EFFECT OF INFARCT LOCATION ON MYOCARDIAL SALVAGE ASSESSED BY TC-99M ISONITRILE

To investigate the influence of infarct location on myocardial salvage, technetium-99m isonitrile was injected into 43 patients with a first myocardial infarction before early reperfusion therapy. Primary coronary angioplasty was performed in 22 patients and successful intravenous thrombolytic therapy was given to 15 patients, both within 6 h of the onset of chest pain. Patency of the infarct-related artery was confirmed by angiography in all 37 patients. In the remaining six patients (three with and three without early thrombolytic therapy) the infarct-related artery remained occluded. Single photon emission computed tomography was performed within 6 h of the administration of technetium-99m isonitrile and repeated at the time of hospital discharge. Radionuclide ejection fraction at discharge was significantly lower for patients with anterior infarction (0.41 +/- 0.12) than for those with inferior infarction (0.56 +/- 0.09, p < 0.001). Early perfusion defect size, a measure of myocardium at risk, was greater in patients with anterior than in those with inferior infarction (52 +/- 9% vs. 18 +/- 10% of the left ventricle, p = 0.0001) as was final defect size (30 +/- 20% vs. 9 +/- 8%, p < 0.01). The change in myocardial perfusion, an estimate of myocardial salvage, was also greater in patients with anterior infarction (24 +/- 16% vs. 10 +/- 7%, p < 0.01). However, the proportion of jeopardized myocardium salvaged (salvage index) was not significantly different between patients with anterior or inferior infarction (0.49 +/- 0.34 vs. 0.59 +/- 0.35, p = NS). Patients with an occluded infarct-related artery demonstrated no significant change in myocardial perfusion by change in defect size (0 +/- 2%) or by salvage index (0.06 +/- 0.07). Patients with anterior infarction have more myocardium at risk than do patients with inferior infarction and, subsequently, more myocardial salvage with reperfusion therapy. However, the proportion of jeopardized myocardium salvaged is independent of infarct location.