Delayed migration due to shortening of the lower part of AFX endograft's main body in angled fusiform abdominal aortic aneurysm.

We encountered two fusiform abdominal aortic aneurysm cases with delayed AFX endograft (Endologix Inc) migration >4 years after placement. These cases showed shortening and slight angulation of the main body in the anteroposterior direction. We speculate that the potential mechanism relates to the AFX portion that is easily shortened at the bifurcation of its stent structure. This portion might contribute to delayed migration after slight angulation of the main body. Preoperative three-dimensional computed tomography should be performed from the anteroposterior and lateral views. Although the AFX is useful for narrow bifurcations, one should consider the patient's anatomy before deciding to use an AFX endograft.

Mechanical Behavior of Radial Support of a Novel Balloon Expandable Tapered Stent / 医用生物力学

Objective To explore influences of the taper and connecting rib form on supporting performance of the stent, and provide an important scientific basis for structural design and clinical selection of the tapered stent. Methods A nonlinear finite element model for radial support performance of a novel balloon-expandable tapered stent was constructed, and the radial stiffness (RS) and stress distributions of the stent at different tapers (0°, 0.565°and 1.13°) and with different structural forms of stent linker (V-shape, I-shape, C-shape, S-shape, M-shape) were analyzed by plane compression. The relationship between structural design of the vascular stent and its radial support performance was studied. Results The RS of 0°stent, 0.565°stent, 1.13° stent was 2.51, 1.61, 0.85 N/mm, respectively. The RS of 0.565°stent and 1.13° stent was 35.86% and 66.14% lower than that of 0°stent (round straight stent), respectively. Except that the RS of C-shape linker stent was 1.48 N/mm, the RS of I, M, S and V-shape linker stents was not significantly different, which was 2.51, 2.61, 2.41, 2.52 N/mm, respectively, indicating that radial compression resistance of these four linker stents was almost the same. Conclusions Compared with traditional round straight stents, the RS of tapered stents will decrease, and the RS of stents will gradually decrease with the the taper increasing. Among all stent types in this study, except C-shape linker stents, the RS of other linker shapes has little effect on the RS of stents. The radial support performance of the stent can be improved by reducing the taper of the tapered stent, without changing the form of stent connecting ribs.

Structural and Hemodynamic Analyses of Different Stent Structures in Curved and Stenotic Coronary Artery.

Coronary artery stenting is commonly used for the treatment of coronary stenosis, and different stent structures indeed have various impacts on the stress distribution within the plaque and artery as well as the local hemodynamic environment. This study aims to evaluate the performance of different stent structures by characterizing the mechanical parameters after coronary stenting. Six stent structures including three commercially-shaped stents (Palmaz-Schatz-shaped, Xience Prime-shaped, and Cypher-shaped) and three author-developed stents (C-Rlink, C-Rcrown, and C-Astrut) implanted into a curved stenotic coronary artery were investigated. Structural analyses of the balloon-stent-plaque-artery system were first performed, and then followed by hemodynamic analyses. The results showed that among the three commercially-shaped stents, the Palmaz-Schatz-shaped had the least stent dogboning and recoiling, corresponding to the greatest maximum plastic strain and the largest diameter change, nevertheless, it induced the highest maximum von Mises stress on plaque, arterial intima and media. From the viewpoint of hemodynamics, the Palmaz-Schatz-shaped displayed smaller areas of adverse low wall shear stress (<0.5 Pa), low time-averaged wall shear stress (<0.5 Pa), and high oscillating shear index (>0.1). Compared to the Cypher-shaped, the C-Rcrown and C-Astrut had smaller recoiling, greater maximum plastic stain and larger diameter change, which indicated the improved mechanical performance of the Cypher-shaped stent. Moreover, both C-Rcrown and C-Astrut exhibited smaller areas of adverse low wall shear stress, and low time-averaged wall shear stress, but only the C-Rcrown displayed a smaller area of adverse high oscillating shear index. The present study evaluated and compared the performance of six different stents deployed inside a curved artery, and could be potentially utilized as a guide for the selection of suitable commercially-shaped stent for clinical application, and to provide an approach to improve the performance of the commercial stents.

