Off-target myocardial necrosis due to incomplete balloon occlusion during retrograde coronary venous ethanol ablation

It is assumed that complete balloon occlusion is necessary for effective lesion formation in retrograde coronary venous ethanol infusion for ventricular arrhythmias.

This study aimed to evaluate the myocardial effects of ethanol infusion under conditions of incomplete balloon occlusion.

12 swine were randomized into acute (n = 6) and chronic (n = 6) cohorts. Ethanol was infused into different coronary veins using single over-the-wire balloons sized to achieve incomplete occlusion. Myocardial injury was assessed by gross pathology, histology, and ultrastructural analysis.

Incomplete balloon occlusion was confirmed in all animals, with distal venous leakage in 9 of 12 and collateral filling in 3 of 12. Myocardial staining was observed in only 4 of 12, faint and poorly localized. Despite this, all acute animals developed lesions, with transmural infarction in 5 of 6. Gross lesion dimensions reached up to 30 mm in width, 86 mm in length, and 15.0 mm in depth. Acute histology revealed eosinophilic changes, vacuolar degeneration, and cardiomyocyte necrosis. Ultrastructural analysis demonstrated plasma membrane rupture, sarcomeric dissolution, mitochondrial swelling, and intercalated disk disruption. In the chronic phase, 4 of 6 swine presented with transmural fibrotic scars (up to 46 mm wide, 58 mm long, and 14.8 mm deep), characterized by replacement fibrosis, myocyte atrophy, and inflammation. Chronic ultrastructural changes included mitochondrial degeneration, intercalated disk remodeling, sarcomere disorganization, and vacuolar pathology.

Incomplete balloon occlusion during retrograde coronary venous ethanol infusion can still produce large, transmural infarctions. These findings underscore the potential for off-target necrosis and the need for precise procedural control in ethanol ablation for ventricular arrhythmias.