Mapping and ablation of nerves within arteries and tissues

Abstract

Method and systems for ablating nerves including measurement of physiological parameters and/or electrical conduction. The method may include ablating nerves within an artery of a patient such as the renal artery and may include advancing a catheter into the artery, measuring a physiological parameter, emitting an electrical pulse into a wall of the artery, measuring the physiological parameter during or after the step of emitting the electrical pulse, ablating the artery wall, then repeating the steps of measuring the physiological parameter, emitting an electrical pulse, and measuring the physiological parameter during or after the step of emitting the electrical pulse. The change in the physiological parameter caused by the electrical pulse before ablation may be compared to the change in the physiological parameter caused by the electrical pulse after ablation to determine the degree of nerve ablation achieved and whether or not to perform further ablation.

1 . A method of ablating nerves within an artery of a patient comprising: a) advancing a catheter into the artery to a first location, the catheter comprising a first stimulation electrode and an ablation element; b) measuring a physiological parameter of the patient; c) after step b, emitting an electrical pulse from the first stimulation electrode into a wall of the artery at the first location; d) measuring the physiological parameter during or after step d); e) ablating the artery wall at the first location after step d); h) after step e), measuring the physiological parameter of the patient at the first location; i) after step h), emitting an electrical pulse from the first electrode at the first location; and j) after step i), measuring the physiological parameter during or after step i). 
     
     
         2 . The method of  claim 1  wherein the physiological parameter comprises blood velocity in the artery or artery diameter at the first location. 
     
     
         3 . The method of  claim 2  wherein the catheter further comprises a blood velocity sensor. 
     
     
         4 . The method of  claim 1  wherein the electrical pulse of step c) has an amplitude and duration equal to that of the electrical pulse of step i). 
     
     
         5 . The method of  claim 1  further comprising calculating a first change in the physiological parameter as a difference between a measurement obtained in step b) and a measurement obtained in step d), and calculating a second change in the physiological parameter as a difference between a measurement obtained in step h) and a measurement obtained in step i). 
     
     
         6 . The method of  claim 5  further comprising calculating a difference between the first change in the physiological parameter and the second change in the physiological parameter. 
     
     
         7 . The method of  claim 6  wherein if the difference between the first change in the physiological parameter and the second change in the physiological parameter is insufficient to indicate a desired amount of ablation, ablating the artery wall at the first location again. 
     
     
         8 . The method of  claim 1  further comprising, after performing steps a)-j): k) repositioning the catheter within the artery to a second location; l) after step k), emitting an electrical pulse from the first electrode at the second location; n) after step l), measuring the physiological parameter at the second location; o) after step n), ablating the artery wall at the second location. 
     
     
         9 . The method of  claim 8  further comprising measuring the physiological parameter at the second location between steps k) and l). 
     
     
         10 . The method of  claim 1  wherein the catheter further comprises a second stimulation electrode, the method further comprising, after performing steps a)-j): k) emitting an electrical pulse from the second stimulation electrode at a second location in the artery; l) after step k), measuring the physiological parameter at the second location, m) after step l), ablating the artery wall at the second location. 
     
     
         11 . The method of  claim 1  wherein the artery is a renal artery. 
     
     
         12 . A method of ablating a nerve within a renal artery of a patient comprising: a) advancing a catheter into the artery, the catheter comprising a stimulation electrode and an ablation element, wherein the stimulation electrode and the ablation element may be one element or may be separate elements; b) positioning the stimulation electrode against a wall of the artery at a first location; c) measuring blood velocity in the artery at the first location; d) emitting an electrical pulse from the first electrode after step c); e) measuring blood velocity in the artery at the second location during or after step d); f) ablating the artery wall at the first location after step e); h) after step f), performing steps b), c), d) and e) a second time; i) if a difference between a first change in blood velocity and a second change in blood velocity is insufficient to indicate a desired amount of ablation, ablating the artery wall at the first location a second time; wherein the first change in the physiological parameter comprises a difference between a blood velocity measurement obtained in step b) and a blood velocity measurement obtained in step d) from the first time those steps were performed, and wherein the second change in blood velocity comprises a difference between a blood velocity measurement obtained in step b) and a blood velocity measurement obtained in step d) from the second time those steps were performed. 
     
     
         13 . The method of  claim 12  wherein the catheter further comprises a blood velocity sensor. 
     
     
         14 . The method of  claim 12  further comprising repeating steps b)-i) at a second location. 
     
     
         15 . The method of  claim 12  wherein the electrical pulse of step d) has an amplitude and duration equal when performed a first time as when performed a second time. 
     
     
         16 . A method of ablating nerves within an artery of a patient comprising the steps of: a) advancing a catheter into the artery, the catheter comprising a first mapping electrode, a second mapping electrode, and an ablation element, wherein the ablation element may be one of the first or second mapping electrodes or may be a separate element; b) positioning the first electrode against a wall of the artery at a first location and positioning the second electrode against the wall of the artery at a second location; c) emitting a first electrical pulse from the first electrode; d) detecting the first electrical pulse in the second electrode, wherein a characteristic of the detected pulse indicates conduction by a nerve; and e) after emitting and detecting the first electrical pulse, ablating the artery wall at or near the first and/or second locations; and f) during or after step e), emitting a second electrical pulse from the first electrode at the first location and detecting the second electrical pulse in the second electrode at the second location. 
     
     
         17 . The method of  claim 16  wherein the step of emitting a second electrical pulse from the first electrode at the first location and detecting the second electrical pulse in the second electrode at the second location occurs during the step of ablating the renal artery wall. 
     
     
         18 . The method of  claim 16  wherein step f) comprises continuously emitting electrical pulses from the first electrode at the first location and detecting the electrical pulses in the second location during step e). 
     
     
         19 . The method of  claim 18  wherein the step e) is stopped when a desired level of ablation is achieved as determined by the detected electrical pulses. 
     
     
         20 . The method of  claim 19  wherein the desired level of ablation is less than complete ablation.