DOES THE BASE-LINE IMPEDANCE MEASUREMENT DURING RADIOFREQUENCY CATHETER ABLATION INFLUENCE THE LIKELIHOOD OF AN IMPEDANCE RISE

Most radiofrequency energy delivery systems provide a baseline (pre-ab lation) impedance measurement; however, the application of this value, particularly in avoiding catheter overheating and coagulum formation, has not been described. We evaluated the ability of the product of th e power output P and the baseline impedance Z (P x Z) to predict the l ikelihood of an impedance rise and coagulum formation during radiofreq uency energy delivery in 62 consecutive patients undergoing successful catheter ablation of the slow atrioventricular (AV) nodal pathway or an accessory pathway. The mean P x Z during the 114 pulses resulting i n an impedance rise was 3,770 +/- 846 W Omega; only 42 impedance rises in 14 patients occurred at a P x Z < 3,500. For comparison, the P x Z during the single radiofrequency pulse that resulted in loss of preex citation or the slow AV nodal pathway in the entire patient group was 3,118 +/- 590 (p = 0.001) and in only 9 patients was the P x Z > 3,500 . This data suggest that adjusting the power during each radiofrequenc y pulse to maintain the P x Z < 3,500 should enable the operator to av oid most impedance rises,