Reperfusion of the ischemic canine myocardium: effect on vascular exchange and resistance.

In order to see if changes in hemodynamic resistance following reperfusion of ischemic myocardium could be related to alterations in microvascular exchange, we measured resistance (R), permeability surface-area for sucrose (PS), and distribution volumes for tritiated water (V) and for sucrose (VS) in nine anesthetized dogs in which blood to the left anterior descending coronary artery was supplied via a shunt from the carotid artery. Measurements were made during four periods: baseline, reduced coronary artery flow, reperfusion, and a second period of reduced flow. Increase in resistance following reperfusion (R2 = 1.8 +/- 3, R4 = 2.5 +/- .5 mmHg/min/ml, mean +/- s.e.m.) was significantly greater than in nine control dogs in which reperfusion was omitted. Also, the series of interventions including reperfusion lowered PS and V (PS4/PS1 = .54 +/- .07, V4/V1 = .58 +/- .08). Our results suggest that increases in resistance due to reperfusion may be accompanied by a loss in functioning capillary surface area.