Utilization of implantable cardiac monitors in detecting type 1 patterns in brugada syndrome

Abstract

Abstract Introduction In individuals with Brugada syndrome, the presence of the type 1 pattern (BP1) is linked to an elevated risk of severe arrhythmias. However, the identification and measurement of BP1 can be challenging due to its intermittent nature. Implantable cardiac monitors (ICMs) provide extended continuous monitoring, potentially overcoming the limitations of intermittent ambulatory ECG monitoring in detecting spontaneous BP1. Nevertheless, their specific application for this purpose remains unevaluated. Methods From November 2022 to September 2023, all patients presenting with pharmacologically induced BP1 were enrolled at our centre. An ICM was surgically placed in the left second intercostal space at a 45° angle, enabling readings with a morphology similar to the right precordial ECG leads during ajmaline testing (AT). Patients were remotely monitored, and in addition to routine automatic transmissions, each patient was provided with a remote control to transmit in case of fever or symptomatic events. Transmissions were scrutinized to detect: 1) ST-segment elevation; 2) ventricular arrhythmias; 3) burden of ventricular extrasystoles (PVC). A reading was classified as positive for BP1 if it bore a similar morphology to that recorded during AT. The frequency of BP1-positive transmissions was evaluated across four hourly intervals. Results The ICM was successfully implanted in 21 patients (male-to-female ratio 1.62:1, mean age 43.9±13.1 years). Over an average follow-up of 168±70.6 days, a total of 7818 transmissions were received, evenly spread across hourly intervals (minimum of 1296 transmissions per interval). Among these, 173 transmissions were identified as BP1 positive (2.2%), originating from 6 patients (28.6% of the total, all newly diagnosed with spontaneous BP1). The median duration between implantation and the diagnosis of spontaneous BP1 was 16.5 days (range 2-23). The median number of days with at least one positive transmission was 30.2 (range 13.4-73.9). The evening period (6 pm to midnight) displayed a significantly higher rate of positive transmissions compared to the morning (p=0.04) and afternoon (p=0.01); however, not in contrast to the nighttime (p=0.8). No sustained ventricular arrhythmias were observed, and there were no significant differences in PVC burden among patients. Conclusions The utilization of ICM for continuous monitoring in patients with pharmacologically induced BP1 led to the identification of spontaneous BP1 patterns in almost 30% of cases during an approximately 6-month follow-up. Evening and nighttime periods exhibited the highest incidence of BP1. This methodology shows promise in quantifying BP1 incidence and could serve as a tool for stratifying arrhythmic risk in individuals with Brugada syndrome.