Radiofrequency ablation using cold saline irrigation allows safe prolonged energy delivery and creates deep lesions

Background Long application time radiofrequency (RF) ablation is useful for ablating arrhythmias originating deep within the myocardium; however, this procedure carries a relatively high risk of steam pop. Purpose This experimental study (approved by our institution) was performed to clarify whether long-duration RF ablation using 4°C cold saline (COLD) irrigation can be performed safely while creating deeper lesions, compared with ablation using room-temperature (RT) catheter irrigation. Methods Healthy porcine hearts (19±2 mm thickness) were prepared as coronary perfusion segments, and unipolar RF ablation (40 W, 20-g contact force) was performed in an experimental setting using either RT or COLD irrigation (15 mL/min) (Figure A). The following three procedures were conducted: 90-second ablation using RT and COLD irrigation in 30 applications each (RT-90, COLD-90), and 120 seconds ablation with COLD irrigation (COLD-120) in another 30 applications. In addition to the longest lesion diameter on the surface (LLD), maximum lesion width (MLW) and lesion depth (LD) beneath the surface were measured in cross-sectioned myocardium after ablation. Results Steam pop: Steam pops occurred in 3/30 (10.0%) applications in the RT-90 but in none of the COLD-90 and COLD-120 (Figure B,C). Incidence of steam pops was larger in RT than in COLD irrigation (3/30 vs. 0/60). Lesions: LLD, MLW and LD in COLD-90 were smaller than those in RT-90. However, those parameters in COLD-90 became larger as the ablation time increased to 120 seconds (COLD-120), and showed no statistical difference between RT-90 and COLD-120 (Figure C). Impedance: The percent total impedance decline (%TID) was smaller in COLD-90 followed by Cold-150 and RT-90 (Figure C). In the RT-90, RF applications associated with steam pops showed greater %TID compared with those without steam pops. Discussion Unlike RT irrigation, COLD irrigation actively cools the subsurface myocardium, where steam pops are likely to occur due to excessive temperature elevation, thereby allowing long application time ablation which enhanced conductive heating to be performed more safely. Conclusions Compared with RT irrigation, COLD irrigation may allow long-duration ablation to be performed more safely while creating deeper lesions and suppressing incidence of steam pops. This simple technique may contribute to improved ablation outcomes for arrhythmias in various clinical settings.