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.

Ultrasound contrast agents can influence the respiratory burst activity of human neutrophil granulocytes.

Activated leucocytes can bind and, subsequently, phagocytose microbubbles that are used as ultrasound (US) contrast agents. The purpose of this study was to investigate whether or not microbubbles can influence the inflammatory response of human neutrophil granulocytes. Granulocytes isolated from healthy volunteers were activated with various stimuli, for example, the bacterial peptide N-formyl-methyonyl-leucyl-phenylalanine (fMLP), the calcium ionophore A23187, the protein kinase C activator phorbol myristate acetate (PMA) and the cytokine tumor necrosis factor alpha (TNF-alpha), and incubated with albumin or phospholipid microbubbles. Neutrophil respiratory burst activity and elastase release were quantified. Albumin (Optison) and phospholipid (SonoVue) contrast agents induced an extensive oxidative response of human granulocytes to all the stimuli used, and these effects could be significantly impaired by preincubation of the cells with cytochalasin B. Left heart contrast agents used for contrast-enhanced US assessment can activate human neutrophil granulocytes, inducing an extensive respiratory burst to secondary stimuli. The potential clinical relevance of this effect needs to be elucidated.