Occlusive Acute Myocardial Infarct on 16 Multidetector-row Helical CT: An Experimental Study in Rabbits

PURPOSE: We wanted to evaluate the findings and diagnostic accuracy of MDCT for diagnosing occlusive acute myocardial infarction in rabbits. MATERIALS AND METHODS: Myocardial infarction was induced in 14 rabbits. MDCT was performed in the early and delay phases at 1 minute and 6 minutes, respectively, after intravenous contrast injection. The rabbits were sacrificed after scanning. The cardiac specimens were sliced and then stained with triphenyltetrazolium chloride (TTC). The agreement in the transmural extent of infarction between the MDCT scans and the TTC-stained specimens were analyzed by using kappa values. RESULTS: Acute myocardial infarction was found in 9 of 14 rabbits on the TTC-stained specimens and MDCT. The infarcted myocardium was demonstrated as a low-attenuation area on the early phase and as a central low-attenuation area with rim-like enhancement along the endocardial and pericardial sides of the myocardial wall on the delay phase. There was excellent agreement in the scores of the transmural extent of myocardial infarction between the TTC-stained specimens and the early phase scan (kappa value = 0.882, p = 0.000), and there was fair to good agreement between the TTC-stained specimens and the delay phase scan (kappa value = 0.439, p = 0.000). Microscopic examination of the cardiac specimens revealed necrosis of myocardial cells in the central portion and granulation tissue along the endocardial and pericardial sides of the necrotic myocardium. CONCLUSION: 16 slice MDCT scan was useful for the diagnosis of acute myocardial infarction. The early phase scan was more accurate than the delay phase scan for evaluating the transmural extent of myocardial infarction. Histopathologic examination suggested that the low-attenuation area on the delay phase might correspond to necrotic myocardium and the enhanced area might correspond to granulation tissue.

Occlusive Acute Myocardial Infarct on 16 Multidetector-row Helical CT: An Experimental Study in Rabbits

PURPOSE: We wanted to evaluate the findings and diagnostic accuracy of MDCT for diagnosing occlusive acute myocardial infarction in rabbits. MATERIALS AND METHODS: Myocardial infarction was induced in 14 rabbits. MDCT was performed in the early and delay phases at 1 minute and 6 minutes, respectively, after intravenous contrast injection. The rabbits were sacrificed after scanning. The cardiac specimens were sliced and then stained with triphenyltetrazolium chloride (TTC). The agreement in the transmural extent of infarction between the MDCT scans and the TTC-stained specimens were analyzed by using kappa values. RESULTS: Acute myocardial infarction was found in 9 of 14 rabbits on the TTC-stained specimens and MDCT. The infarcted myocardium was demonstrated as a low-attenuation area on the early phase and as a central low-attenuation area with rim-like enhancement along the endocardial and pericardial sides of the myocardial wall on the delay phase. There was excellent agreement in the scores of the transmural extent of myocardial infarction between the TTC-stained specimens and the early phase scan (kappa value = 0.882, p = 0.000), and there was fair to good agreement between the TTC-stained specimens and the delay phase scan (kappa value = 0.439, p = 0.000). Microscopic examination of the cardiac specimens revealed necrosis of myocardial cells in the central portion and granulation tissue along the endocardial and pericardial sides of the necrotic myocardium. CONCLUSION: 16 slice MDCT scan was useful for the diagnosis of acute myocardial infarction. The early phase scan was more accurate than the delay phase scan for evaluating the transmural extent of myocardial infarction. Histopathologic examination suggested that the low-attenuation area on the delay phase might correspond to necrotic myocardium and the enhanced area might correspond to granulation tissue.

The Significance of Perfusion Defect at Myocardial Perfusion MR Imaging in a Cat Model of Acute Reperfused Myocardial Infarction

OBJECTIVE: To determine whether the size of a perfusion defect seen at myocardial perfusion MR imaging represents the extent of irreversibly damaged myocardium in acute reperfused myocardial infarction. MATERIALS AND METHODS: In nine cats, reperfused myocardial infarction was induced by occlusion of the left anterior descending coronary artery for 90 minutes and subsequent reperfusion for 90 minutes. At single-slice myocardial perfusion MR imaging at the midventricular level using a turbo-FLASH sequence, 60 short-axis images were sequentially obtained with every heart beat after bolus injection of gadomer-17. The size of the perfusion defect was measured and compared with both the corresponding unstained area seen at triphenyl tetrazolium chloride (TTC) staining and the hyperenhanced area seen at gadophrin-2-enhanced MR imaging performed in the same cat six hours after myocardial perfusion MR imaging. RESULTS: The sizes of perfusion defects seen at gadomer-17-enhanced perfusion MR imaging, unstained areas at TTC staining, and hyperenhanced areas at gadophrin-2-enhanced MR imaging were 20.4+/-4.3%, 29.0+/-9.7%, and 30.7+/-10.6% of the left ventricular myocardium, respectively. The perfusion defects seen at myocardial perfusion MR imaging were significantly smaller than the unstained areas at TTC staining and hyperenhanced areas at gadophrin-2-enhanced MR imaging (p < .01). The sizes of both the perfusion defect at myocardial perfusion MR imaging and the hyperenhanced area at gadophrin-2- enhanced MR imaging correlated well with the sizes of unstained areas at TTC staining (r = .64, p = .062 and r = .70, p = .035, respectively). CONCLUSION: In this cat model, the perfusion defect revealed by myocardial perfusion MR imaging underestimated the true size of acute reperfused myocardial infarction. The defect may represent a more severely damaged area of infarction and probably has prognostic significance.