Pancreatic duct pressure: A review of technical aspects and clinical significance.

Pancreatic duct pressure (PDP) dynamics comprise an intricately modulated system that helps maintain homeostasis of pancreatic function. It is affected by various factors, including the rate of pancreatic fluid secretion, patency of the ductal system, sphincter of Oddi function, and pancreatic fluid characteristics. Disease states such as acute and chronic pancreatitis can alter the normal PDP dynamics. Ductal hypertension or increased PDP is suspected to be involved in the pathogenesis of pancreatic pain, endocrine and exocrine pancreatic insufficiency, and recurrent pancreatitis. This review provides a comprehensive appraisal of the available literature on PDP, including the methods used in the measurement and clinical implications of elevated PDP.

Reconstructing the pressure field around swimming fish using a physics-informed neural network.

Fish detect predators, flow conditions, environments and each other through pressure signals. Lateral line ablation is often performed to understand the role of pressure sensing. In the present study, we propose a non-invasive method for reconstructing the instantaneous pressure field sensed by a fish's lateral line system from two-dimensional particle image velocimetry (PIV) measurements. The method uses a physics-informed neural network (PINN) to predict an optimized solution for the pressure field near and on the fish's body that satisfies both the Navier-Stokes equations and the constraints put forward by the PIV measurements. The method was validated using a direct numerical simulation of a swimming mackerel, Scomber scombrus, and was applied to experimental data of a turning zebrafish, Danio rerio. The results demonstrate that this method is relatively insensitive to the spatio-temporal resolution of the PIV measurements and accurately reconstructs the pressure on the fish's body.

Quantifying the Effect of Body Habitus on Cardiac Auscultation Via Computational Hemoacoustics.

The effect of body habitus on auscultation of heart murmurs is investigated via computational hemoacoustic modeling. The source of the heart murmur is first obtained from a hemodynamic simulation of blood flow through a stenosed aortic valve. This sound source is then placed at the aortic valve location in four distinct human thorax models, and the propagation of the murmur in each thorax model is simulated by solving the elastic wave equations in the time-domain. Placing the same sound source in different thorax models allows for the disambiguation of the effect of body habitus on cardiac auscultation. The surface acceleration resulting from the murmur on each subject's chest surface shows that subjects with higher body-mass index and thoracic cross-sectional area yield smaller acceleration values for the S1 sound. Moreover, the spectral analysis of the signal shows that slope from linear regression in the normal heart sound frequency range (10-150 Hz) is larger for children at the aortic, pulmonic, and mitral auscultation points compared to that for adults. The slope in the murmur frequency range (150-400 Hz) was larger for female subjects at the mitral point compared to that for male subjects. The trends from the results show the potential of the proposed computational method to provide quantitative insights regarding the effect of various anatomical factors on cardiac auscultation.

Efficient trapping and destruction of SARS-CoV-2 using PECO-assisted Molekule air purifiers in the laboratory and real-world settings.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted human-to-human via aerosols and air-borne droplets. Therefore, capturing and destroying viruses from indoor premises are essential to reduce the probability of human exposure and virus transmission. While the heating, ventilation, and air conditioning (HVAC) systems help in reducing the indoor viral load, a targeted approach is required to effectively remove SARS-CoV-2 from indoor air to address human exposure concerns. The present study demonstrates efficient trapping and destruction of SARS-CoV-2 via nano-enabled filter technology using the UV-A-stimulated photoelectrochemical oxidation (PECO) process. Aerosols containing SARS-CoV-2 were generated by nebulization inside an air-controlled test chamber where an air purifier (Air Mini+) was placed. The study demonstrated the efficient removal of SARS-CoV-2 (99.98 %) from the test chamber in less than two minutes and PECO-assisted destruction (over 99%) on the filtration media in 1 h. Furthermore, in a real-world scenario, the Molekule Air-Pro air purifier removed SARS-CoV-2 (a negative RT-qPCR result post-running the filter device) from the circulating air in a COVID-19 testing facility. Overall, the ability of two FDA-approved class II medical devices, Molekule Air-Mini+ and Air-Pro air purifiers, to remove and destroy SARS-CoV-2 in indoor settings was successfully demonstrated. The study indicates that as the "tripledemic" of COVID-19, influenza, and respiratory syncytial virus (RSV) overwhelm the healthcare facilities in the USA, the use of a portable air filtration device will help contain the spread of the viruses in close door facilities, such as in schools and daycare facilities.

