Assessing the relation between coronary reflow and myocardial reflow

Abstract

Since the recognition that prompt reperfusion of the infarct-related artery decreases mortality after acute myocardial infarction (MI), we have been interested in optimizing therapeutic regimens to accelerate the establishment of infarct-related artery patency. Although the major endpoint of many angiographic trials has been the acquisition of a patent infarct-related artery, this may not correlate with actual tissue perfusion because of the no-reflow phenomenon. With myocardial contrast echocardiography (MCE), we assessed the success of myocardial reperfusion at the microvascular level in patients with an acute anterior MI. We documented that 21% of the study patients exhibited Thrombolysis in Myocardial Infarction (TIMI) grade 2 flow after coronary angioplasty, and all of them showed substantial “no reflow” on MCE. Conversely, no reflow was observed on MCE in only 16% of patients with TIMI grade 3 flow. Early TIMI grade 3 flow resulted in a significantly better left ventricular functional outcome compared with those with TIMI grade 2. In view of microvascular perfusion, TIMI grade 2, despite the absence of coronary obstruction, cannot be regarded as successful reperfusion. Our study, using a Doppler guidewire probe, documented the specific coronary flow pattern in patients with TIMI grade 2. Patients with TIMI grade 3 flow exhibited systolic antegrade flow followed by the predominant diastolic flow. TIMI grade 2 flow represented features of a to-and-fro coronary flow velocity pattern. This latter is characterized by (1) the abnormal retrograde flow in the early systole; (2) the reduction in the systolic antegrade flow; and (3) the rapid deceleration of the diastolic flow velocity. This pattern would be explained by an increase in vascular impedance and a decrease in myocardial blood volume.