P4-72: Catheter based cryoablation and radiofrequency ablation for atrial fibrillation results in conductive heat transfer from and to the esophagus

Abstract

Left atrial ablation using radiofrequency (RF) energy has been associated with injury to the esophagus (ESO). Cryoablation (CRYO) is an alternative ablation modality for pulmonary vein isolation (PVI); but, the character of heat transfer from the ESO in humans during focal CRYO has not been described. We report on luminal ESO temperature (LET) changes in 10 patients (54 ± 9.8 y) undergoing PVI using a hybrid RF/CRYO ablation strategy. RF ablation was done with an 8mm tip catheter (30-65W) and CRYO was done with a 6 mm cryo catheter (−75 °C). LET was recorded with a temperature probe advanced to the level of the ablation catheter during all left atrial lesions. RF ablation in proximity to the ESO resulted in a rise in LET in all patients (26/683 lesions ≥ 0.5 °C rise, ΔT = 0.67 ± 0.3 °C). RF was discontinued when a temperature rise was evident, and these areas were marked for CRYO. Each CRYO was continued for 250 s regardless of observed LET. An average of 16.8 ± 14.3 CRYO lesions per patient were placed along the posterior left atrium where ablation was required adjacent to the ESO. All patients exhibited ESO cooling during CRYO. For 61 of 168 CRYO lesions, LET decreased at least 0.1 °C. Temperatures declined up to 15.6 °C from baseline (2.1 ± 3.1 ° C, mean ± SD). Minimum LET occurred after discontinuation of CRYO in 33% of lesions. The lowest LET recorded was 21.0 °C and the largest temperature drop after discontinuation of CRYO was 1.6 °C. In locations where RF produced a rapid temperature rise, a rapid temperature decrease was observed with CRYO. All LET changes occurred when CRYO was applied within 2.1 cm of the luminal ESO marker. We conclude that: 1) the relationship between the esophagus and left atrium often favors efficient energy transfer during RF or CRYO ablation; 2) CRYO can produce significant ESO cooling; and 3) similarity in the time course of LET changes during RF or CRYO ablation suggests that conduction is a mechanism for RF to act as a heat source or CRYO to act as a heat sink during left atrial ablation. Further studies are required to assess the character and consequence of energy transfer from the esophagus during catheter based focal CRYO.