Relevant bibliographies by topics / Stenosis

Academic literature on the topic 'Stenosis'

Author: Grafiati
Published: 4 June 2021
Last updated: 30 July 2024

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Journal articles on the topic "Stenosis"

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Al-Azawy, Mohammed Ghalib, Zahraa Ahmed Hamza, and Alaa Ahmed Alkinani. "Non-invasive evaluation of blood flow through a healthy and stenosed coronary artery." Wasit Journal of Engineering Sciences 10, no. 3 (February 21, 2023): 58–74. http://dx.doi.org/10.31185/ejuow.vol10.iss3.369.

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The current numerical analysis was utilised to compare the hemodynamic effects caused by flow disruptions in coronary arteries with and without stenosis in order to evaluate the hemodynamic importance of patient-specific coronary stenosis using Computational Fluid Dynamics (CFD) to provide information to the public, particularly surgeons, and assist them in reducing the risk of stenosis. Assuming the flow is turbulent and non-Newtonian viscosity, the Carreau model is incorporated by utilizing STAR-CCM+ 2021.2.1. The test model is a patient-specific coronary stenosis with area stenosis (60%). The velocity, shear stress, and strain rate were evaluated and revealed that the stenosed artery experiences more hemodynamic impacts as the flow rate increases compared to the normal artery. The turbulent kinetic energy and turbulent viscosity ratio findings showed that the TKE and TVR are almost the same downstream of the stenoses, with the TKE and TVR being somewhat higher with the stenosed artery model than the unstenosed artery model, and it increases as the flow increases. Moreover, to determine the stenosis severity, the coefficient of pressure drop (CDP) and lesion flow coefficient (LFC) were used and showed that the CDP value be higher in stenosed artery (107pa) compared to a normal artery (5.2pa) but it was less when the flow increased (84.4pa), (2.5pa) respectively. whereas the LFC value in the stenoses artery is higher (0.61) and rises as flow increases (0.69).
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BANERJEE, MOLOY K., DEBABRATA NAG, RANJAN GANGULY, and AMITAVA DATTA. "HEMODYNAMICS IN STENOSED ARTERIES — EFFECTS OF STENOSIS SHAPES." International Journal of Computational Methods 07, no. 03 (September 2010): 397–419. http://dx.doi.org/10.1142/s021987621000226x.

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A numerical analysis has been carried out to investigate the hemodynamic flow through stenosed arteries having mild (S = 25%) to severe (S = 65%) occlusions and under different regimes of flow Reynolds numbers ( Re ) ranging from 50 to 400. Influence of different stenosis shapes (rectangular, trapezoidal, cosine, and Gaussian) on key hemodynamic parameters e.g., recirculation length, wall shear stress (WSS), pressure drop, and irreversible pressure loss coefficient (C I ) are studied. It has been observed that for S = 25%, no flow separation takes place with cosine and Gaussian shaped stenoses for all the Re values considered, while for rectangular or trapezoidal shapes the flow begins to separate at Re = 400. At higher degrees of stenosis, post-stenotic recirculation is noticed for all the shapes considered — the largest recirculation length being observed with the rectangular shape. The peak centerline velocity in the stenosed region is more sensitive to a change in the degree of occlusion for rectangular stenosis than the other shapes. From the study, it is also revealed that the irreversible pressure loss coefficient (C I ) is the maximum for rectangular shaped stenosis, while it is the least for Gaussian shape. It is observed that at high Re regime, C I becomes insensitive to Re values and can be approximated to be a function of the degree of stenosis (S) and the stenosis shape only.
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Liu, H., X. Wu, Y. Xing, K. Liu, and H. Zhang. "Neurology (Stroke)." Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 42, S1 (May 2015): S36. http://dx.doi.org/10.1017/cjn.2015.165.

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Background: Cerebral artery stenosis is an important risk factor for ischemic strokes. This study aims to explore intracranial and extracranial artery stenosis in a large northeast Chinese cohort. Methods: We recruited 14793 outpatients and hospitalized patients to identify cerebral artery stenosis. Artery stenosis screening was done with transcranial Doppler (TCD) for intracranial arteries and carotid duplex sonography for extracranial arteries. Results: More intracranial than extracranial artery stenoses were identified (4255 versus 2809, i.e. 28.8% versus 19.0%, P<0.05). Similarly, mere intracranial stenosis was significantly more common than extracranial artery stenosis in this population (2632 versus 1186, i.e. 17.8% versus 8%, P<0.05). Among all identified intracranial arteries stenoses, the proportion of middle cerebral artery (MCA) stenosis was the highest. More intracranial than extracranial artery stenoses was seen within each age group, and rates of both increased with age. Intracranial and extracranial artery stenosis was more frequently identified in males than females. Conclusions: Incidence of cerebral artery stenosis in the population increases with age. Intracranial artery stenosis is more common than extracranial artery stenosis and the MCA stenosis accounted for the highest proportion, within each age group. More males suffer from intracranial or extracranial artery stenosis than females.
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Tong, Y., P. G. Matthews, and J. P. Royle. "Outcome of Endovascular Intervention for Infrainguinal Vein Graft Stenosis." Cardiovascular Surgery 10, no. 6 (December 2002): 545–50. http://dx.doi.org/10.1177/096721090201000605.

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Assisted graft patency rate following revision of a graft stenosis is far better than that following thrombectomy of an occluded graft. Graft revision by endovascular means has been proposed as a suitable alternative to more invasive surgery. This study reports our experience with endovascular treatment of vein graft stenosis. Between December 1992 and September 2000, percutaneous transluminal balloon angioplasty (PTA) was performed on 90 vein graft stenoses in 87 infrainguinal vein bypass grafts identified by routine graft duplex scan (peak systolic velocity, PSV > 300 cm/sec). All 90 stenoses treated by PTA were retrospectively analysed for stenosis-free patency rate (life-table analysis). Re-stenosis was defined by PSV exceeding 300 cm/sec at the same site of the vein graft where a stenosis was dilated. Ninety vein graft stenoses (72 primary stenoses and 18 recurrent stenoses) in 33 femoropopliteal (above knee), 30 femoropopliteal (below knee) and 24 femorotibial vein bypass grafts were treated by PTA. The timing of PTA ranged from one to 252 months (mean. 23.9 months) from the initial surgery. Cumulative stenosis-free patency rate after PTA was 55.8% at 6 months, 54.0% at one year and 45.0% at three years. Stenosis-free patency rate at six months was significantly lower for revision of recurrent stenosis (25.9%) than for primary stenosis (61.6%) ( P = 0.01). The revision of duplex scan detected vein graft stenosis with endovascular intervention was associated with an acceptable stenosis-free patency rate. However, recurrent stenosis treated by PTA had a significantly inferior outcome. Direct surgical revision would be more appropriate for recurrent lesions.
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Liu, Biyue, and Dalin Tang. "Influence of Distal Stenosis on Blood Flow Through Coronary Serial Stenoses: A Numerical Study." International Journal of Computational Methods 16, no. 03 (March 17, 2019): 1842003. http://dx.doi.org/10.1142/s0219876218420033.

