Coronary CT angiography (CCTA) using third-generation dual-source CT for ruling out in-stent restenosis

Late in-stent restenosis (ISR) has become increasingly important, in particular due to neo-atherosclerosis. CCTA is a highly sensitive method for detecting coronary plaques. Its diagnostic accuracy regarding ISR is controversial. Stent artifacts can impede image quality, but recent developments in CT-technology may help to overcome some of these problems and allow for improved diagnostic accuracy.

Consecutive patients after previous coronary revascularization who had stable symptoms or signs of possible disease progression were examined using a third-generation dual-source CT scanner. After the scan, patients were followed for clinical events (MACE) over a mean of 399 days. Patients with high-grade stenoses were referred for invasive coronary angiography (ICA), unclear findings were further evaluated either by ICA or functional testing.

Overall, 226 patients were included. A total of 457 stents were evaluated (2.0 ± 1.4 per patient). Mean stent diameter was 2.9 ± 0.45 mm. In 61%, a high-pitch protocol was employed. Mean dose-length product (DLP) of CCTA was 159.2 mGy cm, corresponding to 2.2 mSv using a conversion factor of k = 0.014. Mean amount of contrast agent was 58.3 ± 12.5 ml. In 145 patients (64%), CCTA was negative. In this group, one MACE occurred (acute coronary syndrome) during follow-up in a patient who had also undergone unremarkable ICA. In 23 patients (10%), CCTA detected 28 ISR which were confirmed and treated by ICA (true positive). In 27 patients (12%), ISR was suspected by CCTA but excluded by ICA (false positive), 30 patients (13%) had unclear findings and normal non-invasive tests. No MACE occurred during follow-up in these patients. One patient was misclassified in CCTA as having intermediate and not high-grade ISR who underwent revascularization within 3 months. Eleven patients (5%) were lost to follow-up. During follow-up, eight patients had myocardial infarctions due to five ISRs and three de novo lesions. No patient died. In cases with unclear or false-positive findings, the amount of stents was significantly higher, stents were smaller and patients had a higher BMI.

In almost two-thirds of symptomatic patients with previous coronary stent implantation, ISR could be ruled out by CCTA. 10% of patients had definite ISR. The rate of false-negative findings was low (< 1%), whereas the rate of false positive or inconclusive findings was 25%, leading to invasive rule-out of ISR by ICA in 12%. CCTA appears valuable as a tool for safely excluding ISR. It might help to avoid invasive diagnostic procedures. Further analyses are warranted, in particular regarding the influence of stent dimensions and the total amount of stents in a patient.