Optimizing the deformation behavior of stent with nonuniform Poisson's ratio distribution for curved artery.

Stent implantation at a highly curved artery has always been a challenge, considering the relatively high chance of in-stent restenosis (ISR) caused by severe straightening effect and high strain energy over the vessel wall. In this paper, a novel optimization based design method was proposed to manipulate the deformation behavior of the common ring-and-link stent. By changing the location of the connection point between rings and links, traditional ring-and-link structure was modified to achiever tunable Poisson's ratio (PR). With the nonuniform cellular structure design method proposed in a previous study, PR distribution of the stent structure was optimized to achieve the desired curvature. As a result, the obtained stent structure with nonuniform PR could perfectly fit into the curved artery after expansion, without causing any obvious vessel straightening. To validate the proposed method, two different vessel models were introduced. Firstly, a short vessel with a constant curvature was set as the design objective, and both numerical and experimental tests were conducted. Further, a patient-specific vessel was applied. Both test results showed that optimized stents would cause much smaller vessel straightening. Moreover, vessels stented by the optimized structures had much lower stress concentration and strain energy. All those properties will decrease the possibility of ISR significantly.

Occurrence of longitudinal stent compression before stent deployment: Two case studies.

Several recent reports have described the occurrence of longitudinal stent deformation (LSD, defined as the distortion or shortening of a stent along the longitudinal axis), following its successful deployment. However, few reports have described LSD prior to any stent deployment. This previously unrecognized complication is the result of modifications to stent design. It has been noted that the new-generation stent platforms have a reduced number of connectors, which in turn causes a reduction in longitudinal stent strength. To corroborate previous findings by our lab and others (Vijayvergiya et al, 2013), we describe here two cases of LSD prior to stent deployment that occurred due to crushing of the proximal stent edge by the guide catheter while attempting to withdraw the crimped stent. In addition, we discuss the associated risk factors, such as the length of the stent, and specific management strategies, including technical guidelines and use of fluoroscopic guidance for maneuvering the stent during the procedure.

Device closure of a pseudoaneurysm of the right ventricular outflow tract in an infant with right ventricle-to-pulmonary artery homograft.

Pseudoaneurysm of the right ventricular outflow tract (RVOT) is a rare complication following surgical repair of congenital heart disease involving a homograft or conduit. Traditionally, surgical intervention is indicated due to risk for rupture, thrombosis, compression of adjacent structures, and infection. We describe a case of a RVOT pseudoaneurysm in a 5 kg patient that was palliated with interventional catheterization utilizing an Amplatzer Ductal Occluder with four years follow-up. Interventional catheterization can successfully manage this complication in small patients for the long-term and thus avoids additional surgery and delays conduit replacement.

Safety and efficacy metrics for primary nitinol stenting in femoropopliteal occlusive disease: a meta-analysis and critical examination of current methodologies.

BACKGROUND: The efficacy and safety of primary stenting for superficial femoral artery (SFA) disease have been benchmarked against historically derived performance goals. However, contemporary evidence evaluating SFA stenting is accumulating. The objective of this systematic review and meta-analysis was to quantitatively assess outcomes after primary SFA stenting with nitinol stents in contemporary practice, to compare these rates with commonly used efficacy and safety goals, and to discuss the clinical and regulatory implications of these findings. METHODS AND RESULTS: We searched MEDLINE, the US Food and Drug Administration (FDA) website, reference lists of qualifying articles, and conference proceedings until October 2012. Studies prospectively assessing primary nitinol stenting for diseased SFA were sought. Data from 11 prospective clinical trials were included. The twelve-month primary patency (PP) rate was reported in five trials. The meta-analytic 12-month PP rate was 71.6% (95% confidence interval [CI] 66.4-76.7%). The meta-analytic rate of 30-day freedom from a composite of death, target limb amputation, and reintervention was 99.9% (95% CI 100.0-90.0%). CONCLUSION: Contemporary nitinol-based bare-metal stents performed well in controlled settings. Occurrence of the 1-month composite safety endpoint was extremely uncommon.

