Mechanical Properties of the Myocardium Post-Alcohol Ablation in Transcatheter Mitral Valve Implantation

Alcohol septal ablation (ASA) has become a minimally invasive alternative to septal myectomy for treating left ventricular outflow tract (LVOT) obstructions. ASA has gained popularity, especially among patients undergoing transcatheter mitral valve replacement (TMVR). This study aimed to determine the effect of ASA on the mechanical properties of myocardial tissue.

Twenty-four square samples were excised from the septal regions of fresh-frozen swine hearts. Mechanical testing was conducted using a biaxial tester. Half of the samples underwent 3-minute ablation, while the other half underwent 5-minute ablation.

All samples exhibited a nonlinear response to strain in the fiber and cross-fiber directions. After 3 min of ablation, the mean force required to achieve 20% displacement increased from 182.08-mN to 347.42-mN (true stress from 11.0-KPa to 24.1-KPa) in the fiber direction and from 66.83-mN to 110.75-mN (true stress from 4.3-KPa to 8.2-KPa) in the cross-fiber direction. Following 5 min of ablation, mean force values rose from 178.0-mN to 452.8-mN (true stress from 11.0-KPa to 32.4-KPa) in the fiber direction, and from 70.0-mN to 154.8-mN (true stress from 4.8-KPa to 12.0-KPa) in the cross-fiber direction. All changes were statistically significant (p ≤ 0.002). Histological analysis also revealed that alcohol ablation progressively disrupted myocardial architecture.

This study demonstrates that ASA significantly alters the passive mechanical properties of the myocardium, increasing tissue stiffness in the septal region over the short term. The extent of stiffening is directly proportional to the duration of ablation, with longer ablation times causing greater stiffness, necessitating careful selection of ablation time before TMVR procedures.