Does Radiographic Alignment Correlate With Patient-Reported Functional Outcomes and Posttreatment Complications in Older Patients Treated for Wrist Fractures?

PURPOSE: Surgical treatment of distal radius fractures provides better fracture alignment than closed reduction; however, surgical treatment does not lead to better patient-reported function at 12 months. The aims of this study were to report the radiographic outcomes from the Combined Randomized and Observational Study of Surgery for Fractures In the distal Radius in the Elderly trial, investigate the association between radiographic outcomes and patient-reported function, and explore whether this association was affected by posttreatment complications and direction of malalignment. METHODS: This study used the outcomes of the Combined Randomized and Observational Study of Surgery for Fractures In the distal Radius in the Elderly trial, which is a combined randomized and observational trial that compared volar-locking plate fixation with closed reduction and cast immobilization, to treat distal radius fractures in patients aged ≥60 years. Four radiographic outcomes (dorsal angulation, radial inclination, ulnar variance, and articular step) were reported at the following three time frames: (1) baseline, (2) after treatment, and (3) ≥6 weeks by treatment group. Secondary analysis was correlation of 12-month patient-reported function scores with 6-week radiographic measures for each of four radiographic parameters, and a subgroup analysis was conducted to investigate if this was affected by posttreatment complications. Tertiary analysis investigated if direction of malalignment affected the secondary analysis. RESULTS: We recruited 300 participants (166 randomized and 134 observational); 113 had volar-locking plate fixation, and 187 had closed reduction. There were no between-group differences for each of the four pretreatment radiographic parameters, but there were between-treatment group differences for all four radiographic parameters apart from articular step. We found no association between patient-reported function at 12 months and each of the four radiographic parameters at 6 weeks. This lack of association was unaffected by posttreatment complications and the direction of malalignment. CONCLUSIONS: For patients with wrist fractures aged ≥60 years, final radiographic alignment did not correlate with patient-reported function at 12 months. These findings were not affected by treatment type, and there was no association between radiographic alignment and posttreatment complications. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Computational Modeling of Aortic Stenosis With a Reduced Degree-of-Freedom Fluid-Structure Interaction Valve Model.

In this study, a novel reduced degree-of-freedom (rDOF) aortic valve model is employed to investigate the fluid-structure interaction (FSI) and hemodynamics associated with aortic stenosis. The dynamics of the valve leaflets are determined by an ordinary differential equation with two parameters and this rDOF model is shown to reproduce key features of more complex valve models. The hemodynamics associated with aortic stenosis is studied for three cases: a healthy case and two stenosed cases. The focus of the study is to correlate the hemodynamic features with the source generation mechanism of systolic murmurs associated with aortic stenosis. In the healthy case, extremely weak flow fluctuations are observed. However, in the stenosed cases, simulations show significant turbulent fluctuations in the ascending aorta, which are responsible for the generation of strong wall pressure fluctuations after the aortic root mostly during the deceleration phase of the systole. The intensity of the murmur generation increases with the severity of the stenosis, and the source locations for the two diseased cases studied here lie around 1.0 inlet duct diameters (Do) downstream of the ascending aorta.

A Noninvasive Assessment of Flow Based on Contrast Dispersion in Computed Tomography Angiography: A Computational and Experimental Phantom Study.

