Cardiac intervention using high-intensity focused ultrasound: creation of interatrial communication in beating heart of an anesthetized rabbit.

Abstract

Current fetal cardiac intervention for restrictive atrial septum is invasive and technically demanding. We investigated the feasibility of computer-assisted high-intensity focused ultrasound (HIFU) for cardiac intervention on the atrial septum of a beating heart. To create an interatrial communication in the beating heart of nine anesthetized rabbits, the heart was exposed surgically and placed under a water-filled tank, in contact with the tank's membranous base. A HIFU transducer (3.3 MHz) coupled with a diagnostic ultrasound probe (10.0 MHz) was placed in the tank over the beating heart. The focus of the HIFU transducer was set so that it could create a hole in the target area on the atrial septum during the early diastolic phase. HIFU delivery was controlled based on ultrasound images captured with real-time image-recognition software. We attempted to create interatrial communication using HIFU and assessed the cardiac tissue specimen pathologically. In eight of nine rabbits, small holes in the atrial septum were successfully created. Serious complications occurred in two animals: a fatal atrioventricular block in one and a cardiac tamponade in the other. HIFU combined with a computer-assisted imaging system might be useful to create interatrial communication in beating hearts. This procedure may be helpful for making current fetal cardiac intervention less invasive.