Pulsed field ablation: have we finally found the holy grail?

In vitro characterization of radiofrequency ablation lesions in equine and swine myocardial tissue

Radiofrequency ablation is a promising technique for arrhythmia treatment in horses. Due to the thicker myocardial wall and higher blood flow in horses, it is unknown if conventional radiofrequency settings used in human medicine can be extrapolated to horses. The study aim is to describe the effect of ablation settings on lesion dimensions in equine myocardium. To study species dependent effects, results were compared to swine myocardium. Right ventricular and right and left atrial equine myocardium and right ventricular swine myocardium were suspended in a bath with circulating isotonic saline at 37 °C. The ablation catheter delivered radiofrequency energy at different-power-duration combinations with a contact force of 20 g. Lesion depth and width were measured and lesion volume was calculated. Higher power or longer duration of radiofrequency energy delivery increased lesion size significantly in the equine atrial myocardium and in equine and swine ventricular myocardium (P < 0.001). Mean lesion depth in equine atrial myocardium ranged from 2.9 to 5.5 mm with a diameter ranging from 6.9 to 10.1 mm. Lesion diameter was significantly larger in equine tissue compared to swine tissue (P = 0.020). Obtained data in combination with estimated wall thickness can improve lesion transmurality which might reduce arrhythmia recurrence. Optimal ablation settings may differ between species.

Clinical utility of oesophageal temperature monitoring in AF ablation: An updated meta-analysis and review of literature

BACKGROUND

Atrial fibrillation (AF) ablation can lead to oesophageal thermal injuries (ETI). These are thought to be the precursor of the much rarer but frequently fatal atrio-oesophageal fistulas. Many centers performing AF ablation routinely use oesophageal temperature monitoring (ETM). This meta-analysis aims to determine the utility of ETM in preventing ETI in the context of radiofrequency catheter ablation of AF.

METHODS

A systematic search of PubMed, Embase databases and Cochrane registry was performed comparing ETI between ETM and non-ETM strategies in AF ablation. Data on endoscopically determined ETI, AF recurrence, procedure time and ablation time were extracted. Statistical analyses including subgroup and covariate analyses were performed using random effect model in R platform.

RESULTS

ETI were similar in both ETM (n = 864) and non- ETM groups (n = 639) (RR 1.04, 95 % CI 0.34-3.23) across 12 studies. AF recurrence was statistically similar in both groups (IRR 0.92, 95 % CI 0.73-1.17) but showed a lower trend in non-ETM group. Ablation time was numerically lower in the ETM group and procedure time was numerically higher trend in the ETM group; but they were not statistically significant. Covariate analysis found that posterior wall ablation power setting, additional linear ablation, BMI, use of GA or prophylactic PPI after ablation had no significant correlation in the incidence of ETI.

CONCLUSION

ETM was not associated with a reduced incidence of ETI during AF ablation. Evidence supporting the routine use of ETM to reduce the risk of ETI or atrio-oesophageal fistulas is lacking.

High power short duration versus low power long duration ablation in patients with atrial fibrillation: A meta-analysis of randomized trials

BACKGROUND

High-power-short-duration (HPSD) radiofrequency (RF) ablation is a viable alternative to low-power-long-duration (LPLD) RF for pulmonary vein isolation (PVI). Nevertheless, trials showed conflicting results regarding atrial fibrillation (AF) recurrences and few data concerning complications. Therefore, we conducted a meta-analysis of randomized trials comparing HPSD versus LPLD.

METHODS

We systematically searched the electronic databases for studies published from inception to March 31, 2023 focusing on HPSD versus LPLD. The study endpoints were AF recurrence, procedural times and overall complications.

