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Post-MI Fat Associated With Longer Post-Infarction Period

December 2, 2009
Written by: , Filed in: Cardiac Imaging
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The objective of a recent study was to analyze myocardial fat using CT in patients who have had myocardial infarction (MI).

The results have shown that myocardial fat appears to be associated with a longer post-infarction time frame and to be associated with worse wall motion abnormality.

Design
Retrospective study.

Participants
161 patients who previously had an MI and had undergone CT coronary angiography (CTA).

Methodology
CTs were performed with a 16-MDCT scanner. The protocol for CT was a non-contrast CT for purposes of coronary calcium scoring, followed by a contrast-enhanced CTA. The non-contrast CT used a prospective ECG-triggered protocol and low-dose technique.

The CTA used 100 to 120 mL of contrast and retrospective ECG gating. Images were reconstructed with 1-mm slice thickness at 0.5-mm increments. Presence of fat was evaluated on axial images and reformatted short-axis and long-axis images. If fat attenuation was seen on non-contrast CT, it was assumed that the myocardium contained fat.

Using regions of interest (ROIs), a mean CT attenuation for each region of myocardial fat was measured. Similar ROIs were measured on contrast-enhanced CTA images in regions that corresponded to fat attenuation regions on non-contrast CT. The distribution of myocardial fat by analyzing coronary artery territories and transmural extent of myocardial fat was also analyzed.

Cardiac CTA: What You Need to Know
 
 University of California San Francisco, Department of Radiology
 Course Director: Gautham P. Reddy, MD, MPH

 
  Coronary artery disease is the leading cause of morbidity and mortality in industrialized countries. With the advent of 64-detector CT scanners, CT has become an essential tool for evaluation of the heart and great vessels, and is a promising technique for assessment of the coronary arteries.
 
  Click here to read more or order:
  Cardiac CTA: What You Need to Know

Results
Myocardial fat was seen in 43 coronary artery territories in 40 of 161 patients. Thirty-six of 43 patients (22.4% of 161 patients) had myocardial fat present in the same coronary artery territory where MI had occurred. In each case, fat was located in the sub-endocardial layer of the myocardium.

The transmural extent of fat was never >75% of the thickness of the left ventricular wall. Mean attenuation of fat was -29.6 HU (range, -90.5 to 8.8 HU) on non-contrast CT and -11.2 HU (range -75.6 to 33.7 HU) on contrast-enhanced CTA.

The incidence of myocardial fat was higher as the time after infarction grew longer
9.1% within one year, 20.7% between years two and three, 37.0% between years four and seven7, and 46.4% after seven years.

Coronary stenoses in areas of infarction were milder in patients with myocardial fat, and there were fewer vessels that had stenoses in patients with myocardial fat. In those patients who had echocardiography, patients with prior MI who had myocardial fat more often had akinesia compared with those who did not have myocardial fat.

Conclusions
Fat was seen in the infarcted myocardium of 22.4% of patients. Myocardial fat was associated with a longer post-infarction time frame and was associated with worse wall motion abnormality.

Reviewer’s Comments
The authors have demonstrated some interesting observations regarding myocardial fat deposition post-infarction. It would be interesting to study if there are any differences in delayed hyper enhancement during viability imaging with MRI in patients with post-infarction myocardial fat deposition compared with those without fat deposition.

Author: Vineet R. Jain, MD

Reference:
Ahn SS, Kim Y-J, et al. CT Detection of Subendocardial Fat in Myocardial Infarction. AJR Am J Roentgenol; 2009;192 (February): 532-537.

Cardiac CTA: What You Need to Know
 
 University of California San Francisco, Department of Radiology
 Course Director: Gautham P. Reddy, MD, MPH

 
  Coronary artery disease is the leading cause of morbidity and mortality in industrialized countries. With the advent of 64-detector CT scanners, CT has become an essential tool for evaluation of the heart and great vessels, and is a promising technique for assessment of the coronary arteries.
 
  Click here to read more or order:
  Cardiac CTA: What You Need to Know
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