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.