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Myocardial Bridging More Often Seen With CT

March 1, 2008
Written by: , Filed in: Cardiac Imaging
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The objective of a recent study was to evaluate MB seen on CT with conventional coronary angiography.

The study has concluded that CT more often demonstrates myocardial bridging (MB) than does conventional invasive coronary angiography, and the degree of systolic compression of the tunneled coronary artery segment correlates with the depth of the tunneled segment, not its length.

Participants
One hundred patients who underwent both CT coronary angiography (CTA) and conventional coronary angiography. An additional 50 patients who only underwent CTA were also analyzed.

Methodology
A 64-section CT was used. Dose modulation was not employed. In each patient, 10 CT data sets were reconstructed from 10% to 100% of the cardiac cycle. Multiplanar and curved planar reformations were constructed in two planes.

MB is where a portion of a coronary artery courses through myocardium and does not lie in its usual epicardial location. The length and depth of the tunneled coronary artery segment was measured. The mean diameter of the tunneled portion of the coronary artery at maximum depth was measured in both end-systole and end-diastole.

On conventional invasive coronary angiography, MB, which is imaged indirectly, was felt to be present if a coronary artery segment demonstrated narrowing of its diameter during systole, if a milking effect was seen, defined as narrowing of a restricted coronary artery segment with drawing out of contrast not explained by normal coronary arterial flow, and/or a step down-step up phenomena characterized as a local change in vessel course direction toward the ventricle.

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 of the Study
In the 100 patients evaluated with conventional angiography and CT, MB was seen with conventional angiography in 12% of patients and with CT in 26%. In the 150 total patients evaluated with CT, the mean length of tunneled coronary segment was 24.3 mm +/- 10.0 mm (range, 8 to 50 mm).

Mean depth was 2.6 mm +/- 0.8 mm (range, 1.4 to 4.8 mm), and mean systolic compression of the tunneled coronary artery segment was 15.6% +/- 13.6% (range, 0% to 45%). Correlation was present between the percentage of systolic compression and depth of the tunneled coronary artery segment (r = 0.65; P <0.01). No correlation was seen between percentage of systolic compression and length of the tunneled coronary artery segment (r = 0.16; P =0.25). In patients who had MB identified on CT but not conventional angiography (n=14), the depth, length, and amount of systolic compression was significantly less than in patients who had MB seen on both CT and conventional angiography. Conclusions
MB is more often seen with 64-section CT than with conventional angiography and the percentage of systolic compression correlates with the depth of the tunneled coronary artery segment.

Reviewer’s Comments
The authors note that although MB is in itself usually benign, the coronary artery segment immediately proximal to the area of bridging has a higher chance of developing plaque likely due to less wall shear stress proximal to an area of bridging.

Author: Vineet R. Jain, MD

Reference
Leschka S, Koepfli P, et al. Myocardial Bridging: Depiction Rate and Morphology at CT Coronary Angiography–Comparison With Conventional Coronary Angiography.
Radiology; >/i>2008; 246 (March): 754-762:

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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