Left Atrial Appendage Function and Stroke Risk.

Abstract

About 30% to 40% of ischemic stroke is of unknown cause.1,2 Recently, biomarkers of atrial dysfunction, or atrial cardiopathy, have been associated with embolic stroke risk even in the absence of atrial fibrillation (AF), suggesting that the presence of AF is not required for left atrial thromboembolism to occur.3 Most left atrial thrombi occur in the left atrial appendage (LAA), but there is limited use of LAA dysfunction parameters, such as LAA flow velocity and morphology, to predict ischemic stroke risk. Here we review the literature on the association between LAA pathology and dysfunction and ischemic stroke, with a focus on patients with unexplained, or cryptogenic, stroke. Each year, at least 200000 people in the United States experience a cryptogenic stroke.1,2 The classification of cryptogenic stroke, a subgroup of stroke of undetermined cause, was conventionally made when the initial stroke evaluation was unrevealing, regardless of whether the evaluation was exhaustive, routine, or incomplete.4 More recently, investigators have used the term embolic stroke of undetermined source in reference to a nonlacunar infarction occurring in the absence of a specific identifiable high-risk stroke mechanism, such as AF, valvular heart disease, or large artery stenosis.5 The idea that such infarctions are caused by a distant source of embolus is supported by findings from the National Institute of Neurological Disorders and Stroke Databank, indicating that undocumented cardiac or aortic sources of embolism were found in about two thirds of patients with cryptogenic stroke on follow-up testing.2 One of the most common mechanisms often found in a delayed fashion after cryptogenic stroke is paroxysmal AF, which is detected in ≤30% of patients with cryptogenic stroke on outpatient heart-rhythm monitoring.6,7 However, more than half of cryptogenic strokes remain a mystery even after long-term …