Chronic histological transmurality of high-intensity focused ultrasound ablation.

We evaluated histologic results for surgical left maze with an high-intensity focused ultrasound (HIFU) energy source. Two patients came to our attention 6 and 48 months, respectively, after ablation concomitant to a valve procedure. Tissue specimens, obtained from the lesion site on the mitral isthmus and from the "box lesion" around the pulmonary veins were analyzed histologically. A complete transmural lesion was found in all specimens. Chronic lesions exhibited replacement of the muscular band with connective tissue. The atrial wall maintained normal thickness and vascularization. HIFU ablation represents an acceptable energy source to create transmural lesions on the beating human left atrium.