Left atrial appendage morphology and the risk of stroke

In patients with non-valvular atrial fibrillation (AF) the risk of stroke is five times higher than in patients with sinus rhythm. Moreover, stroke is likely to be more severe in the AF patient population. Left atrial appendage (LAA) is the most common source of emboli in AF-related stroke. LAA thrombus is present in 15% of AF patients. Therefore, numerous studies aimed to evaluate the role of LAA structure and function in stroke formation. Higher LAA volume and bigger LAA orifice have been reported to be associated with increased risks of stroke. Moreover, not only the size, but also the shape of the LAA influences thrombus formation. The presence of an obvious bend in the proximal part of the dominant LAA lobe, described as chicken wing LAA morphology has been reported to be protective against stroke. However, other studies are not consistent with this finding and there is no consensus about LAA morphology categories. LAA has reservoir, contractile, electric and endocrine functions, that can provide essential information about the risk of clot formation and embolic events. Decreased LAA flow velocity, reflecting lower LAA contractility has been described to be associated with higher stroke risk. All in all, even if the LAA plays an important role in stroke formation, there are controversial literature data, therefore further studies are needed to evaluate the underlying mechanisms.