Impedance and Temperature Monitoring Improve the Safety of Closed‐Loop Irrigated‐Tip Radiofrequency Ablation

INTRODUCTION: Irrigated-tip catheter ablation allows larger ablation lesions to be created, but also decreases catheter temperature monitoring accuracy. It is unclear which parameters should be monitored to optimize efficacy and safety during irrigated-tip ablation. METHODS AND RESULTS: Freshly excised hearts from eight male pigs were perfused and superfused using oxygenated swine blood in an ex vivo model. Ablations were performed for 1 minute using one of five different ablation protocols: (1) Temperature Control (42 degrees C 40 W), (2) Fixed Power 20 W, (3) Fixed Power 30 W, (4) Impedance Control (target 10 ohm impedance drop), and (5) Impedance Control (target 20 ohm drop). All ablations were performed with a perpendicular orientation of the catheter to the endocardial surface. Ablation lesions depth was significantly lower in the temperature control group (5.0 +/- 1.7 mm) compared with the fixed power ablation groups (6.5 +/- 1.0 mm for Power 20 W, 6.6 +/- 1.2 mm for Power 30 W). Impedance-controlled ablation created lesions intermediate in depth between fixed power and temperature controlled (6.0 +/- 1.6 for Impedance 10 ohms and 6.2 +/- 1.4 mm for Impedance 20 ohms groups). There was a significantly greater incidence of pops and thrombus formation in the Power 20 W (9/14), Power 30 W (10/14), and Impedance 20 ohms (10/16) groups than the Temperature Control (1/16) and Impedance control 10 ohms (2/16) groups. CONCLUSION: Temperature control improved the safety profile during irrigated-tip ablation in comparison with fixed-power ablations, but resulted in significantly smaller lesions. Impedance-controlled ablation lesions (target 10 ohm drop) created lesions of comparable size to fixed-power ablations with a significantly better safety profile.