Cardiac Magnetic Resonance Can Assess At-Risk Myocardium After Myocardial Infarction
NEW YORK, June 4, 2009 — Cardiac magnetic resonance (CMR) with T2-weighted short tau inversion recovery (T2-STIR) can identify myocardium at risk up to 1 week after opening of an occluded coronary artery.
CMR can also quantify salvaged myocardium as the difference between myocardium at risk and final infarct size, according to a report by Swedish researchers in the May issue of the Journal of the American College of Cardiology: Cardiovascular Imaging.
"To assess the efficacy of reperfusion therapy, it is necessary to determine how much myocardium is salvaged by measuring the final infarct size in relation to the initial myocardium at risk," Dr Hakan Arheden et al from Lund University observed.
The authors noted that myocardium at risk—defined as hypoperfused myocardium during acute coronary occlusion—can be assessed by single-photon emission computed tomography (SPECT), but SPECT involves radioactive isotope injection in patients with acute coronary occlusion, scanning with a gamma camera, and other requirements that "could interfere with patient care in the acute setting."
In a study designed to validate the accuracy of T2-STIR over time for identification of myocardium at risk, 16 patients with acute ST-segment elevation myocardial infarction (STEMI) received injections of 99mTc tetrofosmin before primary percutaneous coronary intervention (PCI). SPECT was performed within 4 hours after primary PCI to determine myocardium at risk. CMR with T2-STIR was performed within 1 day, 1 week, 6 weeks, and 6 months. At 1 week, patients received injections of a gadolinium-based contrast agent for quantification of infarct size.
According to the article, "Myocardium at risk on T2-STIR did not differ from SPECT, at day 1 . . . or week 1 . . . but declined at week 6 . . . and month 6."
"The clinical usefulness of the present study is mainly that the size of myocardium at risk and myocardial infarction, and therefore myocardial salvage, can be assessed at the same image session within 1 week after acute coronary occlusion, without interfering with patient care in the acute setting," the authors concluded.
Source: Reuters Health Information