Intimal hyperplasia and vascular remodeling after everolimus-eluting and sirolimus-eluting stent implantation in diabetic patients: the randomized Diabetes and Drug-Eluting Stent (DiabeDES) IV Intravascular Ultrasound trial.

OBJECTIVE: To evaluate the effects of the everolimus-eluting Xience™/Promus™ stent (EES) and the sirolimus-eluting Cypher™ stent (SES) on intimal hyperplasia (IH) in diabetic patients. BACKGROUND: Patients with diabetes mellitus have increased risk of in-stent restenosis after coronary stent implantation due to intimal hyperplasia (IH). METHODS: In a sub study of the Randomized Comparison of Everolimus-Eluting and Sirolimus-Eluting Stents in Patients Treated with Percutaneous Coronary Intervention (SORT OUT IV trial), serial intravascular ultrasound (IVUS) 10-month follow-up data were available in 88 patients, including 48 EES and 40 SES treated patients. IVUS endpoints included IH volume, in-stent % volume obstruction and changes in external elastic membrane (EEM) volume. RESULTS: Compared with the SES group, IH volume was increased in the EES group [median (interquartile range): 2.8 mm(3) (0.0-12.6) vs. 0.0 mm(3) (0.0-1.1), P = 0.001]. In-stent % volume obstruction was increased in EES compared to SES [median (interquartile range): 1.6% (0.0-8.2) vs. 0.0% (0.0-1.0), P = 0.001]. Peri-stent external elastic membrane (EEM) volume: (post procedure vs. follow-up EES [300 mm(3) (219-491) vs. 307 mm(3) (223-482), P = 0.73] and SES [316 mm(3) (235-399) vs. 323 mm(3) (246-404), P = 0.05]) and peri-stent plaque volume: EES [163 mm(3) (103-273) vs. 184 mm(3) (115-291), P = 0.18] and SES [186 mm(3) (139-248) vs. 175 mm(3) (153-243), P = 0.26]) were unchanged in both groups. In the proximal reference segment a significant increase in plaque area was seen in the EES group only, without vascular remodeling. CONCLUSION: In diabetic patients, EES stent implantation was associated with increased IH volume obstruction without involvement of vascular remodeling.

Optical coherence tomography evaluation of late strut coverage patterns between first-generation drug-eluting stents and everolimus-eluting stent.

OBJECTIVES: To compare strut coverage patterns between everolimus-eluting stent (EES) and first-generation drug-eluting stents (DES) at more than 12 months after successful implantation, using optical coherence tomography (OCT). BACKGROUND: No sufficient OCT data has been reported comparing late strut coverage patterns between EES and first-generation DES. The favorable late results after EES implantation could be related to lower rates of uncovered and malapposed struts. METHODS: A total of 66 DES (21 EES, 23 SES, and 22 PES) that were implanted at least 1 year in advance in 40 patients and met good late angiographic results were evaluated by OCT. The percentage of uncovered and malapposed struts, calculated as the ratio of uncovered or malapposed struts to total struts in all cross-sectional images per stent, was compared among the three groups. RESULTS: A total of 35,061 struts were analyzed: 11,967 from EES, 11,855 from SES, and 11m239 from PES. The average tissue coverage thickness of the struts per stent was greater in EES than in SES and PES (109 ± 40 µm vs. 72 ± 27 µm and 83 ± 26 µm, respectively; P = 0.001). The percentage of uncovered struts (1.9 ± 4.1% in EES vs. 11.6 ± 12.7% in SES, P = 0.01 and vs. 7.1 ± 5.2% in PES, P < 0.001) and malapposed struts (0.1 ± 0.3% in EES vs. 1.8 ± 3.5% in SES, P = 0.01 and vs. 3.5 ± 5.1% in PES, P = 0.02) was much lower in EES than in first-generation DES, with no significant differences between SES and PES. CONCLUSIONS: Late strut coverage patterns are not similar between EES and first-generation DES. EES showed a lower percentage of uncovered and malapposed struts.

