CYLINDRICAL ULTRASONIC TRANSDUCERS FOR CARDIAC CATHETER ABLATION

This study was designed to evaluate the feasibility of using cylindric al ultrasound transducers mounted on a catheter for the ablation of ca rdiac tissues, In addition, the effects of ultrasound frequency and po wer was evaluated both using computer simulations and in vitro experim ents, Frequencies of 4.5, 6, and 10 MHz were selected based on the sim ulation studies and manufacturing feasibility, These transducers were mounted on the tip of 7-French catheters and applied in vitro to fresh ventricular canine endocardium, submerged in flowing degassed saline at 37 degrees C, When the power was regulated to maintain transducer i nterface temperature at 90-100 degrees C, the 10-, 6-, and 4.5-MHz tra nsducers generated a lesion depth of 5.9 +/- 0.2 mm, 4.6 +/- 1.0 mm, a nd 5.3 +/- 0.9 mm, respectively. The 10-MHz transducer was chosen for the in vivo tests since the maximum lesion depth was achieved with the lowest power. Two dogs mere anesthetized and sonications were perform ed in both the left and right ventricles, The 10-MHz cylindrical trans ducers caused an average lesion depth of 6.4 +/- 2.5 mm, In conclusion , the results show that cylindrical ultrasound transducers can be used for cardiac tissue ablation and that they may be able to produce deep er tissue necrosis than other methods currently in use.