Ultra-low temp cryoablation eliminates monomorphic VT: Is it ready for primetime?

Treatment of monomorphic ventricular tachycardia (VT) with a novel ultra-low-temperature cryoablation catheter (vCLAS) eliminates VT in most patients with ischaemic or non-ischaemic cardiomyopathy in the first-in-human Cryocure-VT trial.

Clinical VT was noninducible in 94 percent of the patients after the procedure. No device- or procedure-related major adverse events occurred within 30 days of ablation.

At 6 months, 60.3 percent of the patients remained free from VT lasting >30 seconds. Eighty-one percent remained free from implantable cardioverter-defibrillator (ICD) shocks, with no significant difference between ischaemic and non-ischaemic cohorts.

VT is a leading cause of sudden death in patients with heart failure and a reduced ejection fraction, with 30 percent of patients with ischaemic and non-ischaemic cardiomyopathies developing ventricular arrhythmias, including VT.

Therapies to prevent VT include antiarrhythmic medication, such as amiodarone, and an implantable cardioverter-defibrillator (ICD).

Ablation is another important option to eliminate VT, according to study investigator Dr Atul Verma from McGill University Health Centre, Montreal, Canada, who presented at EHRA 2024. “But there have been no significant advancements in this therapy since radiofrequency (RF) was developed many years ago.”

He continued that ablation of VTs using RF catheters remains a “vexing problem” due to the limited lesion depth to deliver full-thickness treatment in the scar tissue and the persistent complications in patients with cardiomyopathy. “A change in energy source for ablation may help improve the situation.”

Study discussant Dr Usha Tedrow from Brigham and Women’s Hospital in Boston, Massachusetts, US, agreed that a powerful but titratable energy source is needed to penetrate deeper intramural substrates without collateral damage. “Cryocure-VT is an encouraging first step with a novel ablation source.”

New catheter design

What is novel in the Cryocure-VT is the catheter can deliver ultra-low-temperature cryoablation down to -180°C and create lesions of different tissue depths depending on the duration of the freeze, said Verma.

“By estimating the tissue depth, either from preprocedural or intraprocedural imaging, the operator can choose the depth required to treat VT and deliver the required duration of cryoablation,” he explained.

The trial enrolled 64 adult patients (mean age 67 years, 95.3 percent male) referred for de novo or second ablations of recurrent monomorphic VT of both ischaemic and nonischaemic aetiologies. Patients were from nine centres in Belgium, Canada, Czechia, France, Germany, and the Netherlands. All were refractory to at least one antiarrhythmic drug and had an ICD implanted or planned for placement post-ablation. [EHRA 2024, Late-Breaking Science Session; Europace 2024;26:euae076]

The patients’ mean LVEF was 35 percent. Seventy-nine percent had ischaemic cardiomyopathy, and the rest had nonischaemic substrates.

Intracardiac echocardiography was used in 68.8 percent of cases. All patients underwent ablation using ultra-low temperature cryoablation catheter and the operator’s choice of electroanatomical mapping system.

The mean procedure time was 188 minutes, which Verma said was reasonable for a scar-based cardiomyopathy VT ablation. The mean number of lesions per patient was 8.9. The average freeze time was 3.8 minutes per lesion.

ULTC a success

The primary success rate (noninducible clinical VT) was 94.4 percent. The secondary success rate (no inducible VT of any kind) was 85.2 percent. More than 97 percent of clinical VTs were eliminated.

At 6 months, freedom from recurrent sustained monomorphic VT or appropriate ICD therapy was similar regardless of the type of underlying cardiomyopathy. In 47 patients who had an ICD for 6 months before the ablation, the VT burden was reduced from a median of 4 ICD events to 0.

“Additionally, the use of antiarrhythmic drugs was reduced, specifically amiodarone in 60 percent of patients,” reported Verma.

There were two cases of trivial/small pericardial effusions, one asymptomatic false aneurysm in 2-mm tissue, and one case of haemodynamic instability during the procedure that required extracorporeal membrane oxygenation support. But all were resolved without clinical sequelae.

More questions remain

Commenting on the study, Dr K.R. Julian Chun from CardioAngiologisches Centrum Bethanien, Frankfurt, Germany, said the technology could be beneficial for treating specific types of premature ventricular complexes, such as those in papillary muscle, because of the increased stability of the catheter when it adheres to the tissue.

“However, as the data were preliminary, we need to learn more. We need to see how this works within a 3D mapping system … We need to understand where to ablate and where the substrate is.”

Tedrow, for his part, said that even though safety was reasonable in this study, the occurrence of asymptomatic false aneurysm in very thin tissue was potentially concerning. “We don’t know if we did routine imaging of all the patients or if something like that would be identified in more patients.”

The ultra-low temperature cryoablation system received CE mark approval in Europe in March 2024 to treat monomorphic VT. Verma said more studies on the device, including FULCRUM-VT which is set to enrol 20 patients in the US, are in progress.