Late Incomplete Apposition and Coronary Artery Aneurysm Formation following Paclitaxel-Eluting Stent Deployment: Does Size Mat
Case Presentation. A 43-year-old female with stable angina pectoris underwent stenting of a 99% stenosis in a small left anterior descending coronary artery (Figure A). In an uneventful procedure, a 2.25 x 8 mm Taxus® Express paclitaxel-eluting stent (Boston Scientific Corp., Natick, Massachusetts) was deployed at 12 atm, achieving an optimal angiographic result, with slight oversizing of the stented segment in relation to the reference vessel (Figure B). Two months later, angiography revealed localized CAA formation within the mid-portion of the stent (Figure C). Intravascular ultrasound (IVUS) confirmed incomplete stent apposition and a “black hole” effect consistent with coronary artery aneurysm (CAA) at the same site (Figures 1–3). Late incomplete apposition (LIA) formation may be either late and acquired, or acute and persistant.1 It may be defined as a continuum from malapposed stent struts to the extreme situation of CAA formation.1
Discussion. LIA and CAA formation following paclitaxel drug-eluting stenting (DES) in a small vessel are presented in the above case to highlight the need for more data and close follow up of patients with small vessels treated with DES. LIA is relatively common following DES, and appears to be more common in DES compared to bare-metal stents (BMS). LIA is found in 8–13% of patients receiving DES at IVUS follow up in the pivotal initial trials.1–4 In contrast, CAA formation occurs rarely following either DES or BMS.1,5–7 While the pathologic mechanisms and clinical importance of such findings are debated,1,7,8 the possibility has been raised that for DES, either the drug or polymer may impair vessel healing and contribute to both of these entities.8
The Taxus Express system utilizes an identical 2-cell stent crimped onto a 2.25, 2.5 or 2.75 mm balloon, with a different 3-cell stent for 3.0 mm and larger balloons. Such economy in stent sizing means the same stent — and the same drug andpolymer dose — are delivered to a 2.25 mm diameter vessel as to a 2.75 mm vessel. Although an association between small vessel size or increased drug dose and LIA and CAA following paclitaxel-eluting stent implantation has not been reported previously, the patient numbers studied so far are small,1–4 and itremains intriguing that the LIA and CAA observed here occurred in a 2.25 mm vessel, where the dose of both paclitaxel and polymer are likely to have been maximal. More data and close follow up of such patients are needed.
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