Hypertrophic cardiomyopathy: Clinical impact of a prolonged mHealth-based arrhythmia monitoring by single-channel ECG (HCM-PATCH)

Background: Patients (pts) with hypertrophic cardiomyopathy (HCM) are at increased risk of sudden cardiac death (SCD) due to ventricular arrhythmias (VA) and developing other arrhythmias, e.g. atrial fibrillation (AF). Intensified monitoring may increase the detection rate of VA and thus identify more pts with an increased SCD risk.

Objective: This prospective single-center study measured the prevalence of VA and other arrhythmias in pts with HCM detected by mHealth-based continuous rhythm monitoring over 14 days, compared to standard practice (24- and 48-h long-term ECG).

Methods: 41 pts with a low or intermediate risk for SCD, assessed by the HCM Risk-SCD Calculator, were recruited between June 2023 to October 2024. All pts received an ECG patch (AT-Patch by ATSens®) that continuously recorded a single-lead ECG over a 14-day period. In addition, data from cardiac magnetic resonance imaging (cMRI) and genetic testing were integrated into risk stratification.

Results: The median wearing time was 330 hours per pt (Q1: 312; Q3: 336.8). Seven of the 41 pts were excluded due to insufficient wearing time of ECG patch or failure to return it. Median age was 49 years [21-68], 38.2% of pts were female. 17 pts were classified as low-risk according to the HCM-Risk SCD Calculator, while 17 were classified as intermediate-risk.

Non-sustained ventricular tachycardia (nsVT, i.e., ventricular tachycardia of >3 beats to <30 seconds at >120 beats per minute) was detected in 58% of pts (median of 3 episodes/pt), in 1 pt during the first 24 hours of recording and in 4 pts in the first 48 hours. Detected arrhythmias changed the risk classification in 58.8 % of pts, in 32.3% fulfilling the indication for prophylactic ICD implantation. In 5 pts (14.7%) AF was detected, of which AF had not been previously documented in 4 (11.8%).

19 pts underwent genetic testing, 11 of these (58%) had a positive result (defined as at least one variant of ACMG class ≥ 3). In most pts, this involved a variant in the MYBPC3 gene. A recent MR scan was available in 30/34 pts (88%), which showed late gadolinium enhancement (LGE) in 83%.

14/17 pts (82.3%) who had a MR scan and were diagnosed with nsVT also had LGE on MR - on the other hand, 11/30 patients (36.7%) who had a MR scan, also showed LGE, but no nsVT. 63.6% of patients with positive gene findings had nsVT.

Table 2: Study results of 34 study participants; continuous variables are given as median (Q1; Q3) and categorical variables as number (proportion).

Study results
Wearing period (h), median (Q1; Q3)	330 (312; 336.8)
Patients with detected NSVT, n (%)	20 (58%)
Patients with detected AF, n (%)	5 (14.7%)
Number of detected nsVT per patient, median (Q1; Q3)	3 (1.5; 7)
First Appearance (h), median (Q1; Q3)	100 (95;162)
Post PATCH Risk Score (%), median (Q1; Q3)	4.8% (3.7; 8.2)
Change in risk class, n (%)	20 (58.8%)
Genetic testing performed, n (%)	19 (56%)
Positive genetic findings, n (%)	11 (58%)
Appearance of nsVT in patients with positive genetic findings, n (%)	7 (63.6%)
LGE in MR, n (%)	25 (83.3%)

Conclusion: Compared to a standard 24- or 48-h long-term ECG, prolonged rhythm monitoring using an mHealth ECG patch detected nsVT more frequently, often increasing the HCM Risk-SCD score and potentially identifying more ICD candidates. In addition, an association was found between sarcomere mutations and the frequency of nsVT. However, no evidence for an association was found between the occurrence of nsVT and LGE burden.