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Thermomechanical Fractional Model of TEMHD Rotational Flow.

ABSTRACT: In this work, the fractional mathematical model of an unsteady rotational flow of Xanthan gum (XG) between two cylinders in the presence of a transverse magnetic field has been studied. This model consists of two fractional parameters ? and ? representing thermomechanical effects. The Laplace transform is used to obtain the numerical solutions. The fractional parameter influence has been discussed graphically for the functions field distribution (temperature, velocity, stress and electric current distributions). The relationship between the rotation of both cylinders and the fractional parameters has been discussed on the functions field distribution for small and large values of time.

SUBMITTER: Hamza F

PROVIDER: S-EPMC5207645 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Thermomechanical Fractional Model of TEMHD Rotational Flow.

Hamza F F Abd El-Latief A A Khatan W W

PloS one 20170103 1

In this work, the fractional mathematical model of an unsteady rotational flow of Xanthan gum (XG) between two cylinders in the presence of a transverse magnetic field has been studied. This model consists of two fractional parameters α and β representing thermomechanical effects. The Laplace transform is used to obtain the numerical solutions. The fractional parameter influence has been discussed graphically for the functions field distribution (temperature, velocity, stress and electric curren ...[more]

PMID: 28045941

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Fractional flow reserve.

Project description:Physiologically driven coronary revascularization has been shown to be superior in terms of better outcomes and optimum resource utilization for percutaneous interventions. However, its applicability to surgical myocardial revascularization lacks evidence base. GRAFITTI Trial aims at bridging this gap and Dr. F Casselman discusses its rationale and design.

| S-EPMC7525716 | biostudies-literature

Hybrid Instantaneous Wave-Free Ratio-Fractional Flow Reserve versus Fractional Flow Reserve in the Real World.

Project description:BackgroundThe instantaneous wave-free ratio (iFR) is a novel method to assess the ischemic potential of coronary artery stenoses. Clinical trial data have shown that iFR has acceptable diagnostic agreement with fractional flow reserve (FFR), the reference standard for the functional assessment of coronary stenoses. This study compares iFR measurements with FFR measurements in a real world, single-center setting.Methods and resultsInstantaneous wave-free ratio and FFR were measured in 50 coronary artery lesions in 42 patients, with FFR ≤ 0.8 classified as functionally significant. An iFR-only technique, using a treatment cut-off value, iFR ≤ 0.89, provided a classification agreement of 84% with FFR ≤ 0.80. Use of a hybrid iFR-FFR technique, incorporating FFR measurement for lesions within the iFR gray zone of 0.86-0.93, would improve classification agreement with FFR to 94%, with diagnosis achieved without the need for hyperemia in 57% patients.ConclusionThis study in a real-world setting demonstrated good classification agreement between iFR and FFR. Use of a hybrid iFR-FFR technique would achieve high diagnostic accuracy while minimizing adenosine use, compared with routine FFR.

| S-EPMC5447668 | biostudies-literature

Fractional flow reserve: a clinical perspective.

Project description:Fractional flow reserve (FFR) is a reference invasive diagnostic test to assess the physiological significance of an epicardial coronary artery stenosis. FFR-guided percutaneous coronary intervention in stable coronary artery disease has been assessed in three seminal clinical trials and the indications for FFR assessment are expanding into other clinical scenarios. In this article we review the theoretical, experimental and clinical basis for FFR measurement. We place FFR measurement in the context of the comprehensive invasive assessment of coronary physiology in patients presenting with known or suspected angina pectoris in daily clinical practice, and review the recent developments in FFR assessment.

| S-EPMC5489582 | biostudies-literature

Fractional Flow Reserve: Patient Selection and Perspectives.

Project description:The aim of this review was to discuss the current practice and patient selection for invasive FFR, new techniques to estimate invasive FFR and future of coronary physiology tests. We elaborate on the indication and application of FFR and on the contraindications and concerns in certain patient populations.

| S-EPMC8684425 | biostudies-literature

The Impact of Fractional Flow Reserve on Revascularization.

