ESTIMATION OF TEMPERATURE DURING RADIOFREQUENCY CATHETER ABLATION USING IMPEDANCE MEASUREMENTS

Temperature monitoring during radiofrequency catheter ablation is usef ul but requires specialized equipment that is not generally available. Previous studies have shown that impedance characteristically decreas es as the result of heating at the electrode-tissue interface. The pur pose of the current study was to determine if impedance changes during radiofrequency current application could be used to estimate endocard ial temperature in patients undergoing catheter ablation. Data from 43 patients treated with a thermistor ablation catheter were retrospecti vely analyzed. The slope of the initial 2 seconds of the impedance cur ve and subsequent changes in impedance were incorporated into an equat ion for estimation of temperature in real-time. The accuracy of this e quation was assessed by prospectively comparing the calculated and mea sured temperatures in 19 patients. Of the 88% of energy applications t hat were suitable for analysis, the average difference between calcula ted and measured temperatures was 5.2 +/- 5.6 degrees C. The average e rror was < 10 degrees C in 89% of applications. The results of this st udy suggest that impedance measurements can be used to quantify tissue temperature in real-time during radiofrequency catheter ablation. Thi s method is sufficiently accurate to allow titration of power output t o produce temperatures in the useful range (50-80 degrees C) while avo iding excessive heating (> 90 degrees C).