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Biomedical Engineering Online Jan 2017Although stents have great success of treating cardiovascular disease, it actually undermined by the in-stent restenosis and their long-term fatigue failure. The...
BACKGROUND
Although stents have great success of treating cardiovascular disease, it actually undermined by the in-stent restenosis and their long-term fatigue failure. The geometry of stent affects its service performance and ultimately affects its fatigue life. Besides, improper length of balloon leads to transient mechanical injury to the vessel wall and in-stent restenosis. Conventional optimization method of stent and its dilatation balloon by comparing several designs and choosing the best one as the optimal design cannot find the global optimal design in the design space. In this study, an adaptive optimization method based on Kriging surrogate model was proposed to optimize the structure of stent and the length of stent dilatation balloon so as to prolong stent service life and improve the performance of stent.
METHODS
A finite element simulation based optimization method combing with Kriging surrogate model is proposed to optimize geometries of stent and length of stent dilatation balloon step by step. Kriging surrogate model coupled with design of experiment method is employed to construct the approximate functional relationship between optimization objectives and design variables. Modified rectangular grid is used to select initial training samples in the design space. Expected improvement function is used to balance the local and global searches to find the global optimal result. Finite element method is adopted to simulate the free expansion of balloon-expandable stent and the expansion of stent in stenotic artery. The well-known Goodman diagram was used for the fatigue life prediction of stent, while dogboning effect was used for stent expansion performance measurement. As the real design cases, diamond-shaped stent and sv-shaped stent were studied to demonstrate how the proposed method can be harnessed to design and refine stent fatigue life and expansion performance computationally.
RESULTS
The fatigue life and expansion performance of both the diamond-shaped stent and sv-shaped stent are designed and refined, respectively. (a) diamond-shaped stent: The shortest distance from the data points to the failure line in the Goodman diagram was increased by 22.39%, which indicated a safer service performance of the optimal stent. The dogboning effect was almost completely eliminated, which implies more uniform expansion of stent along its length. Simultaneously, radial elastic recoil (RR) at the proximal and distal ends was reduced by 40.98 and 35% respectively and foreshortening (FS) was also decreased by 1.75%. (b) sv-shaped stent: The shortest distance from the data point to the failure line in the Goodman diagram was increased by 15.91%. The dogboning effect was also completely eliminated, RR at the proximal and distal ends was reduced by 82.70 and 97.13%, respectively, and the FS was decreased by 16.81%. Numerical results showed that the fatigue life of both stents was refined and the comprehensive expansion performance of them was improved.
CONCLUSIONS
This article presents an adaptive optimization method based on the Kriging surrogate model to optimize the structure of stents and the length of their dilatation balloon to prolong stents fatigue life and decreases the dogboning effect of stents during expansion process. Numerical results show that the adaptive optimization method based on Kriging surrogate model can effectively optimize the design of stents and the dilatation balloon. Further investigations containing more design goals and more effective multidisciplinary design optimization method are warranted.
Topics: Algorithms; Dilatation; Equipment Failure Analysis; Finite Element Analysis; Prosthesis Design; Stents; Stress, Mechanical
PubMed: 28086895
DOI: 10.1186/s12938-016-0307-6 -
Experimental Brain Research Feb 2021We investigated whether Early Posterior Negativity (EPN) indicated the subjective dilation of time when judging the duration of arousing stimuli. Participants performed...
We investigated whether Early Posterior Negativity (EPN) indicated the subjective dilation of time when judging the duration of arousing stimuli. Participants performed a visual temporal bisection task along with high-level and low-level arousing auditory stimuli, while we simultaneously recorded EEG. In accordance with previous studies, arousing stimuli were temporally overestimated and led to higher EPN amplitude. Yet, we observed that time dilation and EPN amplitude were significantly correlated and this effect cannot be explained by confounds from stimulus valence. We interpret our findings in terms of the pacemaker-accumulator model of human timing, and suggest that EPN indicates an arousal-based increasing of the speed of our mental clock.
Topics: Arousal; Dilatation; Emotions; Humans; Time Perception
PubMed: 33277996
DOI: 10.1007/s00221-020-05991-9 -
BMC Pediatrics Apr 2024Plummer-Vinson syndrome (PVS) is characterized by a triad of symptoms consisting of microcytic hypochromic anaemia, oesophageal webs, and dysphagia. PVS is commonly...
BACKGROUND
Plummer-Vinson syndrome (PVS) is characterized by a triad of symptoms consisting of microcytic hypochromic anaemia, oesophageal webs, and dysphagia. PVS is commonly found in women in the fourth and fifth decades of life and is rarely reported in the paediatric population.