Project description:IntroductionFractional flow reserve (FFR) is recommended by society guidelines for assessment of the hemodynamic significance of intermediate coronary lesions when non-invasive evidence of myocardial ischemia is unavailable. However, the prevalence of FFR usage in current practice and how FFR values impact revascularization decisions are not well known.MethodsAt a single-center Veterans Administration Hospital, all subjects referred for coronary angiography for any indication from the period from May 2012 until January 2014 were prospectively entered into a database. FFR was measured in all intermediate coronary lesions (30-70% stenosis). Based on the FFR results, the lesions were categorized into 3 different groups: FFR > 0.80 (non-ischemic), FFR 0.75-0.80 (gray zone), and FFR < 0.75 (ischemic).ResultsA total of 1482 cardiac catheterizations were performed during the study period. FFR was performed in 347 (23%) of these procedures. The total numbers of intermediate coronary lesions evaluated with FFR were 429. The mean FFR value was 0.79 (median = 0.80; interquartile range 0.64-0.96). Among 211 non-ischemic lesions, revascularization was deferred in 201 (95%). In the gray-zone group (73 lesions), 35 (48%) lesions were treated with percutaneous coronary intervention (PCI), 11 (15%) lesions were referred for coronary artery bypass grafting surgery (CABG), and 27 (37%) lesions were treated medically. In the ischemic group (145 lesions), 82 (57%) lesions were treated with PCI, 41 (28%) lesions were referred for CABG, and 22 (15%) lesions were treated medically.ConclusionAt a Veterans Administration Hospital, FFR was performed in approximately one out of four total catheterizations. FFR documented lack of ischemia in about half of the intermediate coronary lesions, and thus reduced the need for many revascularization procedures.

| S-EPMC4675752 | biostudies-literature

Comparison of Computed Tomography derived Fractional Flow Reserve to invasive Fractional Flow Reserve in Diagnosis of Functional Coronary Stenosis: A Meta-Analysis.

Project description:Computed Tomography derived Fractional Flow Reserve (CTFFR) is an emerging non-invasive imaging modality to assess functional significance of coronary stenosis. We performed a meta-analysis to compare the diagnostic performance of CTFFR to invasive Fractional Flow reserve (FFR). Electronic search was performed to identify relevant articles. Pooled Estimates of sensitivity, specificity, positive likelihood ratio (LR+), negative likelihood ratio (LR-) and diagnostic odds ratio (DOR) with corresponding 95% confidence intervals (CI) were calculated at the patient level as well as the individual vessel level using hierarchical logistic regression, summary receiver operating characteristic (SROC) curve and area under the curve were estimated. Our search yielded 559 articles and of these 17 studies was included in the analysis. A total of 2,191 vessels in 1294 patients were analyzed. Pooled estimates of sensitivity, specificity, LR+, LR- and DOR with corresponding 95% CI at per-patient level were 83% (79-87), 72% (68-76), 3.0 (2.6-3.5), 0.23 (0.18-0.29) and 13 (9-18) respectively. Pooled estimates of sensitivity, specificity, LR+, LR- and DOR with corresponding 95% CI at per-vessel level were 85% (83-88), 76% (74-79), 3.6 (3.3-4.0), 0.19 (0.16-0.22) and 19 (15-24). The area under the SROC curve was 0.89 for both per patient level and at the per vessel level. In our meta-analysis, CTFFR demonstrated good diagnostic performance in identifying functionally significant coronary artery stenosis compared to the FFR.

| S-EPMC6070545 | biostudies-literature

Residual Quantitative Flow Ratio to Estimate Post-Percutaneous Coronary Intervention Fractional Flow Reserve.

