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History:
52 year old asymptomatic male smoker with mildly elevated cholesterol
and family history of coronary artery disease, volunteered for CT
coronary angiography at Main Street Radiology.
Technique:
Oral beta-blocker was administered the night prior to the exam to
reduce the heart rate below 70 bpm. 100 cc of intravenous contrast was
administered during a 20 second breath-hold. EKG-gated images were
obtained on a 16-detector spiral CT.
Findings:
3D anterior image of heart (figure 1) outlines normal anatomy (AO =
aorta; PA = pulmonary artery; RA = right atrium; RCA = right coronary
artery; LAD = left anterior descending artery; RV = right ventricle;
LV = left ventricle; DX = diagonal branch). 3D oblique image of the
left coronary arteries (figure 2) demonstrates no significant stenosis
(LCX = left circumflex artery; RI = ramus intermedius). 3D oblique
image of the RCA demonstrates focal stenosis proximally (arrow). A
non-calcified (soft) plaque (arrow) is seen on the 2D axial-oblique
image of the right coronary artery (figure 4), with approximately 40%
stenosis.
Recommendations:
Aggressive intervention to reduce risk factors.
Discussion:
In October 2003, MSR installed the first
16-detector spiral CT in Queens. With this new technology, we are one
of the first facilities in the New York area to perform many
sophisticated studies including CT coronary angiography.
The 16-detector CT enables
"isotropic" volume acquisition, where true 3D images can be
obtained in every projection. Previously available CT technology
suffered from loss in resolution when images were viewed at different
angles. Coronary arteries can now be viewed at the highest resolution,
not dependent on its orientation. In addition, due to it's
unprecedented speed, the 16 detector CT can effectively
"freeze" cardiac motion for heart rates less than 70 bpm.
Early reports indicate that CT coronary
angiography may ultimately replace diagnostic cardiac catheterization,
with reported sensitivity of 95% (Nieman, Circulation 2002; 106 (16):
2051-4).
Advantages of CT coronary angiography
include:
- CT angiography is non-invasive, only
requiring IV injection of iodinated contrast
- Less expensive
- Aside from the lumen, the vessel
wall and plaque can be imaged and characterized ("soft"
vs. "hard" plaque)
- 2D and 3D images can be viewed at
every angle and in cross section, increasing accuracy of grading
of stenosis
As up to 50% of diagnostic cardiac
catheterizations fail to show significant disease, CT coronary
angiography may take on an important role in screening patients with
indications for cardiac catheterization. As more studies are published
in the medical literature, indications for CT coronary angiography
should be better defined.