Transluminal attenuation gradient (TAG), defined as the gradient of the contrast agent attenuation drop along the vessel, is an imaging biomarker that indicates stenosis in the coronary arteries. The transluminal attenuation flow encoding (TAFE) equation is a theoretical platform that quantifies blood flow in each coronary artery based on computed tomography angiography (CTA) imaging. This formulation couples TAG (i.e., contrast dispersion along the vessel) with fluid dynamics. However, this theoretical concept has never been validated experimentally. The aim of this proof-of-principle phantom study is to validate TAFE based on CTA imaging. Dynamic CTA images were acquired every 0.5 s. The average TAFE estimated flow rates were compared against four predefined pump values in a straight (20, 25, 30, 35, and 40 ml/min) and a tapered phantom (25, 35, 45, and 55 ml/min). Using the TAFE formulation with no correction, the flow rates were underestimated by 33% and 81% in the straight and tapered phantoms, respectively. The TAFE formulation was corrected for imaging artifacts focusing on partial volume averaging and radial variation of contrast enhancement. After corrections, the flow rates estimated in the straight and tapered phantoms had an excellent Pearson correlation of r = 0.99 and 0.87 (p < 0.001), respectively, with only a 0.6%±0.2 mL/min difference in estimation of the flow rate. In this proof-of-concept phantom study, we corrected the TAFE formulation and showed a good agreement with the actual pump values. Future clinical validations are needed for feasibility of TAFE in clinical use.

Interpreter proxy versus healthcare interpreter for administration of patient surveys following arthroplasty: a pilot study.

BACKGROUND: Clinical quality registries and other systems that conduct routine post-discharge surveillance of patient outcomes following surgery may have difficulty surveying patients who have limited proficiency in the language of the healthcare provider. Interpreter proxies (family and carers) are often used due to limited access to certified healthcare interpreters (due to cost or availability). The aim of this study was to assess the reliability of engaging interpreter proxies compared with certified healthcare interpreters for the administration of patient-reported health-related surveys for people with limited English proficiency (LEP). METHODS: People with LEP and due for a routine 6-month telephone follow-up post knee or hip arthroplasty were invited to participate. Participants were randomly allocated to having their first interview with an interpreter proxy or a certified healthcare interpreter followed by the second (crossover) interview within 2 weeks (range: 4 to 12 days) after the first interview using the alternative method. Agreement between the two methods was assessed using quadratic weighted Cohen's kappa, intraclass correlation and concordance correlation co-efficient where appropriate for EQ-5D health domains, total Oxford hip and knee scores, patient satisfaction, operation success, readmission, reoperation, and post-surgical complication responses. The mean of the differences between the same data items collected by each of the two methods was also calculated. RESULTS: Eighty five participants (96%) completed the study. There was substantial to excellent inter-rater agreement (kappa = 0.69-0.87 and ICCs above 0.74) for all but one measure. The mean differences between family proxy and healthcare interpreter scores for each participant were small, ranging from 0.01 (score range of 1-5) to 0.72 (score range of 0-100). CONCLUSION: These results suggest that using interpreter proxies is a reliable alternative to certified healthcare interpreters in conducting patient-reported health surveys, potentially making this process easier and cost effective for researchers and registries.

Computational Modeling and Analysis of Murmurs Generated by Modeled Aortic Stenoses.

