Local adenosine infusion and myocardial oxygen supply and consumption in reperfused canine myocardium

The aim was to determine whether a local infusion of adenosine could increase coronary blood flow to restore fully the O2 supply to consumption balance in reperfused myocardium.

The left anterior descending coronary artery was occluded for 2 h followed by a 4 h reperfusion with and without simultaneous local infusion of adenosine (50 micrograms.kg-1.min-1). In another group, adenosine was infused for 4 h. Small artery and vein O2 saturations (microspectrophotometry) and regional flow (radioactive microspheres) were determined.

25 anaesthetised open chest mongrel dogs, divided in three groups, were used in this study.

In the central group, 2 h occlusion decreased regional blood flow below normal. After 4 h of reperfusion, blood flow was less than normal in the affected area, at 57(SD39) affected v 85(31) ml.min-1.100 g-1 control. O2 extraction was higher in the reperfused area, with 61% of veins having O2 saturations less than 35%. For the experimental group, adenosine was infused into the left anterior descending artery at a dose of 50 micrograms.kg-1.min-1. Adenosine coupled with reperfusion increased regional blood flow above control in the affected area, to 267(238) ml.min-1.100 g-1, but this was less than was found with adenosine alone. O2 extraction in this area was lower than with reperfusion alone, with only 1% of veins having O2 saturations less than 35%.

A large flow reserve is present in reperfused tissue and the low O2 saturations found in reperfused myocardium cannot be due to vessel blockage (greater than 20 microns in diameter). Thus local adenosine can be used to mobilise the reserve to improve the O2 supply to consumption balance.