TIMI Myocardial Perfusion Grade and ST Segment Resolution: Association With Infarct Size as Assessed by Single Photon Emission Computed Tomography Imaging

Abstract

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...

Early Resolution of ST-Segment Elevation Correlates With Myocardial Salvage Assessed by Tc-99m Sestamibi Scintigraphy in Patients With Acute Myocardial Infarction After Mechanical or Thrombolytic Reperfusion Therapy

“…In addition, the extent of ST-segment resolution was a sensitive parameter to identify the superiority of stenting over thrombolysis as reperfusion strategy in patients with AMI. Previous studies in patients treated with thrombolysis or primary percutaneous coronary intervention for AMI showed that the extent of the early ST-segment resolution correlates with the angiographic flow to the infarct area, 7,8 the enzymatic 9 and scintigraphic final infarct size, 10 the left ventricular function, and clinical outcome. 7,8,11 We also found a good correlation between a greater STsegment resolution and a smaller scintigraphic final infarct size and better survival rate at 6 months.…”

Relationship of Admission QRS Duration and Changes in QRS Duration With Myocardial Reperfusion in Patients With Acute ST Segment Elevation Myocardial Infarction (STEMI) Treated With Fibrinolytic Therapy

“…In this study, as a surrogate of reperfusion, we used a myocardial blush as the TMP grade, which was previously shown to be related to enzymatic infarct size, the extent of ST segment elevation resolution, left ventricular function, long-term mortality 8 and degree of myocardial salvage assessed by scintigraphy 9,11 in patients with acute MI. We used TMP grades obtained from coronary angiograms that were performed at a mean of 3 days after acute MI.…”

“…As the surrogate of tissue level reperfusion, we used angiographic myocardial blush grade, which was shown to be a reliable index of microvascular integrity in previous reports. [8][9][10][11] …”

Coronary and Myocardial Angiography

“…It is notable that both the ST segment resolution and the TMPG provide independent prognostic information with respect to SPECT infarct size. 11 Likewise, with respect to clinical outcomes, 2 additional studies have now documented the complementary prognostic information provided by the ECG (degree of ST resolution) and the angiographic blush, with failure to achieve ST resolution and a closed myocardium on angiography following primary PCI carrying a particularly poor prognosis. 59,69 These data suggest a potential electromechanical dissociation between microvascular blood flow and myocyte function.…”