In this study, coupled hemodynamic-acoustic simulations are employed to study the generation and propagation of murmurs associated with aortic stenoses where the aorta with a stenosed aortic valve is modeled as a curved pipe with a constriction near the inlet. The hemodynamics of the poststenotic flow is investigated in detail in our previous numerical study (Zhu et al., 2018, "Computational Modelling and Analysis of Haemodynamics in a Simple Model of Aortic Stenosis," J. Fluid Mech., 851, pp. 23-49). The temporal history of the pressure on the aortic lumen is recorded during the hemodynamic study and used as the murmur source in the acoustic simulations. The thorax is modeled as an elliptic cylinder and the thoracic tissue is assumed to be homogeneous, linear and viscoelastic. A previously developed high-order numerical method that is capable of dealing with immersed bodies is applied in the acoustic simulations. To mimic the clinical practice of auscultation, the sound signals from the epidermal surface are collected. The simulations show that the source of the aortic stenosis murmur is located at the proximal end of the aortic arch and that the sound intensity pattern on the epidermal surface can predict the source location of the murmurs reasonably well. Spectral analysis of the murmur reveals the disconnect between the break frequency obtained from the flow and from the murmur signal. Finally, it is also demonstrated that the source locations can also be predicted by solving an inverse problem using the free-space Green's function. The implications of these results for cardiac auscultation are discussed.

Flow Dynamics in the Aortic Arch and Its Effect on the Arterial Input Function in Cardiac Computed Tomography.

The arterial input function (AIF)-time-density curve (TDC) of contrast at the coronary ostia-plays a central role in contrast enhanced computed tomography angiography (CTA). This study employs computational modeling in a patient-specific aorta to investigate mixing and dispersion of contrast in the aortic arch (AA) and to compare the TDCs in the coronary ostium and the descending aorta. Here, we examine the validity of the use of TDC in the descending aorta as a surrogate for the AIF. Computational fluid dynamics (CFD) was used to study hemodynamics and contrast dispersion in a CTA-based patient model of the aorta. Variations in TDC between the aortic root, through the AA and at the descending aorta and the effect of flow patterns on contrast dispersion was studied via postprocessing of the results. Simulations showed complex unsteady patterns of contrast mixing and dispersion in the AA that are driven by the pulsatile flow. However, despite the relatively long intra-aortic distance between the coronary ostia and the descending aorta, the TDCs at these two locations were similar in terms of rise-time and up-slope, and the time lag between the two TDCs was 0.19 s. TDC in the descending aorta is an accurate analog of the AIF. Methods that use quantitative metrics such as rise-time and slope of the AIF to estimate coronary flowrate and myocardial ischemia can continue with the current practice of using the TDC at the descending aorta as a surrogate for the AIF.

The effectiveness of inpatient rehabilitation after uncomplicated total hip arthroplasty: a propensity score matched cohort.

BACKGROUND: Inpatient rehabilitation is an expensive option following total hip arthroplasty (THA). We aimed to determine if THA patients who receive inpatient rehabilitation report better hip and quality of life scores post-surgery compared to those discharged directly home. METHODS: Prospective, propensity score matched cohort involving 12 private hospitals across five Australian States. Patients undergoing THA secondary to osteoarthritis were included. Those receiving inpatient rehabilitation for reasons other than choice or who experienced significant health events within 90-days post-surgery were excluded. Comparisons were made between those who did and did not receive inpatient rehabilitation for patient-reported hip pain and function (Oxford Hip Score, OHS) and 'today' health rating (EuroQol 0-100 scale). Rehabilitation provider charges were also estimated and compared. RESULTS: Two hundred forty-six patients (123 pairs, mean age 67 (10) yr., 66% female) were matched on 19 covariates for their propensity to receive inpatient rehabilitation. No statistically nor clinically significant between-group differences were observed [OHS median difference (IQR): 0 (- 3, 3), P = 0.60; 0 (- 1 to 1), P = 0.91, at 90 and 365-days, respectively; EuroQol scale median difference 0 (- 10, 12), P = 0.24; 0 (- 10, 10), P = 0.49; 5 (- 10, 15), P = 0.09, at 35-, 90- and 365-days, respectively]. Median rehabilitation provider charges were 10-fold higher for those who received inpatient rehabilitation [median difference $7582 (5649, 10,249), P <  0.001]. Sensitivity analyses corroborated the results of the primary analyses. CONCLUSION: Utilization of inpatient rehabilitation pathways following THA appears to be low value healthcare. Sustainability of inpatient rehabilitation models may be enhanced if inpatient rehabilitation is reserved for those most impaired or who have limited social supports. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01899443 .

