Assessing the relation between coronary reflow and myocardial reflow

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.