Angiographic evaluation of epicardial and microvascular coronary flow.

P harmacological or mechanical relief of coronary obstruction with restoration of normal flow in the culprit coronary artery has been the goal of therapy in patients with acute myocardial infarction. Although primary percutaneous catheter intervention is highly successful in the restoration of epicardial blood flow, achieving full angiographic patency (TIMI grade 3 flow) in the infarct-related epicardial coronary artery of > 90% of the patients [1,2], tissue perfusion in the area at risk frequently continues to be compromised. Persistent microcirculatory impairment is associated with poor recovery of contractile function [3-9] and adverse clinical outcome [3,10-13]. The major causes of insufficient tissue reperfusion despite a fully patent infarct-related epicardial artery are ischemic microvascular damage, reperfusion-induced regional inflammatory responses, and distal embolization of plaque and thrombus material. The current concept of optimal reperfusion in acute MI includes not only the rapid and sustained restoration of blood flow in the epicardial infarct-related coronary artery, but also the restoration of perfusion at the tissue level within the jeopardized myocardium [13-16]. Failure to achieve an adequate blood supply at this level has been associated with a greater