Case Report: Double Micro-Guidewire Technique for Emergent Rescue of Proximal Stent Collapse During Recanalization of Nonacute Occlusion of Vertebral Artery

Cerebral arteries are usually tortuous, and in the treatment of cerebrovascular diseases with stenting, a stent deployed may be collapsed at one end, leading to reduced blood flow and subsequent stent occlusion. Immediate rescuing measures should be implemented to prevent severe ischemic events. In this case report, we present a case with V4 segment occlusion of the right vertebral artery treated with endovascular stent angioplasty. An Enterprise stent deployed at the occlusion segment was collapsed at the proximal end after withdrawal of the delivery system. Immediate rescuing measures were taken by navigating a micro-guidewire through the lateral stent mesh at the proximal end into the stent lumen followed by advancing a second micro-guidewire right through the reopened proximal stent end into the stent lumen for deployment of a supporting balloon-expandable Apollo stent to prevent stent collapse. Follow-up digital subtraction angiography 6 months later demonstrated patent stents and unobstructed blood flow.

Stent evaluation by coronary computed tomography angiography: a comparison between Iopamidol-370 and Ioversol-320 hypo-osmolar iodine concentration contrasts

Objective: Qualitative and quantitative image analysis between Iopamidol-370 and Ioversol-320 in stents´ evaluation by coronary computed tomography angiography (CTA). Methods: Sixty-five patients with low-risk stable angina undergoing stent follow-up with coronary CTA were assigned to Iopamidol I-370 (n = 33) or Ioversol I-320 (n = 32) in this prospective, double-blind, non-inferiority, randomized trial. Stent lumen image quality was graded by 5-point Likert Scale. Lumen mean attenuation was measured at native coronary segments: pre-stent, post-stent, distal segments and at coronary plaques. Lumen attenuation increase (LAI) ratio was calculated for all stents. Heart rate (HR) variation, premature heart beats (PHB), heat sensation (HS), blooming and beam hardening were also assessed. Results: Image quality was similar between groups, with no significant difference (Likert score 4.48 ± 0.75 vs 4.54 ± 0.65, p = 0.5). There were similarities in LAI ratio between I-370 and I-320 (0.39 ± 0.42 vs 0.48 ± 0.44 HU, p = 0.08). Regarding lumen mean attenuation at native coronary segments, a significant difference was observed, with I-320 presenting lower values, including contrast mean attenuation in distal segments. After statistical multivariate analysis, three variables correlated with stent image quality: 1) stent diameter, 2) HR variation and 3) stent lumen LAI ratio. Conclusions: There was no significant difference between Iopamidol-370 mgI ml−1 and Ioversol-320 mgI ml−1 contrasts regarding overall stent lumen image quality, which was mainly influenced by stent diameter, HR and LAI ratio. Advances in knowledge: Coronary CTA allows adequate stents' visualization and image quality is influenced by stent diameter, HR variation and LAI ratio. Stents' image quality showed no difference between different concentration contrasts (I-370 vs. I-320); however, higher concentration contrasts may provide an improved overall visualization, especially regarding coronary distal segments.

PERFORMANCE TEST AND EXPERIMENTAL STUDY OF SPECIAL STENT FOR TREATMENT OF ILIAC VEIN STENOSIS

Objective: Animal experiments and clinical trials were carried out to evaluate the efficiency of a new stent for the treatment of iliac vein stenosis. Methods: The new iliac vein stent and the control stent were implanted, respectively, into the 12 experimental pigs. Digital Subtraction Angiography was done separately at the same day, 14th, 30th, 60th and 90th day after stent implantation to observe the stent deployment. One patient was implanted with a new iliac vein stent. Digital subtraction angiography (DSA) was done after the operation to calculate the lumen loss value and lumen loss rate of the stent and evaluate the performance of the new iliac vein stent at 12 months of follow-up. Results: The mechanical experiment and finite element analysis of the stent proved that the radial support force of the new stent is significantly better than that of the control stent. In animal experimental verification, both groups of stent were released satisfactorily during implantation. No obvious stent displacement was found at each time point. The patency rate of stents was 100%. Except for a small amount of old thrombosis in the stent in the control group, no other stents were found in that condition. The diameter of the stent lumen was retracted in different degrees in both groups after the operation, but no significant statistical difference was found in the comparison of the stent lumen loss rate at each relative inspection day. Conclusion: The new nickel-titanium alloy iliac vein stent has excellent radial support performance, which may be an ideal iliac vein stent.