CASE PRESENTATION
We report the case of a 1-year-old male South Asian child who presented with dysphagia and anaemia for 4 months and frequent episodes of vomiting after ingesting semisolid and solid food. A complete blood analysis revealed microcytic hypochromic anaemia. An oesophagogram revealed circumferential narrowing of the upper thoracic oesophagus. Based on these findings, our suspicion was that the patient had an oesophageal web and vascular ring. Oesophageal dilation was performed with a Savary-Gilliard dilator; initially, 5 mm and 7 mm probes were used, and final dilation with a 9 mm probe was performed.
CONCLUSION
Although rare in paediatric patients, a high suspicion of this syndrome is necessary in these patients to provide relief to the patient for better growth and development. Iron supplements increase the haemoglobin level but do not subside dysphagia, and oesophageal dilation is needed to open the blocked enteral pathway.
Topics: Humans; Plummer-Vinson Syndrome; Male; Infant; Deglutition Disorders; Dilatation
PubMed: 38678196
DOI: 10.1186/s12887-024-04750-x -
European Heart Journal Dec 2008The aim of the present study was to describe a 10 years single-centre experience in pacing and defibrillating leads removal using an effective and safe modified...
Transvenous removal of pacing and implantable cardiac defibrillating leads using single sheath mechanical dilatation and multiple venous approaches: high success rate and safety in more than 2000 leads.
AIMS
The aim of the present study was to describe a 10 years single-centre experience in pacing and defibrillating leads removal using an effective and safe modified mechanical dilatation technique.
METHODS AND RESULTS
We developed a single mechanical dilating sheath extraction technique with multiple venous entry site approaches. We performed a venous entry site approach (VEA) in cases of exposed leads and an alternative transvenous femoral approach (TFA) combined with an internal transjugular approach (ITA) in the presence of very tight binding sites causing failure of VEA extraction or in cases of free-floating leads. We attempted to remove 2062 leads [1825 pacing and 237 implantable cardiac defibrillating (ICD) leads; 1989 exposed at the venous entry site and 73 free-floating] in 1193 consecutive patients. The VEA was effective in 1799 leads, the TFA in 28, and the ITA in 205; in the overall population, we completely removed 2032 leads (98.4%), partially removed 18 (0.9%), and failed to remove 12 leads (0.6%). Major complications were observed in eight patients (0.7%), causing three deaths (0.3%).
CONCLUSION
Mechanical single sheath extraction technique with multiple venous entry site approaches is effective, safe, and with a good cost effective profile for pacing and ICD leads removal.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Cardiac Catheterization; Child; Defibrillators, Implantable; Device Removal; Dilatation; Female; Humans; Male; Middle Aged; Monitoring, Physiologic; Pacemaker, Artificial; Treatment Outcome; Young Adult
PubMed: 18948356
DOI: 10.1093/eurheartj/ehn461 -
International Braz J Urol : Official... 2016Urethral stricture disease is still a major problem in men. Many procedures are available for the treatment of urethral strictures; urethral dilatation is one of the...
INTRODUCTION
Urethral stricture disease is still a major problem in men. Many procedures are available for the treatment of urethral strictures; urethral dilatation is one of the oldest. The blind dilatation of urethral strictures may be a difficult and potentially dangerous procedure. The purpose of this study was to describe safe urethral dilatation using amplatz renal dilator and to report outcomes.
MATERIALS AND METHODS
From 2010 to 2014, a total of 26 men with primary urethral strictures were managed by urethral dilatation using amplatz renal dilators. The parameters analyzed included presentation of patients, retrograde urethrography (RGU) findings, pre-and postoperative maximum flow rate (Qmax) on uroflowmetry (UF) and post-void residual urine (PVR). Patients were followed-up at 1.6 and 12 months. The technique described in this paper enables such strictures to be safely dilated after endoscopic placement of a suitable guidewire and stylet over which amplatz renal dilators are introduced.
RESULTS
The mean age of the patients was 57.6 (35-72) years. The median stricture length was 0.82 (0.6-1.5)cm. Pre-operative uroflowmetry showed Qmax of 7.00 (4-12) mL/sec and ultrasonography showed PVR of 75.00 (45-195)mL. Postoperatively, Qmax improved to 18.00 (15-22)mL/sec (p<0.001) at 1 month, 17.00 (13-21)mL/sec (p<0.001) at 6 months and 15.00 (12-17)mL/sec (p<0.001) at 12 months. The post-operative PVR values were 22.50 (10-60)mL (p<0.001), 30.00 (10-70)mL (p<0.001) and 30.00 (10-70) mL (p<0.001) at 1.6 12 months, respectively. The median procedure time was 15.00 (12-22) minutes. None of the patients had a recurrence during a 12-month period of follow-up.