Project description:ObjectivesQuantitative flow ratio (QFR) computes fractional flow reserve (FFR) based on invasive coronary angiography (ICA). Residual QFR estimates post-percutaneous coronary intervention (PCI) FFR. This study sought to assess the relationship of residual QFR with post-PCI FFR.MethodsResidual QFR analysis, using pre-PCI ICA, was attempted in 159 vessels with post-PCI FFR. QFR lesion location was matched with the PCI location to simulate the performed intervention and allow computation of residual QFR. A post-PCI FFR < 0.90 was used to define a suboptimal PCI result.ResultsResidual QFR computation was successful in 128 (81%) vessels. Median residual QFR was higher than post-PCI FFR (0.96 Q1-Q3: 0.91-0.99 vs. 0.91 Q1-Q3: 0.86-0.96, p < 0.001). A significant correlation and agreement were observed between residual QFR and post-PCI FFR (R = 0.56 and intraclass correlation coefficient = 0.47, p < 0.001 for both). Following PCI, an FFR < 0.90 was observed in 54 (42%) vessels. Specificity, positive predictive value, sensitivity, and negative predictive value of residual QFR for assessment of the PCI result were 96% (95% confidence interval (CI): 87-99%), 89% (95% CI: 72-96%), 44% (95% CI: 31-59%), and 70% (95% CI: 65-75%), respectively. Residual QFR had an accuracy of 74% (95% CI: 66-82%) and an area under the receiver operating characteristic curve of 0.79 (95% CI: 0.71-0.86).ConclusionsA significant correlation and agreement between residual QFR and post-PCI FFR were observed. Residual QFR ≥ 0.90 did not necessarily commensurate with a satisfactory PCI (post-PCI FFR ≥ 0.90). In contrast, residual QFR exhibited a high specificity for prediction of a suboptimal PCI result.

| S-EPMC8426071 | biostudies-literature

Project description:Sex-specific differences affect the evaluation, treatment, and prognosis of coronary artery disease. We tested the hypothesis that long-term outcomes of fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI) are different between women and men.Consecutive 1090 patients, referred for PCI and undergoing FFR measurements at the Mayo Clinic between October 2002 and December 2009, were included in this registry study. Clinical events were compared between the sexes during a median follow-up of 50.9 months. Of all patients, women had higher FFR adjusted by visual coronary stenosis than men (P=0.03). The Kaplan-Meier percent of major adverse cardiac events at 5 years was 35% in women and 38% in men (P=0.54). Interestingly, in patients undergoing PCI with an FFR <0.75, the incidence of death or myocardial infarction was significantly higher in women than in men (hazard ratio, 2.16; 95% confidence interval, 1.04-4.51; P=0.04). Moreover, compared with patients with FFR >0.80, deferral of PCI for those with FFR between 0.75 and 0.80 was associated with an increased rate of major adverse cardiac events, particularly death or myocardial infarction in women (hazard ratio, 3.25; 95% confidence interval, 1.56-6.74; P=0.002) and revascularization in men (hazard ratio, 2.66; 95% confidence interval, 1.66-4.54; P<0.001).Long-term outcome differs between women and men undergoing FFR-guided PCI. Our data suggest that the sex-based treatment strategy is necessary to further optimize prognosis of patients with coronary artery disease.

| S-EPMC3904351 | biostudies-literature

Angiography-Based Fractional Flow Reserve: State of the Art.

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| S-EPMC9188492 | biostudies-literature

Fractional Flow Reserve Assessment of Coronary Artery Stenosis.

Project description:Objective proof of focal lesions is mandatory, and the best invasive method of physiological testing is fractional flow r eserve (FFR). The increased trans-stenotic gradient is measured via the guiding catheter and pressure transducer on a 0.014" coronary wire at maximal hyperaemia induced by adenosine. Patients with a FFR of less than 0.8 should undergo myocardial revascularisation by percutaneous coronary intervention or coronary artery bypass graft, particularly if the proximal and middle segments of the main coronary arteries and large side-branches are affected; there is no prognostic revascularisation benefit in patients with moderate stenoses and FFR greater than 0.80. FFR assessment of coronary lesions is superior to other invasive morphological studies, such as intracoronary ultrasound or optical coherence tomography. Its use in non-culprit vessels in acute coronary syndromes is currently under scrutiny. Recent advances in computed tomographic technique allow non-invasive assessment of FFR, but clinical validation has yet to be obtained.

| S-EPMC6159406 | biostudies-other

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