Andrea Morotti, MD
Many patients experiencing cryptogenic stroke with an embolic pattern lack a documented source of thromboembolism, even after an extensive diagnostic workup and prolonged follow-up. In particular, atrial fibrillation (AF) is detected in less than half of these patients. Increasing evidence suggested that atrial dysfunction may lead to thromboembolism independently of AF. In this large, multicenter prospective study, Dr. Kamel and colleagues explored the association between markers of atrial cardiopathy and the risk of incident ischemic stroke.
Patients aged > 65 were prospectively enrolled and followed with phone calls twice a year matching the data with Medicare claims. The main exclusion criteria were as follows: active cancer, severe dependency, previous ischemic or hemorrhagic stroke and known AF. P-wave terminal force in ECG lead V1 (PTFV1), N terminal pro B type natriuretic peptide (NT-proBNP), left atrial dimension on echocardiogram and incident AF were the exposures of interest. The association between these markers of atrial cardiopathy and the risk of ischemic stroke was investigated with Cox proportional Hazards models.
During a median follow-up of nearly 13 years, 585 (15.7%) of the 3723 enrolled subjects experienced an ischemic stroke. PTFV1 (hazard ratio per 1000 μV*ms 1.04), log-transformed NT-proBNP (hazard ratio per doubling of NT-proBNP 1.09) and incident AF (hazard ratio 2.04) were independently associated with increased risk of ischemic stroke. Conversely, left atrial size was not a predictor of incident ischemic stroke.
The main limitation of the study is the lack of standardized prolonged monitoring of heart rhythm, leading to possible underestimation of AF burden. AF remained anyway the strongest predictor of future ischemic stroke, but the association between atrial cardiopathy markers and ischemic stroke raised the intriguing hypothesis that thromboembolism from the left atrium may occur also in the absence of AF. This may have relevant implications in clinical practice given the availability of safe and effective antithrombotics drugs to reduce the risk of embolic stroke. If prospectively confirmed, robust markers of atrial cardiopathy may be incorporated in commonly used scores to predict the risk of incident ischemic stroke.