Presence and Duration of Atrial Fibrillation Detected by Continuous Monitoring: Crucial Implications for the Risk of Thromboembolic Events

AF and the Risk of Thromboembolic Events. Introduction: Asymptomatic atrial fibrillation (AF) can expose patients to the risk of stroke. The primary objective of this study was to assess the incidence of thromboembolic events in relationship with CHADS₂ (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, and prior stroke, or transient ischemic attack) score and AF presence/duration. The secondary objective was to compare intermittent versus continuous monitoring strategies. Methods and Results: Data from patients with an implanted pacemaker and a history of AF were analyzed. Thromboembolic risk was quantified through CHADS₂ score. Three AF groups were considered: patients with <5‐minutes AF on 1 day (AF‐free); patients with >5‐minutes AF on 1 day but <24 hours (AF‐5 minutes); patients with AF episodes >24 hours (AF‐24 hours). Monitoring strategies involving 24‐hour Holter, 1‐week Holter, and 30‐day Holter were simulated. Data from 568 patients continuously monitored for 1 year were analyzed: 171 (30%) had CHADS₂ score = 0; 269 (47%) had CHADS₂ score = 1; 111 (20%) had CHADS₂ score = 2; and 17 (3%) had CHADS₂ score ≥ 3. During follow‐up, 14 patients (2.5%) had an ischemic thromboembolic event. AF‐24 hours patients numbered 223 (39.2%); AF‐5 minutes, 179 (31.5%); and AF‐free, 29.2%. By combining AF presence/duration with CHADS₂ score, two subpopulations with markedly different risks of events (0.8% vs 5%, P = 0.035) were identified, the former corresponding to AF‐free with CHADS₂≤2, or AF‐5 minutes with CHADS₂≤1, or AF‐24 hours with CHADS₂= 0. The mean sensitivity in detecting an AF episode lasting >5 minutes was 44.4%, 50.4%, and 65.1% for 24‐hour Holter, 1‐week Holter, and 1‐month Holter monitoring, respectively. Conclusion: In patients with recurrent AF episodes, risk stratification for thromboembolic events can be improved by combining CHADS₂ score with AF presence/duration. (J Cardiovasc Electrophysiol, Vol. 20, pp. 241‐248, March 2009)