Performance of implantable loop recorders. Role of R vector and detection algorithms.

INTRODUCTION: We evaluated the performance of implantable loop recorders (ILRs) with different detection algorithms and looked for artifacts and therapeutic consequences and their dependence on patient factors. METHODS AND RESULTS: 586 RevealLinq™ ILRs (first generation (NT): n = 335; second generation with TruRhythm™ (TR): n = 251) were implanted during 2014-2021 (syncope n = 206; embolic stroke of unknown source (ESUS) n = 380). Automatically detected EGM episodes (n = 18,650) were classified as correct or incorrect for asystole (AS), atrial fibrillation (AF) or tachycardia (TA). Incorrect episodes were caused by loss of signal (LO), noise (NO), extrasystole (ES) and T-wave oversensing (TWO). Left directed R axes, lower R-amplitudes and older age were related to artifacts. Results were separated by indication. In ESUS patients TR reduced total median artifact episodes: 0.6 (0-7) vs 0 (0-5) (p < 0.03) and median artifact examination time: 0.3 (0-3.5) vs 0 (0-2.5) (p = 0.03) per patient-year. This benefit is caused by significant reductions in total AS and ES-AS artifacts. The total positive predictive value (PPV) improved only in syncope patients (45 vs 71%, p = 0.002). Accordingly in syncope patients with TR more therapeutic consequences could be established (log rank 0.003). DISCUSSION: Patients R-axis and measured R-amplitudes during implantation predicted artifacts. This should be taken into account during ILR implantation. Total artifacts, AS artifacts and time spent for artifact analysis was reduced by the new TR detection algorithm in ESUS patients, whereas total artifacts remained unchanged in syncope patients despite reduction of AS artifacts. However TR had no effect on AF and TA episode detection and therefore has to be improved.

Experience with a Wearable Cardioverter-defibrillator in 436 Patients.

The aim of the present study was to review the safety and efficiency of wearable cardioverter-defibrillators (WCDs) under current guideline-directed medical therapy (GDMT). We retrospectively analyzed 436 consecutive WCD patients seen in the years 2014-2020. Detected automatic arrhythmia alarm (AA) episodes were validated and classified as correct or incorrect. The positive predictive value (PPV) was calculated. GDMT was optimized in our outpatient clinic to maximal tolerated doses. During a total wear time (WT) of 23,527 days, 3,135 AAs were transmitted from 206 of 436 (47.2%) patients. Visual analysis revealed correct diagnoses of non-sustained ventricular tachycardia (VT) in 38 AAs from 6 patients (total PPV, 1.21%; PPV in VT patients, 41%); the remaining AAs were artifacts. No appropriate or inappropriate shocks and fatalities were recorded. LVEF significantly improved (P < .001) during the WT from 25% (range, 20%-30%) to 40% (range, 34%-46%). Defibrillators were implanted in 109 patients (27%). The PPV for VT of the WCD was very low. There were fewer instances of true VT than previously reported, and no shocks (appropriate or inappropriate) were delivered. The majority of patients greatly improved with GDMT, and device implantation rates were lower than previously reported. Improvements in arrhythmia detection algorithms are warranted. Based on our results, WCDs are rarely needed for lifesaving shocks under optimal GDMT.

Analysis of causes of death in patients with implanted defibrillators.

AIMS: Implantable cardioverter defibrillators (ICDs) are used for primary or secondary prevention of sudden cardiac death. We sought to clarify prognosis and causes of death after ICD implantation. METHODS AND RESULTS: A total of 2743 patients with ICDs implanted during 1990-2020 were analyzed. Median age was 68.5 (59.6-74.6) years; 21% women, median left ventricular ejection fraction (LVEF) was 30 (23-35), 52% had an ischemic etiology and 77% had a primary preventive indication. Mortality rate after 10 years was 22, 44, 55, and 72% in the 1st, 2nd, 3rd, and 4th age quartile, respectively. The calculated median sex and age adjusted loss of life years compared to the average German population was 9.7 (6.1-14.0) years. Prognosis was independently related to sex, age, LVEF, and glomerular filtration rate. 713 out of 852 deaths could be classified to a specific cause. Congestive heart failure (CHF) accounted for death in 214 (30%) and sudden death (SD) for 144 patients (20%). Postmortem interrogation of devices in 74 patients revealed VT/VF in 39 and no episodes in 35 patients. Cancer was identified as the cause of death in 121 patients (17% of cases), of which 36 were bronchial carcinomas. 73 (10%) of patients died due to infection. 67 patients (9%) died within 24 h of procedures. Compared to other causes, significantly more life years were lost associated with procedures and SD: 9.3 (5.7-12.9) versus 12.1 (7.4-15.2) and 11.9 (7.6-17.8) years. CONCLUSION: Life expectancy of ICD patients is lower than for the general population. Mortality is predominantly due to CHF, but there is still a considerable rate of SD. The occurrence of cancers, most importantly bronchial carcinomas, and infections, warrants protective measures. Some deaths during procedures are possibly preventable. Patients with ICDs comprise a vulnerable cohort, and treatment has to be optimized in many directions to improve prognosis.