CONCLUSION
Urethral dilatation with amplatz renal dilators avoids the risks associated with blind dilatation techniques. This tecnique is a safe, easy, well-tolerated and cost-effective alternative for treatment of urethral strictures.
Topics: Adult; Aged; Dilatation; Equipment Design; Follow-Up Studies; Humans; Male; Middle Aged; Operative Time; Postoperative Period; Prospective Studies; Recurrence; Reproducibility of Results; Risk Factors; Statistics, Nonparametric; Time Factors; Treatment Outcome; Urethra; Urethral Stricture; Urinary Catheterization
PubMed: 27256192
DOI: 10.1590/S1677-5538.IBJU.2014.0578 -
The Israel Medical Association Journal... May 2021Management of acquired laryngotracheal stenosis (LTS) is challenging and often requires recurrent procedures. (Comparative Study)
Comparative Study
BACKGROUND
Management of acquired laryngotracheal stenosis (LTS) is challenging and often requires recurrent procedures.
OBJECTIVES
To compare the efficacy and safety of balloon dilatation (BD) versus rigid dilatation (RD) in the treatment of LTS.
METHODS
A retrospective study of patients undergoing endoscopic intervention for LTS was performed.
RESULTS
The study included 69 balloon (BD) and 48 rigid dilations (RD). Most cases were grade 3 Cotton-Meyer stenosis. Mean time interval to recurrence after BD and RD were 27.9 and 19.6 weeks, respectively. Remission of over 8 weeks was achieved in 71% of BD compared to 31.2% of RD (P < 0.05). In the BD group, dilatation of subglottic stenosis showed higher rates of remission of over 8 weeks compared to upper and mid-tracheal stenosis (92% vs. 62% and 20%, respectively, P < 0.05). Complications were encountered in 4.2% of RD and 2.9% of BD.
CONCLUSIONS
BD and RD are effective and safe procedures. Overall, BD achieved slightly better long-term results compared to RD.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Child; Dilatation; Endoscopy; Equipment Design; Female; Humans; Laryngostenosis; Male; Middle Aged; Recurrence; Remission Induction; Retrospective Studies; Time Factors; Tracheal Stenosis; Treatment Outcome; Young Adult
PubMed: 34024046
DOI: No ID Found -
Circulation. Cardiovascular Imaging Nov 2017
Topics: Aorta; Athletes; Body Mass Index; Dilatation; Football
PubMed: 29122846
DOI: 10.1161/CIRCIMAGING.117.007157 -
Diseases of the Esophagus : Official... Aug 2018Treatment endpoints in eosinophilic esophagitis (EoE) are response of eosinophilic inflammation and of symptoms. Steroids and diet therapy are effective in inducing... (Meta-Analysis)
Meta-Analysis
Treatment endpoints in eosinophilic esophagitis (EoE) are response of eosinophilic inflammation and of symptoms. Steroids and diet therapy are effective in inducing histologic response in EoE, but there may be poor correlation between histologic and symptomatic response. Despite this, we find that in clinical practice symptoms are commonly used to guide management without assessing histologic response. We hypothesized that symptom response alone is not reliable in assessing response to therapy and is confounded by endoscopic dilation. We conducted a systematic review and meta-regressions to estimate the association of histologic and symptomatic response, stratified by whether concurrent dilation was permitted. We performed a systematic search of PubMed, EMBASE, and Web of Science for studies describing both histologic and symptomatic responses to dilation, steroid, and diet therapies. We abstracted the proportion of histologic response and symptom response. Studies were stratified by whether dilation was permitted. We performed meta-regressions of the association between the proportions with histologic and symptomatic response, stratified by whether dilation was permitted. We identified 1359 articles, of which 62 articles were assessed for eligibility, and 23 were included providing data on 1202 patients with EoE. Unstratified meta-regression of histologic versus symptomatic response showed moderate association and large heterogeneity (inconsistency index [I2] = 89%). In adult studies in which dilation was allowed, there was weak association between symptomatic and histologic response (β1 = 0.21), minimal symptomatic response of 67% and the heterogeneity persisted, I2 = 77%. In studies that prohibited dilation, maximal symptomatic response was 72% and was moderately associated with histologic response (β1 = 0.39) with less heterogeneity, I2 = 59%. Studies of EoE that permit dilation obscure the relation between histologic and symptomatic response and have a high floor effect for symptomatic response. Studies that prohibit dilation demonstrate moderate association between histologic and symptomatic response, but have a ceiling effect for symptomatic response. Our results demonstrate that success of dietary or medical management for EoE cannot be judged by symptoms alone, and require histologic assessment, particularly if dilation has been performed.
