Cooled microwave pulmonary denervation

Abstract

A device and method is disclosed for creating a lesion in tissue in a vicinity of a bronchus that contains nerve trunks, thereby thermally damaging the nerve trunks, while protecting the bronchus from injury. A catheter carrying a microwave antenna is positioned within the bronchus. Cooling fluid is circulated around the microwave antenna in thermal contact with the mucosa wall of the bronchus. Power is supplied to the microwave antenna to cause microwave energy to be emitted from the microwave antenna. The power supplied to the microwave antenna and the cooling fluid circulated around the microwave antenna are controlled to cause nerve trunks in the tissue in the vicinity of the bronchus to be heated to a temperature sufficient to cause thermal damage while the mucosa wall is maintained at a temperature where thermal damage does not occur.

1 . A catheter configured to create a lesion in tissue in a vicinity of a bronchus that contains nerve trunks, thereby thermally damaging the nerve trunks, while protecting the bronchus from injury, the catheter comprising:
 a catheter body having at least one fluid passage therein;   a balloon in communication with the at least one fluid passage to receive cooling fluid for inflating the balloon into a shape that surrounds the catheter body and contacts a mucosa wall of the bronchus when the catheter body is positioned in the bronchus, so that the catheter body is surrounded by the balloon when inflated at both a proximal end and a distal end of the balloon and the bronchus is occluded, the cooling fluid having a temperature that is less than basal body temperature; and   a microwave antenna carried by the catheter, spaced from a wall of the balloon when inflated, the microwave antenna being connectable to a microwave generator to supply power to the microwave antenna to cause microwave energy to be emitted from the microwave antenna, thereby heating the nerve trunks in the tissue in the vicinity of the bronchus to a temperature sufficient to cause thermal damage while the mucosa wall of the bronchus is maintained at a temperature above freezing where thermal damage does not occur by virtue of circulation of cooling fluid in the balloon around the microwave antenna,   wherein the microwave antenna comprises at least one antenna coil wound around an outside of a coaxial cable, and the balloon surrounds an entire length of the at least one antenna coil.   
     
     
         2 . The catheter of  claim 1 , further comprising heat shrink material around the at least one antenna coil to separate the at least one antenna coil from the cooling fluid in the balloon. 
     
     
         3 . The catheter of  claim 1 , wherein the at least one antenna coil comprises a single antenna coil connected to a center conductor of the coaxial cable at a first location. 
     
     
         4 . The catheter of  claim 1 , wherein the at least one antenna coil comprises:
 a first antenna coil connected to a center conductor of the coaxial cable at a first location; and   a second antenna coil connected to an outer conductor of the coaxial cable at a second location.   
     
     
         5 . The catheter of  claim 1 , wherein the balloon is configured such that the shape of the balloon when inflated causes the microwave antenna to be positioned offset from a radial center of the balloon, with a first portion of the balloon that is configured to face in a direction toward the nerve trunks having a first radial thickness, and a second portion of the balloon that is configured to face in a direction away from the nerve trunks having a second radial thickness greater than the first radial thickness. 
     
     
         6 . The catheter of  claim 1 , wherein the lesion is formed at a distance between 1.5 and 2.5 millimeters from the mucosa wall. 
     
     
         7 . The catheter of  claim 1 , wherein a central portion of the lesion where a maximum temperature is achieved includes the nerve trunks contained in the bronchus. 
     
     
         8 . The catheter of  claim 7 , wherein the maximum temperature is at least 50° C. 
     
     
         9 . The catheter of  claim 1 , wherein the microwave antenna is configured to produce a specific absorption rate (SAR) pattern having a single peak in a central region of the microwave antenna. 
     
     
         10 . The catheter of  claim 1 , wherein the microwave antenna is configured to produce a specific absorption rate (SAR) pattern having two peaks spaced apart from one another. 
     
     
         11 . The catheter of  claim 1 , further comprising at least one temperature sensor carried by the catheter to sense a temperature near the mucosa wall. 
     
     
         12 . A method of creating a lesion in tissue in a vicinity of a bronchus that contains nerve trunks, thereby thermally damaging the nerve trunks, while protecting the bronchus from injury, the method comprising:
 positioning a catheter carrying a microwave antenna within the bronchus, the microwave antenna being spaced from a mucosa wall of the bronchus;   inflating a balloon having a first axial length with circulating cooling fluid flowing between the microwave antenna and the mucosa wall of the bronchus in thermal contact with the mucosa wall of the bronchus, the balloon being inflated to completely surround the microwave antenna and to occlude the bronchus, and the cooling fluid having a temperature that is less than basal body temperature; and   supplying power to the microwave antenna to cause microwave energy to be emitted from the microwave antenna along a second axial length that is less than the first axial length of the balloon;   wherein the power supplied to the microwave antenna and the cooling fluid circulated around the microwave antenna are controlled to cause the tissue in the vicinity of the bronchus to be heated to a temperature for a time sufficient to cause thermal damage while the mucosa wall is maintained at a temperature above freezing where thermal damage does not occur.   
     
     
         13 . The method of  claim 12 , wherein the microwave antenna is positioned in the bronchus offset from a radial center of the balloon and the bronchus, with a first portion of the balloon facing toward the nerve trunks having a first radial thickness, and a second portion of the balloon facing away from the nerve trunks having a second radial thickness greater than the first radial thickness. 
     
     
         14 . The method of  claim 12 , wherein the tissue in the vicinity of the bronchus that contains nerve trunks is heated to a temperature of at least 50° C. for a time of no greater than 120 seconds. 
     
     
         15 . The method of  claim 14 , wherein the mucosa wall is maintained at a temperature below 40° C. 
     
     
         16 . The method of  claim 12 , wherein the power supplied to the microwave antenna and the cooling fluid circulated around the microwave antenna are controlled to maintain smooth muscle and cartilage adjacent to the mucosa wall at a temperature above freezing where thermal damage does not occur. 
     
     
         17 . The method of  claim 16 , wherein the smooth muscle and cartilage adjacent to the mucosa wall is maintained at a temperature below 43° C. 
     
     
         18 . The method of  claim 12 , the lesion is formed at a distance between 1.5 and 2.5 millimeters from the mucosa wall. 
     
     
         19 . The method of  claim 18 , wherein tissue at a distance of greater than 2.5 millimeters from the mucosa wall is not thermally damaged. 
     
     
         20 . The method of  claim 12 , further comprising measuring a temperature near the mucosa wall with at least one temperature sensor carried by the catheter.