Evaluation of Hemolysis and Acute Kidney Injury Post Ventricular Arrhythmia Ablation Using a Novel Ultra-Low-Temperature Cryoablation System

Background
Recent advancements in cardiac ablation technologies have introduced new methods for treating arrhythmias, such as pulsed field ablation (PFA) for pulmonary vein isolation (PVI). However, reports of potential adverse effects like hemolysis and acute kidney injury (AKI) with PFA have prompted a closer examination of the safety profiles of both existing and new ablation technologies. One such emerging technology is ultra-low-temperature cryoablation (ULTC), using nitrogen cryogen at -196°C to create more controlled and deeper lesions. While promising in preliminary studies, ULTC's impact on biomarkers for hemolysis and kidney injury has not yet been investigated.

Aim 
This study aimed to investigate whether there is an elevation of markers indicative of acute hemolysis and/or kidney injury following ablation of either ventricular tachycardias (VT) and/or premature ventricular contractions (PVC) using the novel ULTC system.

Methods 
Consecutive male patients with VT and/or PVC were prospectively enrolled at a tertiary ablation center between April and June 2024. Blood samples were collected pre-procedure (at the day of the procedure) and post-procedure (at the first post-procedural day) to assess markers including blood count, haptoglobin, bilirubin, lactate dehydrogenase (LDH), creatinine, glomerular filtration rate (GFR), C-reactive protein, troponin, and creatine kinase. For statistical analyses, continuous variables were examined for normality using the Shapiro-Wilk test. Normally distributed data were presented as means ± standard deviations and compared using paired-samples t-tests, while non-normally distributed variables were expressed as medians with interquartile ranges (25th and 75th percentiles) and analysed using Wilcoxon signed-rank tests.

Results
A total of 7 patients (100% male, aged 64 ± 10 years, 57% with VT, 14% with PVC, and 29% with both) were enrolled. Mean procedure duration was 124 ± 25 min, with a mean freeze duration of 29 ± 10 minutes, a mean minimum freeze temperature of -153 ± 17 °C, with the lowest freeze temperature at -172 °C. Contrast dye was solely used for transseptal puncture (mean amount 3 ± 2 ml). There was a numeric, but not significant, increase in markers of hemolysis, with LDH increasing from 218 [177; 232] U/l pre-ablation to 310 [279; 325] U/l post-ablation (p = 0.109), haptoglobin decreasing from 1.2 ± 0.2 g/l pre-ablation to 0.8 ± 0.4 g/l post-ablation (p = 0.099), and total bilirubin increasing from 8.0 ± 5.8 µmol/l pre-ablation to 11.7 ± 4.2 µmol/l post-ablation (p = 0.153),There was no increase in markers of acute kidney injury, with GFR improving from 60 ± 21 ml/min pre-ablation to 69 ± 22 ml/min post-ablation (p = 0.003). Additionally, there was a change of inflammatory markers, with leukocytes increasing from 6.9 ± 1.1 *10^9/l pre-ablation to 8.3 ± 2.2 *10^9/l post-ablation (p = 0.039) and CRP rising from 2.5 [0.7; 10.5] mg/l pre-ablation to 9.8 [3.8; 10.9] mg/l post-ablation (p = 0.138). No major or minor acute periprocedural or postprocedural complications were observed.

Conclusion
Despite achieving very low temperatures with the novel ULTC ablation system, no significant postprocedural hemolysis or acute kidney injury was observed. Nonetheless, given the small sample size comprising solely male participants, further investigations are warranted to assess both acute and long-term safety outcomes associated with this innovative ablation technology.