Cardiac Ultrasound in Stroke Investigation

This chapter describes various aspects of cardiac ultrasound in stroke investigation. The value of transthoracic echocardiography (TTE) for stratification of thromboembolic risk in patients with atrial fibrillation was established in the Stroke Prevention in Atrial Fibrillation trial. TTE also plays a major role in the assessment of stroke risk in patients with acute myocardial infarction prone to development of left ventricular mural thrombus. Transesophageal echocardiography (TEE) is increasingly employed as a window on pathogenetic processes related to thromboembolism not readily accessible by other diagnostic technology. In comparison with TTE, visualization of the heart by TEE offers the advantages of higher transducer frequency and proximity, resulting in improved imaging resolution of the left atrium, appendage, endocardium, and aortic intima. Optimal ultrasound examination of the left atrial appendage is obtained with biplane TEE. Although adequately visualized by routine gray-scale imaging, the B-color modality may allow more confident differentiation of thrombi from the ruffled wall. False readings produced by a small pectinate muscle or appendicular rugae can be minimized by thorough interrogation in multiple planes and by B-color imaging. It is found that TEE has been helpful in younger patients with stroke without clinical evidence of heart disease, though the yield is greater in the presence of TTE abnormalities.