PO-03-223 EXTENDED AMBULATORY ECG MONITORING ENHANCES IDENTIFICATION OF HIGHER-RISK PATIENTS WITH HYPERTROPHIC CARDIOMYOPATHY

Abstract

In the 2020 AHA/ACC hypertrophic cardiomyopathy (HCM) guidelines, a 24 or 48 hour continuous ambulatory ECG monitor is recommended for risk stratification to detect nonsustained ventricular tachycardia (NSVT), with greatest weight placed on frequent, long, and/or rapid runs as a sudden death (SD) risk marker. ECG monitoring devices with extended wear capability are now available, although the utility of longer monitoring in HCM is uncertain. To evaluate the prevalence, burden and clinical significance of NSVT identified during initial 48 hours of continuou ambulatory monitoring compared to 14 days. We evaluated 236 HCM patients (49 ± 12 years; 72% male) without primary prevention ICDs judged previously to be at low or intermediate SD risk with 14-day continuous ambulatory monitoring (Zio-patch XT, iRhythm Technologies). Episodes of NSVT were evaluated during the initial 48 hours of monitoring and compared to NSVT identified in subsequent 2 to 14 days. NSVT episodes with ≥1 of the following criteria was considered higher risk as a SD marker: ≥ 200 bpm, ≥ 8 beats, ≥ 3 runs within consecutive 48 hour period. Among the 236 patients, 114 (48%) had ≥ 1 runs of NSVT, with a median of 2 runs (IQR: 1-4) during the complete monitoring period, including 86 patients with ≤ 4 runs (36%), 13 with 5-9 runs (6%), and 15 with ≥10 runs (7%). Median length of NSVT was 7 beats (5-13) at 167 bpm (148-186). Diagnostic yield of detecting NSVT was 18% during the first 48 hours of monitoring compared to 48% at 14 days, with 63% of the initial NSVT episodes occurring after the first 48 hours (72 of 114). Similarly, diagnostic yield of detecting high risk NSVT episodes was 8% during the first 48 hours as compared to 24% at 14 days, with 64% of the initial high-risk NSVT runs occurring after the first 48 hours (36 of 56). There was no significant difference in clinical profile between patients with NSVT at < 48 hours and those with NSVT from 2-14 days, including age or presence of ≥1 major SD risk markers. In HCM, prevalence of NSVT is common, occurring in nearly half of patients over 14 days of continuous monitoring. Diagnostic yield for detecting NSVT was substantially increased using 14 days of monitoring, with 48 hours of monitoring missing nearly two-thirds of patients with high risk NSVT episodes that impact risk stratification. These data support 14-day ambulatory monitoring periods to enhance identification of higher risk HCM patients.