Correlation between ECG and myocardial perfusion after mechanical reperfusion of acute myocardial infarction

The identification of viable myocardium after myocardial infarction (MI) carries major prognostic impact. Due to myocardial stunning early after successful mechanical reperfusion of acute myocardial infarction, analysis of myocardial perfusion but not of contractile function can be used to differentiate between necrotic and viable myocardium. Although being widely regarded as an indicator of infarct transmurality, the relation between post-infarct Q-wave formation and the amount of viable myocardium has not been studied. We hypothesized that there was a correlation between the extent of Q-wave formation and the extent of perfusion abnormalities on myocardial contrast echocardiography early after successful mechanical reperfusion of first acute myocardial infarction and that the extent of post-infarct Q-wave formation might therefore be used as a simple estimate of the amount of viable myocardium. Methods and results: 47 patients with first MI and treated by direct PCI were enrolled. Patients were divided into 3 groups according the presence and number of abnormal Q waves (group A-no abnormal Q wave; group B-≤2 abnormal Q waves, group C-≥3 abnormal Q waves). Left ventricular pumpfunction was defined by ejection fraction (EF) on ventriculography and wall motion score index (WMSI) on echocardiography. Myocardial perfusion was defined by perfusion score index (PSI) on myocardial contrast echocardiography. Patients in group A had significantly better LV function than patients in other groups [EF 57 ± 5 vs. 48 ± 11% (group B) and 47 ± 10% (group C); p < 0.05], also WMSI was the best in this group [1.34 ± 0.22 vs. 1.67 ± 0.39 (group B) and 1.68 ± 0.31 (group C); p < 0.01]. Myocardial perfusion assessed by PSI was best in group A (1.2 ± 0.3, p < 0.05). With respect to PSI, there was a significant difference between group B and C (1.41 ± 0.21 vs. 1.56 ± 0.29; p < 0.05), even though EF and WMSI did not differ in these groups. The amount of perfused segments with severe wall motion abnormality was higher in group B compared to group C (47% vs. 25%; p < 0.05). Methods and results: In patients after successful mechanical reperfusion of first MI, the extent of Q-wave formation on ECG may be regarded as a corollary of the amount of myocardial microvascular damage and may, therefore, be used to estimate the amount of viable myocardium post-infarct.