In vivo pulsed-field ablation in healthy vs. chronically infarcted ventricular myocardium: biophysical and histologic characterization

Abstract

Aims: Data on ventricular pulsed-field ablation (PFA) are sparse in the setting of chronic myocardial infarction (MI). The objective of this study was to compare the biophysical and histopathologic characteristics of PFA in healthy and MI swine ventricular myocardium.

Methods and results: Myocardial infarction swine (n = 8) underwent coronary balloon occlusion and survived for 30 days. We then performed endocardial unipolar, biphasic PFA of the MI border zone and a dense scar with electroanatomic mapping and using an irrigated contact force (CF)-sensing catheter with the CENTAURI System (Galaxy Medical). Lesion and biophysical characteristics were compared with three controls: MI swine undergoing thermal ablation, MI swine undergoing no ablation, and healthy swine undergoing similar PFA applications that included linear lesion sets. Tissues were systematically assessed by gross pathology utilizing 2,3,5-triphenyl-2H-tetrazolium chloride staining and histologically with haematoxylin and eosin and trichrome. Pulsed-field ablation in healthy myocardium generated well-demarcated ellipsoid lesions (7.2 ± 2.1 mm depth) with contraction band necrosis and myocytolysis. Pulsed-field ablation in MI demonstrated slightly smaller lesions (depth 5.3 ± 1.9 mm, P = 0.0002), and lesions infiltrated into the irregular scar border, resulting in contraction band necrosis and myocytolysis of surviving myocytes and extending to the epicardial border of the scar. Coagulative necrosis was present in 75% of thermal ablation controls but only in 16% of PFA lesions. Linear PFA resulted in contiguous linear lesions with no gaps in gross pathology. Neither CF nor local R-wave amplitude reduction correlated with lesion size.

Conclusion: Pulsed-field ablation of a heterogeneous chronic MI scar effectively ablates surviving myocytes within and beyond the scar, demonstrating promise for the clinical ablation of scar-mediated ventricular arrhythmias.

Keywords: Catheter ablation; Pulsed-field ablation; Ventricular arrhythmia; Ventricular tachycardia.

Graphical Abstract

Figure 1

Gross pathology of focal (A) and linear (B) PFA. Linear lesion sets made in the anteroseptal LV endocardium (eight PFA applications, 4 cm long) and inferolateral LV endocardium (16 PFA applications, 5.2 cm long) had no visual gaps. LV, left ventricular; PFA, pulsed-field ablation.

Figure 2

Pulsed-field ablation of surviving myocytes within chronic subendocardial MI scar. The most apical PFA applications of scar BZ are demonstrated on gross pathology (A), electroanatomic mapping (B), sub-gross pathology with haematoxylin and eosin (C) and trichrome (D), and magnified histology demonstrating contraction band necrosis with oedema of surviving myocytes within scar (E and F). BZ, border zone; MI, myocardial infarction; PFA, pulsed-field ablation.

Figure 3

Pulsed-field ablation extends beyond chronic MI scar to its epicardial border. Pulsed-field ablation application at scar BZ is demonstrated on gross pathology (A), electroanatomic mapping (B), sub-gross pathology with haematoxylin and eosin (C) and trichrome (D), and magnified histology demonstrating contraction band necrosis and myocytolysis extending beyond the scar to its epicardial border (E). BZ, border zone; MI, myocardial infarction.

Figure 4

Cellular effects of PFA. Coagulative necrosis (left) was noted much more frequently with thermal ablation than with PFA. Contraction band necrosis and myocytolysis were not noted in chronic MI that was not ablated. PFA, pulsed-field ablation.