Patent ID: 8146603

Claim:
A method for ablating cardiac tissue, said method comprising: advancing a treatment catheter through a patient's vasculature into an atrium of a heart, the treatment catheter comprising an ultrasound emitter disposed near a distal end thereof; positioning the ultrasound emitter to face heart tissue within the left atrium and outside of a pulmonary vein; ablating the heart tissue with ultrasound energy from the ultrasound emitter to form a first lesion outside of a pulmonary vein while rotating the ultrasound emitter about a first rotation axis, wherein the first lesion encircles the ostia of the pulmonary vein, wherein the first lesion is formed without direct contact between the ultrasound emitter and the heart tissue, and wherein the ablating step is performed with the ultrasound energy being directed distally from a distally facing surface of the ultrasound emitter, and wherein the ultrasound energy is initially directed at an inner wall of the heart; sensing a gap distance with a sensor coupled to the treatment catheter, the gap distance extending between the ultrasound emitter and the heart tissue; based on the sensed gap distance, controlling re-positioning of the ultrasound emitter position by adjusting the gap distance between the ultrasound emitter and the heart tissue while maintaining the gap therebetween within an ablation window length, wherein adjusting comprises proximal or distal axial movement of the ultrasound emitter relative to the heart tissue; cooling the ultrasound emitter with fluid wherein the fluid flows past the ultrasound emitter and exits the treatment catheter; and providing a separation between the ultrasound emitter and blood in the atrium to prevent the blood from coagulating on the ultrasound emitter, wherein the separation comprises the fluid.