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Computer simulations of the blood flow through right coronary arteries with two stenoses in the same arterial segment are carried out to investigate the interactions of serial stenoses, especially the effect of the distal stenosis. Various mathematical models are developed by varying the location of the distal stenosis. The numerical results show that the variation of the distal stenosis has significant impact on coronary hemodynamics, such as the pressure drop, flow shifting, wall shear stress and flow separation. Our simulations demonstrate that the distal stenosis has insignificant effect on the disturbed flow pattern in the regions of upstream and across the proximal stenosis. In a curved artery segment with two moderate stenoses of the same size, the distal stenosis causes a larger pressure drop and a more disturbed flow field in the poststenotic region than the proximal stenosis does. A distal stenosis located at a further downstream position causes a larger pressure drop and a stronger reverse flow.
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Lougheed, Nick, Jeff Jaskolka, Rob Beecroft, and Ravi Menezes. "Determination of the Best Parameter for Defining the Hemodynamic Significance of an Iliac Artery Stenosis Detected on Computed Tomography Angiography." Canadian Association of Radiologists Journal 67, no. 3 (August 2016): 298–303. http://dx.doi.org/10.1016/j.carj.2015.09.005.

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Purpose The purpose of this study was to determine the best parameter, derived from computed tomography angiography (CTA) for accurate prediction of a hemodynamically significant stenosis of the common or external iliac artery. Methods A retrospective keyword search was performed on the Radiology Information System at our tertiary academic medical centre. Reports from January 2008 to September 2013 were searched using the keywords iliac, stenosis, and pressure. Patients who had both and CTA and a pelvic angiogram with pressure measurements obtained across a potential stenosis were selected. Using 3D postprocessing software (TeraRecon, Foster City, CA), the CTAs were analysed for the following parameters of each lesion: minimum diameter of stenosis, minimum cross-sectional area of stenosis, percent narrowing of vessel diameter, and percent reduction in vessel area. The percent stenosis was calculated in reference to the outer diameter at the point of maximal narrowing and also in reference to a normal segment of vessel more distal to the stenosis. These parameters were then compared with the measured pressure gradient using receiver-operating characteristic analysis and the Mann-Whitney U test to determine which best predicted a significant stenosis, defined as a greater than 10% drop in systolic pressure across a lesion. Results One hundred and two stenoses in 83 patients (26 women, 57 men; 47-88 years old) were identified. Mean diameter of the stenosis was 2.8 mm for significant stenosis compared to 3.8 mm in nonsignificant stenoses ( P = .005). Mean minimum area for significant stenoses was 11.8 mm2 compared to 17.22 mm2 for nonsignificant stenoses ( P = .032) No other variables showed a significant difference between significant and nonsignificant stenoses. A minimum diameter of ≤4.0 mm at the level of a stenosis is 92% sensitive and 48% specific for predicting a hemodynamically significant iliac artery stenosis, with a positive predictive value of 88%. Conclusions A simple measurement of the minimum diameter of an iliac artery at the level of stenosis is the best predictor of the hemodynamic significance of a stenosis in the common or external iliac artery.
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Varnava, A. M., and M. J. Davies. "Relation between coronary artery remodelling (compensatory dilatation) and stenosis in human native coronary arteries." Heart 86, no. 2 (August 1, 2001): 207–11. http://dx.doi.org/10.1136/hrt.86.2.207.

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OBJECTIVESTo investigate the contribution of plaque size and vessel remodelling to coronary artery stenosis and to assess the role of vessel shrinkage (negative remodelling) across a wide range of lesions.DESIGNPostmortem study of coronary remodelling in perfusion fixed hearts.SUBJECTS24 men and 24 women who died suddenly with coronary artery disease.MAIN OUTCOME MEASURESPercentage stenosis, percentage plaque burden, percentage remodelling, and arc of normal vessel were measured and related to age, sex, smoking status, and history of hypertension.RESULTSThere was a positive relation between percentage stenosis and percentage plaque burden (r = 0.6, p < 0.0001) and an inverse relation between percentage stenosis and percentage remodelling (r = –0.4, p < 0.0001). Multilinear regression modelling showed that luminal stenosis = 1.0 (plaque burden) − 0.4 (vessel remodelling). Remodelling was greater in lesions that would not have been significant at angiography (⩽ 25% stenosis) than in the remaining lesions (25.9 (26)% v10.0 (21.1)%, p < 0.0001, respectively) and was reduced in segments with circumferential plaques (12.7 (24.5)% v20.7 (24.3)% in eccentric plaques, p = 0.001). Remodelling did not correlate with age, sex, or smoking. Negative remodelling was present in 62 lesions with a stenosis > 25% versus 10 lesions with ⩽ 25% stenosis (p < 0.0001). Lesions with negative remodelling had greater plaque burden and luminal stenosis and a reduced arc of normal segment.CONCLUSIONOutward arterial remodelling negates the stenosing effect of increasing plaque size. Significant coronary stenoses arise from a failure of this outward remodelling in the face of a large plaque burden. Coronary arterial remodelling is unrelated to sex or smoking and is plaque specific.
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Loree, H. M., R. D. Kamm, C. M. Atkinson, and R. T. Lee. "Turbulent pressure fluctuations on surface of model vascular stenoses." American Journal of Physiology-Heart and Circulatory Physiology 261, no. 3 (September 1, 1991): H644—H650. http://dx.doi.org/10.1152/ajpheart.1991.261.3.h644.

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Turbulence frequently develops when blood passes through a stenosis. To study the hypothesis that turbulence near a plaque surface can cause pressure fluctuations that may promote plaque rupture, models of intravascular stenoses were studied. Experimental conditions simulated peak flow in the coronary and carotid arteries through a stenosis of 80 or 90% diameter reduction and into a region where the plaque had widened distally to a 50-75% stenosis. For symmetric stenoses at carotid artery flow rates, peak pressure fluctuations were observed 1-1.5 upstream diameters distal to the stenosis, but there were no significant turbulent pressure fluctuations at coronary artery flow rates. Stenosis asymmetry strongly increased the intensity of turbulent pressure fluctuations at flows simulating carotid flow and resulted in significant pressure fluctuations for coronary flow conditions. Increasing stenosis severity from 80 to 90% increased the root mean square pressure fluctuations 3.6-fold. These studies predict peak to peak pressure fluctuations of 15 mmHg in a 90% asymmetric coronary stenosis; it is possible that turbulence may play a role in acute damage of atherosclerotic plaques, particularly in asymmetric stenoses.
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Tirinescu, Dacian Călin, Cosmina Ioana Bondor, Dan Ştefan Vlăduțiu, Ioan Mihai Pațiu, Diana Moldovan, Remus Orășan, and Ina Maria Kacsó. "Ultrasonographic diagnosis of stenosis of native arteriovenous fistulas in haemodialysis patients." Medical Ultrasonography 18, no. 3 (September 18, 2016): 332. http://dx.doi.org/10.11152/mu.2013.2066.183.fis.

