CT Imaging of Coronary Stents: Past, Present, and Future

Abstract

Coronary stenting became a mainstay in coronary revascularization therapy. Despite tremendous advances in therapy, in-stent restenosis (ISR) remains a key problem after coronary stenting. Coronary CT angiography evolved as a valuable tool in the diagnostic workup of patients after coronary revascularization therapy. It has a negative predictive value in the range of 98% for ruling out significant ISR. As CT imaging of coronary stents depends on patient and stent characteristics, patient selection is crucial for success. Ideal candidates have stents with a diameter of 3 mm and more. Nevertheless, even with most recent CT scanners, about 8% of stents are not accessible mostly due to blooming or motion artifacts. While the diagnosis of ISR is currently based on the visual assessment of the stent lumen, functional information on the hemodynamic significance of in-stent stenosis became available with the most recent generation of dual source CT scanners. This paper provides a comprehensive overview on previous developments, current techniques, and clinical evidence for cardiac CT in patients with coronary artery stents.

Figure 1

62-year-old male patient with a history of myocardial infarction and surgical revascularization therapy. 14 years after surgery, he developed CABG stenoses and subsequent stenting. CT was performed for ruling ISR. The 3D-volume rendered CT image shows the course of the stented vein graft to the LAD. A left internal mammary artery graft to a marginal branch is also depicted (a). Multiplanar curved reformats reconstructed with a dedicated sharp convolution kernel (b) and a smooth standard convolution kernel for cardiac CT angiography (c) show three CABG stents with a nominal diameter of 3 mm each. There are two TAXUS stents with 132 μm strut thickness (arrows) and a Xience V stent with 81 μm strut thickness (arrowhead). There is notably more blooming with the thicker struts and the stent lumen is better visible with the dedicated convolution kernel. ISR was ruled out by CT. This finding was confirmed by coronary angiography (d).

Figure 2

68-year-old male patient with a history of percutaneous coronary intervention with implantation of a 2.5 mm Xience V stent in the proximal RCA. CT shows the stent to be patent without relevant ISR, while there is a subtotal occlusion of the RCA distal to the stent (a, b). The finding was confirmed by coronary angiography (c). The stent lumen is better visible on images reconstructed with a dedicated convolution kernel (b), when compared with a standard convolution kernel (a). The use of a sharp convolution kernel goes along with a markedly increased image noise. Thus, the native vessel can be better assessed from images reconstructed with a smooth convolution kernel.

Figure 3

73-year-old male patient with a history of myocardial infarction and percutaneous recanalization of the RCA with implantation of a 3 mm Coroflex blue and 3 mm Vision stent. CT images computed with a dedicated convolution kernel (a) and a smooth kernel (b) show total stent occlusion with distal filling of the vessel (asterisk) via collateral flow. This finding was confirmed by conventional coronary angiography (c). CT also showed a step with incongruent course of the stents, indicating stent fracture.