Effect on coronary artery flow reserve and resistance in the remote area after acute coronary artery occlusion in the pig model

Background: It has been reported that vasodilator function in remote myocar dial regions supplied by "angiographically normal" coronary arteries is imp aired in patients after acute myocardial infarction (MI), The aim of this s tudy was to determine whether coronary artery flow reserve and coronary art ery resistance in remote, nonischemic areas are also altered in experimenta l MI. Methods: Experiments were performed in anesthetized pigs, In group 1 infarc tion was induced by ligation of the left-anterior descending artery (LAD); group 2 consisted of sham-operated animals. Hemodynamic parameters, coronar y artery resistance, and myocardial blood flow (MBF) were measured before a nd 4 hours after MI under rest and during infusion of adenosine. Results: Coronary artery dilation by adenosine caused a similar increase in MBF before and 4 hours after coronary artery occlusion. Resting MBF after acute MI was not altered, although a significant reduction (15%; P < .04) i n mean aortic pressure was observed compared with baseline, Coronary artery resistance was significantly reduced by adenosine (P < .04) before MI, as well as at 4 hours after MI (P < .03). Coronary artery flow reserve was not adversely affected. The sham-operated animals showed similar results witho ut any significant differences between the two study groups. Conclusion: This study indicates that an acute MI in pigs did not increase coronary artery resistance in the remote area after MI and therefore did no t adversely affect coronary artery flow reserve in the nonischemic vascular bed. Further studies are necessary to fully understand the exact mechanism of the alterations in remote flow reserve of patients after MI.