CORRESPONDENCE: LETTER TO THE EDITOR
Quantification of Coronary Lesions by 64-Slice Computed Tomography Compared With Quantitative Coronary Angiography and Intravascular Ultrasound
Jasper S. Wijpkema, MD*,
René A. Tio, MD, PhD and
Felix Zijlstra, MD, PhD
* Department of Cardiology, University Medical Center Groningen, Hanzeplein 1, P.O. Box 30 001, 9700 RB Groningen, the Netherlands (Email: jasper{at}wijpkema.nl).
With great interest we have read the recent study by Leber et al. (1). They report an excellent accuracy of the new 64-slice computed tomography to diagnose proximal coronary lesions and its correlation with intravascular ultrasound. This important study reflects the rapid progression of multidetector computed tomography (MDCT) and underscores the potential of MDCT in clinical practice. In the editorial by Achenbach and Daniel (2) it is stated that, with these rapidly evolving techniques, MDCT will be able to rule out hemodynamically important stenoses in the near future, thereby replacing invasive diagnostic techniques. Although we acknowledge the great improvements in MDCT to diagnose coronary stenoses, we believe there are fundamental limitations to this technique. In this perspective we agree with Achenbach and Daniel that there is "more than meets the (angiographic) eye" when it comes to coronary lesions.
Visual estimation of the degree of coronary stenoses on coronary angiograms remains a difficult problem in clinical practice of interventional cardiologists. This assessment usually results in an overestimation of the stenosis, even when this estimation is performed by an experienced cardiologist (3). Although quantitative coronary angiography will define the degree of stenosis more accurately, it still provides no information on the functional severity of the stenosis. Fractional flow reserve was introduced to eliminate this visual bias and measure the functional significance of a lesion (4). This diagnostic procedure has since been the gold standard for evaluating coronary artery stenoses and has a great value in predicting which lesions will benefit from percutaneous coronary interventions and which lesions will not. Therefore, especially in case of intermediate coronary lesions, other diagnostic tools such as myocardial perfusion imaging with methoxyisobutylisonitrile (MIBI), single-photon emission computed tomography, and fractional flow reserve are needed in addition to coronary angiography to decide on the optimal treatment strategy in individual patients.
Naturally, MDCT has some important advantages over coronary angiography, as MDCT is not only able to show the luminal narrowing, but also provides insight in surrounding tissues and plaque morphology. However, considerable doubt can be raised as to whether stenosis visualization by MDCT will be able to correctly identify and differentiate between functionally significant and nonsignificant stenoses, in particular as quantification of stenoses by MDCT still remains difficult (1,5). So, although MDCT may be very accurate in the detection of coronary artery disease, when treatment strategies have to be made for individual patients more emphasis should be given to functional instead of anatomical tests. Therefore, in our opinion, MDCT will not replace invasive or noninvasive procedures to evaluate the hemodynamic severity of coronary lesions; rather, it will complement the currently available assortment of anatomy-oriented visualization techniques.
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1. Leber AW, Knez A, von Ziegler F, et al. Quantification of obstructive and nonobstructive coronary lesions by 64-slice computed tomographya comparative study with quantitative coronary angiography and intravascular ultrasound. J Am Coll Cardiol 2005;46:147-154.[Abstract/Free Full Text]2. Achenbach S, Daniel WG. Computed tomography of the coronary arteriesmore than meets the (angiographic) eye. J Am Coll Cardiol 2005;46:155-157.[Free Full Text] 3. Fischer JJ, Samady H, McPherson JA, et al. Comparison between visual assessment and quantitative angiography versus fractional flow reserve for native coronary narrowings of moderate severity Am J Cardiol 2002;90:210-215.[CrossRef][Web of Science][Medline] 4. Pijls NH, De Bruyne B, Peels K, et al. Measurement of fractional flow reserve to assess the functional severity of coronary-artery stenoses N Engl J Med 1996;334:1703-1708.[Abstract/Free Full Text] 5. Kefer J, Coche E, Legros G, et al. Head-to-head comparison of three-dimensional navigator-gated magnetic resonance imaging and 16-slice computed tomography to detect coronary artery stenosis in patients J Am Coll Cardiol 2005;46:92-100.[Abstract/Free Full Text]
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