The ability to deliver configurable myocardial lesions was noted as a critical factor to the success of atrial fibrillation (AF) treatment. This article considers the implementation of time reversal acoustics (TRA) principles for ultrasound focusing using an AF cardiac catheter developed for pulmonary vein isolation. Experiments conducted with a single transmitting channel demonstrated that a catheter balloon could be used as an acoustic reverberator to enable focusing and steering of ultrasound short pulses in the TRA mode. The spatial effectiveness of the TRA focusing was improved using a catheter balloon of irregular, asymmetric shape and using a binary mode of ultrasound radiation. The experiments demonstrated the ability of steering the focal point over several millimeters without degradation of the focusing quality. An ability of the TRA mode to produce suitable therapeutic application focusing of long continuous ultrasonic signals was characterized in a theoretical model. (E-mail: yegorasha@yahoo.com).