Low-temperature (50°C) radiofrequency applications caused transient accessory pathway block and predicted permanent ablation success with >90% sensitivity and positive predictive value.
Observational (n=15)
Does low-temperature (50 degrees C) radiofrequency application predict successful accessory pathway ablation sites while minimizing permanent injury in patients undergoing AP ablation?
Low-temperature (50°C) radiofrequency applications can safely and accurately predict successful sites for accessory pathway ablation by inducing reversible conduction block.
Effect estimate: Sensitivity >90%
BACKGROUND: Temperatures near 50 degrees C can cause reversible loss of excitability in myocardial cells. METHODS AND RESULTS: Low-temperature, short-duration applications of radiofrequency energy were used to determine the adequacy of electrophysiological mapping of accessory pathway (AP) locations in 15 patients at 27 target sites using a closed-loop, temperature-controlled generator set to 50 degrees C. Energy was delivered until evidence of conduction block, or for a maximum of 10 seconds. If AP block occurred, a full 70 degrees C set point radiofrequency application was delivered to the same site. In the absence of AP block, tests with higher temperature settings (60 degrees C and 70 degrees C) were delivered to determine if inadequate temperature or catheter position led to failure of the initial 50 degrees C test. At 15 successful target sites where permanent AP block was achieved, the 50 degrees C test resulted in AP block in 14 (93%). Conduction returned in 13 of 14 APs after radiofrequency power was turned off. The time to block for the 70 degrees C applications was significantly shorter than for the 50 degrees C tests, and the peak temperature achieved was significantly higher. At unsuccessful sites where permanent AP block was not achieved, no block was induced with 11 of 12 tests at 50 degrees C, 6 of 6 tests at 60 degrees C, and 1 of 2 tests at 70 degrees C, suggesting that failure was due to incorrect catheter position. The sensitivity and positive predictive values of a 50 degrees C test identifying a successful site were > 90%. CONCLUSIONS: Low-temperature radiofrequency applications that cause transient AP block predict permanent success when a higher-temperature application is delivered at the same site. The time to achieve conduction block is a function of the temperature set point, and low-temperature tests produce reversible conduction block, suggesting minimal permanent injury.
Côté et al. (Thu,) conducted a observational in Accessory pathway (n=15). Low-temperature radiofrequency energy vs. Higher temperature settings (60 degrees C and 70 degrees C) was evaluated on Prediction of successful ablation site (AP block) (Sensitivity >90%). Low-temperature (50°C) radiofrequency applications caused transient accessory pathway block and predicted permanent ablation success with >90% sensitivity and positive predictive value.