Scanning electron microscopic studies on microvascular architecture of human coronary vessels by corrosion casts: normal and focal necrosis.

Microvascular architecture of the normal human heart and myocardial focal necrosis were studied by scanning electron microscopy of corrosion casts. Casts macroscopically identical in form to the left ventricular posterior wall were prepared. The following results were obtained in the normal human heart. Most of the arterioles communicated with capillary plexuses smoothly and straightforwardly in the left ventricular posterior free wall. Arterioles which branched from the arteries ran in various directions and continued into capillaries either at right angles or obliquely in the trabeculae carneae. Capillaries running parallel with the cardiac muscle fibers ran in different directions to cross over with each other in different layers of myocardium. Capillaries in the myocardium formed a continuous and coarse net-like architecture with many bifurcations and anastomoses. Capillaries were about 5-7 micron in diameter. Some veins gathering capillaries in the epicardium ran into the myocardium and the others ran in the epicardium. Veins connecting with capillaries in the myocardium ran in the myocardial layer and communicated with larger veins. An arterio-venous anastomosis and two different types of venous-venous anastomoses were observed in the left ventricular posterior wall. At the site of focal necrosis, cross sections of dilated vessels were observed in large numbers by light microscopy and scanning electron microscopy. At the site of focal necrosis, dilated capillaries running with tortuosity were seen in large numbers by scanning electron microscopy of corrosion casts. When compared with vessels in the normal myocardium, small arterial branches were dilated and run tortuously. These dilated capillary plexuses were observed in the area which communicated with twigs branching off at the right angle from the arterial branch.