic stress during the recording period, the Holter monitor is likely to miss the diagnosis. These data suggest that an in-depth analysis of the Holter monitor, including temporal and adrenergic state, is necessary to determine the probability of CPVT.