Capillary perfusion patterns in reperfused ischemic subendocardial myocardium: experimental study using fluorescent dextran.

The relationship between functional capillary perfusion patterns and sarcolemmal membrane permeability in localized acute myocardial ischemia was investigated in the rat model. The macromolecule dextran (MW 150,000) labeled with fluorescein (FITC) was intravenously injected. In histological sections, the label fluorescence showed those capillaries which had been perfused by the stained plasma; the blood-tissue barrier could be explored by detection of fluorescein in interstitial spaces and/or within the myocardial cells. Morphological parameters were calculated by semiautomatic image analysis. The data obtained indicate that (1) there is a great heterogeneity in the pattern of capillary perfusion within the reperfused ischemic myocardium; (2) as early as 20 min after coronary artery clamping followed by short reperfusion, the macromolecular tracer can be seen in the cytoplasm of muscle cells randomly distributed in subendocardial areas; (3) only the underperfused areas display permeated myocardial cells. It is suggested that capillary perfusion varies from site to site depending on the difference in cellular membrane permeability changes. The ischemia-induced cell changes can lead to capillary filling defects and an increase in coronary flow resistance. Whether the inadequate blood flow upon reperfusion contributes to further myocyte damage remains a matter of debate.