The value of inpatient rehabilitation after uncomplicated knee arthroplasty: a propensity score analysis.

OBJECTIVE: To compare the effectiveness of rehabilitation after total knee arthroplasty (TKA) in models with or without an inpatient rehabilitation component. DESIGN, SETTING AND PARTICIPANTS: A propensity score-matched cohort of privately insured patients with osteoarthritis who underwent primary, unilateral TKA in one of 12 Australian hospitals between August 2013 and January 2015 were included. Those discharged to an inpatient facility because of poor progress or who experienced significant complications within 90 days of surgery were excluded. INTERVENTION: Discharge after surgery to an inpatient rehabilitation facility or home. MAIN OUTCOME MEASURES: Patient-reported knee pain and function (Oxford Knee Score; at 90 and 365 days after surgery) and health rating (EuroQol "today" health scale; at 35, 90 and 365 days). Inpatient and community-based rehabilitation provider charges were also assessed. RESULTS: 258 patients (129 pairs) from a sample of 332 were matched according to their propensity scores for receiving inpatient rehabilitation; covariates used in the matching included age, sex, body mass index, and markers of health and impairment. The only significant difference in outcomes was that EuroQol health scores were better on Day 35 for patients not undergoing inpatient rehabilitation (median difference, 5; IQR, -10 to 19; P = 0.01). Median rehabilitation provider charges were significantly higher for those discharged to inpatient therapy (total costs: median difference, $9500; IQR, $7000-11 497; P < 0.001; community therapy costs: median difference, $749; IQR, $0-1980; P < 0.001). CONCLUSIONS: Rehabilitation pathways incorporating inpatient rehabilitation did not achieve better joint-specific outcomes or health scores than alternatives not including inpatient rehabilitation. Given the substantial cost differences, better value alternatives should be considered for patients after uncomplicated TKA.

A Computational Method for Analyzing the Biomechanics of Arterial Bruits.

A computational framework consisting of a one-way coupled hemodynamic-acoustic method and a wave-decomposition based postprocessing approach is developed to investigate the biomechanics of arterial bruits. This framework is then applied for studying the effect of the shear wave on the generation and propagation of bruits from a modeled stenosed artery. The blood flow in the artery is solved by an immersed boundary method (IBM) based incompressible flow solver. The sound generation and propagation in the blood volume are modeled by the linearized perturbed compressible equations, while the sound propagation through the surrounding tissue is modeled by the linear elastic wave equation. A decomposition method is employed to separate the acoustic signal into a compression/longitudinal component (curl free) and a shear/transverse component (divergence free), and the sound signals from cases with and without the shear modulus are monitored on the epidermal surface and are analyzed to reveal the influence of the shear wave. The results show that the compression wave dominates the detected sound signal in the immediate vicinity of the stenosis, whereas the shear wave has more influence on surface signals further downstream of the stenosis. The implications of these results on cardiac auscultation are discussed.

Predictors of seeking financial compensation following motor vehicle trauma: inception cohort with moderate to severe musculoskeletal injuries.