Accuracy of optical coherence tomography imaging in assessing aneurysmal remnants after flow diversion

BackgroundOptical coherence tomography (OCT) is an ultra-high resolution real-time intravascular imaging method that is gaining interest in cerebrovascular applications.ObjectiveTo compare, in a rabbit elastase aneurysm model, digital subtraction angiography (DSA) and OCT as diagnostic tools for the assessment of aneurysmal remnants and baseline characteristics of aneurysms after flow diverter (FD) implantation.MethodsWith Institutional Animal Care and Use Committee approval, saccular aneurysms were created in 28 rabbits and treated with Derivo FDs. DSA was performed before, and immediately after, stent implantation. As a follow-up, DSA and OCT were performed 28 days after device implantation.ResultsDSA and OCT were successfully performed in 23 cases. OCT could not be achieved in 5 cases owing to navigational difficulties in the stent lumen with the OCT catheter. Residual aneurysms were significantly more often visible with OCT (18/23 (78%) than with DSA 12/23 (52%), p = 0.031).ConclusionOCT was more sensitive than conventional angiography for the assessment of residual aneurysms at 28 days after FD implantation in an animal model.

Case report: intravascular ultrasound sonography-guided re-entry technique in crushed stent

Background Stent thrombosis (ST) is a rare, but potentially fatal complication. Procedural problems, such as stent under-dimension/under-expansion or dual antiplatelet drug resistance may result into ST. These conditions are more frequent during primary percutaneous coronary intervention for ST-elevation myocardial infarction (STEMI). Case summary A 60-year-old male patient presented to our hospital with an inferior STEMI. In the emergency department, a dual antiplatelet therapy was administered with ticagrelor 180 mg and aspirin 250 mg IV. During the observation, the patient experienced a ventricular fibrillation. Urgent coronary angiography showed an occlusion of the proximal right coronary artery. Thrombus aspiration was performed followed by implantation of one drug-eluting stent. After 45 min early ST occurred and was treated by immediate thrombus aspiration and post-dilatation. Intravascular ultrasound sonography (IVUS) showed severe strut malapposition due to a partial crush after post-dilatation. Since it was not possible to directly insert the first guidewire in the stent lumen, the IVUS probe was placed between the vessel wall and the crushed stent to guide the manoeuvre. Discussion Crushed stent is a rare complication, being caused by an incorrect passage of the guidewire between the stent’s struts and the vessel wall in case of severe underexpansion. In this case, an IVUS-guided re-entry could be an option to gain the stent true lumen and avoid a second stent implantation.

Retrograde three-dimensional rotational angiography: A novel method for the detection of plaque protrusion during carotid artery stenting under continuous distal balloon protection

Background To prevent ischemic complications during carotid artery stenting, accurate detection of plaque protrusion and appropriate additional treatment are essential. Here, we introduce a novel method for the detection of plaque protrusion under distal balloon protection using three-dimensional rotation angiography—“retrograde 3DRA.” We evaluated the safety and efficacy of this method. Materials and methods We retrospectively analyzed 28 consecutive carotid artery stenting procedures under distal balloon protection at our hospital between July 2017 and August 2019. The first line of protection was dual balloon protection (proximal and distal balloon). After stent deployment, balloon dilatation, and subsequent blood aspiration, 3DRA was performed with the injection of diluted contrast medium from the aspiration catheter positioned just proximal to the distal protection balloon. The stent lumen was analyzed by obtaining the reconstruction maximum intensity projection image. Results Among the 28 cases, all cases could be assessed for in-stent plaque protrusion using “retrograde 3DRA.” We were able to evaluate the stent lumen clearly. There were three cases (10.7%) in which plaque protrusion could be confirmed. Since additional balloon dilatation was performed for all protrusion cases under continuing balloon protection, no ischemic complications occurred. Conclusion Retrograde 3DRA could be safe and useful for the detection of plaque protrusions and to avoid ischemic complication for tolerable cases of internal carotid artery transient balloon protection.