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Aims: Ultrasound (US) examination is an important tool in the diagnosis of arteriovenous (AVF) stenoses; different US measures are available for assessing the severity of stenoses. The aim of our study was to analyse risk factors and consequences of AVF stenosis and its severity and to compare the usefulness of different US measures of stenoses’ severity. Material and methods: Ninety-seven prevalent patients from a single dialysis centre with patent AVF were included. We recorded history of disease, clinical and laboratory data. US was used to diagnosis the stenosis and to measure blood flow in the brachial artery, resistivity index (RI), and the diameter of the vessels (arteries, anastomosis, venous outflow). Results: Stenosis was present in 54.64% of the patients (59.6% juxtaanastomotic). Stenosis patients had higher age, lower diameter of the brachial artery, lower anastomosis diameter, and lower diastolic blood pressure (DBP). Atherosclerosis, delayed maturation of AVF, and statin treatment were more prominent in the stenosis group. Logistic regression disclosed delayed maturation, cholesterol, atherosclerosis, and DBP as significant predictors of stenosis. When severe stenosis was measured by the diameter reduction, stenosis patients had higher age, lower HDL cholesterol, and poorer dialysis efficacy. Flow in the brachial artery and RI were less useful for identifying risk factors or differences in outcome. Conclusions: Prevalence of stenosis was high in our cohort, more than half of the patients having some degree of stenosis. Risk factors for stenosis were related to atherosclerosis, low DBP, and delayed maturation of AVF. Diameter of stenosis is the most useful marker of severity.
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He, Fan, Lu Hua, and Tingting Guo. "Fluid–structure interaction analysis of hemodynamics in different degrees of stenoses considering microcirculation function." Advances in Mechanical Engineering 13, no. 1 (January 2021): 168781402198901. http://dx.doi.org/10.1177/1687814021989012.

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In developed countries, stenosis is the main cause of death. To investigate hemodynamics within different degrees of stenoses, a stenosis model incorporating fluid–structure interaction and microcirculation function is used in this paper. Microcirculation is treated as a seepage outlet boundary condition. Compliant arterial wall is considered. Numerical simulation based on fluid–structure interaction is performed using finite element method. Our results indicate that (i) the increasing degree of stenosis makes the pressure drop increase, and (ii) the wall shear stress and the velocity in the artery zone may be more sensitive than the pressure with the increase of percentage stenosis, and (iii) there are higher wall shear stress and flow velocity in the post-stenosis region of severer stenosis. This work contributes to understand hemodynamics for different degrees of stenoses and it provides detailed information for stenosis and microcirculation function.
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Dissertations / Theses on the topic "Stenosis"

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Johansson, Elias. "Carotid stenosis." Doctoral thesis, Umeå universitet, Institutionen för folkhälsa och klinisk medicin, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-46396.

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Carotid stenosis is one of several causes of ischemic stroke and entails a high risk of ischemic stroke recurrence. Removal of a carotid stenosis by carotid endarterectomy results in a risk reduction for ischemic stroke, but the magnitude of risk reduction depends on several factors. If the delay between the last symptom and carotid endarterectomy is less than 2 weeks, the absolute risk reduction is >10%, regardless of age, sex, or if the degree of carotid stenosis is 50–69% or 70–99%. Thus, speed is the key. However, if many patients suffers an ischemic stroke recurrence within the first 2 weeks of the presenting event, an additional benefit is likely be obtained if carotid endarterectomy is performed even earlier than within 2 week after the presenting event. Carotid endarterectomy for asymptomatic carotid stenoses carries a small risk reduction for stroke. Screening for asymptomatic carotid stenosis requires a prevalence of >5% in the examined population, i.e., higher than in the general population; however, directed screening in groups with a prevalence of >5% is beneficial. The aims of this thesis were to investigate the length of the delay to carotid endarterectomy, determine the risk of recurrent stroke before carotid endarterectomy, and determine if a calcification in the area of the carotid arteries seen on dental panoramic radiographs is a valid selection method for directed ultrasound screening to detect asymptomatic carotid stenosis. Consecutive patients with a symptomatic carotid stenosis who underwent a preoperative evaluation aimed at carotid endarterectomy at Umeå Stroke Centre between January 1, 2004–March 31, 2006 (n=275) were collected retrospectively and between August 1, 2007–December 31, 2009 (n=230) prospectively. In addition, 117 consecutive persons, all preliminarily eligible for asymptomatic carotid endarterectomy and with a calcification in the area of the carotid arteries seen on panoramic radiographs, were prospectively examined with carotid ultrasound. The median delay between the presenting event and carotid endarterectomy was 11.7 weeks in the first half year of 2004, dropped to 6.9 weeks in the first quarter year of 2006, and had dropped to 3.6 weeks in the second half year of 2009. The risk of ipsilateral ischemic stroke recurrence was 4.8% within 2 days, 7.9% within 1 week, and 11.2% within 2 weeks of the presenting event. For patients with a stroke or transient ischemic attack as the presenting event, this risk was 6.0% within 2 days, 9.7% within 1 week, and 14.3% within 2 weeks of the presenting event. For the 10 patients with a near-occlusion, the risk of ipsilateral ischemic stroke recurrence was 50% at 4 weeks after the presenting event. Among the 117 persons with a calcification in the area of the carotid arteries seen on panoramic radiographs, eight had a 50–99% carotid stenosis, equalling a prevalence of 6.8% (not statistically significantly over the pre-specified 5% threshold). Among men, the prevalence of 50–99% carotid stenosis was 12.5%, which was statistically significantly over the pre-specified 5% threshold. In conclusion: The delay to carotid endarterectomy was longer than 2 weeks. Additional benefit is likely to be gained by performing carotid endarterectomy within a few days of the presenting event instead of at 2 weeks because many patients suffer a stroke recurrence within a few days; speed is indeed the key. The finding that near-occlusion entails an early high risk of stroke recurrence stands in sharp contrast to previous studies; one possible explaination is that this was a high-risk period missed in previous studies. The incidental finding of a calcification in the area of the carotid arteries on a panoramic radiograph is a valid indication for carotid ultrasound screening in men who are otherwise eligible for asymptomatic carotid endarterectomy.
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Lee, Paul Man-Yiu. "Critical coronary stenosis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq23948.pdf.

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Eklöf, Hampus. "On Renal Artery Stenosis." Doctoral thesis, Uppsala University, Department of Oncology, Radiology and Clinical Immunology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5945.

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Renal artery stenosis (RAS) is a potentially curable cause of hypertension and azotemia. Besides intra-arterial renal angiography there are several non-invasive techniques utilized to diagnose patients with suspicion of renal artery stenosis. Removing the stenosis by revascularization to restore unobstructed blood flow to the kidney is known to improve and even cure hypertension/azotemia, but is associated with a significant complication rate.