Topics: Dilatation; Eosinophilic Esophagitis; Esophagus; Glucocorticoids; Humans
PubMed: 29893826
DOI: 10.1093/dote/doy049 -
The Journal of Obstetrics and... Apr 2022Cervical stenosis is traditionally managed by mechanical dilatation under general anesthesia (GA). We aimed to assess the safety, effectiveness, and patient...
AIM
Cervical stenosis is traditionally managed by mechanical dilatation under general anesthesia (GA). We aimed to assess the safety, effectiveness, and patient acceptability of dilatation in the outpatient setting under local anesthesia (LA).
METHODS
Data were collected prospectively from all patients attending the outpatient department with cervical stenosis from March 20, 2015 to September 23, 2020. Mechanical dilatation of the cervix was performed using Hegar dilators under LA. Subsequent colposcopic assessment, cytology, histology, and management were recorded.
RESULTS
One hundred forty-nine cases were referred for cervical dilatation, 63 (43%) of which had complete stenosis. One hundred eighteen (79%) patients had previously undergone cervical procedures. Successful dilatation under LA was achieved in 119 (83%) patients; 5 (3%) declined (requesting GA), 6 (4%) did not tolerate speculum examination, and 19 (13%) had unsuccessful procedures. The median Hegar size used was 8 mm. Dilatation under LA was acceptable in 93% attempted procedures. Thirteen episodes of restenosis were recorded with no major adverse events. Younger age (p = 0.045) and severe (compared to complete) stenosis (p < 0.0001) were associated with procedure success, with improved results over time (p = 0.003). Successful dilatation permitted cervical assessment; eight patients required cervical excisions, two underwent hysterectomies, with one confirmed case of adenocarcinoma.
CONCLUSION
Rigid cervical dilatation in the outpatient setting provides effective, instantaneous treatment for women who have failed cytological or colposcopic assessment. For the vast majority of women, the procedure was well tolerated and preferred to using GA. However, given that 1 in 10 women experienced restenosis, patients should be counseled about the possibility of requiring further management.
Topics: Anesthesia, Local; Cervix Uteri; Colposcopy; Constriction, Pathologic; Dilatation; Female; Humans; Pregnancy; Uterine Cervical Neoplasms
PubMed: 35132727
DOI: 10.1111/jog.15179 -
Journal of Pediatric Urology Feb 2024Historically, ureteral reimplantation (UR) has been the gold standard for treatment of primary obstructive megaureter (POM) with declining renal function, worsening... (Review)
Review
INTRODUCTION
Historically, ureteral reimplantation (UR) has been the gold standard for treatment of primary obstructive megaureter (POM) with declining renal function, worsening obstruction, or recurrent urinary tract infections. In infants, open surgery with reimplantation of a grossly dilated ureter into a small bladder, can be technically challenging with significant morbidity. Therefore, less invasive endoscopic management such as dilatation or incision of the ureter-vesical junction, has emerged as an alternative to reimplantation during the last decades.
OBJECTIVE
To systematically evaluate the effectivity, safety, and potential benefits of endoscopic treatment (dilatation with or without balloon or incision) of POM in comparison to UR.
STUDY DESIGN
A systematic review was conducted. Randomized controlled trials (RCTs), nonrandomized comparative studies (NRSs), and single-arm case series including a minimum of 20 participants and a mean follow-up more than 12 months were eligible for inclusion.
RESULTS
Of 504 articles identified, 8 articles including 338 patients were eligible for inclusion (0 RCTs, 1 NRSs, and 7 case series). Age at time of surgery was minimum 15 days to a maximum of 192 months. Indications for endoscopic treatment (ET) included patients with loss of split renal function (>10%) and worsening of hydroureteronephrosis. The studies analysed reported a success rate ranging from 35% to 97%. Success was defined as stabilization of differential renal function without further procedures. A post-operative complication rate of 23-60% was reported (mostly transient haematuria, urinary tract infections and stent migration or intolerance). In 14% of the cases salvage UR following initial ET, was performed due to relapse of symptomatic POM.
CONCLUSION
Endoscopic treatment for persistent or progressive POM in children is a minimally invasive alternative to UR with a long-term modest success rate. Additionally, it can be performed within a wide age span, with equal success rate and complication rates.
Topics: Infant; Child; Humans; Infant, Newborn; Ureteral Obstruction; Dilatation; Urology; Treatment Outcome; Retrospective Studies; Ureter; Urinary Tract Infections
PubMed: 37758534
DOI: 10.1016/j.jpurol.2023.09.005