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).