for the Limitation of Myocardial Injury following Thrombolysis in Acute Myocardial Infarction (LIMIT AMI) Study GroupBackground-The TIMI myocardial perfusion grade (TMPG) and ST-segment resolution both reflect perfusion and are associated with mortality after thrombolysis for acute myocardial infarction. We hypothesized that these measures would also be associated with infarct size by single photon emission computed tomography (SPECT).
Methods and Results-In the LIMIT AMI trial (Limitation of Myocardial Injury following Thrombolysis in AcuteMyocardial Infarction) of lytic monotherapy versus lytic plus rhuMAb CD18, early 90-minute TMPG (nϭ221) and ST segment resolution (nϭ242) were compared with subsequent SPECT Technetium-99 m Sestamibi, measuring the percentage of the left ventricle with no Sestamibi uptake. Infarct sizes were larger with TMPG 0 or 1 (a closed or stained myocardium) than with TMPG 2 or 3 (open myocardium, median 13% versus 7%, Pϭ0.004). Infarcts were also larger in patients with no ST segment resolution (median 15%) or incomplete resolution (11%) than in those with complete resolution (6%, overall Pϭ0.0001). The difference in infarct size by TMPG persisted when stratified by category of ST resolution. Conclusions-There may be a pathophysiological link between early restoration of tissue-level perfusion and reduced subsequent infarct size that may partially explain why these early angiographic and electrocardiographic measures are associated with long-term survival. Key Words: myocardial infarction Ⅲ microcirculation Ⅲ electrocardiography Ⅲ angiography Ⅲ thrombolysis C urrent treatment of acute myocardial infarction (AMI) focuses on restoring epicardial blood flow. 1,2 Even when epicardial flow is restored, however, the 30-day mortality rate may be 7-fold higher in patients with abnormal microvascular flow compared with those with normal microvascular flow. 3 New therapies that may improve microvascular flow are being developed, as are techniques to measure it. 4 -7 These measurements, along with traditional estimates of infarct size, are associated with mortality after AMI. 3,8 -12 However, their relationships to each other are not well established, particularly the relationship between early angiographic and ECG measures and subsequent infarct size. We hypothesized that early abnormalities in perfusion would be associated with larger infarct size in the recent LIMIT AMI trial (Limitation of Myocardial Injury following Thrombolysis in Acute Myocardial Infarction). 13
MethodsThe LIMIT AMI trial of rhuMAb CD18, a leukocyte adhesion inhibitor, was a randomized, double-blind, placebo-controlled study that enrolled 394 subjects in 60 centers in the United States and Canada between September 1998 and March 2000. 13 Patients presenting within 12 hours of chest pain Ն30 minutes in duration and ST segment elevation on ECG were included. One of 2 doses of rhuMAb CD18 or placebo was administered before tissue plasminogen activator (tPA) or as soon as possible thereafter, along with aspirin and heparin. B...
Myocardial contrast echocardiography (MCE) has undergone many advances in the past several years through remarkable developments in contrast agent and ultrasound equipment technology. Microbubble ultrasound contrast agents can now safely transit the pulmonary circulation to provide opacification of the left ventricular cavity, improved endocardial border definition, and detection of myocardial perfusion. The role of contrast echocardiography in enhancing technically difficult images is now well established in clinical practice, and has proven especially useful in the stress and intensive care unit settings. Major progress has been made in the application of MCE for myocardial perfusion assessment in acute and chronic ischemic heart disease syndromes, and comprises the focus of this review. Advances in novel applications of contrast echocardiography, including targeted delivery of genetic and pharmaceutical materials, have also occurred, but remain in a preclinical phase. In summary, the combination of recent innovations in ultrasound equipment, and microbubble acoustics, allows for exciting exploration of the expanding role of contrast echocardiography in clinical practice.
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