BACKGROUND: Compensation related factors have been repeatedly associated with poor recovery following orthopaedic trauma. There is limited research into the factors associated with seeking financial compensation. Further understanding of these factors could facilitate injury recovery by purposeful compensation scheme design. The aim of this study was to investigate the predictors of seeking financial compensation, namely making a claim and seeking legal representation, following motor vehicle related orthopaedic trauma. The study was conducted in New South Wales (NSW), Australia, in motor vehicle crash and workers' compensation schemes. METHODS: Participants were patients admitted with upper or lower extremity factures following a motor vehicle crash to two trauma hospitals. Data were collected at baseline within two weeks of injury. Participants were followed up at six months. Analysis involved: descriptive statistics for baseline characteristics; comparison of compensable and non-compensable participants with Analysis of Variance (ANOVA) and chi-squared tests; and logistic regression for predictor models. RESULTS: The cohort consisted of 452 participants with a mean age 40 years; 75% male; 74% working pre-injury; 30% in excellent pre-injury health; 56% sustained serious injuries with an Injury Severity Score (ISS) 9-15; 61% had a low-middle range household income; and 35% self-reported at fault in the crash. There was no significant difference in pre-injury/baseline health between compensable and non-compensable participants. Follow up data was available for 301 (67%) participants. The significant predictor of claiming compensation in the adjusted analysis was higher body mass index (BMI) (overweight Odds Ratio [OR] 3.05, 95% Confidence Interval [CI] 1.63-5.68; obese OR 1.63, 95% CI 0.83-3.20). Participants less likely to claim were: involved in a motorcycle crash (OR 0.47, 95% CI 0.28-0.82); socioeconomically less disadvantaged (OR 0.37, 95% CI 0.17-0.82) or least disadvantaged (OR 0.39, 95% CI 0.17-0.90); at risk for short term harm (injury) due to alcohol consumption (OR 0.56, 95% CI 0.32-0.97); and with fair-poor pre-injury health (OR 0.30, 95% CI 0.09-0.94). The predictors for seeking legal representation were speaking a language other than English at home (OR 2.80, 95% CI 1.2-6.52) and lower household income (OR 3.63, 95% CI 1.22-10.72). Participants less likely to seek legal representation were least socioeconomically disadvantaged (OR 0.15, 95% CI 0.04-0.50). CONCLUSIONS: Seeking financial compensation was associated with a higher pre-injury BMI rather than injury-related factors. Seeking legal representation was solely related to socio-economic factors.

Are outcomes reported in surgical randomized trials patient-important? A systematic review and meta-analysis.

BACKGROUND: The dangers of using surrogate outcomes are well documented. They may have little or no association with their patient-important correlates, leading to the approval and use of interventions that lack efficacy. We sought to assess whether primary outcomes in surgical randomized controlled trials (RCTs) are more likely to be patient-important outcomes than surrogate or laboratory-based outcomes. METHODS: We reviewed RCTs assessing an operative intervention published in 2008 and 2009 and indexed in MEDLINE, EMBASE or the Cochrane Central Register of Controlled Trials. After a pilot of the selection criteria, 1 reviewer selected trials and another reviewer checked the selection. We extracted information on outcome characteristics (patient-important, surrogate, or laboratory-based outcome) and whether they were primary or secondary outcomes. We calculated odds ratios (OR) and pooled in random-effects meta-analysis to obtain an overall estimate of the association between patient importance and primary outcome specification. RESULTS: In 350 included RCTs, a total of 8258 outcomes were reported (median 18 per trial. The mean proportion (per trial) of patient-important outcomes was 60%, and 66% of trials specified a patient-important primary outcome. The most commonly reported patient-important primary outcomes were morbid events (41%), intervention outcomes (11%), function (11%) and pain (9%). Surrogate and laboratory-based primary outcomes were reported in 33% and 8% of trials, respectively. Patient-important outcomes were not associated with primary outcome status (OR 0.82, 95% confidence interval 0.63-1.1, I2 = 21%). CONCLUSION: A substantial proportion of surgical RCTs specify primary outcomes that are not patient-important. Authors, journals and trial funders should insist that patient-important outcomes are the focus of study.

