Arteriolar Atherosclerosis and Pathological Intussusceptive Remodeling in Heart Disease

Background. Microvascular dysfunction is a major contributor to morbidity and mortality in various cardiovascular diseases. In patients with congenital heart disease (CHD), rheumatic heart disease (RHD), ischemic heart disease (IHD), structural remodeling of intramyocardial arterioles may play an important role in the development of microvascular dysfunction and progressive cardiac impairment. Materials and Methods. Right atrial appendage specimens were obtained during cardiac surgery. Tissue samples were processed for light microscopy (LM) and transmission electron microscopy (TEM) after embedding in epoxy resin. Histological and ultrastructural analyses were performed to evaluate arteriolar remodeling. Results. Intramyocardial arterioles demonstrated a distinct pattern of pathological intussusceptive growth, which differs from physiological intussusceptive angiogenesis. The formation of de novo arterioles from pre-existing vessels occurred through mechanisms involving vascular invagination and the formation of transluminal tissue pillars (intussusceptive pillars). Vessel lumina varied considerably during this process, and several de novo arterioles could simultaneously arise from a single pre-existing arteriole. Atherosclerosis observed in advanced stages of CHD, RHD, and IHD indicates that pathological intussusceptive arteriolar growth is involved in vascular remodeling in all examined patients. These changes were most pronounced in patients with PVS and CAD. According to a five-point semiquantitative grading system, the severity of pathological microvascular growth reached 4 points, indicating marked structural remodeling. Conclusions. Pathological intussusceptive arteriolar growth appears to represent a previously underrecognized mechanism of microvascular remodeling in cardiovascular diseases. This process may contribute to microvascular dysfunction and progressive myocardial impairment associated with advanced atherosclerotic disease.