Measurement of infarct size and percentage myocardium infarcted in a dog preparation with single photon - emission computed tomography , thallium - 201 , and indium 111 - monoclonal antimyosin

Single photon-emission tomography (SPECT) and indium 1ll-labeled monoclonal antimyosin Fab fragments were used to measure myocardial infarct size in 12 dogs, six subjected to balloon catheter-induced coronary artery occlusion for 6 hr (late reperfusion) and six subjected to occlusion with reperfusion at 2 hr (early reperfusion). Tomographic imaging was performed 24 hr after the intravenous injection of labeled Fab fragments with the use of a dual-head SPECT camera with medium-energy collimators. Immediately after the first tomographic scan, thallium-201 was injected into nine of 12 dogs and imaging was repeated. Estimated infarct size in grams was calculated from transaxially reconstructed, normalized, and background-corrected indium SPECT images with the use of a threshold technique for edge detection. Estimated noninfarcted myocardium in grams was calculated from obliquely reconstructed thallium SPECT images by a similar method. The animals were killed and infarct size in grams and true infarct size as a percentage of total left ventricular myocardial volume were measured by triphenyl tetrazolium chloride staining. Estimated infarct size from indium SPECT images showed an excellent correlation with true infarct size (r = .95, SEE = 4.1 g). Estimated percentage myocardium infarcted was calculated by dividing estimated infarct size from indium images by the sum of estimated infarct size plus estimated noninfarcted myocardium obtained from thallium images. Correlation between the estimated percentage of myocardium infarcted and true percentage of myocardium infarcted was excellent (r = .93, SEE = 4.4%). We conclude that dual-isotope SPECT with indium 11 1-monoclonal antimyosin antibodies and thallium-201 can accurately estimate infarct size and percentage myocardium infarcted. Circulation 76, No. 1, 181-190, 1987. AN ACCURATE and noninvasive radionuclide imaging technique to localize and size acute myocardial infarctions could provide valuable diagnostic and prognostic information for the care of patients and also prove useful in clinical research. With the advent of thrombolytic therapies and percutaneous transluminal angioplasty for acute myocardial infarction, a means to size the amount of myocardium that is irreversibly damaged would be particularly useful. Serial creatine Vol. 76, No. 1, July 1987 kinase (CK)-MB in plasma, electrocardiographic ST segment maps, and gated blood pool measurements of regional left ventricular function have been used in the past to estimate the size of acute myocardial infarction. 1-3 However, each of these techniques has limitations that have precluded widespread clinical use for this purpose. Technetium-99m (91Tc) stannous pyrophosphate is an infarct-avid imaging agent that is used clinically to diagnose myocardial infarction but that has been shown to be poorly delivered into highly avascular tissue in the central portions of infarcts,4 a property that theoretically would prevent it from being an ideal agent for sizing infarcts. Khaw, Haber, and their colleagues5-9 developed 181 From the Departments of Medicine and Radiology, Columbia University, New York. Address for correspondence: Lynne L. Johnson, M.D., Department of Medicine, 630 West 168 St., New York, NY 10032. Received Oct. 13, 1986; revision accepted March 26, 1987. by gest on A ril 2, 2017 http://ciajournals.org/ D ow nladed from