METHODS
The TRAC-AF (ACT DiamondTemp TempeRAture-Controlled and Contact Sensing RF Ablation Clinical Trial for Atrial Fibrillation) trial is a prospective, multi-center, open-label, single-arm study (NCT02821351) that enrolled patients with symptomatic, drug-refractory paroxysmal AF to undergo PVI using a novel catheter with a diamond embedded tip (DiamondTemp Catheter, formerly Epix Therapeutics, Inc., Sunnyvale, CA, now Medtronic, Inc. (Dublin, IR) in March 2019). The study was approved by the institutional review boards at each of the 4 clinical sites. All participants enrolled in this study provided informed consent. Of the 71 patients enrolled in this study, the acute procedure, 3-month PV remapping, and 6 months outcome results were previously reported for 35 patients enrolled in one center (15).
Key inclusion criteria were: (i) age ≥18 years, (ii) recurrent and symptomatic AF with ≥2 episodes in prior 12 months with at least one episode documented by Holter monitoring, (iii) failure of at least one class I-IV anti-arrhythmic drug (AAD), and (iv) able to provide informed consent. Key exclusion criteria were: (i) prior left atrial ablation, (ii) cardiac surgery within prior two months, (iii) intracardiac thrombus on the day of the procedure by transesophageal echocardiography, (iv) active infection, fever, or sepsis, (v) uncontrolled NYHA class III or IV heart failure, (vi) unable or unwilling to take anticoagulants, (vii) women of childbearing age who are pregnant or not willing to use contraception for the duration of the study, and (viii) life expectancy <1 year.
The details of the DiamondTemp (DT) catheter and system have previously been reported (15). Briefly, the DT catheter is 7.5F and has a 4.1 mm composite electrode tip that consists of a two-part platinum-iridium electrode and two industrial grade diamonds that allow the rapid dissipation of heat due to their high thermal diffusivity (Figure 1). The distal aspect of the composite electrode is 0.6 mm and is electrically insulated from the proximal component which allows for high resolution EGM sensing. The rapid heat dissipation allows for a reduced saline irrigation rate of 8 ml/min through 6 irrigation ports. Three proximal and 3 distal thermocouples allow for accurate estimation of tissue temperature. There are two additional proximal ring electrodes. A custom RF generator (EPIX Therapeutics, Santa Clara, California, USA) delivers RF energy in a temperature-control mode.
All ablation procedures were performed under conscious sedation. Procedures were performed using a three-dimensional electroanatomical mapping system (EnSite Velocity, Abbott, Plymouth, Minnesota, USA). Standard double transseptal punctures were performed. The DT catheter was placed within a deflectable sheath (Agilis, Abbott, Plymouth, Minnesota, USA) and 20-pole circular mapping catheter was placed through a second non-deflectable sheath (SL1, Abbot, Plymouth, Minnesota, USA). PVI was performed with standard point-by-point method in a temperature-control mode (limit temperature 60°C, maximum power 50W) until a 75-80% reduction in the split-tip EGM amplitude was achieved. During ablation on the posterior wall of the left atrium, the target temperature was reduced to 55°C. Saline irrigation rate was 2 ml/min during mapping and 8 ml/min during ablation. Ipsilateral PVs were isolated with a wide encircling lesion set (wide area circumferential antral ablation (WACAA), see Figure 2. Additional ablations were permitted in cases of atrial flutter or other concomitant arrhythmias induced during the procedure.
Following ablation, all patients were discharged on oral anticoagulation for at least 3 months. AADs were discontinued at the discretion of the treating physician. Patients were followed with clinic visits at 3 months, 6 months, and 12 months post-procedure and Holter monitoring was conducted at 3 months and 12 months following the procedure.
At 3 months after the index procedure, subgroup of patients from one center underwent a repeat procedure to assess for PV reconnection, regardless of the intervening symptomatology. During this procedure, the durability of PVI was assessed with a circular mapping catheter. If PV reconnection was identified, the DT catheter was used to ablate the site(s) of electric reconnection to achieve re-isolation (15) Eight reablated patients were excluded from evaluation and total number evaluated patients in this work is 63.
Endpoints: The primary effectiveness endpoint was (i) acute procedural success defined as electrical isolation of all clinically releveant PVs with demonstration of block or isolation of signals confirmed after ablation, (ii) freedom from AF during 12 months follow up. The primary safety endpoint consisted of nature and frequency of serious adverse events (SAE) and serious adverse device effects (SADE) during the ablation procedure or within 7 days afterwards. Secondary safety outcome consisted of nature and frequency of SAEs and SADEs up to 12 months post-ablation. Adverse events (AEs) were adjudicated by a team of investigators at the particular center.
Statistical analysis: Continuous variables were described as mean±standard deviation (SD), or median (minimum, maximum).