Cardiac ablation devices

Abstract

A cardiac ablation device treats atrial fibrillation by directing and focusing ultrasonic waves into a ring-like ablation region (A). The device desirably is steerable and can be moved between a normal disposition, in which the ablation region lies parallel to the wall of the heart for ablating a loop-like lesion, and a canted disposition, in which the ring-like focal region is tilted relative to the wall of the heart, to ablate only a short, substantially linear lesion. The ablation device desirably includes a balloon reflector structure ( 18, 1310 ) and an ultrasonic emitter assembly ( 23, 1326 ), and can be steered and positioned without reference to engagement between the device and the pulmonary vein or ostium. A contrast medium (C) can be injected through the ablation device to facilitate imaging, so that the device can be positioned based on observation of the images.

1 - 82 . (canceled) 
     
     
         83 . An apparatus for applying ultrasonic energy to cardiac tissue, the apparatus comprising:
 a catheter;   an ultrasonic transducer disposed on the catheter, the ultrasonic transducer configured to emit ultrasonic energy; and   a plurality of expandable structures disposed around a circumference of the catheter, the expandable structures configured to contact an anatomical structure when expanded to position the ultrasonic transducer relative to the cardiac tissue,   wherein each of the expandable structures is independently expandable.   
     
     
         84 . The apparatus of  claim 83 , wherein the plurality of expandable structures are arranged around the circumference of the catheter when expanded. 
     
     
         85 . The apparatus of  claim 83 , wherein the plurality of expandable structures are arranged around the ultrasonic transducer when expanded. 
     
     
         86 . The apparatus of  claim 83 , wherein the expandable structures comprise balloons. 
     
     
         87 . The apparatus of  claim 86 , wherein the catheter further comprises a plurality of lumens extending from a proximal end of the catheter to corresponding balloons. 
     
     
         88 . The apparatus of  claim 87 , wherein each balloon is configured to be independently expanded by introducing an aqueous liquid to the balloon through the corresponding lumen. 
     
     
         89 . The apparatus of  claim 88 , wherein the aqueous liquid comprises a contrast medium. 
     
     
         90 . The apparatus of  claim 87 , wherein each balloon is configured to be independently expanded by introducing a gas to the balloon through the corresponding lumen. 
     
     
         91 . The apparatus of  claim 83 , wherein at least one of the plurality of expansible structures is configured to reflect ultrasonic energy emitted from the ultrasonic transducer when expanded. 
     
     
         92 . The apparatus of  claim 83 , wherein at least one of the plurality of expansible structures is configured to be non-reflective to ultrasonic energy emitted from the ultrasonic transducer when expanded. 
     
     
         93 . The apparatus of  claim 83 , wherein the catheter further comprises a guidewire lumen. 
     
     
         94 . A method for applying ultrasonic energy to cardiac tissue, the method comprising:
 advancing a catheter adjacent to the cardiac tissue, the catheter having an ultrasonic transducer and a plurality of expandable structures disposed around a circumference of the catheter;   expanding a first expandable structure of the plurality of expandable structures such that the first expandable structure contacts an anatomical structure to position the ultrasonic transducer relative to the cardiac tissue,   wherein each of the expandable structures is independently expandable.   
     
     
         95 . The method of  claim 94 , further comprising expanding a second expandable structure of the plurality of expandable structures such that the second expandable structure contacts an anatomical structure to position the ultrasonic transducer relative to the cardiac tissue. 
     
     
         96 . The method of  claim 95 , wherein the catheter further comprises a first lumen extending from a proximal end of the catheter to the first expandable structure and a second lumen extending from the proximal end of the catheter to the second expandable structure,
 wherein expanding the first expandable structure comprises introducing a fluid to the first expandable structure through the first lumen, and   wherein expanding the second expandable structure comprises introducing a fluid to the second expandable structure through the second lumen.   
     
     
         97 . The method of  claim 94 , further comprising emitting ultrasonic energy from the ultrasonic transducer to cause shrinkage of the cardiac tissue. 
     
     
         98 . The method of  claim 97 , further comprising reflecting the ultrasonic energy emitted from the ultrasonic transducer using the expanded first expandable structure. 
     
     
         99 . The method of  claim 94 , wherein the plurality of expandable structures are arranged around the circumference of the catheter when expanded. 
     
     
         100 . The method of  claim 94 , wherein the plurality of expandable structures are arranged around the ultrasonic transducer when expanded. 
     
     
         101 . The method of  claim 94 , wherein the first expandable structures comprises a balloon, the expanding comprising inflating the balloon with an aqueous liquid. 
     
     
         102 . The method of  claim 101 , further comprising deflating the balloon and removing the apparatus from a human.