Acute Stent Thrombosis after Bifurcation Stenting with the Crush Technique Visualized with 64-Slice Computed Tomography

Among percutaneous coronary interventional procedures, the treatment of bifurcation lesions with stents in both the main vessel (MV) and the side branch (SB) is one of the most complex. Several techniques have been suggested including T-, V-, Y-stenting, the culotte technique and the crush technique.^1,2
The crush technique was introduced by Colombo et al³ in 2002. It involves crushing the SB stent against the MV wall by means of expansion of the MV stent (see reference #3 for a detailed description) which thus ensures full coverage of the SB ostium. Following stent implantation, kissing-balloon inflation in the bifurcation is considered mandatory. However cases of acute/subacute stent thrombosis have been reported and restenosis continues to be a problem.^4,5 Incomplete crushing of the SB stent struts or incomplete apposition of the MV stent may be a cause of thrombosis, but can be difficult to detect during the procedure. Intravascular ultrasound (IVUS) may be necessary in order to assess the procedural result in detail.⁶ Recently, multidetector row computed tomography (MDCT) has shown promising results for the assessment of coronary stent patency⁷ and could prove to be a noninvasive alternative to IVUS for stent control after treatment of bifurcation lesions. We report a case illustrating this new diagnostic principle.

Case Presentation. A 55-year old male with a 6-month history of stable angina was referred to our institution. Coronary angiography showed significant stenosis in the proximal part of the first diagonal branch (D1) and an intermediate lesion in the left anterior descending artery (LAD) (Figure 1). Measurement of the fractional flow reserve (FFR) index across the LAD lesion was 0.7, and treatment in both the LAD and D1 was therefore required.
Two Cypher™ Select (Cordis Corp., Miami Lakes, Florida) drug-eluting stents (2.25 mm x 8 mm in the D1 and 3.0 mm x 33 mm in the LAD) were inserted using the crush technique. Final kissing-balloon postdilatation was performed, yielding a good angiographic result (Figure 2). Appropriate pretreatment with clopidogrel had been administrated and no flow limitations or signs of thrombosis were present during the procedure.
The following day, MDCT coronary angiography (Aqullion 64, Toshiba, Japan) was performed as part of a research project. This showed occlusion of the D1 with no distal runoff of contrast media (Figure 3). The MV stent showed normal contrast enhancement and normal runoff, but incomplete crushing of the SB stent struts in the MV next to and proximal to the ostium. No electrocardiographic changes were present during the CT scan, yet upon return to the department, ST-elevations and chest pain developed and an acute invasive coronary angiogram was performed, which confirmed occlusion of the D1 vessel (Figure 4). The patient was treated with balloon dilatation, securing full expansion of both stents and subsequent abciximab infusion for 12 hours.

Discussion. To our knowledge, this is the first case where acute stent thrombosis has been visualized with MDCT. In this case, the stent thrombosis presented clinically immediately after CT angiography and thus provides insight to conditions that may lead to acute stent thrombosis. In this particular case, it was most likely the incomplete crushing of the SB stent — as visualized by MDCT — that caused the thrombosis. The ideal appearance of a crush stent should be a slight hyperdensity in the crush area representing the three layers of crushed metal with no protrusion into the lumen. We have illustrated this by MDCT in another patient who underwent uncomplicated bifurcation stenting using the Crush-technique (Figure 5). It has already been shown that final kissing balloon postdilatation is mandatory,⁵ but even when this procedure is performed the result may be difficult to evaluate with conventional angiography.
Generally, visualization of stents with MDCT can be difficult due to blooming artifacts, and visualization of the stent lumen depends on both stent size and material. Especially at the site of two overlapping stents, where a large amount of dense stent material is present, blooming may impede the evaluation of in-stent restenosis. In our case, partial in-stent restenosis at the site of the incompletely crushed SB stent would have been more difficult to visualize due to severe blooming artifacts. However, this case demonstrates that MDCT can be used in selected cases to assess the apposition and patency of stents in coronary bifurcation lesions treated with the crush technique.

References

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