Longitudinal stent compression of everolimus-eluting stent: A report of 2 cases.

Second generation drug eluting stents (DES) have shown better safety and efficacy in comparison to first generation DES, because of thinner struts, nondurable polymers and coating with better anti-proliferative drugs. The newer DES with cobalt alloy base have demonstrated a greater trackability, deliverability, conformability, flexibility and radio-opacity. However, these thin strut stents have a downside of poor longitudinal axial strength, and therefore get easily deformed/compressed at their end with a slight trauma during exchange of various catheters. We hereby report two cases of "longitudinal stent compression (LSC)" of everolimus-eluting stent, which happened during percutaneous coronary intervention of right coronary artery. Both the cases were successfully managed with non-compliant balloon dilatation. Various reasons for LSC and its management are discussed in the article.

Morphology of the patent ductus arteriosus does not preclude successful patent ductus arteriosus stent implantation in high-risk patients undergoing hybrid stage I palliation: recommendations to optimize ductal stent positioning.

OBJECTIVE: To describe patent ductus arteriosus (PDA) stenting regardless of ductal morphology in high risk patients with hypoplast physiology undergoing hybrid stage I palliation (PDA stenting and placement of bilateral pulmonary artery bands). BACKGROUND: Hybrid palliation is an accepted alternative for patients with hypoplastic left heart syndrome. Patients weighing less than 2.5 kg, history of prematurity, intracranial hemorrhage, and chromosomal abnormality belong to a high-risk group who otherwise might not be ideal candidates for traditional surgical repair (Norwood Operation). METHODS: Between May 2005 and February 2013, a series of 13 high-risk patients with hypoplast physiology with varying types of ductal morphology underwent PDA stenting as part of hybrid stage I palliation. RESULTS: Three major types of ductal morphology were identified: (1) short and semi horizontal, (2) long and semi horizontal, and (3) tortuous. All patients underwent successful PDA stenting. One patient developed proximal coarctation from inadequate coverage of the pulmonary end of the PDA and was successfully treated with a balloon expandable stent 69 days after the initial procedure. CONCLUSIONS: Mid- to long-term follow-up indicates that PDA stents remain widely patent regardless of ductal morphology until comprehensive stage II repair.

Endovascular stenting in transverse aortic arch hypoplasia.

OBJECTIVES: Describe outcomes from stenting transverse aortic arch hypoplasia. BACKGROUND: Hypoplasia of the transverse arch may result in residual systemic hypertension and may be amenable to stenting. METHODS: Outcomes for transverse aortic arch hypoplasia stenting were collated from four centers between 2000 and 2010. Primary endpoints were reduction in peak systolic catheter gradient, dimensions of the stented segment, and systolic right arm blood pressure. Changes in antihypertensive medication and early and late complications were recorded. Data were collated for 21 patients (16 male, 5 female), median age of 16.5 years (range, 0.25-25.9 years) and median weight of 55 kg (range, 4.5-103 kg). 19/21 patients were hypertensive at baseline, excluding the two neonates after repair of interrupted aortic arch. RESULTS: Median transverse arch diameter increased from 7 to 14 mm after stenting (P < 0.001). Median ratio of the transverse arch to descending aorta at the diaphragm level improved from 0.43 to 0.9 (P < 0.001). Mean gradient across the hypoplastic transverse arch was 38 mm Hg (range, 14-76) at baseline and 5 mm Hg (range, 0-13) after stenting (P < 0.001). There were no deaths and 6 early complications occurred in 5 patients. Follow-up (median 24 months) data were available for 19 patients. 17/19 hypertensive patients had follow-up data. Two neonates developed intimal hyperplasia within the stent with a stent fracture in one. Median systolic blood pressure was 153 mm Hg (range, 117-180) prestent and 130 mm Hg (range, 105-150) poststent (P = 0.0002). In 13/17 patients, the antihypertensive medication could be reduced. CONCLUSIONS: Stenting of transverse aortic arch hypoplasia, although technically challenging, produced good angiographic and haemodynamic results with an early improvement in blood pressure control. These results appear to be sustained in the medium term.