RESULTS

Five studies enrolling 424 patients met the inclusion criteria (mean age 61.1 years; 54.3% paroxysmal AF; mean LVEF 58.2%). Compared to LPLD, HPSD showed a significantly lower AF recurrence rate [16.3% vs. 30,1%; RR: 0.54 (95% CI: 0.38-0.79); p = 0.001] at a mean 10.9 months follow-up. Moreover, HPSD led to a significant reduction in total procedural time [MD: -26.25 min (95%CI: -42.89 to -9.61); p = 0.002], PVI time [MD: -26.44 min (95%CI: -38.32 to -14.55); p < 0.0001], RF application time [MD: -8.69 min (95%CI: -11.37 to -6.01); p < 0.00001] and RF lesion number [MD: -7.60 (95%CI: -10.15 to -5.05); p < 0.00001]. No difference was found in either right [80.4% vs. 78.2%; RR: 1.04 (95% CI: 0.81-1.32); p = 0.77] or left [92.3% vs. 90.2%; RR: 1.02 (95% CI: 0.94-1.11); p = 0.58] first-pass isolation and overall complications [6% vs. 3.7%; RR: 1.45 (95%CI: 0.53-3.99); p = 0.47] between groups.

CONCLUSION

In our metanalysis of randomized trials, HPSD ablation appeared to be associated to a significantly improved freedom from AF and shorter procedures, without increasing the risk of complications.

Cardioneuroablation Using Epicardial Pulsed Field Ablation for the Treatment of Atrial Fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia affecting millions of people worldwide. The cardiac autonomic nervous system (ANS) is widely recognized as playing a key role in both the initiation and propagation of AF. This paper reviews the background and development of a unique cardioneuroablation technique for the modulation of the cardiac ANS as a potential treatment for AF. The treatment uses pulsed electric field energy to selectively electroporate ANS structures on the epicardial surface of the heart. Insights from in vitro studies and electric field models are presented as well as data from both pre-clinical and early clinical studies.

Study of necrotic apoptosis by pulsed electric field ablation in rabbit left ventricular myocardium

Objective

We investigate the characteristics of histological damage to myocardial cells in the ablation region and surrounding areas of the left ventricular epicardium in rabbits using our self-developed cardiac pulsed electric field (PEF) ablation instrument and ablation catheter.

Methods

Forty eight New Zealand rabbits underwent ablation on the left ventricular myocardium after open-heart exposure with a cardiac arrhythmia PEF ablation device and ablation catheter developed by the Medical Translation Laboratory of Pulsed Electric Field Technology in Zhejiang Province. The ablation parameters were set as biphasic electrical pulses; voltage, ±800 V; pulse width, 10 μs; interphase delay, 500 us. Six rabbits were included in the sham group and 42 other rabbits were randomly divided into immediately, 6-h, 1-, 3-day, 1-, 2-, and 4-week post-ablation groups, with six rabbits in each group. Creatine kinase- (CK)-MB isoenzyme (CK-MB), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) levels were measured before and at different time points after PEF ablation to analyze their dynamic evolution. Masson staining of tissue block sections of left ventricular myocardial ablation and adjacent tissue heart specimens was performed, and the occurrence of TUNEL apoptosis in myocardium tissue was analyzed.

Results

All rabbits completed the PEF ablation procedure and the follow-up process. After PEF ablation, the levels of cardiac enzymes, including CK-MB, CK, and AST, increased significantly, peaking 1–3 days after the procedure. In particular, those of CK and CK-MB increased by 15–20 times but returned to the preoperative level after 2 weeks. Based on general observation, it was found that the myocardium in the ablation area was swollen immediately after PEF ablation. Masson staining analysis revealed that cardiomyocytes were broken and infiltrated by erythrocytes after 6 h. After 1 day, the cells started to experience atrophy and necrosis; after 3 days, fibrotic replacement of the necrotic area became obvious. Then, by 4 weeks, the myocardial cells were completely replaced by hyperplasia. Apoptosis occurred significantly at 6 h and peaked at 24 h post-ablation, demonstrating a 37.7-fold increase; apoptotic cell counts decreased significantly at 3 days post-ablation, and no significant apoptotic cardiomyocytes were seen after 1 week.

Conclusion

After PEF ablation, cardiomyocytes showed apoptotic process and dyed, at least partially, through a secondary necrosis, the ablation boundary was clear, the ablation area was replaced by structurally intact fibroblasts, no island myocardium tissue were seen, and the ablation area vessels and nerves were not affected.