DISCUSSION
Point-by-point creation of the ablation lines using externally irrigated ablation catheters in power control mode during PVI remain the standard current procedure through its flexibility and ability to perform extra PV ablation . However, there is still demand for improvement of technologies to make procedure faster and lesions more durable. Introduction of a new ablation system with the possibility of temperature control mode should overcome limitations of standard irrigated tip catheters, lead to deeper and more permanent lesions, and reduce the incidence of the chronic reconnections. The DT Cardiac Ablation System has several features for improved creation of the ablation lesions. The diamond embedded tip of the catheter with very rapid heat diffusion allows for creation of faster lesions and reduced irrigation to 8ml/min. Reduced irrigation with a complex system of surface thermocouples allows the use of temperature control mode with better titration of energy during ablation with variable stability and contact force and subsequently creates lesions more efficiently, reliably, and safely. The composite, dual part tip of the DT catheter enables sensing of high-resolution EGMs, which might be better for monitoring of lesion creation and minimizing collateral injury. It is expected, that ablation with a novel system will be faster and safer with minimizing of pops or char formation.
The TRAC-AF study clearly shows, that despite short RF application time in the majority of patients, durable PVI was achieved with a longterm success rate comparable to patients ablated with standard irrigated tip catheters . Our study confirmed the pilot results of Iwasawa et al with a larger group of patients. We show that temperature-controlled, saline-irrigated RF ablation with the DT Cardiac Ablation System equipped with an array of thermocouples at the tip-tissue interface is very efficient and safe with a high probability of achieving transmural atrial lesions. Preclinical experimental data show that a 75% reduction in voltage was achieved with 13.3 ± 6.0 s of RF, and complete lesion transmurality was achieved in 92.7% of lesions .
A significantly lower total radiofrequency ablation time was seen with the DT catheter compared to AF patients ablated with standard irrigation catheters in other contemporary paroxysmal AF ablation studies, such as the Fire and Ice Study (Cryoballoon or Radiofrequency Ablation for Paroxysmal Atrial Fibrillation) and the Heartlight (CardioFocus, Marlborough, Massachusetts) multicenter clinical trials , see Figure 3.
Total fluoroscopy time was significantly shorter in the DT group as well (9.6 ± 6.6 min for TRACK AF patients, 16,6 ± 17,8 min. and 29.7 ± 21.0 min for Fire and Ice Study and Heartlight resp.), which is well-aligned with the trend to decrease radiation exposure which has been dramatically decreasing over the last decade for PVI. With older technology we exploited our chances to decrease exposure through operator experience, annual case volume, and technology evolution . Contact force catheters are thought to be major contributor to the trend, especially in more lengthy procedures for persistent AF . Inclusion of other modalities in the ablation strategy, such as pre-procedural computed tomography and 3D rotational angiography, has also contributed to lower radiation exposure (11).
DT technology thus further allows to decrease exposure times for patients and attending physicians, further decrease would be possible only by fluorless procedures .
The 12-month rate of freedom from AF of 72.5% is similar to the success rates of catheter ablations with standard irrigated tip catheters , , . This data support noninferiority of the new ablation system regarding efficacy.
From a safety view, the DT catheter seems to be as safe as standard contact force ablation catheters. There were no audible pops, or char formation. There was only one delayed pericardial effusion related to the ablation procedure. Rate of complications nonrelated or possibly related to the investigational device was 4.3% and was comparable with complication rates during catheter ablation with standard irrigated tip catheters
The presented study has several limitations. Our project is the first larger study to deal with the new DT ablation system. The number of patients is limited and the study has nonrandomized, single-arm design. Comparison with other ablation studies is indirect and for a more definitive confirmation of efficacy and safety, a randomized, large study comparing this system with standard irrigated contact force catheters is needed. Such a study which recruited patients with paroxysmal AF has been recently completed and is to be published.