To visualize renal arteries with x-ray techniques a contrast medium must be used. In a randomized, prospective study the complications of two types of contrast media (CO2 and ioxaglate) were compared. CO2 was not associated with acute nephropathy, but induced nausea and had lower attenuation differences compared to Ioxaglate. Acute nephropathy was related to the ioxaglate dose and the risk was evident even at very low doses if the patients were azotemic with creatinine clearance <40 ml/min.

Evaluating patients for clinically relevant renal artery stenosis can be done utilizing several non-invasive techniques. MRA was retrospectively evaluated and shown to be accurate in detecting hemodynamically significant RAS. In a prospective study of 58 patients, evaluated with four methods for renal artery stenosis, it was shown that MRA and CTA were significantly better than ultrasonography and captopril renography in detecting hemodynamically significant RAS. The standard of reference was trans-stenotic pressure gradient measurement, defining a stenosis as significant at a gradient of ≥15 mmHg. The discrepancies were mainly found in the presence of borderline stenosis.

The outcome of percutaneous revascularization procedures showed a technical success rate of 95%, clinical benefit in 63% of treated patients, 30-day mortality 1.5% and major complication rate of 13%. The major complication rate for patients with baseline serum creatinine >300µmol/l was 32%. Our results compare favorably with published studies and guidelines.

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Kragsterman, Björn. "Carotid Artery Stenosis : Surgical Aspects." Doctoral thesis, Uppsala University, Department of Surgical Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6834.

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Randomised controlled trials (RCT) have demonstrated a net benefit of carotid endarterectomy (CEA) in stroke prevention for patients with severe carotid artery stenosis as compared to best medical treatment. Results in routine clinical practice must not be inferior to those in the RCTs. The carotid arteries are clamped during CEA which may impair the cerebral perfusion.

The aim of this thesis was to assess population-based outcomes from CEA, investigate risk factors for perioperative complications/late mortality and to evaluate effects of carotid clamping during CEA. In the Swedish vascular registry 6182 CEAs were registered during 1994-2003. Data on all CEAs were retrieved, analysed and validated. In the validation process no death or disabling stroke was unreported. The perioperative stroke or death rate was 4.3% for those with symptomatic and 2.1% for asymptomatic stenosis (the latter decreasing over time). Risk factors for perioperative complications were age, indication, diabetes, cardiac disease and contralateral occlusion. Median survival time was 10.8 years for the symptomatic and 10.2 years for the asymptomatic group.

Tolerance to carotid clamping during CEA under general anaesthesia was evaluated in 62 patients measuring cerebral oximetry, transit time volume flowmetry and stump pressure. High internal carotid artery flow before clamping and low stump pressure was associated with decreased oxygenation after clamping suggesting shunt indication.

In 18 patients undergoing CEA, jugular bulb blood samples demonstrated significantly altered levels of marker for inflammatory activation (IL-6) and fibrinolytic activity (D-dimer and PAI-1) during carotid clamping as compared to radial artery levels. This indicates a cerebral ischaemia due to clamping although clinically well tolerated.

In conclusion, the perioperative outcome after CEA in Sweden compared well with the RCTs results. Tolerance to carotid clamping may be evaluated by combining stump pressure and volume flow measurements. Although clinically tolerated clamping may induce a cerebral ischaemic response.

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Kragsterman, Björn. "Carotid artery stenosis : surgical aspects /." Uppsala : Acta Universitatis Upsaliensis : Univ.bibl. [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6834.

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McCann, Gerald Patrick. "Exercise limitation in aortic stenosis." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395082.

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Pawade, Tania Ashwinikumar. "Imaging calcification in aortic stenosis." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/29589.

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BACKGROUND Aortic stenosis is a common and potentially fatal condition in which fibro-calcific changes within the valve leaflets lead to the obstruction of blood flow. Severe symptomatic stenosis is an indication for aortic valve replacement and timely referral is essential to prevent adverse clinical events. Calcification is believed to represent the central process driving disease progression. 18F-Fluoride positron emission tomography computed tomography (PET-CT) and CT aortic valve calcium scoring (CT-AVC) quantify calcification activity and burden respectively. The overarching aim of this thesis was to evaluate the applications of these techniques to the study and management of aortic stenosis. METHODS AND RESULTS REPRODUCIBILITY The scan-rescan reproducibility of 18F-fluoride PET-CT and CT-AVC were investigated in 15 patients with mild, moderate and severe aortic stenosis who underwent repeated 18F-fluoride PET-CT scans 3.9±3.3 weeks apart. Modified techniques enhanced image quality and facilitated clear localization of calcification activity. Percentage error was reduced from ±63% to ±10% (tissue-to-background ratio most-diseased segment (MDS) mean of 1.55, bias -0.05, limits of agreement - 0·20 to +0·11). Excellent scan-rescan reproducibility was also observed for CT-AVC scoring (mean of differences 2% [limits of agreement, 16 to -12%]). AORTIC VALVE CALCIUM SCORE: SINGLE CENTRE STUDY Sex-specific CT-AVC thresholds (2065 in men and 1271 in women) have been proposed as a flow-independent technique for diagnosing severe aortic stenosis. In a prospective cohort study, the impact of CT-AVC scores upon echocardiographic measures of severity, disease progression and aortic valve replacement (AVR)/death were examined. Volunteers (20 controls, 20 with aortic sclerosis, 25 with mild, 33 with moderate and 23 with severe aortic stenosis) underwent CT-AVC and echocardiography at baseline and again at either 1 or 2-year time-points. Women required less calcification than men for the same degree of stenosis (p < 0.001). Baseline CT-AVC measurements appeared to provide the best prediction of subsequent disease progression. After adjustment for age, sex, peak aortic jet velocity (Vmax) ≥ 4m/s and aortic valve area (AVA) < 1 cm2, the published CT-AVC thresholds were the only independent predictor of AVR/death (hazard ratio = 6.39, 95% confidence intervals, 2.90-14.05, p < 0.001). AORTIC VALVE CALCIUM SCORE: MULTICENTRE STUDY CT-AVC thresholds were next examined in an international multicenter registry incorporating a wide range of patient populations, scanner vendors and analysis platforms. Eight centres contributed data from 918 patients (age 77±10, 60% male, Vmax 3.88±0.90 m/s) who had undergone ECG-gated CT within 3 months of echocardiography. Of these 708 (77%) had concordant echocardiographic assessments, in whom our own optimum sex-specific CT-AVC thresholds (women 1377, men 2062 AU) were nearly identical to those previously published. These thresholds provided excellent discrimination for severe stenosis (c-statistic: women 0.92, men 0.88) and independently predicted AVR and death after adjustment for age, sex, Vmax ≥4 m/s and AVA < 1 cm2 (hazards ratio, 3.02 [95% confidence intervals, 1.83-4.99], p < 0.001). In patients with discordant echocardiographic assessments (n=210), CT-AVC thresholds predicted an adverse prognosis. BICUSPID AORTIC VALVES Within the multicentre study, higher continuity-derived estimates of aortic valve area were observed in patients with bicuspid valves (n=68, 1.07±0.35 cm) compared to those with tri-leaflet valves (0.89±0.36 cm p < 0.001,). This was despite no differences in measurements of Vmax (p=0.152), or CT-AVC scores (p=0.313). The accuracy of AVA measurments in bicuspid valves was therefore tested against alternative markers of disease severity. AVA measurements in bicuspid valves demonstrated extremely weak associations with CT-AVC scores (r2=0.08, p=0.02) and failed to correlate with downstream markers of disease severity in the valve and myocardium and against clinical outcomes. AVA measurements in bicuspid patients also failed to independently predict AVR/death after adjustment for Vmax ≥4 m/s, age and gender. In this population CT-AVC thresholds (women 1377, men 2062 AU) again provided excellent discrimination for severe stenosis. CONCLUSIONS Optimised 18F-fluoride PET-CT scans quantify and localise calcification activity, consolidating its potential as a biomarker or end-point in clinical trials of novel therapies. CT calcium scoring of aortic valves is a reproducible technique, which provides diagnostic clarity in addition to powerful prediction of disease progression and adverse clinical events.
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Boyd, C. S. "Radiological evaluation of renal artery stenosis." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426973.

