Occlusive Myocardial Infarct in Rabbits as Detected by the Use of Multidetector-row CT: A Radiological-pathological Correlation According to the Infarct Age

Abstract

Purpose: This study was designed to evaluate the imaging findings and the diagnostic accuracy for determining the transmural extent of a myocardial infarct (MI) in rabbits with the use of multidetector row CT (MDCT) according to the infarct age, and we determined the radiological and pathological correlation. Materials and Methods: MIs were demonstrated in 10 of 15 rabbits in which ligation of the left coronary arteries was performed. The cardiac scans were obtained according to the infarct age (hyperacute (within 24 hours), acute (24 hours to seven days) or chronic (eight weeks)) by using a 16-MDCT scanner in the contiguous transverse plane with 120.75 mm collimation, 420 ms rotation and retrospective ECG-gating. Early and late scans were obtained at one minute and six minutes, respectively, after intravenous contrast injection. The rabbits were sacrificed according to the infarct age. Slices of the cardiac specimens stained with triphenyltetrazolium chloride (TTC) and the MDCT images were evaluated for scoring the transmural extent of the MIs. The agreement of the scores between the MDCT images and TTC-stained specimens was statistically analyzed. The radiological and pathological correlation was determined for the specimens and the MDCT images. Results: The presence of an infarcted myocardium in the hyperacute phase was demonstrated as a mixed low and high-attenuation area on the early and late scans. In the acute phase, a low-attenuation area was seen on the early scan and a low-attenuation area with enhancement along the endocardial and pericardial sides was seen on the late scan. In the chronic phase, a high-attenuation area was seen on the late scan. There was fair agreement for the scores of the MDCT scan in hyperacute MI (kappa value = 0.380) and excellent agreement of the early scan in acute MI and the late scan of chronic MI (kappa value = 0.865 and 0.858, respectively). A pathological examination of the TTC-unstained areas of the MI specimens demonstrated the presence of necrosis of myocardial cells and the increased inflammatory infiltrates and repair process surrounding the damaged myocytes, according to the infarct age. Conclusion: The MDCT findings of MI were various according to the infarct age, which might be caused by the degree of the inflammatory and repair process. For diagnosing the transmural extent of MI, the early MDCT scan was useful for the acute MI and the late scan was useful for the chronic MI. However, MDCT was not useful for diagnosing the transmural extent of the hyperacute MI.