Stent Hyperplasia Research Articles

RAPID PROGRESSION FROM UNILATERAL TO BILATERAL RENAL ARTERY STENOSIS (RAS) IN A PATIENT WITH FLASH PULMONARY OEDEMA, HYPERTENSIVE ENCEPHALOPATHY AND RENAL SHUT-DOWN

Objective: Atherosclerotic renal artery stenosis (RAS) affects the most proximal portion of the renal artery and approximately 20% of patients have bilateral RAS. We describe an elderly patient with unilateral RAS, post renal artery angioplasty presenting with resistant hypertension, hypertensive encephalopathy, flash pulmonary oedema and renal shutdown after progressing to bilateral RAS kidneys. Design and method: We present a case of 71 year old Indian women with known history of hypertension secondary to right renal artery stenosis underwent right renal artery stenting in March 2016, who was admitted in April 2018 with hypertensive urgency. Results: Ultrasound Doppler of renal artery showed more than 50% stenosis with stent hyperplasia throughout length of the stented right renal artery. There was no evidence of RAS on the left side on ultrasound Doppler. Right renal artery angioplasty was done in view of poorly controlled hypertension with systolic blood pressure ranging between 190 to 230mmHg. During right renal angioplasty, there was incidental finding 50–60% stenosis of the left renal artery. Day 2 post stenting, patient's systolic blood pressure rose to 220 mmHg and started complaining of bi-frontal headache and vomiting. Computed tomography of the brain revealed subtle vasogenic oedema in bilateral frontal lobes likely posterior reversible encephalopathy syndrome (PRES). The patient clinically deteriorated with worsening renal function (creatinine value: 440mmol/L from a baseline of 64mmol/L), metabolic acidosis, oliguria, acute pulmonary oedema and high blood pressure requiring eight (including diuretics) anti-hypertensive. Hemodialysis was initiated and urgent CT angiogram was done to evaluate left renal artery which showed 90% left renal artery stenosis and stented subsequently. Post left renal artery stenosis, patient's blood pressure stabilised and the number of anti- hypertensive were reduced to 5 types. The patient's renal function normalised (creatinine value: 72mmol/L) and recovered from acute pulmonary oedema. Conclusions: In a patient with unilateral RAS post stenting presenting with resistant hypertension, it is important to rule out stent thrombosis versus progression to bilateral RAS and rapid reversal with revascularization is crucial in order to prevent cardiovascular and renal complications, reduce the mortality and morbidity and restore the renal function.

Self-expanding nitinol stents of high versus low chronic outward force in de novo femoropopliteal occlusive arterial lesions (BIOFLEX-COF trial): study protocol for a randomized controlled trial

BackgroundSelf-expanding nitinol stents must be oversized at least by a minimal amount to ensure contact with the vessel wall and prevent migration. Once the stent is deployed it exerts a continuous force upon the vascular wall, termed chronic outward force (COF). Animal studies have found an increased neointimal hyperplasia in stents with high oversizing and thus high COF. Data about correlation between COF and neointimal hyperplasia in humans are currently lacking. The objective of the BIOFLEX-COF trial is to prospectively investigate differences in formation of intimal hyperplasia at 1 and 2 years after implantation of nitinol stents with high versus low COF in de novo femoropopliteal occlusive arterial lesions.MethodsThe BIOFLEX-COF trial is a prospective, quantitative, randomized study. Eighty subjects with symptomatic peripheral arterial lesions eligible for endovascular stent implantation will be enrolled and randomly assigned to either a high COF group (LifeStent Flexstar, Bard Peripheral Vascular Inc., Tempe, AZ, USA) or low COF group (Pulsar, Biotronik AG, Bülach, Switzerland) using an online randomization program to generate a random 1:1 group allocation (block randomization). After implantation and dilatation, COF at every 2 mm along the stent axis will be calculated from the actual stent diameter versus its nominal diameter.There will be two follow-up evaluations at 12 and 24 months. Primary endpoint is the amount of in-stent neointima at 1 year, assessed by contrast-enhanced CT angiography (CTA). In the control examinations, stent diameter and true lumen diameter will be measured on DICOM images every 2 mm along the stent axis to quantify the relative amount of in-stent restenosis.Secondary objectives are the amount of in-stent neointima at 2 years, device- and procedure-related adverse events and target lesion revascularization (TLR) rate.The scheduled time for recruitment is 2 years. Recruitment is expected to be complete in October 2017.DiscussionThis trial is the first to prospectively investigate the influence of COF on stent patency. If successful, the results will aid in a more precise selection of stent type and size in a given target vessel.The present study is challenging in that it compares two different self-expanding nitinol stents head-to-head against each other. To optimize the power of this study, traditional binary outcome parameters such as TLR and restenosis at Doppler ultrasound were dropped as primary endpoints. Instead, the amount of neointima inside the stent accessed by CTA was selected as (continuous) outcome parameter.Trial registrationClinicalTrials.gov Identifier: NCT03097679. Date of registration: 14 March 2017 (retrospectively registered).