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Kattach, Hassan. "Blood pressure control in aortic stenosis." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526473.

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Försth, Peter. "On Surgery for Lumbar Spinal Stenosis." Doctoral thesis, Uppsala universitet, Institutionen för kirurgiska vetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-262525.

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The incidence of lumbar spinal stenosis (LSS) is steadily rising, mostly because of a noticeably older age structure. In Sweden, LSS surgery has increased continuously over the years and is presently the most common argument to undergo spine surgery. The purpose of the surgery is to decompress the neural elements in the stenotic spinal canal. To avoid instability, there has been a tradition to do the decompression with a complementary fusion, especially if degenerative spondylolisthesis is present preoperatively. The overall aims of this thesis were to evaluate which method of surgery that generally can be considered to give sufficiently good clinical results with least cost to society and risk of complications and to determine whether there is a difference in outcome between smokers and non-smokers. The Swespine Register was used to collect data on clinical outcome after LSS surgery. In two of the studies, large cohorts were observed prospectively with follow-up after 2 years. Data were analysed in a multivariate model and logistic regression. In a randomised controlled trial (RCT, the Swedish Spinal Stenosis Study), 233 patients were randomised to either decompression with fusion or decompression alone and then followed for 2 years. The consequence of preoperative degenerative spondylolisthesis on the results was analysed and a health economic evaluation performed. The three-dimensional CT technique was used in a radiologic biomechanical pilot study to evaluate the stabilising role of the segmental midline structures in LSS with preoperative degenerative spondylolisthesis by comparing laminectomy with bilateral laminotomies. Smokers, in comparison with non-smokers, showed less improvement after surgery for LSS. Decompression with fusion did not lead to better results compared with decompression alone, no matter if degenerative spondylolisthesis was present preoperatively or not; nor was decompression with fusion found to be more cost-effective than decomression alone. The instability caused by a decompression proved to be minimal and removal of the midline structures by laminectomy did not result in increased instability compared with the preservation of these structures by bilateral laminotomies. In LSS surgery, decompression without fusion should generally be the treatment of choice, regardless of whether preoperative degenerative spondylolisthesis is present or not. Special efforts should be targeted towards smoking cessation prior to surgery.
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Books on the topic "Stenosis"

1

Parakh, Neeraj, Ravi S. Math, and Vivek Chaturvedi, eds. Mitral Stenosis. Boca Raton, FL : CRC Press/Taylor & Francis Group, [2018]: CRC Press, 2018. http://dx.doi.org/10.1201/9781315166735.

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Abbas, Amr E., ed. Aortic Stenosis. London: Springer London, 2015. http://dx.doi.org/10.1007/978-1-4471-5242-2.

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Ibrahim, Ashraf, and Talal Al-Malki. Congenital Esophageal Stenosis. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-10782-6.

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Manfrè, Luigi, ed. Spinal Canal Stenosis. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-26270-3.

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Postacchini, Franco. Lumbar Spinal Stenosis. Vienna: Springer Vienna, 1989. http://dx.doi.org/10.1007/978-3-7091-9021-0.

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Postacchini, Franco. Lumbar spinal stenosis. Wien: Springer-Verlag, 1989.

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D, Rittenberg Joshua, ed. Lumbosacral spinal stenosis. Philadelphia, Pa: W.B. Saunders, 2003.

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1942-, Andersson Gunnar, and McNeill Thomas W. 1936-, eds. Lumbar spinal stenosis. St. Louis: Mosby Year Book, 1991.

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National Institute of Diabetes and Digestive and Kidney Diseases (U.S.), ed. Renal artery stenosis. Bethesda, MD]: U.S. Dept. of Health and Human Services, National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, 2007.

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Denaro, Vincenzo. Stenosis of the cervical spine: Causes, diagnosis, and treatment. Berlin: Springer-Verlag, 1991.

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Book chapters on the topic "Stenosis"

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Wood, Frances O., and Amr E. Abbas. "General Considerations and Etiologies of Aortic Stenosis." In Aortic Stenosis, 1–20. London: Springer London, 2015. http://dx.doi.org/10.1007/978-1-4471-5242-2_1.

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Gallagher, Michael J. "Prosthetic Aortic Valves and Diagnostic Challenges." In Aortic Stenosis, 147–69. London: Springer London, 2015. http://dx.doi.org/10.1007/978-1-4471-5242-2_10.

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Mack, Michael J., and Amr E. Abbas. "Risk Prediction Models, Guidelines, Special Populations, and Outcomes." In Aortic Stenosis, 171–96. London: Springer London, 2015. http://dx.doi.org/10.1007/978-1-4471-5242-2_11.

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Shannon, Francis L., Marc P. Sakwa, and Robert L. Johnson. "Surgical Management of Aortic Valve Stenosis." In Aortic Stenosis, 197–217. London: Springer London, 2015. http://dx.doi.org/10.1007/978-1-4471-5242-2_12.

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Berman, Aaron David. "Balloon Aortic Valvuloplasty." In Aortic Stenosis, 219–30. London: Springer London, 2015. http://dx.doi.org/10.1007/978-1-4471-5242-2_13.

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Poon, Karl K. C. "Imaging for Transcatheter Aortic Valve Replacement." In Aortic Stenosis, 231–51. London: Springer London, 2015. http://dx.doi.org/10.1007/978-1-4471-5242-2_14.

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Hanzel, George S. "Transcatheter Aortic Valve Replacement." In Aortic Stenosis, 253–69. London: Springer London, 2015. http://dx.doi.org/10.1007/978-1-4471-5242-2_15.

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Zacharias, Sibin K., and James A. Goldstein. "Clinical Assessment of the Severity of Aortic Stenosis." In Aortic Stenosis, 21–28. London: Springer London, 2015. http://dx.doi.org/10.1007/978-1-4471-5242-2_2.

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Abbas, Amr E., and Philippe Pibarot. "Physiological Basis for Area and Gradient Assessment: Hemodynamic Principles of Aortic Stenosis." In Aortic Stenosis, 29–48. London: Springer London, 2015. http://dx.doi.org/10.1007/978-1-4471-5242-2_3.

