Relationship between depth of rf destruction of myocardium and initial tissue resistance under various temperature conditions

Objective. The aim of the study is to analyze the efficacy of RF ablation at different temperature conditions of the surgical area. Methods. 20 isolated hearts were studied. To evaluate the effectiveness of radio frequency exposure, use was made of two temperature settings: myocardial normothermia (36.6 °C) and myocardial hypothermia (20 °C). The hearts were placed on the electrophysiology bench heated to 36.6 °C; the ablation depth and temperature of the epicardium, endocardium and myocardium at the exposed points were then measured and evaluated. Tissue impedance was measured before and after RF ablation. RF energy was applied by means of a 40 W unipolar irrigated ball electrode over a period of 7 s. Results. It was found out that under hypothermia the myocardium has low resistance which hinders adequate heating of its deep layers and in this connection there arises a high risk for recovery of cardiomyocyte membrane potentials and for retention of their function. Conclusion. When the ablation time in both temperature settings is the same, RF exposure at low temperatures causes a lesser depth of damage.