Metabolically controlled reperfusion in acute myocardial infarction: should the polarizing solution be given subselectively?

BACKGROUND

In working rat hearts, metabolic support of injured tissue enhances recovery after acute myocardial infarction. Clinical experience with a systemic "polarizing solution" supports this claim.

OBJECTIVE

In a dog model of ischemia/reperfusion, we tested the feasibility of subselectively supplying adapted metabolic substrates before instituting blood reperfusion.

METHODS

Thirty-five dogs underwent ligation of the proximal left anterior descending artery and collaterals for 90 minutes. The animals were randomly assigned to receive direct blood reperfusion (Group I), intracoronary glucose, insulin, and potassium (Group II), or intracoronary glucose, insulin, and potassium plus propionyl-L-carnitine (PLC) (Group III). After 30 minutes of artificial reperfusion, prograde blood flow was resumed in groups II and III. A routine necropsy was performed 3 to 5 days later. Primary endpoints were severe arrhythmias, death, markers of infarct size, and specific histologic features.

RESULTS

We excluded 4 dogs for technical reasons and 2 others for preexisting cardiomyopathy. In the remaining 29 animals, large apical infarctions were documented ventriculographically during arterial ligation. One dog died of irreversible ventricular fibrillation during the initial ischemic period, and 9/28 dogs (32.1%) died during early reperfusion. Ventricular fibrillation was more common with 10% (versus 5%) dextrose concentrations and was eliminated by PLC. Irreversibly injured (versus jeopardized) areas of myocardium were more common in Group III (85.9 19.3%) than in Groups I and II (16.9 10.8%).

CONCLUSIONS

Subselective infusion of metabolically supportive solutions during acute myocardial infarction is technically feasible. To prevent osmotic endothelial damage, the perfusate must have a low (< 5%) dextrose content.