Frequency of steam-pops
Our analysis suggests that high power, high contact force, long RF duration and large impedance decrease were independent predictors of steam-pop, which is consistent with previous studies (6-9). Additionally, our study demonstrated that parallel catheter placement was positively associated and use of the FlexAbilityTMSE catheter was negatively associated with steam-pops. The safety of the TactiCathTM SE catheter has been shown in a randomized controlled clinical study for paroxysmal atrial fibrillation patients (10). However, the superiority of the FlexAbilityTM SE catheter in avoiding steam-pops was demonstrated in the present study (20W:0% 30W:1.1% 40W: 12.2% in FlexAbilityTMSE, and 20W:0% 30W:8.9% 40W:57.8% in TactiCathTM SE), whilst the incidence of steam-pops with the TactiCathTM SE catheter was similar to the previous reports of TactiCathTM Quartz catheter (Abbott, St. Paul, MN) and IntellaNav MiFi OI catheter (Boston Scientific, Marlborough, MA) (11,12).
Since temperature control plays an essential role in preventing steam-pops and char formation, the FlexAbilityTM SE catheter benefits from a high temperature control rate. Although parallel catheter placement was an independent predictor of steam-pop in our study, this finding has not yet been confirmed by other studies. One study reported that greater tissue heating with a perpendicular compared to parallel catheter placement is accompanied by increased incidence of steam pops (13). In contrast, larger lesion volume and larger impedance decrease, known as predictors of steam pop, have been observed more frequently with a parallel than perpendicular catheter placement in several studies (14,15).
Although the ultimate reason for the higher incidence of steam-pops with a parallel catheter placement in our study is unknown, we propose the following possibilities. With the TactiCathTM SE catheter, the current density is known to be higher at the proximal region of the tip than the distal region. When the catheter is placed parallel to the tissue, the area of high current density connects with the tissue. In the TactiCathTM SE catheter, a lower incidence of RF regulation based on the temperature-control setting may result in a higher average power with parallel catheter placement, leading to increased incidence of steam pops. However, the incidence of steam-pops with the FlexAbilityTM SE catheter was generally low, and further studies including tissue temperature monitoring are required to better understand the impact of catheter contact angle.