Simultaneous Control of Power and Irrigation During Ablation

Abstract

Apparatus, consisting of a probe configured to be inserted into contact with a myocardium, and an electrode attached to the probe. A temperature sensor, incorporated in the probe, is configured to output a temperature signal. A pump irrigates the myocardium, via the probe, with an irrigation fluid at a controllable rate, and a radiofrequency (RF) signal generator applies RF power via the electrode to the myocardium, so as to ablate the myocardium. The apparatus also has processing circuitry that measures a temperature of the probe, based on the temperature signal, while the RF power is applied and, when the measured temperature exceeds a preset target temperature, iteratively reduces the RF power applied by the signal generator and concurrently iteratively varies a rate of irrigation of the irrigation fluid provided by the pump, until the measured temperature is reduced to the preset target temperature.

1 .- 8 . (canceled) 
     
     
         9 . A method, comprising:
 inserting a probe into contact with a myocardium;   attaching an electrode to the probe;   incorporating a temperature sensor in the probe;   irrigating the myocardium, via the probe, with an irrigation fluid at a controllable rate;   applying radiofrequency (RF) power via the electrode to the myocardium, so as to ablate the myocardium;   measuring a temperature of the probe while the RF power is applied, using the temperature sensor; and,   when the measured temperature exceeds a preset target temperature, iteratively reducing the RF power based upon a preset power delta and concurrently iteratively varying a rate of irrigation of the irrigation fluid until the measured temperature is reduced to the preset target temperature.   
     
     
         10 . The method according to  claim 9 , and comprising, when the measured temperature does not exceed the preset target temperature, iteratively increasing the RF power until the measured temperature is equal to the preset target temperature. 
     
     
         11 . The method according to  claim 9 , wherein the controllable rate comprises an idle irrigation rate and a high irrigation rate greater than the idle irrigation rate, and wherein varying the rate of irrigation comprises reducing the rate by pulsing the rate from the high irrigation rate to the idle irrigation rate and returning to the high irrigation rate. 
     
     
         12 . The method according to  claim 11 , wherein pulsing the rate comprises receiving a single pulse of the irrigation fluid at the idle irrigation rate and smoothing the rate of irrigation at the probe to be 50% of the high irrigation rate. 
     
     
         13 . The method according to  claim 9 , wherein the controllable rate comprises an idle irrigation rate and a high irrigation rate greater than the idle irrigation rate, and wherein varying the rate of irrigation comprises increasing the rate by pulsing the rate from the idle irrigation rate to the high irrigation rate and returning to the idle irrigation rate. 
     
     
         14 . The method according to  claim 13 , wherein pulsing the rate comprises receiving a single pulse of the irrigation fluid at the high irrigation rate and smoothing the rate of irrigation at the probe so that the rate increases by between 50% and 100% of the idle irrigation rate. 
     
     
         15 . The method according to  claim 9 , wherein the controllable rate comprises an idle irrigation rate and a high irrigation rate greater than the idle irrigation rate, the method further comprising, when the measured temperature is less than a low target temperature below the preset target temperature, reducing the rate of irrigation from the high irrigation rate to the idle irrigation rate. 
     
     
         16 . The method according to  claim 15 , and comprising, when the measured temperature is between the preset target temperature and the low target temperature, maintaining the rate of irrigation at the high irrigation rate.