A method of treating tissue is provided, including positioning a stimulation device proximate a phrenic nerve； stimulating the phrenic nerve with the stimulation device； measuring a physiological response to the stimulation； defining a threshold physiological response value based at least in part on the measured physiological response； positioning a thermal treatment element proximate to an arrhythmogenic cardiac tissue region； applying a thermal treatment regimen to the cardiac tissue region with the medical device； measuring a physiological parameter during the thermal treatment regimen application； and conveying the measured physiological parameter to a controller, the controller comparing the measured physiological parameter to the defined physiological response value threshold, the controller adjusting the thermal treatment regimen in response to the comparison of the measured physiological parameter to the defined physiological response value threshold.
