Clinical and echocardiographic measures governing thromboembolism destination in atrial fibrillation

Although infrequent, embolic occlusion to non-cerebral arteries may result in limb loss, organ failure, and death. The aim of this study was to define clinical and echocardiographic characteristics determining thromboembolism destination in non-valvular atrial fibrillation. An inception cohort of individuals (n=72) were identified with incident peripheral embolism in the setting of non-valvular atrial fibrillation (1995-2005). A randomly selected group of atrial fibrillation related stroke patients (n=100) were identified for comparison. Arteries of the extremities were the most common site of embolism (85%); lower extremity involvement was twice as common compared with the upper extremity. Clinical features distinguishing peripheral embolism from stroke included age>75, heart failure and hypertension. Severe left ventricular dysfunction, spontaneous echo contrast and left atrial thrombus were 2-3 fold more common in peripheral embolism patients. Mean CHADS-2 scores were low and comparable for both groups. By multivariate analysis, age>5 years (hazard ratio [HR] 2.3, 95% confidence interval [CI] 1.3-3.9; p=0.05) was predictive of peripheral embolism. After adjustment for age>75 years, severe left atrial enlargement (HR 1.8, 95% CI 0.99-3.1; p=0.055) and CHADS score (HR 1.2, 95% CI 0.99-1.6; p=0.06) were of borderline significance. In conclusion, several clinical and echocardiographic measures distinguish the clinical presentation of thromboembolism in non-valvular atrial fibrillation. Small emboli are destined to lodge in the cerebral circulation as a result of hydrodynamic, anatomic, and physical factors. Advanced age, atrial enlargement and other co-morbidities may increase the propensity for the formation of larger thrombi which may bypass the carotid orifice merely as a function of size.