CONTEXTE: Les dangers de l'utilisation de critères de substitution sont bien documentés. Ils peuvent avoir peu de liens, voire aucun, avec leurs corrélats importants pour le patient, menant à l'approbation et à l'utilisation d'interventions inefficaces. Nous avons tenté de déterminer si les résultats primaires d'essais cliniques randomisés en chirurgie sont plus susceptibles d'être des résultats importants pour le patient que des critères de substitution ou des résultats de laboratoire. MÉTHODES: Nous avons examiné des essais cliniques randomisés portant sur l'évaluation d'une intervention chirurgicale, publiés en 2008 et 2009 et répertoriés dans MEDLINE, EMBASE ou le Cochrane Central Register of Controlled Trials. Après l'essai du critère de sélection, un examinateur a choisi les essais et un autre examinateur a vérifié la sélection. Nous avons obtenu les renseignements sur les caractéristiques des résultats (importants pour le patient, de substitution ou de laboratoire) et déterminé s'il s'agissait de résultats primaires ou secondaires. Nous avons calculé le rapport des cotes (RC) et regroupé une méta-analyse à effets aléatoires afin d'obtenir une estimation globale du lien entre l'importance pour le patient et la spécification du résultat primaire. RÉSULTATS: Un total de 8258 résultats ont été signalés dans les 350 essais cliniques randomisés inclus (pour une médiane de 18 par essai). La proportion moyenne (par essai) de résultats importants pour le patient était de 60 %, et 66 % des essais précisaient un résultat primaire important pour le patient. Les résultats primaires importants pour le patient les plus couramment signalés étaient les événements morbides (41 %), les résultats liés à une intervention (11 %), le fonctionnement (11 %) et la douleur (9 %). Des résultats primaires de substitution ou de laboratoire ont été signalés dans 33 % et 8 % des essais, respectivement. Les résultats importants pour le patient n'étaient pas associés à la situation du résultat primaire (RC 0,82, intervalle de confiance de 95 %, 0,63-1,1, I2 = 21 %). CONCLUSION: Un nombre important d'essais cliniques randomisés en chirurgie précisent des résultats primaires qui ne sont pas importants pour le patient. Les auteurs, les revues et les organismes de financement des essais devraient insister pour que les résultats importants pour le patient soient l'objet principal de l'étude.

A coupled chemo-fluidic computational model for thrombogenesis in infarcted left ventricles.

A coupled chemo-fluidic computational model for investigating flow-mediated thrombogenesis in infarcted left ventricles (LVs) is proposed. LV thrombus (LVT) formation after the acute myocardial infarction (AMI) may lead to thromboembolic events that are associated with high mortality and morbidity, and reliable stratification of LVT risk is the key to managing the treatment of AMI patients. There have been several studies emphasizing the importance of LV blood flow patterns on thrombus formation; however, given the complex interplay between ventricular flow dynamics and biochemistry of thrombogenesis, current understanding is mostly empirical. In the present model, blood flow in the LV is obtained by solving the incompressible Navier-Stokes equations, and this is coupled to the biochemical modeling of the coagulation cascade, platelet activation, and fibrinogen polymerization. The coupled model is used to examine the effect of ventricular flow patterns on thrombogenesis in modeled ventricles. It is expected that the method developed here will enable in-depth studies of thrombogenesis in patient-derived infarcted LV models.

Hemodynamics in the Left Atrium and Its Effect on Ventricular Flow Patterns.

In the present study, we investigate the hemodynamics inside left atrium (LA) and understand its impact on the development of ventricular flow patterns. We construct the heart model using dynamic-computed tomographic images and perform simulations using an immersed boundary method based flow solver. We show that the atrial hemodynamics is characterized by a circulatory flow generated by the left pulmonary veins (LPVs) and a direct stream from the right pulmonary veins (RPVs). The complex interaction of the vortex rings formed from each of the PVs leads to vortex breakup and annihilation, thereby producing a regularized flow at the mitral annulus. A comparison of the ventricular flow velocities between the physiological and a simplified pipe-based atrium model shows that the overall differences are limited to about 10% of the peak mitral flow velocity. The implications of this finding on the functional morphology of the left heart as well the computational and experimental modeling of ventricular hemodynamics are discussed.

Computational Study of Computed Tomography Contrast Gradients in Models of Stenosed Coronary Arteries.

