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.

Usefulness of real-time myocardial perfusion imaging in the evaluation of patients with first time chest pain.

In patients who have acute coronary syndrome (ACS), rapid and accurate risk stratification is crucial. Real-time myocardial contrast echocardiography (MCE) extends the evaluation of wall motion abnormalities by assessing myocardial perfusion. We investigated whether MCE could contribute to clinical and biochemical markers in identifying patients who have ACS when presenting to the emergency department. Consecutive patients (n = 100) who presented with first occurrence of chest pain underwent MCE to evaluate myocardial perfusion. Contrast images were also analyzed quantitatively off-line by measuring peak signal intensity (A) and slope of signal intensity increase (beta) in 16 myocardial segments. Thirty-seven of 100 patients had ACS. MCE showed perfusion defects in 9 of 12 patients (75%) who had unstable angina and had high-grade stenotic lesions on an angiogram that were missed by assessment of troponin T. MCE identified all 6 patients who had non-ST-elevation myocardial infarction and no initial increase in troponin T and 17 of 19 patients who had non-ST-elevation myocardial infarction and an initial increase in troponin T. In 2 patients who had chest pain and increased troponin T, MCE excluded ACS by identifying perimyocarditis as the underlying cause. Multivariate logistic regression analysis showed that MCE was the strongest predictor of ACS, thus adding significant diagnostic value to conventional tests. Initial perfusion defect size correlated strongly with increased troponin T at 96 hours (r = 0.73, p <0.001) and with ejection fraction at 4 weeks of follow-up (r = -0.79, p <0.001). Thus, our data suggest that MCE can accurately identify patients who have ACS.