Performance of a multisensor implantable defibrillator algorithm for HF monitoring in the presence of atrial fibrillation

Background: Some implantable cardioverter defibrillators (ICD) are equipped with diagnostic algorithms that combine data from multiple sensors. The HeartLogic Index was shown to accurately stratify patients at risk of heart failure (HF) events. However, there are no data on its performance in the presence of atrial fibrillation (AF). We evaluated and compared the performance of the algorithm during sinus rhythm and during long-lasting AF episodes. Methods: The feature was activated in 568 ICD patients from 26 centers. We analyzed stored data to identify periods of ≥30 consecutive days with atrial high-rate episode (AHRE) burden <1hour/day, and periods with AHRE burden ≥20hours/day. Then, we identified patients who met both conditions during their follow-up (AHRE group, N=53), to allow pairwise comparison of periods. For control purposes, we identified patients with AHRE burden <1h during the entire follow-up and we implemented a 2:1 propensity score matching versus the AHRE group (Matched non-AHRE group, N=106). Results: In the AHRE group, the rate of HeartLogic alerts was 1.2 (95%CI:1.0-1.5) /patient-year during periods with AHRE burden <1hour/day and 2.0 (95%CI:1.5-2.6) /patient-year during AHRE burden ≥20hours/day periods (p=0.004). Significantly higher values of the combined index were recorded during periods with AHRE burden ≥20 hours/day (in Figure the average combined index– Day 0: alert day). The rate of HF hospitalizations was 0.34 (95%CI:0.15-0.69) /patient-year during IN-alert periods and 0.06 (95%CI:0.02-0.14) /patient-year during OUT-of-alert periods (p<0.001). The IN/OUT-of-alert state incidence rate ratio of HF hospitalizations was 8.59 (95%CI:1.67-55.31) during periods with AHRE burden <1hour/day and 2.70 (95%CI:1.01-28.33) during AHRE burden ≥20hours/day periods. In the Matched non-AHRE group, the rate of HF hospitalizations was 0.29 (95%CI:0.12-0.60) /patient-year during IN-alert periods, and 0.04 (95%CI:0.02-0.08) /patient-year during OUT-of-alert periods (p<0.001). The incidence rate ratio was 7.11 (95% CI: 2.19-22.44). Conclusions: Patients seemed more exposed to alerts during periods of AF. The ability of the algorithm to identify increased risk of HF events was confirmed during AF, despite a lower IN/OUT-of-alert incidence rate ratio when compared to non-AF periods and non-AF patients.