Rapid high-current, temperature-controlled point-by-point pulmonary vein isolation (PVI) and linear ablation has been shown to be clinically feasible and safe in a first-in-human study of an expandable radiofrequency lattice tip catheter. Other findings from the same study, announced last month, also found the lesion sets to be “highly durable”.
Published in JACC: Clinical Electrophysiology by Elad Anter (Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, USA) et al, the study evaluated the safety and acute performance of a novel catheter that has an expandable lattice structure with a wide thermal footprint for the treatment of atrial flutter and fibrillation (AF). The catheter incorporates multiple surface thermocouples/mini-electrodes in high-resolution mapping and high-current temperature-controlled radiofrequency ablation (RFA).
Anter and colleagues write: “This first-in-human study demonstrates the workflow advantages of integrating high resolution mapping with high-power ablation into a single catheter. But most importantly, this novel lattice-tip catheter highlights the advantages of radiofrequency ablation with a large thermal footprint: one retains both the flexibility of point-by-point catheters and the ease-of-use of one-shot technologies to create PVI, cavo-tricuspid isthmus (CTI), mitral isthmus and left atrial (LA) roof lines.”
A continuation of this study was presented at a late breaking trial session last month at AF Symposium 2020 (23–25 January, Washington, DC, USA), and simultaneously published in JACC: Clinical Electrophysiology by Vivek Y Reddy (Homolka Hospital, Prague, Czech Republic, and Icahn School of Medicine at Mount Sinai, New York, USA) et al. This found that temperature-controlled lattice-tip point-by-point ablation not only resulted in PVI lesion sets that were highly durable, but that there was also durable contiguity of linear atrial lesions.
Patients with typical right atrial flutter or AF were prospectively enrolled in a single arm study at three centres. Flutter patients underwent CTI ablation. Patients with paroxysmal AF underwent PVI, and CTI if desired, and for persistent AF patients, mitral isthmus and LA roof lines were also permitted. Mapping was performed with the lattice (Sphere-9) catheter and a novel compatible electroanatomical mapping system (Prism-1). RFA was performed in a point-by-point fashion (Tmax 73–80°C; two to seven seconds). Patients were followed for three months. In all, 71 patients underwent ablation: 65 PVI, 38% persistent AF; 22 mitral isthmus, 24 roof, and 48 CTI lines.
Anter et al noted that PVI was achieved in 64/65 (98.5%) using the lattice alone, and required 2.7±0.7 RFA minutes. Mitral block was achieved in 100% using 11.5±10.7 applications and 1.0±0.92 RFA minutes; only one patient required adjunctive epicardial coronary sinus ablation. Roof line and CTI block were achieved in 95.8% and 100% of patients, using 4.9±1.9 and 5.9±3.1 applications for 0.4±0.16 and 0.5±0.24 RFA minutes, respectively. At three months, there were no deaths, strokes, tamponade or atrioesophageal fistula.
Reddy and colleagues found that the pulmonary veins (PVs) remained durably isolated in all but one reconnected PV, translating to durable isolation in 99.1% of PVs, or 96.3% of patients with all PVs isolated. Of 47 linear atrial lesions initially placed during the index procedure, durability was observed in 10 of 11 (90.9%) mitral isthmus lines, all 11 (100%) roof lines, and all 25 (100%) CTI lines. After a median follow-up of 270 days, the 12-month Kaplan-Meier estimate for freedom from atrial arrhythmias was 94.4%±3.2%.
Anter et al highlight the low rate of safety events “without evidence of the major complications related to AF ablation”, saying: “Over three months’ follow-up, there were no primary adverse events. Specifically, there was no instance of atrioesophageal fistula, cardiac tamponade, death, severe pericarditis, valvular damage, major vascular access complication or bleeding, intra-procedural device complications requiring cardiac surgery, myocardial infarction, phrenic nerve paralysis, PV stenosis, stroke, thromboembolism or transient ischaemic attack.”
However, as the focus of the first-in-human study was on safety and acute efficacy of the technology, they say: “Data from long-term follow-up will be necessary to evaluate the true clinical efficacy of this technology; continued follow-up of this cohort, as well as future cohorts from additional studies will help clarify this. On the other hand, the observed ability to achieve linear block of the various lesion sets with limited numbers of applications may hint toward its long-term effectiveness.”
Anter and colleagues concede that the small sample size, short follow-up and the observational design of the study “precludes robust direct comparison to other ablation technologies, thereby limiting our ability to draw definitive conclusions about its relative safety and efficacy”, and suggest that a multicentre study with prespecified settings, long-term follow-up and comparison to conventional technologies should be conducted.
On lesion durability, Reddy et al point to several features of the lattice catheter that may account for the high rates: “Foremost is a tendency of the catheter tip to remain in stable contact with the target tissue during ablation. This seems related to both the compressibility of the spherical mesh, and the fact that the surface topography of this tip may mitigate sliding/dislodgement of the catheter away from the target site.”
They also comment: “These lattice-tip outcomes suggest that durable ablation lesion sets—PVI for PAF and PVI plus linear lesions for PerAF—are crucial missing variables to achieving high success of AF ablation.”
And, although they describe the data as “compelling”, they too concede that the small size of the cohort and the fact that there were only three centres in the study are “important caveats”.
Nevertheless, they conclude: “This first-in-human study shows that the novel lattice-tip catheter, by virtue of its large thermal footprint, creates contiguous point-by-point temperature-controlled RFA lesions with high rates of linear lesion durability—for PVI, for LA linear lesions at the mitral isthmus and roof, and for CTI ablation.”
