Myocardial infarct size determined by computed transmission tomography in canine infarcts of various ages and in the presence of coronary reperfusion

MRI and CT in the diagnosis of coronary artery disease: indications and applications

In recent years, technical advances and improvements in cardiac computed tomography (CT) and cardiac magnetic resonance imaging (MRI) have provoked increasing interest in the potential clinical role of these techniques in the non-invasive work-up of patients with suspected coronary artery disease (CAD) and correct patient selection for these emerging imaging techniques. In the primary detection or exclusion of significant CAD, e.g. in the patient with unspecific thoracic complaints, and also in patients with known CAD or advanced stages of CAD, both CT and MRI yield specific advantages. In this review, the major aspects of non-invasive MR and CT imaging in the diagnosis of CAD will be discussed. The first part describes the clinical value of contrast-enhanced non-invasive CT coronary angiography (CTCA), including the diagnostic accuracy of CTCA for the exclusion or detection of significant CAD with coronary artery stenoses that may require angioplastic intervention, as well as potentially valuable information on the coronary artery vessel wall. In the second section, the potential of CT for the imaging of myocardial viability and perfusion will be highlighted. In the third and final part, the range of applications of cardiac MRI in CAD patients will be outlined.

Assessment of myocardial perfusion and viability from routine contrast-enhanced 16-detector-row computed tomography of the heart: preliminary results

To assess the diagnostic accuracy of 16-detector-row computed tomography (16DCT) of the heart in the assessment of myocardial perfusion and viability in comparison to stress perfusion magnetic resonance imaging (SP-MRI) and delayed-enhancement magnetic resonance imaging (DE-MRI). A number of 30 patients underwent both 16DCT and MRI of the heart. Contrast-enhanced 16DCT data sets were reviewed for areas of myocardium with reduced attenuation. Both CT and MRI data were examined by independent reviewers for the presence of myocardial perfusion defects or myocardial infarctions (MI). Volumetric analysis of the hypoperfusion areas in CT and the infarct sizes in DE-MRI were performed. According to MRI, myocardial infarctions were detected in 11 of 30 cases, and perfusion defects not corresponding to an MI were detected in six of 30 patients. CTA was able to detect ten of 11 MI correctly (sensitivity 91%, specificity 79%, accuracy 83%), and detected three of six hypoperfusions correctly (sensitivity 50%, specificity 92%, accuracy 79%). Assessing the volume of perfusion defects correlating to history of MI on the CT images, a systematic underestimation of the true infarct size as compared to the results of DE-MRI was found (P<0.01). Routine, contrast-enhanced 16-detector row CT of the heart can detect chronic myocardial infarctions in the majority of cases, but ischemic perfusion defects are not reliably detected under resting conditions.

Features of cardiac disease demonstrated on CT pulmonary angiography

The heart and mediastinal structures can be overlooked at CT pulmonary angiogram (CTPA). This pictorial review will demonstrate the features of cardiac disease that may be evident on a CTPA. CTPA allows assessment of not only the pulmonary arteries for embolism, but also of the bronchi, lung parenchyma, mediastinum and heart. Co-existent underlying or incidental cardiac disease is often present. Potentially life-threatening alternative diagnoses in a patient with chest symptoms can be reliably identified. Pathologies of the myocardium including hypertrophic cardio myopathy, pericardial disease, valvular disease, coronary artery disease, and intracardiac abnormalities are demonstrated pictorially. CTPA is increasingly used for the detection of pulmonary embolism. Most patients investigated have pathology other than PE as a cause of their symptoms. Frequently information about the heart is produced that provides important clues to determine the cause for the presenting symptoms and signs or reveals co-existing pathology. It is important to have a clear understanding of the features of cardiac disease which may be seen on a CTPA.

Effects of beta-adrenergic blockade on the natural progression of myocardial infarct size and compensatory hypertrophy

Using contrast-enhanced computed tomography, the effects of beta-adrenergic blockade were assessed on experimentally produced myocardial infarcts in dogs evaluated serially over the course of approximately 1 month. Infarct size, initial perfusion defect (jeopardized segment) and noninfarcted muscle mass were studied in two groups of conditioned mongrel dogs. Group 1 (n = 11) served as the control group and Group 2 (n = 10) was pretreated with propranolol (2 mg/kg). Each animal in the propranolol-treated group was given identical amounts of the agent twice daily for 7 days after coronary occlusion. Both groups developed increases in the noninfarcted muscle mass of the left ventricle (compensatory hypertrophy). The mean increase averaged 19.8% over 30 days when the two groups were included together. Infarct size was smaller in the propranolol-treated group, and averaged 28% less (p less than 0.05) than that of the control group 30 days after initial myocardial infarction. Thus, pharmacologic interventions were shown by computed tomography to alter the size of an acute experimental myocardial infarct, particularly when examined over the time course of infarct healing. Moreover, compensatory hypertrophy occurred in both the control and propranolol-treated groups.

Computed tomographic analysis of the effects of hyperosmolar mannitol and methylprednisolone on myocardial infarct size

Using contrast-enhanced computed tomography, the effects of hyperosmolar mannitol and methylprednisolone on experimentally produced myocardial infarcts were evaluated serially over the course of approximately 1 month. Infarct size, initial perfusion defect (jeopardized segment) and noninfarcted muscle mass were determined in three groups of conditioned mongrel dogs. Group 1 (n = 11) served as the control group, groups 2 and 3 were pretreated with mannitol (375 mg/kg, n = 10) or methylprednisolone (7.5 mg/kg, n = 11). Each animal in the treatment groups was treated with identical doses of the originally administered agent twice daily for 7 days after coronary occlusion. Each group developed increases in the noninfarcted muscle mass of the left ventricle (compensatory hypertrophy). The mean increase averaged more than 20% over 30 days when all groups were included together. Infarct size was smaller in both of the treatment groups. However, at 4 days after infarction, mannitol-treated dogs had a mean infarct size that was 68 +/- 8% (+/- standard error of the mean) of the size of control infarcts (p less than 0.01) and methylprednisolone-treated dogs had a mean infarct size that was 77 +/- 6% of the size of control infarcts (p less than 0.01) (referenced to the initial perfusion defect). At 30 days, these differences were less substantial (though still significant), 88 +/- 4% and 85 +/- 5%, respectively. Pharmacologic interventions can be shown to alter the size of an acute myocardial infarction, particularly when examined over the time course of infarct healing.(ABSTRACT TRUNCATED AT 250 WORDS)