Ex vivo efficacy assessment of ultralow temperature cryoablation versus standard RF ablation applied to surgical ventricular patches: implications for ventricular ablation in patients with repaired congenital heart disease.

Background: Clinical experience during trans-patch ventricular ablations shows difficult lesion formation when using standard RF ablation technology. The aim of this exploratory study is to test if ultralow temperature cryoblation (ULTC) technology could be suitable for trans-patch ventricular ablations.

Materials And Methods: Ex vivo ablations were performed on 16 porcine tenderloin specimens of 5 × 7 × 3 cm, eight with and eight without pericardial patch (Supple Peri-Guard Repair Patch, Baxter, USA). RF energy was applied for 1 min, with a power of 40W. ULTC was applied as a 2 × 2 min freeze. Temperature was measured using an array of thermocouples ranging between 0.5 and 13.1 mm below the tissue surface.

Results: For RF, the maximum temperatures without and with patch respectively reached 58.9 °C and 48.5 °C. The thermocouple closest to the tissue surface displayed a 41% temperature range drop when RF energy was applied trans-patch, whereas the same thermocouple showed a 16% and 13% drop for the first and second ULTC freeze cycle when ULTC was applied trans-patch. The 45 °C isotherm depth was reduced by 55% for RF ablations, whereas the - 25 °C isotherm depth was reduced by 23% and 19% for the first and second freeze cycles, respectively.

Conclusion: Both energy modalities show reduced efficacy for trans-patch ablations when considering absolute temperature differences and estimated lesion depths. However, when considering relative differences, ULTC is more effective than RF for trans-patch lesions. Additionally, ULTC did not show visible damage to either the patch or the ex vivo specimen, while RF resulted in visible damage to both the tissue and patch.