Recent computed tomography coronary angiography (CCTA) studies have noted higher transluminal contrast agent gradients in arteries with stenotic lesions, but the physical mechanism responsible for these gradients is not clear. We use computational fluid dynamics (CFD) modeling coupled with contrast agent dispersion to investigate the mechanism for these gradients. Simulations of blood flow and contrast agent dispersion in models of coronary artery are carried out for both steady and pulsatile flows, and axisymmetric stenoses of severities varying from 0% (unobstructed) to 80% are considered. Simulations show the presence of measurable gradients with magnitudes that increase monotonically with stenotic severity when other parameters are held fixed. The computational results enable us to examine and validate the hypothesis that transluminal contrast gradients (TCG) are generated due to the advection of the contrast bolus with time-varying contrast concentration that appears at the coronary ostium. Since the advection of the bolus is determined by the flow velocity in the artery, the magnitude of the gradient, therefore, encodes the coronary flow velocity. The correlation between the flow rate estimated from TCG and the actual flow rate in the computational model of a physiologically realistic coronary artery is 96% with a R2 value of 0.98. The mathematical formulae connecting TCG to flow velocity derived here represent a novel and potentially powerful approach for noninvasive estimation of coronary flow velocity from CT angiography.

Computational study of hemodynamic effects of abnormal E/A ratio on left ventricular filling.

Three-dimensional numerical simulations are employed to investigate the hemodynamic effects of abnormal E/A ratios on left ventricular filling. The simulations are performed in a simplified geometric model of the left ventricle (LV) in conjunction with a specified endocardial motion. The model has been carefully designed to match the important geometric and flow parameters under the physiological conditions. A wide range of E/A ratios from 0 to infinity is employed with the aim to cover all the possible stages of left ventricle diastolic dysfunction (DD). The effects of abnormal E/A ratios on vortex dynamics, flow propagation velocity, energy consumption as well as flow transport and mixing are extensively discussed. Our results are able to confirm some common findings reported by the previous studies, and also uncover some interesting new features.

Minimal detectable change for mobility and patient-reported tools in people with osteoarthritis awaiting arthroplasty.

BACKGROUND: Thoughtful use of assessment tools to monitor disease requires an understanding of clinimetric properties. These properties are often under-reported and, thus, potentially overlooked in the clinic. This study aimed to determine the minimal detectable change (MDC) and coefficient of variation per cent (CV%) for tools commonly used to assess the symptomatic and functional severity of knee and hip osteoarthritis. METHODS: We performed a test-retest study on 136 people awaiting knee or hip arthroplasty at one of two hospitals. The MDC95 (the range over which the difference [change] for 95% of patients is expected to lie) and the coefficient of variation per cent (CV%) for the visual analogue scale (VAS) for joint pain, the six-minute walk test (6MWT), the timed up-and-go (TUG) test, the Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Hip Disability and Osteoarthritis Outcome Score (HOOS) subscales were calculated. RESULTS: Knee cohort (n = 75) - The MDC95 and CV% values were as follows: VAS 2.8 cm, 15%; 6MWT 79 m, 8%; TUG +/-36.7%, 13%; KOOS pain 20.2, 19%; KOOS symptoms 24.1, 22%; KOOS activities of daily living 20.8, 17%; KOOS quality of life 26.6, 44. Hip cohort (n = 61) - The MDC95 and CV% values were as follows: VAS 3.3 cm, 17%; 6MWT 81.5 m, 9%; TUG +/-44.6%, 16%; HOOS pain 21.6, 22%; HOOS symptoms 22.7, 19%; HOOS activities of daily living 17.7, 17%; HOOS quality of life 24.4, 43%. CONCLUSIONS: Distinguishing real change from error is difficult in people with severe osteoarthritis. The 6MWT demonstrates the smallest measurement error amongst a range of tools commonly used to assess disease severity, thus, has the capacity to detect the smallest real change above measurement error in everyday clinical practice.