Atrial Fibrillation Burden and Short-Term Risk of Stroke

Abstract

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. Methods and Results— We identified 9850 patients with cardiac implantable electronic devices remotely monitored in the Veterans Administration Health Care System between 2002 and 2012. There were 187 patients with acute ischemic stroke and continuous heart rhythm monitoring for 120 days before the stroke (age, 69±8.4 years; 98% with an implantable defibrillator). We compared each patient’s daily AF burden in the 30 days before stroke (case period) with their AF burden during days 91 to 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, whereas 3 had positive AF burden in the control but not in the case period (warfarin-adjusted odds ratio for stroke, 4.2; 95% confidence interval, 1.5–13.4). Odds ratio for stroke was highest (17.4; 95% confidence interval, 5.39–73.1) in the 5 days immediately after a qualifying occurrence of AF and decreased toward 1.0 as the period after 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.

Uncovering Atrial Fibrillation Beyond Short-Term Monitoring in Cryptogenic Stroke Patients

“…Studies performed in patients with cardiac implanted electronic devices have shown that their stroke risk is significantly increased in the presence of device-detected atrial arrhythmias, despite the lack of a close temporal relationship between the detected arrhythmia and occurrence of stroke. [32][33][34] Although we are unable to discern whether the ICM detected incident or prevalent AF, these patients have CHADS 2 and CHA 2 DS 2-VAS C scores of at least 2 and, therefore, are indicated for OAC therapy upon AF detection, regardless of its relationship to the index event. 35 Preventive therapies are usually directed at identifiable causes of future stroke.…”

Rates of Atrial Fibrillation in Black Versus White Patients With Pacemakers

“…Because pacemakers in our cohort were not implanted primarily to screen for AF, some cases of brief AF captured on pacemaker interrogations may have been considered clinically insignificant and thus not documented. This is especially true given ongoing uncertainty about the pathogenic significance of brief AF episodes 28, 29. If failure to document AF occurred with similar frequency among black and white patients, nondifferential misclassification of diagnoses would have served to introduce a conservative bias by attenuating associations between race and outcomes and thereby reducing our ability to detect differences in AF rates between white and black patients.…”

Atrial Fibrillation and the Risk of Stroke

“…The current study by Dr Turakhia et al 12 addresses this issue by evaluating continuous cardiac rhythm monitoring over 120 days before an ischemic stroke in 187 patients. The unique study design and robust analysis deserve additional examination.…”