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Abbas, Amr E. "Different Classifications of Aortic Stenosis." In Aortic Stenosis, 49–54. London: Springer London, 2015. http://dx.doi.org/10.1007/978-1-4471-5242-2_4.

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Conference papers on the topic "Stenosis"

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D’Souza, Gavin, Srikara V. Peelukhana, and Rupak K. Banerjee. "Misinterpretation of Stenosis Severity in the Presence of Serial Coronary Stenoses: An In-Vitro Study." In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14623.

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In patients with multiple stenoses in the same coronary artery, the severity of one stenosis influences the diagnosis of the serial stenosis. Currently used diagnostic end-point, Fractional Flow Reserve, FFR (ratio of distal to proximal pressure of a stenotic region), has a cut-off point of 0.75. A value of FFR < 0.75 leads to a clinical intervention. However, FFR may fail to account for multiple stenoses interactions and might lead to clinical misinterpretation of one serial stenosis severity. In order to assess the effect of one stenosis on the other serial stenosis, we tested three combinations of serial stenoses: 80%–64%, 80%–80% and 80%–90% area stenosis (AS) respectively, using an in-vitro experimental setup. The hyperemic flow decreased from 136.4 ml/min to 126.4 ml/min and further to 90.7 ml/min as downstream stenosis severity increased from 64% AS to 80% AS and further to 90% AS, respectively. More importantly, the individual FFR values of the upstream stenosis (80% AS) increased from 0.76 to 0.79 and further to 0.88 as the downstream stenosis increased from 64% AS to 80% AS and further to 90% AS, respectively. On the contrary, the combined FFR across both the stenosis was below the threshold value of 0.75. These results indicate that the presence of a downstream stenosis might lead to a clinical misinterpretation of the upstream stenosis severity and also the combined stenosis severity.
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Kolli, Kranthi K., Mohamed Effat, Imran Arif, Tarek Helmy, Massoud Leesar, Lloyd H. Back, Srikara V. Peelukhana, and Rupak K. Banerjee. "Functional and Anatomical Diagnosis of Coronary Artery Stenoses: A Retrospective Study in Humans." In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80552.

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Fractional flow reserve (FFR: ratio of distal to proximal pressure of a stenotic section) is used to evaluate hemodynamic significance of epicardial stenosis. However, FFR and coronary flow reserve (CFR: ratio of hyperemic blood velocity to that of resting condition) are used in conjunction to evaluate combination of both epicardial and microvascular disease. It has been proposed that optimization of cutoff values for diagnostic parameters in determining stenosis severity depends on coupling functional (pressure and velocity) and anatomical data (% area stenosis). We hypothesize that, pressure drop coefficient (CDP: the ratio of trans-stenotic pressure drop to distal dynamic pressure) which has the functional information of pressure and velocity in its formulation correlates significantly with FFR and CFR, and lesion flow coefficient (LFC: ratio of % area stenoses to CDP at throat region) which combines both functional and anatomical (% area stenoses) information in its formulation correlates significantly with FFR, CFR and % area stenosis. We retrospectively analyzed the hemodynamic information from Meuwissen et al [3] to test this hypothesis. It was observed that, CDP, a functional index based on pressure drop and velocity, correlated linearly and significantly with FFR and CFR. And, LFC (combined functional and anatomic parameter) also correlated significantly with FFR, CFR (both hemodynamic endpoints) and % area stenosis (anatomic endpoint).
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Bergman, Harris L., John M. Siegel, John N. Oshinski, Roderic I. Pettigrew, and David N. Ku. "Computational Simulation of Magnetic Resonance Angiograms in Stenotic Vessels: Effect of Stenosis Severity." In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-1231.

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Abstract Post stenotic signal loss limits the widespread use of magnetic resonance (MR) angiography. The signal loss causes ambiguity when determining the degree of stenosis and when assessing patency. Thus it is important to devise strategies for reducing signal loss associated with stenoses.
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Mahmoudzadeh Akherat, Seyed Mohammad Javid, and Morteza Kimiaghalam. "A Numerical Investigation on Pulsatile Blood Flow Through Consecutive Axi-Symmetric Stenosis in Coronary Artery." In ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-24534.

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The objective of this research is the determination of the wall shear stress (WSS) and velocity distribution patterns in axi-symmetric single or repeated stenoses in coronary arteries. The blood flow is modeled as an incompressible laminar flow with Re = 500 and the analysis is performed for both Newtonian and non-Newtonian blood behaviors. For the single stenosis cases, the area reduction of 25%, 64% and 75% are considered, while for the consecutive stenosis cases two sets of 64%, 25%, and 75%, 64% for the first and second stenosis are examined numerically respectively. Single stenosis cases are also employed for validation purposes, since experimental data are available for them. Present results indicate that regions of high and low shear stress may play an important role in the rupture of atherosclerotic lesions. Both sides of the stenotic area with high WSS and intense WSSG (Wall Shear Stress Gradient) are the most vulnerable sites of plaques. For the cases of consecutive stenoses, results show that displacement of the secondary plauque does not have any effect on the flow pattern. Moreover, the effect of the progression and the area reduction percentage of the consecutive stenoses were studied numerically. It was concluded that the progression of the first and the second stenoses creates high alterations in WSS and velocity distribution and increases the vulnerability of creation of new plaques. Furthermore, the pulsatile property of blood was considered. An accurate velocity waveform was implemented to predict the pulsatile behavior of blood. Results significantly vary from those of the laminar analysis in terms of velocity distribution and the magnitude of the maximum velocity. The flow patterns are studied for several time sections in one period.
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Goswami, Ishan, Srikara V. Peelukhana, Marwan Al-Rjoub, Lloyd H. Back, and Rupak K. Banerjee. "Influence of Variable Native Arterial Diameter on Fractional Flow Reserve: An In-Vitro Study." In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80881.

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Fractional flow reserve (FFR), the ratio of the pressures distal (Pd) and proximal (Pa) to a stenosis, and coronary flow reserve (CFR), the ratio of flows at maximal vasodilation to the resting condition, are widely used for determining the functional severity of a coronary artery stenosis. However, the diameter of the native artery might influence the FFR values. Therefore, using an in-vitro experimental study, we tested the variation of FFR for two arterial diameters, 2.5 mm (N1) and 3 mm (N2). We hypothesize that FFR is not influenced by native arterial diameter. For both N1 and N2, vasodilation-distal perfusion pressure (CFR-Prh) curves were obtained using a 0.35 mm guidewire by simulating physiologic flows under different blockage conditions: mild (64% area stenosis (AS)), intermediate (80% AS) and severe (90% AS). The FFR values for the two arterial models differed insignificantly, within 3%, for mild and intermediate stenoses but differed appreciably for severe stenosis (∼25%). This significant difference in FFR values for severe stenosis can be attributed to relatively larger difference in guidewire obstruction effect at the stenotic throat region of the two native arterial models. These findings confirm that FFR will not differ for the clinically relevant cases of mild and intermediate stenosis for different arterial diameters.
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Tang, Dalin, Chun Yang, Zhongdan Huan, and David N. Ku. "Effects of Stenosis Asymmetry on Blood Flow in Stenotic Arteries and Wall Compression." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0384.

