Frequency of Interatrial Block in Patients With Sinus Rhythm Hospitalized for Stroke and Comparison to Those Without Interatrial Block

Interatrial block (IAB; P wave ≥110 ms) is a potent correlate of left atrial (LA) enlargement and electromechanical dysfunction and a strong predictor of atrial tachyarrhythmias, in particular, atrial fibrillation. Although these associations increase its risk for embolism, i.e., cardioembolic stroke, such a phenomenon has been inadequately investigated. We investigated 85 general hospital patients who had been admitted to the neurologic unit between January 2003 and December 2004 for embolic stroke. Of those, 66 patients who had electrocardiograms that showed sinus rhythm were evaluated for IAB and categorized as those with IAB and those without (controls). Medical records were then reviewed for common co-morbidities and stroke risk factors, high-resolution carotid artery Doppler ultrasonographic study reports, and 2-dimensional echocardiograms obtained during the current admission for embolic stroke; 40 patients (61%) had IAB. There was a 55% prevalence of LA enlargement (diameter in the parasternal long-axis view ≥40 mm, p <0.001). LA thrombi and/or spontaneous contrast (“smoke”) were noted on echocardiograms in 6 patients with IAB (15%) but not in any of the controls (p = 0.038). Five of those 6 patients with such LA thrombi had dilated LA cavities. In conclusion, IAB could be a risk for embolic stroke due to its known sequelae of LA dilation and electromechanical dysfunction that predispose to thrombosis. If prospective studies prove this to be so, the need for anticoagulation use in such patients should be investigated.