Feasibility of improving vascular imaging in the presence of metallic stents using spectral photon counting CT and K-edge imaging

Correct visualization of the vascular lumen is impaired in standard computed tomography (CT) because of blooming artifacts, increase of apparent size, induced by metallic stents and vascular calcifications. Recently, due to the introduction of photon-counting detectors in the X-ray imaging field, a new prototype spectral photon-counting CT (SPCCT) based on a modified clinical CT system has been tested in a feasibility study for improving vascular lumen delineation and visualization of coronary stent architecture. Coronary stents of different metal composition were deployed inside plastic tubes containing hydroxyapatite spheres to simulate vascular calcifications and in the abdominal aorta of one New Zealand White (NZW) rabbit. Imaging was performed with an SPCCT prototype, a dual-energy CT system, and a conventional 64-channel CT system (B64). We found the apparent widths of the stents significantly smaller on SPCCT than on the other two systems in vitro (p < 0.01), thus closer to the true size. Consequently, the intra-stent lumen was significantly larger on SPCCT (p < 0.01). In conclusion, owing to the increased spatial resolution of SPCCT, improved lumen visualization and delineation of stent metallic mesh is possible compared to dual-energy and conventional CT.

Application of zero echo time MR angiography in follow-up of intracranial aneurysm remnant and in-stent lumen after embolization: a comparison study with digital subtraction angiography

Background Intracranial aneurysm with endovascular treatment needs to be followed-up with a proper imaging method. Purpose To evaluate the performance of magnetic resonance angiography (MRA) with zero echo time at 1.5-T in assessing the intracranial aneurysm remnant and in-stent lumen as compared with time-of-flight MRA, with digital subtraction angiography as the gold standard. Material and Methods A total of 46 patients (17 men; mean age = 56.6±13.7 years) with 54 aneurysms who underwent coil embolization with or without stent were enrolled in this study. The presence of aneurysm remnant and the visualization of in-stent lumen were evaluated. The agreement of remnant identification between MRA with zero echo time and time-of-flight MRA with digital subtraction angiography was evaluated using Cohen’s kappa analysis. The performance of in-stent lumen visualization between MRA with zero echo time and time-of-flight MR angiography was compared with Chi-square test. Results Of 54 aneurysms, 27 were found to have remnants by digital subtraction angiography. The kappa value in identification of remnant of aneurysm was 0.852 between MRA with zero echo time and digital subtraction angiography and 0.741 between time-of-flight MRA and digital subtraction angiography. In detecting remnant of aneurysm, the sensitivity, specificity, positive predictive value, and negative predictive value were 96.3%, 88.9%, 89.7%, and 96.0% for MRA with zero echo time and 91.7%, 83.3%, 81.5%, and 92.6% for time-of-flight MRA, respectively. In visualizing in-stent lumen, MRA with zero echo time had better performance than time-of-flight MRA ( P < 0.001). Conclusion MR angiography with zero echo time might be a better non-invasive approach in assessing remnant of aneurysms and in-stent lumen as compared with time-of-flight MRA.

Magnetic Particle Imaging–Guided Stenting

Purpose:To assess the feasibility of magnetic particle imaging (MPI) to guide stenting in a phantom model. Materials and Methods: MPI is a new tomographic imaging method based on the background-free magnetic field detection of a tracer agent composed of superparamagnetic iron oxide nanoparticles (SPIOs). All experiments were conducted on a custom-built MPI scanner (field of view: 29-mm diameter, 65-mm length; isotropic spatial resolution 1–1.5-mm). Stenosis phantoms (n=3) consisted of polyvinyl chloride (PVC) tubes (8-mm inner diameter) prepared with centrally aligned cable binders to form a ~50% stenosis. A dedicated image reconstruction algorithm allowed precise tracking of endovascular instruments at 8 frames/s with a latency time of ~115 ms. A custom-made MPI-visible lacquer was used to manually label conventional guidewires, balloon catheters, and stainless steel balloon-expandable stents. Vascular stenoses were visualized by injecting a diluted SPIO tracer (ferucarbotran, 10 mmol iron/L) into the vessel phantoms. Balloon angioplasty and stent placement were performed by inflating balloon catheters and stent delivery balloons with diluted ferucarbotran. Results: After deployment of the stent, the markers on its ends were clearly visible. The applied lacquer markers were thin enough to not relevantly alter gliding properties of the devices while withstanding friction during the experiments. Placing an optimized flexible lacquer formulation on the preexisting radiopaque stent markers provided enough stability to withstand stent expansion. Final MPA confirmed successful stenosis treatment, facilitated by the disappearance of the lacquer markers on the stent due to differences in SPIO concentration. Thus, the in-stent lumen could be visualized without interference by the signal from the markers. Conclusion: Near real-time visualization of MPI-guided stenting of stenoses in a phantom model is feasible. Optimized MPI-visible markers can withstand the expansion process of stents.