Cryoablation of ventricular tachycardia using ultra-low temperature technology: acute success and insights from the post-interventional CMR

Abstract

Abstract Background Radiofrequency catheter ablation (RFCA) has good acute and long-term success rates in idiopathic and ischemic ventricular arrhythmia (VA). Drawbacks of the RFCA are reversibility of the edema and limited penetration of the RF energy into the tissue which explain a worse effectiveness in midmyocardial substrates. In comparison to RFCA, the lesions produced by ultra-low temperature cryoablation (ULTC) which uses near-critical nitrogen cryogen at -1960C can be both deeper and irreversible, depending on the duration of the freeze. Purpose We aimed to evaluate the acute effectiveness of a new ULTC technology for VA by examining post-interventional cardiac magnetic resonance images (CMR) with late gadolinium enhancement (LGE), as a part of multi-center Cryocure-VT study. Methods Between December 2022 and May 2023, we ablated 6 patients (age 63±16%; 5 male) with sustained VA and structural heart disease. Three patients had previous myocardial infarction; 1 cardiac sarcoidosis, 1 LMNA/C dilated cardiomyopathy and 1 post-myocarditis VA. LGE-CMR was available in all patients before the ULTC. At first, electro-anatomical mapping and VA induction were performed followed by ULTC using transseptal access. Each application consisted of freeze-thaw-freeze cycle with freeze duration at operator’s discretion based on manufacturer-recommended duration-depth curve. At the end, induction protocol was repeated to assess the acute success. Additionally, LGE-CMR was performed after ablation as an attempt to visualize the cryo-lesions. Results Median of 6 applications (IQR 4.75-7.5) of cryo-energy were applied per patient. Median procedure time was 180 min (IQR 97-180), and median fluoroscopy time of 20 min (IQR 15-26). Septal VA exits were detected in 3/6 patients; in 1 the exit was at aorto-mitral continuity; in 2 – basal inferior. After ablation, no VAs were inducible in 5/6 (83%) patients. The only patient with failure to ablate all VAs had fewer applications (n=4) and shorter freeze duration of 30 sec., as compared to the rest. Post-procedural CMR revealed new LGE with up to 75% transmurality in 5/6 patients; microvascular obstruction in 4/6 patients. Only LV edema, but no LGE was observed in the patient with shortest freeze time, who also had intra-hospital recurrence. No complications occurred. Conclusions Cryoablation of VA using a new ultra-low temperature technology is effective and safe to ablate VT even in patients with mid-septal substrates. New LGE in result of ULTCA can be observed in CMR and the lesions depth depends on the duration of application.