Usefulness of Real-Time Myocardial Perfusion Imaging to Evaluate Tissue Level Reperfusion in Patients With Non-ST-Elevation Myocardial Infarction

Microvascular integrity is a prequisite for functional recovery in patients who have myocardial infarction after recanalization of the infarct-related coronary artery. In this study, we investigated whether impaired myocardial perfusion is present in patients who have non-ST-elevation myocardial infarction and whether the extent and time course of myocardial tissue reperfusion as assessed by myocardial contrast echocardiography (MCE) are related to functional recovery. Consecutive patients (n = 32) who presented with a first non-ST-elevation myocardial infarction were included in our study. MCE was performed on admission, 1 to 4 hours after angioplasty, and at 24 hours, 4 days, and 4 weeks of follow-up. Contrast images were analyzed visually and quantitatively. Myocardial blood flow was estimated by calculating the product of peak signal intensity and the slope of signal intensity increase. Improvement of wall motion on follow-up echocardiograms after 4 weeks served as a reference for functional recovery of impaired left ventricular function. Of 496 segments available for analysis, 128 (26%) were initially dysfunctional and 96 (75%) recovered at 4 weeks of follow-up. Myocardial tissue reperfusion occurred gradually, expanding over the first 24 hours after percutaneous coronary intervention (myocardial blood flow of 0.4 ± 0.3 initially, 0.6 ± 0.4 at 24 hours, and 1.6 ± 0.7 dB/s at 4 weeks of follow-up, p <0.001). Extent of tissue reperfusion was closely related to grade of improvement of global ejection fraction (r2 = 0.76, p <0.001). MCE predicted functional recovery with a sensitivity of 81%, a specificity of 88%, and accuracy of 83% on a segmental level. Thus, impaired microvascular integrity is suggested by MCE in patients who present with non-ST-elevation myocardial infarction. Improvement of regional tissue perfusion after revascularization is closely related to functional recovery. This information may aid risk stratification and allow monitoring of the effectiveness of reperfusion therapy in these patients.