Evaluation of Long Coronary Artery Stents With Third-generation Dual-source Computed Tomography Angiography

This prospective study complied with the Declaration of Helsinki and was approved by the ethics committee of Helsinki University Central Hospital. All patients gave a written informed consent prior to the beginning of the study.

Patient selection A registry that included chronic total occlusion (CTO) patients with stable coronary artery disease treated for CTO with percutaneous coronary angioplasty (CTO PCI) in Helsinki University Central Hospital starting from 2014 was used for this study. The study population included consecutive, prospectively recruited patients from 2014 to 2019. All patients meeting the study criteria were included in the study.

Definition Segments 5 mm proximal and 5 mm distal to the stent were considered as part of the stent for in-stent restenosis (ISR) evaluation, as proposed by the Academic Research Consortium and were included in CCTA performance analyses. Long CTO stents consisted of one or more coronary artery stents with possible combination of different stent types. The combined stent length was reported without possible overlap for multiple stents. The diameter of the largest stent or post-dilation balloon was reported. Based on previous CT studies and guidelines radiological ISR in CCTA was defined as luminal narrowing of ≥ 50% in the long CTO stent. CCTA result was considered negative if ISR was ruled out and positive if ISR was detected or if the result was inconclusive. Therefore, two groups defined by the CCTA result were formed. In patient-based analyses patients with two long CTO stents of which at least one was a CCTA positive stent were considered as CCTA positive. In native coronary arteries less than 25% was considered minimal, 25-49% mild, 50-69% moderate and 70-99% severe stenosis and 100% as an occlusion. Assessment of stenosis was based on direct visualisation. The study's experienced cardiac radiologist with over 15 years of experience was blinded for symptomatic data, stent type and stent quantity. The target vessel of implanted coronary artery stents was provided.

All patients underwent third-generation dual-source CCTA. In CCTA a non-contrast calcium score using standard 120 kilovolt (kV) acquisition and 3 mm slice thickness was obtained. Stented segments were manually subtracted from the score. Second, third-generation dual-source CCTA (Somatom Force, Siemens) was performed. Prospective ECG-triggering was applied regular heart rate < 70/min and/or in the case of previous stent implantation of right coronary artery (RCA) to avoid motion artefacts and FLASH- mode if the heart rate was regular and < 60/min. If the presenting heart rate was > 70/min, metoprolol 5-15 mg was administered intravenously. For patients with higher heart rates (> 70/min) prospective ECG-gating and widening of the acquisition window (padding) were used. Sublingual nitroglycerin was administered before scanning. A tube voltage of 100 kV, rotation time of 0.25 s, temporal resolution of 66 ms, collimation of 2 x 192 x 0.6 mm and pitch of 3.2 were used. Approximately 50 ml of contrast medium containing 350 mg/ml of iodine (Omnipaque 350, GE Healthcare) was injected intravenously at a flow rate of 5-5.7 ml/s, followed by a 47 ml saline solute. Axial images were reconstructed with 0.6 mm slice and evaluated using multiplanar reformation. Bv40 kernel, Advanced Modeled Iterative Reconstruction 3 (ADMIRE 3) and Iterative metal artefact reduction (iMAR) were utilised.

Clinical information and CCTA results were assessed by the interventional cardiologists and the following patients were offered invasive coronary angiography (ICA):