Effect of guidewire on contribution of loss due to momentum change and viscous loss to the translesional pressure drop across coronary artery stenosis: An analytical approach

<p>Abstract</p> <p>Background</p> <p>Guidewire (GW) size and stenosis dimensions are the two major factors affecting the translesional pressure drop. Studying the combined effect of these parameters on the mean pressure drop (Δ<it>p</it>) across the stenosis is of high practical importance.</p> <p>Methods</p> <p>In this study, time averaged mass and momentum conservation equations are solved analytically to obtain pressure drop-flow, Δ<it>p</it>-<it>Q</it>, curves for three different percentage area blockages corresponding to moderate (64%), intermediate (80%), and severe (90%) stenoses. Stenosis is considered to be axisymmetric consisting of three different sections namely converging, throat, and diverging regions. Analytical expressions for pressure drop are obtained for each of these regions separately. Using this approach, effects of lesion length and GW insertion on the mean translesional pressure drop and its component (loss due to momentum change and viscous loss) are analyzed.</p> <p>Results and Conclusion</p> <p>It is observed that for a given percent area stenosis (AS), increase in the throat length only increases the viscous loss. However, increase in the severity of stenosis and GW insertion increase both loss due to momentum change and viscous loss. GW insertion has greater contribution to the rise in viscous loss (increase by 2.14 and 2.72 times for 64% and 90% AS, respectively) than loss due to momentum change (1.34% increase for 64% AS and 25% decrease for 90% AS). It also alters the hyperemic pressure drop in moderate (48% increase) to intermediate (30% increase) stenoses significantly. However, in severe stenoses GW insertion has a negligible effect (0.5% increase) on hyperemic translesional pressure drop. It is also observed that pressure drop in a severe stenosis is less sensitive to lesion length variation (4% and 14% increase in Δ<it>p </it>for without and with GW, respectively) as compared to intermediate (10% and 30% increase in Δ<it>p </it>for without and with GW, respectively) and moderate stenoses (22% and 48% increase in Δ<it>p </it>for without and with GW, respectively). Based on the contribution of pressure drop components to the total translesional pressure drop, it is found that viscous losses are dominant in moderate stenoses, while in severe stenoses losses due to momentum changes are significant. It is also shown that this simple analytical solution can provide valuable information regarding interpretation of coronary diagnostic parameters such as fractional flow reserve (FFR).</p

In vitro Quantification of Guidewire Flow-Obstruction Effect in MODEL CORONARY STENOSES FOR INTERVENTIONAL DIAGNOSTIC PROCEDURE

The objective is to quantify the guidewire ( and preangioplasty). The diagnostic parameters measured before guidewire insertion (CFR and FFR) and during guidewire insertion (gCFR and gFFR) were validated numerically and correlated with the new diagnostic parameter &quot;lesion flow coefficient (LFC).&quot; There was significant flow reduction with increased trans-stenotic pressure drop due to guidewire insertion. The FFR-gFFR and CFR-gCFR correlations wer

Hemodynamic wall shear stress profiles influence the magnitude and pattern of stenosis in a pig AV fistula

Venous stenosis is a significant problem in arteriovenous fistulae, likely due to anatomical configuration and wall shear stress profiles. To identify linkages between wall shear stress and the magnitude and pattern of vascular stenosis, we produced curved and straight fistulae in a pig model. A complete wall stress profile was calculated for the curved configuration and correlated with luminal stenosis. Computer modeling techniques were then used to derive a wall shear stress profile for the straight arteriovenous fistula. Differences in the wall shear stress profile of the curved and straight fistula were then related to histological findings. There was a marked inverse correlation between the magnitude of wall shear stress within different regions of the curved arteriovenous fistula and luminal stenosis in these same regions. There were also significantly greater differences in wall shear stress between the outer and inner walls of the straight as compared to curved arteriovenous fistula, which translated into a more eccentric histological pattern of intima-media thickening. Our results suggest a clear linkage between anatomical configuration, wall shear stress profiles, and the pattern of luminal stenosis and intima-media thickening in a pig model of arteriovenous fistula stenosis. These results suggest that fistula failure could be reduced by using computer modeling prior to surgical placement to alter the anatomical and, consequently, the wall shear stress profiles in an arteriovenous fistula

