Atrial Fibrillation Burden and Short-Term Risk of Stroke: A Case-Crossover Analysis of Continuously Recorded Heart Rhythm from Cardiac Electronic Implanted Devices
Background—The temporal relationship of atrial fibrillation (AF) and stroke risk is controversial. We evaluated this relationship via a case-crossover analysis of ischemic strokes in a large cohort of patients with cardiac implantable electronic devices (CIED).
Methods and Results—We identified 9850 patients with CIEDs remotely monitored in the Veterans Administration Health Care System between 2002-2012. There were 187 patients with acute ischemic stroke and continuous heart rhythm monitoring for 120 days pre-stroke (age 69±8.4 years; 98% with an implantable defibrillator). We compared each patient's daily AF burden in the 30 days pre-stroke ("case" period) with their AF burden during days 91-120 pre-stroke ("control" period). Defining positive AF burden as ≥5.5 hours of AF on any given day, 156 patients (83%) had no positive AF burden in both periods and, in fact, had little to no AF; 15 (8%) patients had positive AF burden in both periods. Among the discordant ("informative") patients, 13 exceeded 5.5 hours of AF in the case period but not in the control period, while 3 had positive AF burden in the control but not the case period (warfarin-adjusted odds ratio (OR) for stroke of 4.2 (95% CI: 1.5-13.4). OR for stroke was highest (17.4; 95% CI: 5.39-73.1) in the five days immediately following a qualifying occurrence of AF and decreased towards one as the period following the AF occurrence increased beyond 30 days.
Conclusions—In this population with continuous heart rhythm recording multiple hours of AF had a strong but transient effect raising stroke risk.
- Received December 12, 2014.
- Revision received July 1, 2015.
- Accepted July 2, 2015.