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64-MDCT Demonstrates Altered Perfusion of Ischemic Myocardium

July 1, 2009
Written by: , Filed in: Cardiac Imaging
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A recent study was conducted to evaluate the perfusion of ischemic myocardium on 64-MDCT coronary angiography.

The study, reported in AJR, concluded that in general, on 64-MDCT coronary angiography, ischemic myocardium is characterized by less perfusion of the subendocardium during systole and normal perfusion during diastole.

The Study
The study group included 34 patients who either had effort or rest stable angina or were asymptomatic, but had strong risk factors for coronary artery disease, or had abnormal exercise electrocardiography findings.

Exclusion criteria included acute MI, unstable angina, left ventricular ejection fraction <20%, class IV congestive heart failure, and patients with near fat attenuation of subendocardium because this suggested prior subendocardial infarction.

The control group included 28 patients of similar age who had no symptoms of cardiac disease and were not taking any medications.

Methodology
The study group underwent both 64-MDCT and stress/rest 201Tl myocardial perfusion scintigraphy (MPS).

For CT, an oral beta-blocker was given as needed to maintain a heart rate <65 bpm.

Forty to 60 mL of contrast (ioversol 320) was administered.

Long-axis and short-axis images of the heart were reconstructed at end-systole (R-R interval, 40%) and end-diastole (R-R interval, 75%).

The attenuation of the subendocardium in each of the 17 segments of the myocardium was measured by the use of a region of interest.

Systolic myocardial perfusion and diastolic myocardial perfusion was calculated by division of the attenuation value of the subendocardium at systole or diastole, respectively, for each segment by the mean attenuation value across all 34 segments.

Differences in myocardial perfusion during the cardiac cycle were measured as the difference between systolic perfusion and diastolic perfusion.

All CT angiograms also had the coronary arteries evaluated for significant (>50%) stenosis.

SPECT images were evaluated for myocardial perfusion in each vascular territory.

Control subjects only underwent 64-MDCT and not 201Tl MPS.

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
The systolic perfusion for ischemic segments was significantly lower than for nonischemic segments in 15 of the 17 segments. The diastolic perfusion for ischemic segments was not significantly different compared with nonischemic segments in 15 of the 17 segments.

The difference between systolic perfusion and diastolic perfusion was significantly less for ischemic segments than it was for nonischemic segments in 14 of the 17 segments.

Conclusions
In general, ischemic myocardium is characterized by subendocardial hypoperfusion during systole, and normal perfusion during diastole on contrast-enhanced 64-MDCT coronary angiography.

Reviewer’s Comments

The authors have demonstrated that despite limitations, 64-MDCT coronary angiography has the potential to detect myocardial ischemia at rest.

Author: Vineet R. Jain, MD

Reference:

Nagao M, Matsuoka H, et al. Quantification of Myocardial Perfusion by Contrast-Enhanced 64-MDCT: Characterization of Ischemic Myocardium. AJR; 2008; 191 (July): 19-25

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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