Risks of appropriate implantable cardioverter defibrillator therapy and cardiac hospitalization are increased around device-detected atrial high-rate episodes longer than 6 minutes

Background The use of cardiac implantable electronic devices (CIEDs) with an atrial lead allows continuous detection of atrial high-rate episodes (AHRE), providing valuable insights into the incidence and clinical relevance of subclinical atrial fibrillation in patients with CIEDs. The prognostic significance of device-detected AHRE in patients with implantable cardioverter defibrillator (ICD) remains poorly understood. Purpose We aimed to evaluate the temporal relationship between device-detected AHRE ≥6 minutes and appropriate ICD shock therapy during long-term follow-up in patients with ICD and predominantly sinus rhythm. Secondary aims were to assess associations to cardiac hospitalization and risk of any appropriate ICD therapy (shocks and antitachycardia pacing (ATP)). Methods We included consecutive patients with dual chamber or cardiac resynchronization therapy ICDs (DDD-ICD or CRT-D) and sinus rhythm, followed by remote monitoring. We compared risk of ICD therapy, cardiac hospitalization and thromboembolism inside each 60-day peri-AHRE period (from 30 days before to 30 days after AHRE detection) with risk outside the peri-AHRE period. Only appropriate ICD therapies were included. Adjusted extended Cox model with time-varying exposure analysis was used to assess potential associations between AHRE, and ICD therapies and hospitalization. Incidence presented as 30-day risk with adjusted hazard ratio [aHR] with 95% confidence interval [CI]. Analyses were adjusted for a priori selected variables; heart failure, use of amiodarone and betablocker, coronary artery disease and primary vs. secondary ICD indication. All-cause mortality was treated as a competing risk. Results We included 882 patients, 81% male. Median age 67 (interquartile range; 59-73) years, 76% had coronary artery disease, and 61% CRT-D. During a median follow-up of 4.4 years (IQR, 3.2-5.9), 438 patients (50%) had at least one AHRE ≥6 min and a total of 18,163 AHRE ≥6 min. The risk of appropriate ICD shock was 0.8% inside the peri-AHRE periods compared with 0.2% outside the peri-AHRE periods (aHR: 3.04 [1.67-5.52], p<0.001). For any appropriate ICD therapy, the risk was increased within the peri-AHRE periods compared to the outside peri-AHRE periods (1.2% vs 0.4%, aHR: 1.71 [1.14-2.57] p=0.01). Cardiac hospitalization was higher within the peri-AHRE periods (3.1% vs 1.0%, aHR: 1.42 [1.05-1.92], p=0.02). Risk of thromboembolic events was low and not different between peri-AHRE periods and outside peri-AHRE periods (0.08% vs. 0.07%, aHR: 0.76 [0.20 to 2.95], p=0.70). Conclusions Risk of appropriate ICD shock is elevated during a 60-day period surrounding AHRE detection. A comparable temporal pattern was noted for cardiac hospitalizations, supporting that AHREs reflect a period of general clinical deterioration.