Role of Coronary Computed Tomographic Angiography in Coronary Stent Selection

   The importance of atherosclerotic lesion characteristics in determining long-term vessel patency and rate of complications after a percutaneous coronary intervention (PCI) has been recognized virtually since the inception of coronary angioplasty.¹ Ample consideration has been devoted to stent technology improvements and prevention of stent-related complications (such as with dual antiplatelet therapy),^2,3 but only a limited number of studies in the past decade addressed the issue of appropriate stent selection beyond vessel size and patients’ clinical characteristics (such as presence of diabetes).⁴ Despite the impressive improvement of intravascular ultrasound (IVUS) in determining stent sizing, its impact on clinical outcomes has not been validated and most interventional centers still rely on visual estimation of coronary arteries for stent placement.⁵ Such an approach certainly requires less time, money and expertise, but is no longer acceptable when we balance limited benefits against possible life-threatening iatrogenic complications of stent placement in stable coronary artery disease.    In the current issue of this journal, Kass et a16 propose an interesting approach to coronary lesion estimation prior to stenting by comparing various established methods for preprocedural stent selection: visual estimation, quantitative angiography and IVUS – with cardiac computed tomographic angiography (CCTA). They compared several lesion characteristics such as luminal diameter, lesion length and ACC/AHA lesion type in 17 patients with a total of 26 coronary lesions. Despite a relatively small sample size and a pilot design of the study, they found good agreement between CCTA and IVUS for lumen diameter and lesion length (r = 0.86 and 0.71, respectively), with an inter-test variability that was similar to the inter-observer variability of IVUS (interclass correlation coefficient of 0.85 and 0.90, respectively).    More importantly, CCTA performed at least as well as visual estimation of lesion characteristics and predicted stent placement with fair accuracy. Over the past years, CCTA has emerged as a promising noninvasive method, not only for the detection of coronary stenosis,⁷ but also for characterization of atherosclerotic plaques.⁸ With the introduction of 64-slice multidetector modalities, CCTA further advanced as an important aid in PCI by improving patient selection, lesion identification and risk stratification and by better determining in-stent restenosis and helping in percutaneous procedure planning.⁹ Moreover, improvements in image acquisition such as prospective ECG-gating significantly reduced radiation exposure, making CCTA an even more attractive noninvasive method for direct visualization of the coronary tree and lesions in all three planes. In this respect, CCTA represents a complementary tool to IVUS, which is limited by the longitudinal motion of the coronary arteries and a reliance on “pullback.” CCTA also offers a distinctive advantage over invasive coronary angiography by imaging the vessel wall as well as the lumen from a 360-degree perspective despite the superior temporal and spatial resolution of the latter.    Lastly, CCTA offers significant aid in lesions with complex anatomic characteristics. Although IVUS remains the gold standard for the accurate appreciation of coronary lesions for appropriateness of stenting, the scarce implementation of IVUS limits its clinical applicability in everyday practice. At present, CCTA cannot be recommended as the method of choice or as an adequate surrogate for IVUS in preinterventional stent selection, but it can certainly provide the interventional cardiologist with additional information in patients who had a CCTA performed prior to elective interventional procedures. Especially in lesions with complex anatomy, agreement between CCTA and visual estimation of a coronary plaque can reinforce the decision to use a particular stent, while a substantial disagreement may trigger further investigation with IVUS before a final decision can be made. Large-scale studies ultimately justifying stent selection by means other than IVUS are still lacking, but the ability to identify plaque types and vessel characteristics for optimal stent selection and placement with a noninvasive preprocedural imaging technique such as CCTA provides a promising research avenue. From the *Division of Cardiology, LA Biomedical Research Institute at Har- bor UCLA Medical center, Torrance, California, and §Department of Vascular Diseases, University Medical Center Ljubljana, Slovenia. The authors report no conflicts of interest regarding the content herein. Address for correspondence: Mohit Gupta, MD, Los Angeles Biomedical Research Institute at Harbor-UCLA, 1124 W Carson St Bldg E5, Torrance, CA, 90502. E-mail: mohit_gupta13@yahoo.com References

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