Subendocardial ischemic-like state in patients with severe aortic stenosis: insights from myocardial histopathology and ultrastructure

Abstract Background myocardial adaptation to severe aortic stenosis (AS) is a complex process that involves myocardial fibrosis (MF) beyond cardiomyocyte hypertrophy. Perfusion impairment is believed to be involved in myocardial remodeling in chronic pressure overload. Aim to describe morphological and ultrastructural myocardial changes at EMB, possibly reflecting subendocardial ischemia, in a group of patients with severe AS referred to surgical aortic valve replacement (AVR), with no previous history of ischemic cardiomyopathy. Methods one-hundred-fifty-eight patients (73 [68-77] years, 50% women) referred for surgical AVR because of severe symptomatic AS with pre-operative clinical and imaging study and no previous history of ischemic cardiomyopathy. Intra-operative septal EMB was obtained in 129 patients. Tissue sections were stained with Masson ́s Trichrome for MF quantification and periodic acid-Schiff (PAS) staining was performed to assess the presence of intracellular glycogen. Ultrastructure was analyzed through Transmission electron microscopy (TEM). Results MF totalized a median fraction of 11.90% [6.54-19.97%] of EMB, with highly prevalent perivascular involvement (95.3%). None of the samples had histological evidence of myocardial infarction. In 58 patients (45%) we found subendocardial groups of cardiomyocytes with cytoplasmatic enlargement, vacuolization and myofiber derangement, surrounded by extensive interstitial fibrosis. These cardiomyocytes were PAS positive, PAS-diastase resistant and Alcian Blue/PAS indicative of the presence of neutral intracellular glyco-saccharides. At TEM there were signs of cardiomyocyte degeneration with sarcomere disorganization and reduction, organelle rarefaction but no signs of intracellular specific accumulation. Conclusion almost half of the patients with severe AS referred for surgical AVR have histological and ultrastructural signs of subendocardial cardiomyocyte ischemic insult. It might be inferred that local perfusion imbalance contributes to myocardial remodeling and fibrosis in chronic pressure overload.