Metallic coronary artery stents represent a significant challenge for CT angiography because they create the same kind of artifacts as heavy calcification: blooming and beam hardening, which can either obscure or mimic neointimal proliferation. Unlike grafts which tend to be larger than the native coronary lumen, stents tend to be slightly smaller, further aggravating the diagnostic problem.
The first patient has a patent stent with minimal neointimal proliferation:
The next patient has known occlusion of an LAD stent which subsequently led to bypass surgery with multiple grafts of the distal LAD and diagonal arteries:
The final patient has a stent with mild-moderate neointimal proliferation:
Given the inherent problems with stents, it should not be surprising that there have been only two published studies comparing CT angiography and conventional angiography in the assessment of restenosis. Both have relatively similar findings. CT angiography is accurate in determining that stents are occluded, normal, or exhibit minimal neointimal proliferation. Correlation in stents with moderate degrees of neointimal proliferation is too poor to be clinically useful.