The effects of myocardial ischemia followed by reperfusion on perfused coronary capillarity.

: To determine the effects of ischemia and reperfusion on myocardial perfused capillary density, rat hearts were excised, kept ischemic for thirty minutes then reperfused with blood from a support animal. Control hearts were isolated and perfused for either 10 or 60 minutes before injection of a vascular marker (Monastral Blue-blood mixture, 30 sec at 100 mmHg). The ischemic hearts were perfused with Blue after 10 minutes of reperfusion. The perfused capillary density (theta) and capillary/fiber ratio (C/F) were measured from frozen transverse sections of the left ventricle. For 10- and 60-minute control hearts, the epicardial theta values were 2324 +/- 476 caps/mm2 and 2378 +/- 330 SD. The endo/epi theta ratio was not significantly less than unity for either control group. For the ischemic group, theta was significantly decreased both in the epicardium (707 +/- 515 caps/mm2) and endocardium (130 +/- 30 caps/mm2) (p less than 0.05). The endo/epi theta ratio was significantly less than unity for the ischemic group (P less than 0.05). The C/F ratio analysis yielded the same results. The decrease in both theta and CF ratio indicate that 30 minutes of ischemia followed by 10 minutes of reperfusion caused a marked "No-reflow" phenomena in isolated, supported hearts. The No-reflow was most pronounced in the endocardium.