Incremental Value of an Insertable Cardiac Monitor in Patients with Hypertrophic Cardiomyopathy with Low or Intermediate Risk for Sudden Cardiac Death

Aims: The aim of the present study was to compare the rate of actionable arrhythmic events between patients with hypertrophic cardiomyopathy (HCM) who are monitored with an insertable cardiac monitor (ICM) or Holter monitoring. Methods: We studied 50 patients (mean age 52 years, 72% men) with HCM at low or intermediate risk for sudden cardiac death (SCD), of whom 25 patients received an ICM between November 2014 and February 2019. We retrospectively identified a control group of 25 patients who were matched on age, sex, and HCM Risk-SCD score category. The mean HCM Risk-SCD score was 3.41 ± 1.31 and 3.31 ± 1.43 for the ICM and Holter groups, respectively. The primary endpoint was an actionable event which was defined as an arrhythmic event resulting in a change in patient management. The secondary endpoint was the occurrence of ventricular tachycardia (VT). Results: The cumulative actionable event rate at 30 months was higher in the ICM group (51 vs. 27%, log-rank p value <0.01). De novo atrial fibrillation requiring oral anticoagulation occurred only in the ICM group (n = 3). Overall, 4 implantable cardioverter-defibrillators were implanted for primary prevention (n = 2 in each group). The cumulative rate of VT episodes at 30 months was similar between groups (23% [ICM group] vs. 42% [Holter group], log-rank p value = 0.71). Furthermore, the characteristics of VT were similar between groups with regard to the number of beats and rate. Conclusions: In adults with HCM, an ICM will detect more arrhythmic events requiring an intervention than a conventional Holter strategy. In contrast, the diagnostic yield of detecting VT seems similar for both groups.