Remote monitoring of implantable cardiac monitors in patients with unexplained syncope: Predictors of false-positive alert episodes.

BACKGROUND: Remote monitoring is recommended for patients with implantable cardiac monitors (ICMs), but compared to other cardiac implantable devices, ICMs are less accurate and transmit a higher number of alerts. OBJECTIVE: The aim of this study was to investigate the predictors of false-positive (FP) arrhythmic alerts in patients with unexplained syncope who were implanted with ICM and followed by an automatic remote monitoring system. METHODS: We retrospectively evaluated all consecutive patients who received a long-sensing vector ICM for unexplained syncope between January 2019 to September 2021 at our Syncope Unit. The primary endpoint was the incidence of the first FP episode. The secondary endpoints included assessing the incidence of FP episodes for all types of algorhythms and indentifying the reasons for the misdetection of these episodes. RESULTS: Among 105 patients (44.8% males, median age 51 years), 51 (48.6%) transmitted at least one FP alert during a median follow-up of 301 days. The presence of pre-ventricular complexes (PVCs) on the resting electrocardiogram was the only clinical characteristic associated with an increased risk of FP alerts (adjusted Hazard ratio [HR] 5.76 [2.66-12.4], p = 0.010). The other significant device-related variables were a low-frequency filter at 0.05 Hz versus the default 0.5 Hz (adjusted HR 3.82 [1.38-10.5], p = 0.010) and the R-wave amplitude (adjusted HR 0.35 [0.13-0.99], p = 0.049). CONCLUSION: Patients who have PVCs are at higher risk of inappropriate ICM activations. To reduce the occurrence of FP alerts, it may be beneficial to target a large R-wave amplitude during device insertion and avoid programming a low-frequency filter at 0.05 Hz.

Remote monitoring of implantable loop recorders reduces time to diagnosis in patients with unexplained syncope: a multicenter propensity score-matched study.

Background: There are little data on remote monitoring (RM) of implantable loop recorders (ILRs) in patients with unexplained syncope and whether it confers enhanced diagnostic power. Objective: To evaluate the effect of RM in ILR recipients for unexplained syncope for early detection of clinically relevant arrhythmias by comparison with a historical cohort with no RM. Methods: SyncRM is a propensity score (PS)-matched study prospectively including 133 consecutive patients with unexplained syncope and ILR followed up by RM (RM-ON group). A historical cohort of 108 consecutive ILR patients with biannual in-hospital follow-up visits was used as control group (RM-OFF group). The primary endpoint was the time to the clinician's evaluation of clinically relevant arrhythmias (types 1, 2, and 4 of the ISSUE classification). Results: The primary endpoint of arrhythmia evaluation was reached in 38 patients (28.6%) of the RM-ON group after a median time of 46 days (interquartile range, 13-106) and in 22 patients (20.4%) of the RM-OFF group after 92 days (25-368). The PS-matched adjusted ratio of rates of arrhythmia evaluation was 2.53 (95% confidence interval, 1.32-4.86) in the RM-ON vs. RM-OFF group (p = 0.005). Conclusion: In our PS-matched comparison with a historical cohort, RM of ILR patients with unexplained syncope was associated with a 2.5-fold higher chance of evaluations of clinically relevant arrhythmias as compared with biannual in-office follow-up visits.

Recording of Brugada electrocardiogram pattern by an implantable cardiac monitor.

A 51-year-old man with Brugada syndrome (BrS) electrocardiogram (ECG) type I pattern underwent implantable cardiac monitor (ICM) insertion. After pre-insertion potential mapping, we could observe the patient-specific repolarization abnormalities on the subcutaneous ECG provided by the ICM. A few weeks later, we received remotely a device recording with a higher ST-segment elevation and a longer duration of the interval between the onset of the coved elevation and its termination at the isoelectric line. Our observation supports the conceptual premise that ICM could add information on quantifying the amount of time with abnormal ECG patterns rather than only for the diagnosis of cardiac arrhythmias.

Remote assessment of QT interval: A new perspective for implantable cardiac monitors.

BACKGROUND: There is an unmet need for simple tools for monitoring QT intervals. The feasibility of measuring the QT interval on the single­lead subcutaneous electrocardiogram (subECG) recorded and transmitted by implantable cardiac monitors (ICMs) has never been tested. METHODS: We performed a standard ECG in patients who had already been implanted with a long sensing vector ICM (BIOMONITOR, Biotronik SE&Co.) to calculate the corrected QT interval in lead II (QTc ECG). The QTc was then evaluated on the subECG provided by ICM both by using the programmer printout (QTc subECG) and the snapshot transmitted via home monitoring (QTc HM). Values were compared with Bland-Altman analyses. RESULTS: The study cohort consisted of 23 ICM recipients (age 58 ± 19 years, 35% female) implanted mainly for unexplained syncope (78%). The mean QTc ECG interval was 404 ± 31 ms. The T-wave was visible and QTc could be calculated in all patients using the ICM programmer printout and in 21 (91%) patients remotely. The QTc subECG and QTc HM were 405 ± 34 and 406 ± 32 ms. Compared to the QTc ECG, Bland-Altman analyses revealed a bias of -0.9 (95% confidence interval: -6.8/4.9) ms and 0.1 (-12.7/12.9) ms for QTc subECG and QTc HM, respectively. CONCLUSIONS: The QTc interval can be reliably estimated on in-person and remote subECG in most patients without bias compared to the ECG lead II assessment. This technology has the potential to facilitate remote QT interval monitoring.