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Abstract Severe stenoses in arteries cause critical flow conditions which may be related to thrombus formation, artery compression and plaque cap rupture. The exact mechanism of these events and the conditions causing them are not well understood. Considerable work for flow in stenotic tubes have been reported in last twenty years and many interesting phenomena such as flow limitation, choking, flutter and wall collapse have been observed [3]. Stenosis severity, wall compliance and pressure conditions have been identified as dominating factors affecting wall deformation and flow and pressure fields. However, real arteries are rarely axisymmetric. Stenosis asymmetry may have considerable effects on wall stress and the critical flow characteristics.
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Liepsch, D., G. Pflugbeil, J. Fischer, and C. Weigand. "Flow Visualization and LDA Measurements in Human Carotid Artery Models." In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-1187.

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Abstract Flow parameters including pulsatile flow, wall distensibility, the non-Newtonian flow of blood in flow separation regions and high/low blood pressure, were studied in models of a healthy carotid artery model (37° bifurcation angle between the internal and external carotid artery), a 90% stenosis in the internal carotid artery and an 80% stenosis in both the internal and external carotid arteries. The goal of the study was to analyze the flow in detail, measuring the local velocity components. This knowledge is important for the interpretation of ultrasound measurements in vivo. Elastic silicon rubber models having a compliance similar to human vessels and the same surface structure as in the biological intima were prepared from casts of human carotid arteries taken at autopsy. Studies were done at various Reynolds numbers. Flow was visualized with colored dyes (steady flow) and with a photoelasticity apparatus and birefringent solution (pulsatile studies). Flow separation regions and reattachment points could be easily localized with these methods and recorded on video tape. The local velocity was measured with a 1-, 2-, or 3-D laser-Doppler-anemometer (LDA). The flow in the unstenosed model was Re = 250. In the stenosed models, the Reynolds number decreased to Re-213 under the same experimental conditions. High velocity fluctuations with vortices were found in the stenosed models. The jet flow in the stenosis increased up to 4 m/s. With an increasing bifurcation angle, the separation regions in the external and internal carotid artery increased. Increased blood pressure (a higher Re number) led to an increase in flow separation and to high velocity shear gradients. The highest shear stresses were nearly 20 times higher than normal. The 90% stenosis created very high velocity shear gradients and high velocity fluctuations. In addition to the ratio of the stenosis, the form (geometry) of the stenosis also played a major role in determining the flow structure. Behind the stenoses large eddies were found over the whole cross section. In these separation regions, particles may stick more easily to the wall and to existing stenoses. Sharp edged stenoses will grow faster than smooth stenosis formations. In the healthy carotid artery model only a slight flow separation region was observed in the internal carotid artery at the branching cross section. The flow in the healthy carotid artery model was almost ideal, whereas in the stenosed models the flow separations regions extended far into the internal carotid artery. Figure 1 shows the axial velocity component of a healthy carotid artery at Re = 350. The velocity profiles over the cross section 10mm downstream of the bifurcation in the internal carotid artery are shown for a blood-like fluid. The Womersley parameter was α = 4.15. The phase shown in 90°. Figure 2 shows the vertical velocity component at a phase of 90°. Figure 3 shows the velocity profiles in a model with a 90% stenosis in the internal carotid artery at a phase 90°. The differences in the velocity distribution can be clearly seen. High velocity fluctuations were recorded which may lead to chemical reactions in the blood cells. We conclude that a detailed understanding of flow is necessary before vascular surgery is performed especially before artificial grafts are implanted. Models should be prepared to help to optimize such grafts and no flow parameter can be neglected especially at bends and bifurcations.
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Ju, Siyeong, and Linxia Gu. "Numerical Analysis of Blood Flow Through Discrete Stenosis: Role of Eccentricity and Spacing Ratio." In 2017 Design of Medical Devices Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/dmd2017-3546.

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Stenosis or narrowing of arteries induces a turbulent flow region downstream. Multiple stenosis may lead to flow interference and further disturb the blood flow. This has important clinical implications [1], such as disturbed blood flow and flow recirculation which were correlated with the development of atherosclerosis by upregulating the endothelial cells genes and proteins that cause atherogenesis [2]. Numerical simulation of concentric stenoses by Lee et al [3] have shown that the recirculation zone following the first concentric stenosis affected the flow field at the downstream of the second one, which was dependent on the spacing ratio and degree of stenosis. However, the majority of stenosis is eccentric [2] and the detailed fluid dynamics of multiple stenoses with eccentric constrictions is lacking. The aim of this study is to investigate the interactions between double stenoses with eccentricity using computational fluid dynamics (CFD) simulation. The role of spacing ratio on the recirculation zone and turbulence intensity (TI) were characterized and also compared to concentric cases.
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D’Souza, Gavin A., Srikara V. Peelukhana, and Rupak K. Banerjee. "Misinterpretation of Stenosis Severity in the Presence of Serial Coronary Stenoses." In ASME 2013 Conference on Frontiers in Medical Devices: Applications of Computer Modeling and Simulation. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fmd2013-16180.

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Diagnosis of the functional severity of an epicardial coronary stenosis using parameters like Fractional Flow Reserve, FFR (ratio of distal to proximal pressure of a stenotic region), might be affected in the presence of an additional downstream stenosis. In order to assess this effect, we have performed an in-vitro experiment which is used to validate a computational study. Three combinations of serial stenoses were tested: 80%-64%, 80%-80% and 80%-90% area stenosis (AS). The physiological mean hyperemic flow (flow at maximal arterial dilatation) values were obtained using an in-vitro experimental set-up. These flow rates were used as steady flow inputs by time-averaging the spatially averaged flow pulse over two cardiac cycles for the computational study. FFR values were calculated at hyperemic flow using both the experimental and numerical pressure data. As the downstream severity increased from 64% AS to 80% AS, hyperemic coronary flow decreased from 136.4 ml/min to 126.4 ml/min. Flow decreased further to 90.7 ml/min with a downstream severity of 90% AS. FFR of the intermediate stenosis increased from 0.76 to 0.79 and further to 0.88 as the downstream stenosis increased from 64% to 80% with a final severity of 90% AS. Similarly, numerically obtained FFR values increased to 0.83, 0.80 and 0.92 for the corresponding cases indicating an error within 7% of the experimental values. These results indicate that the presence of a downstream stenosis might lead to a clinical misinterpretation of the upstream stenosis severity.
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Roy, Abhijit Sinha, Lloyd H. Back, Ronald W. Millard, Saeb Khoury, and Rupak K. Banerjee. "In Vitro Pressure Flow Relationship in Model of Significant Coronary Artery Stenosis." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-61657.