Recent advances in drug eluting stents

One of the most common medical interventions to reopen an occluded vessel is the implantation of a coronary stent. While this method of treatment is effective initially, restenosis, or the re-narrowing of the artery frequently occurs largely due to neointimal hyperplasia of smooth muscle cells. Drug eluting stents were developed in order to provide local, site-specific, controlled release of drugs that can inhibit neointima formation. By implementing a controlled release delivery system it may be possible to control the time release of the pharmacological factors and thus be able to bypass some of the critical events associated with stent hyperplasia and prevent the need for subsequent intervention. However, since the advent of first-generation drug eluting stents, long-term adverse effects have raised concerns regarding their safety. These limitations in safety and efficacy have triggered considerable research in developing biodegradable stents and more potent drug delivery systems. In this review, we shed light on the current state-of-the-art in drug eluting stents, problems related to them and highlight some of the ongoing research in this area.

Long‐term results of a self‐expanding wallstent in the treatment of urethral stricture

To report the long-term outcome over 12 years of using the urethral Urolume wallstent (AMS, Minnetonka, MI, USA) for treating recurrent bulbar urethral stricture disease. The case-notes of 60 consecutive men with urethral Urolume wallstents placed for treating recurrent bulbar strictures were reviewed retrospectively. Information was collected on patient demographics, stricture aetiology, stent-related complications and the need for further surgery to treat stent- or stricture-related complications. The mean (range) age of the men was 58 (32-76) years. The most common cause of stricture was iatrogenic, arising after previous endoscopic surgery or after an indwelling catheter (45%). Thirty-five men had complications, with re-operation required in 27 (45%) of them. The most frequent nonsurgical complications were post-micturition dribble (32%) and recurrent urinary tract infections (27%). The most common surgical interventions required were transurethral resection of obstructing stent hyperplasia (32%), urethral dilatation or urethrotomy for stent obstruction or stricture (25%) and endoscopic litholapaxy for stent encrustation or stone (17%). The Urolume wallstent should only be used in patients who are unfit for or who refuse a bulbar urethroplasty.

A chemically modified dextran inhibits smooth muscle cell growth in vitro and intimal in stent hyperplasia in vivo

Purpose: Intimal smooth muscle cell (SMC) hyperplasia is a main component of the arterial wall response to injury. We have investigated the capacity of a water-soluble nonanticoagulant functionalized dextran (E9) in inhibition of SMC growth in vitro and in vivo. Methods: E9 was obtained with chemical substitutions with anionic and hydrophobic groups on the dextran backbone. SMC proliferation (cell counting, thymidine uptake, cell cycle analysis) was followed in culture in the presence of E9. Western blot analysis against phosphorylated mitogen-activated protein kinase (MAPK), extracellular signal-regulated protein kinase 1/2, and assessment of MAPK activity on serum-stimulated SMCs also were investigated. Binding/displacement experiments, electron microscopy, and cell fractionations were used to follow the binding and internalization of radiolabeled and fluorescentlabeled E9. New Zealand white rabbit iliac arteries were injured with balloon dilatation and stent deployment. Animals were treated for 14 days with saline solution or E9 (5 mg/kg injected subcutaneously, twice daily). Morphometric analyses were carried out in each group (n = 6 arteries, 18 sections). Results: Nonanticoagulant E9 inhibited SMC proliferation in vitro. Tyrosine phosphorylation of MAPK 1/2 and MAPK activity were inhibited with E9 within 5 minutes of incubation. The binding and rapid cytoplasmic internalization of the synthetic compound was evidenced, but, in contrast to heparin, we did not detect any nuclear localization of the antiproliferative E9. In the in vivo model, qualitative modifications of neointimal structure with a thinner fibrocellular neointima were noticed after E9 treatment. Morphometric analyses of stented arteries in E9-treated animals indicated an important reduction (P <.01) of intimal growth: 33% and 45% for intimal area and intima/media ratio, respectively. Conclusion: Cytoplasmic internalization of the synthetic polysaccharide correlated to the SMC growth inhibition that involved the MAPK pathway. In vivo inhibition of intimal instent hyperplasia with this nonanticoagulant derived dextran is shown providing a new candidate for a potential selective treatment of SMC proliferation. (J Vasc Surg 2002;35:973-81.)

Intravascular ultrasound volumetric assessment of intimal hyperplasia in stents treated with intracoronary radiation

Iridium-192 (gamma)-radiation is effective in preventing recurrent in-stent restenosis by reducing neointimal hyperplasia as illustrated by intravascular ultrasound study and plaque area-length plot. This analytic technique will further our understanding of vessel behavior to radiant energy source both inside and outside the stented coronary artery segments.