Continous remote surveillance of arrhythmic patterns by implantable cardiac monitors (ICMs) in drug-induced Brugada type 1 patients

Background Brugada syndrome primarily affects young individuals with a structurally normal heart and may lead to sudden cardiac death, which can occur as the first clinical event. Patients who display a drug-induced type 1 Brugada ECG pattern, in whom a spontaneous type 1 pattern has been reliably excluded through 24-hour Holter monitoring, are generally considered to be at very low risk. However, intermittent ECG monitoring via Holter has significant limitations as it may miss transient arrhythmic episodes or transient Brugada type 1 pattern manifestation. In contrast, continuous rhythm surveillance through implantable cardiac monitors (ICMs) offers a more reliable assessment of arrhythmic risk, particularly crucial in the large subset of asymptomatic patients who comprise the majority of those with Brugada syndrome. Purpose This study aim was to evaluate the strategic role of continous cardiac rhythm and sECG pattern monitoring by ICMs equipped with remote monitoring (HM). Methods Between November 2022 and July 2024 we consecutively screened all asymptomatic patients who underwent a provocative drug test for suspected Brugada syndrome (BrS). Patients who exhibited a type 1 BrS electrocardiographic (ECG) pattern during the drug challenge were considered eligible for implantable cardiac monitor (ICM) insertion in the I-II left intercostal space at a 45° tilt. Patients were followed using the HM system. Results During follow-up, 11,383 daily home monitoring transmissions were collected, with a median transmission success rate of 96% (IQR 88–98%). These transmissions comprised 50,666 subECG recordings (mean 5.1 ± 1.0 episodes per patient/day). All recordings were systematically analyzed for the presence of a type 1 ECG pattern. A total of 1,740 recordings were classified as positive for type 1 ECG pattern, corresponding to a GEE-corrected prevalence of 3.4% (95% CI 2.1–5.7%). Detection probability was independent of R-wave amplitude and 24-hour HRV, but showed a trend toward higher likelihood with lower mean 24-hour heart rate (p = 0.065). Recordings were evenly distributed across timeslots; however, positivity was significantly more frequent at night (7.4%, 95% CI 3.0–9.5%) compared with morning (3.5%, p = 0.042), afternoon (1.7%, p < 0.001), and evening (2.6%, p = 0.006). The burden of positive recordings was inversely correlated with the ajmaline dose required to induce a type1 pattern during drug challenge (regression coefficient −0.0015; p = 0.010). Among 20 patients with spontaneous diagnosis, the proportion of positive recordings ranged from 1.4% to 21.7% across individuals. Conclusion Remote monitoring with ICMs provides reliable detection of spontaneous type 1 ECG patterns, with a higher yield during nocturnal periods. The burden of positive recordings correlates with pharmacological inducibility, supporting the role of ICMs in refining risk stratification and diagnostic accuracy in patients with suspected Brugada syndrome.