By Luigi Di Biase
Atrial fibrillation is a substantial cause of morbidity and mortality. It increases the risk of stroke, other embolic complications, congestive heart failure, and death. Although cardiac vegetation, valvular disease, dilated cardiomyopathy, atrial septal aneurysm, atrial septal defect, patent foramen ovale, atheroma and cerebral vascular disease could be responsible for stroke; left atrial appendage thromboembolism represents the dominant etiology of stroke in patients with atrial fibrillation.
Several scores have been developed to identify patients with atrial fibrillation at a higher risk for stroke. The CHADS score, the CHADS2 score, and more recently, the CHADSvasc score represent the most utilised classification to guide the identification and the decision on oral anticoagulation in these patients. Although these scores have an important predictive value, we still have patients with a low score that experience stroke.
Our study (Di Biase et al. J Am Coll Cardiol. 2012; 60(6):531-8) sought to contribute to the field of atrial fibrillation and stroke prevention with an original observation. We quantitatively studied various morphologic parameters of the left atrial appendage in 932 patients with drug-refractory atrial fibrillation, in USA and Italy, who were planning to undergo catheter ablation. We used computed tomography and magnetic resonance imaging to categorise different left atrial appendage morphologies and we tried to correlate the morphology with the history of stroke/transient ischaemic attack (TIA). The left atrial appendage was classified as Chicken Wing, Cactus,Windsock and Cauliflower (figures), based on its morphologies. Interestingly, around 50% of the general population had Chicken Wing morphology.
After controlling for CHADS2 score, gender and atrial fibrillation type, the Chicken Wing morphology was found to be a protective left atrial appendage morphology from prior TIA/ stroke 2.95 (95% CI 1.75-4.99, p=0.041). When compared to the Chicken Wing morphology, Cactus were four times (OR 4.1, 95%, p= 0.046) more likely to have prior stroke/TIA; Windsock five times (OR 4.8, p=0.038) and Cauliflower eight times (OR 8.0, p=0.056).
Moreover, the rate of stroke/TIA across Chicken Wing and non-Chicken Wing morphologies was confirmed in patients with a CHADS2 score 0–1. This is clinically relevant since these are the patients with the lower stroke risk in the general population. Essentially, even in the CHADS2 score 0–1 patients, the non-Chicken Wing morphology increased the risk of prior stroke/TIA more than six fold compared to the Chicken Wing left atrial appendage morphology.
Our study suggests that patients presenting with the Chicken Wing morphology are less likely to have an embolic event even after controlling for comorbidities. If confirmed by further studies, these results could have a relevant impact on the oral anticoagulation management and occlusion device management of patients with an intermediate risk for stroke.
Luigi Di Biase is associate professor of Medicine (Cardiology) with Albert Einstein Medical School at Montefiore Hospital, New York, USA, and senior researcher at Texas Cardiac Arrhythmia Institute, St David’s Medical Center, Austin, USA.