Background: 

Implantable cardiac monitors (ICM) are leadless subcutaneous devices used for long-term monitoring of arrhythmias. The BIOTRONIK BIOMONITOR III (BM III) is a novel, ICM with a miniaturized profile, long sensing vector and simplified implantation technique with a dedicated single-step insertion tool and wireless telemetry options. In this single-center, observational study, we assessed the insertion procedure, investigated the reliability of sensing quality and detection performance in the BM III.

Methods: 

The ICM was implanted in the left parasternal region between the suprasternal notch and the left nipple, preferentially at a 45° angle to the sternum. R-wave amplitude was recorded immediately post implantation and 1 day post implantation, followed by extensive patient instruction. Follow-up was scheduled after 3 months, or after an event. Data from the BM III were retrieved, with documentation of all episodes and R-wave amplitude. The anatomical position of the ICM was determined 1 day post implantation and after 3 months. A patient questionnaire was conducted after 3 months. The questionnaire gathered information on pain after implantation, prolonged paresthesia, restriction of daily activity, handling of the HomeMonitoring system and overall satisfaction regarding the BM III device.

Results: 

In 30 consecutive patients (mean age 67±13 years, 40% male) a BM III was inserted. Mean body mass index was 26.1±3.9 kg/m². All insertions were successful. Indications for ICM implantation were: unexplained syncope (n= 24, 80%), suspected atrial fibrillation (n=1, 3%) and cryptogenic stroke (n=5, 17%). Median time from skin cut to wound closure was 6 [IQR 5-7] minutes. No complications occurred. The mean R-wave amplitude at insertion was 0.73±0.11 mV. At the first day post implantation, the mean R-wave amplitude was 0.77±0.15 mV (p=0.59). After a mean follow-up of 107±59 days, the mean R-wave amplitude was 0.81±0.15 mV (p=0.39). The day after the implantation and during the 3-month follow-up visit, the position of the device was determined, demonstrating an anatomically stable position of the ICM. Vertical distance from the fossa jugularis to the lowest part of the ICM was 14.5±6.8 cm at implantation and 14.5±7.5 cm at follow-up (p=0.94). The horizontal cranial sternal to device distance was 4.4±7.1 cm and 4.3±6.8 cm, respectively (p=0.87). The horizontal caudal sternal to device distance was 6.0±9.1 cm and 5.7±9.8 cm, respectively (p=0.7). Time to first event after implantation was 12 [IQR 2 -38] days. In 13 (43%) patients, true episodes were detected. False arrhythmia alerts were detected in 12 (40%) patients, in 7/12 (58%) false atrial fibrillation alerts due to recurrent premature atrial contractions (PAC) were recorded. Total number of false detections was low. Patient-satisfaction rate was high, with very few limitations in daily activity.

Conclusion: 

Insertion of the novel BIOTRONIK BIOMONITOR III ICM is fast, uncomplicated and keeps an anatomically stable position of the ICM device over time. Initial sensing values are good and improve insignificantly over time. False arrhythmia alert, mainly due to PACs, occurred in 40% of the patients, with a low total number of false detections. New algorithms like RhythmCheck in the BM IIIm may further reduce episodes falsely detected.