EFFECT OF ACCESSORY PATHWAY LOCATION ON THE EFFICIENCY OF HEATING DURING RADIOFREQUENCY CATHETER ABLATION

During radiofrequency catheter ablation of accessory pathways there is a poor correlation between applied power and temperature at target si tes for catheter ablation. This study was designed to examine the rela tion between power and temperature during radiofrequency catheter abla tion in patients with accessory pathways and to identify the factors t hat affect the efficiency of heating, defined as the ratio of applied power and temperature. Twenty-nine patients underwent radiofrequency c atheter ablation of an accessory pathway. Among 257 energy application s, 108 were applied for ablation of a right-sided accessory pathway, 1 05 for a left-sided accessory pathway, and 44 for a posteroseptal acce ssory pathway. During each application of radiofrequency energy, tempe rature was continually monitored by use of an ablation catheter with a thermistor embedded in the tip of the distal electrode. During some a pplications of energy, fluctuations in temperature were observed. The average power, impedance, temperature, and efficiency of heating for a ll applications of radiofrequency energy was 37 +/- 11 W, 100 +/- 9 oh ms, 53 +/- 9 degrees C, and 1.7 +/- 0.8 degrees C/W (range 0.9 degrees to 6.6 degrees C/W), respectively. The efficiency of heating varied b y location (p < 0.0001), with the greatest efficiency of heating for p osteroseptal energy applications (2.3 +/- 1.2 degrees C/W, which were significantly greater than for left-sided (1.8 +/- 0.8 degrees C/W; p < 0.01) or right-sided (1.2 +/- 0.4 degrees C/W; p < 0.0001) applicati ons. Phasic fluctuation in temperature was observed during 127 (49%) e nergy applications, and the efficiency of heating was 1.5 +/- 0.7 degr ees C/W. For the 130 applications with a stable temperature curve, the efficiency was 1.8 +/- 0.9 degrees C/W (p < 0.02). The mean impedance during energy applications correlated weakly with efficiency (r = 0.2 , p = 0.0012). In conclusion, the efficiency of heating varies accordi ng to the location of the application of radiofrequency energy. Inadeq uate contact, as manifested by fluctuating temperature during ablation , results in less efficient heating.