Abstract
BACKGROUND: While atrial fibrillation (AF) is a key risk factor for stroke, recent studies have suggested that atrial cardiomyopathy may also increase stroke risk in the absence of AF. This study aimed to evaluate genetic determinants for left atrial (LA) function and volumes and risk of stroke. METHODS AND RESULTS: Polygenic scores (PGSs) for LA measures were constructed and used in 380 017 individuals in the UK Biobank, without history of ischemic stroke, systemic arterial embolism, or AF at enrollment. Risk of ischemic stroke was estimated using time-to-event models, considering all-cause death and incident AF as competing events. Systemic arterial embolism was investigated as a secondary end point. The PGS for LA passive emptying fraction was associated with risk of ischemic stroke. Individuals with a PGS for LA passive emptying fraction in the lowest quartile had a hazard ratio (HR) of 1.12 for ischemic stroke compared with those in the top quartile (P=0.004). These associations were robust in a subgroup free of prevalent cardiovascular disease at baseline (HR for lowest quartile versus top quartile, 1.22; P<0.001). No associations were found for 4 other PGSs for LA measures or for risk of systemic arterial embolism. Two-sample Mendelian randomization was conducted between LA measures and cardioembolic stroke and indicated a protective effect of higher LA functional measurements. CONCLUSIONS: The PGS for LA passive emptying fraction was significantly associated with incident ischemic stroke when considering AF as a competing risk. Consistent results were found in Mendelian randomization analyses. These findings suggest that atrial dysfunction may influence stroke risk independently of AF.