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Simultaneous measurement of pressure and flow rate has been found to be helpful in evaluating the physiologic significance of obstructive coronary artery disease and in the diagnosis of microvascular disease. This experimental study seeks to find important pressure-flow relationship in an in-vitro model of significant coronary artery stenoses using a non-Newtonian liquid, similar to blood showing a shear thinning behavior, using significant stenotic in-vitro model (minimal area stenosis = 90%). The geometry for the stenotic model is based on data provided in an in vivo study by Wilson et al., (1988). For 90% area stenosis, the maximum recorded pressure drop for steady flow rate of 55, 79 and 89 are 14, ~24 and ~32 mmHg respectively. The maximum pressure drop at flow rate of 115 ml/min (the physiological limit) is 50.3 mmHg respectively. Using a power law curve fit, the maximum pressure drop (in mmHg) related with flow rate (in ml/min) provided a power law index of 1.72. Shorter distal length than required in the in-vitro model did not allow the recording of complete pressure recovery. This preliminary data provides reference values for further experimentation both in vitro with pulsatile flow as in physiological conditions, and in vivo.
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Reports on the topic "Stenosis"

1

Schneider, Michael. Lumbar Spinal Stenosis. Patient-Centered Outcomes Research Institute® (PCORI), May 2021. http://dx.doi.org/10.25302/2.2019.cer.587ce.

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wu, ruiqing. Efficacy and Complications of Extreme Lateral Interbody Fusion (XLIF) for lumbar spinal stenosis：A Meta-Analysis and Systematic Review. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, February 2022. http://dx.doi.org/10.37766/inplasy2022.2.0085.

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Review question / Objective: P? Patients with Lumbar Spinal Stenosis. I? Extreme Lateral Interbody Fusion (XLIF). C? Other lumbar interbody fusions. O?Predefined outcome measures were preoperative and postoperative visual analogue scale back and/or leg pain (VAS-BP) and Oswestry Disability Index (ODI) score; operation time; intraoperative blood loss; length of hospital stay; and the complications, reoperation and fusion rate. S: randomized controlled trials (RCTs) or nonrandomized cohort studies. Condition being studied: Extreme Lateral Interbody Fusion (XLIF) can be widely used for the treatment of lumbar spinal stenosis, and this study aims to summarize the efficacy and complications of this procedure for lumbar spinal stenosis. Extreme Lateral Interbody Fusion (XLIF) for the treatment of Lumbar Spinal Stenosis.for the treatment of lumbar spinal stenosis, and this study aims to summarize the efficacy and complications of this procedure for lumbar spinal stenosis.Extreme Lateral Interbody Fusion (XLIF) for the treatment of Lumbar Spinal Stenosis.
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Charatsi, Dimitra, Polyxeni Vanakara, Michail Nikolaou, Aikaterini Evaggelopoulou, Dimitrios Korfias, Foteini Simopoulou, Nikolaos Charalampakis, et al. Vaginal Dilator Use to Promote Sexual Wellbeing After Radiotherapy in Gynaecological Cancer Survivors: A Prospective Observational Study. Science Repository, October 2021. http://dx.doi.org/10.31487/j.ijcst.2021.03.01.sup.

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Background: Since continuing advances in radiotherapy technology broaden the role of radiotherapy in the treatment of gynaecologic malignancies, the use of vaginal dilators has been introduced in order to mitigate the risk of vaginal stenosis. The main aims of this study were to investigate the vaginal dilator use efficacy in the treatment of radiation-induced vaginal stenosis and the vaginal dilator effect on sexual quality of life. Methods: We studied fifty-three patients with endometrial or cervical cancer. The participants were treated with radical or adjuvant external beam radiotherapy and/or brachytherapy. They were routinely examined at four time points post-radiotherapy when also they were asked to fill in a validated sexual function-vaginal changes questionnaire. A p-value less than 0.05 was considered statistically significant. Results: The vaginal stenosis grading score was decreased and the size of the vaginal dilator comfortably insertable was gradually increased throughout the year of vaginal dilator use while radiation-induced vaginal and sexual symptoms were improved throughout the year of VD use. All patients with initial grade 3 showed vaginal stenosis of grade 2 after 12 months of vaginal dilator use and 65.8% of the patients with grade 2 initial vaginal stenosis demonstrated final vaginal stenosis grade 1 while 77.8% of the participants with initial 1st size of vaginal dilators reached the 3rd vaginal dilator size after 12 months. Starting time of dilator therapy <= 3 months after the end of radiotherapy was associated with a significant decrease in vaginal stenosis. Additionally, there was an overall upward trend regarding patients’ satisfaction with their sexual life. Conclusion: Endometrial and cervical cancer survivors should be encouraged to use vaginal dilators for the treatment of vaginal stenosis and sexual rehabilitation after radiotherapy.
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Dingli, Philip, Nieves Gonzalo, and Javier Escaned. Intravascular Ultrasound-guided Management of Diffuse Stenosis. Radcliffe Cardiology, April 2018. http://dx.doi.org/10.15420/rc.2018.m005.

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Gelbard, Alexander, and David Francis. Comparing Results of Three Treatments for Idiopathic Subglottic Stenosis. Patient-Centered Outcomes Research Institute (PCORI), April 2020. http://dx.doi.org/10.25302/04.2020.cer.140922214.

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Li, Yu, Wenhao Cui, Jukun Wang, Xin Chen, Chao Zhang, Linzhong Zhu, Shijun Cui, and Tao Luo. Percutaneous revascularization for atherosclerotic renal artery stenosis: a meta-analysis. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, July 2022. http://dx.doi.org/10.37766/inplasy2022.7.0052.

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Zhang, Meilin, and Ang Zheng. Percutaneous revascularization for atherosclerotic renal artery stenosis: a meta-analysis. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, July 2022. http://dx.doi.org/10.37766/inplasy2022.7.0053.

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Schneider, Michael, Carlo Ammendolia, Donald Murphy, Ronald Glick, Sara Piva, Elizabeth Hile, Dana Tudorascu, and Sally Morton. A Comparison of Nonsurgical Treatment Methods for Patients With Lumbar Spinal Stenosis. Patient- Centered Outcomes Research Institute (PCORI), February 2019. http://dx.doi.org/10.25302/2.2019.cer.141025056.

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Schneider, Michael, Carlo Ammendolia, Donald Murphy, Ronald Glick, Sara Piva, Elizabeth Hile, Dana Tudorascu, and Sally Morton. A Comparison of Nonsurgical Treatment Methods for Patients With Lumbar Spinal Stenosis. University of Pittsburgh at Pittsburgh, February 2019. http://dx.doi.org/10.25302/2.2019.cer.587.

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Dimitrov, Svetoslav, Iliyan Petrov, Violeta Grudeva, Valentin Govedarski, Todor Zahariev, and Gencho Nachev. Assessment of Carotid Artery Stenosis – Comparative Anаlysis between Duplex Ultrasonography and CT Angiography. "Prof. Marin Drinov" Publishing House of Bulgarian Academy of Sciences, March 2020. http://dx.doi.org/10.7546/crabs.2020.03.14.

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