The nucleon-nucleon interaction

We review the major progress of the past decade concerning our understanding of the nucleon-nucleon interaction. The focus is on the low-energy region (below pion production threshold), but a brief outlook towards higher energies is also given. The items discussed include charge-dependence, the precise value of the $\pi NN$ coupling constant, phase shift analysis and high-precision NN data and potentials. We also address the issue of a proper theory of nuclear forces. Finally, we summarize the essential open questions that future research should be devoted to.Comment: 42 pages, 12 figures, iopart.cls style; Topical Review prepared for J. Phys. G: Nucl. Part. Phy

Changes in microvascular resistance following percutaneous coronary intervention - From the ILIAS global registry

BACKGROUND: Microvascular resistance (MR) has prognostic value in acute and chronic coronary syndromes following percutaneous coronary intervention (PCI), however anatomic and physiologic determinants of the relative changes of MR and its association to target vessel failure (TVF) has not been investigated previously. This study aims to evaluate the association between changes in MR and TVF. METHODS: This is a sub-study of the Inclusive Invasive Physiological Assessment in Angina Syndromes (ILIAS) registry which is a global multi-centre initiative pooling lesion-level coronary pressure and flow data. RESULTS: Paired pre-post PCI haemodynamic data were available in n = 295 vessels out of n = 828 PCI treated patients and of these paired data on MR was present in n = 155 vessels. Vessels were divided according to increase vs. decrease % in microvascular resistance following PCI (ΔMR % ≤ 0 vs. ΔMR > 0%). Decreased microvascular resistance ΔMR % ≤ 0 occurred in vessels with lower pre-PCI fractional flow reserve (0.67 ± 0.15 vs. 0.72 ± 0.09 p = 0.051), coronary flow reserve (1.9 ± 0.8 vs. 2.6 ± 1.8 p 0%. In a cox regression model ΔMR % > 0 was associated with increased rate of TVF (hazard ratio 95% CI 3.6 [1.2; 10.3] p = 0.018). CONCLUSION: Increased MR post-PCI was associated with lesions of less severe hemodynamic influence at baseline and higher rates of TVF at follow-up

Microvascular resistance reserve: diagnostic and prognostic performance in the ILIAS registry

Aims: The microvascular resistance reserve (MRR) was introduced as a means to characterize the vasodilator reserve capacity of the coronary microcirculation while accounting for the influence of concomitant epicardial disease and the impact of administration of potent vasodilators on aortic pressure. This study aimed to evaluate the diagnostic and prognostic performance of MRR. Methods and results: A total of 1481 patients with stable symptoms and a clinical indication for coronary angiography were included from the global ILIAS Registry. MRR was derived as a function of the coronary flow reserve (CFR) divided by the fractional flow reserve (FFR) and corrected for driving pressure. The median MRR was 2.97 [Q1-Q3: 2.32-3.86] and the overall relationship between MRR and CFR was good [correlation coefficient (Rs) = 0.88, P < 0.005]. The difference between CFR and MRR increased with decreasing FFR [coefficient of determination (R2) = 0.34; Coef. - 2.88, 95% confidence interval (CI): -3.05 - 2.73; P < 0.005]. MRR was independently associated with major adverse cardiac events (MACE) at 5-year follow-up [hazard ratio (HR) 0.78; 95% CI 0.63-0.95; P = 0.024] and with target vessel failure (TVF) at 5-year follow-up (HR 0.83; 95% CI 0.76-0.97; P = 0.047). The optimal cut-off value of MRR was 3.0. Based on this cut-off value, only abnormal MRR was significantly associated with MACE and TVF at 5-year follow-up in vessels with functionally significant epicardial disease (FFR <0.75). Conclusion: MRR seems a robust indicator of the microvascular vasodilator reserve capacity. Moreover, in line with its theoretical background, this study suggests a diagnostic advantage of MRR over other indices of vasodilatory capacity in patients with hemodynamically significant epicardial coronary artery disease

Sex differences in prevalence and outcomes of the different endotypes of chronic coronary syndrome in symptomatic patients undergoing invasive coronary angiography: Insights from the global ILIAS invasive coronary physiology registry

Background and aims: The management of chronic coronary syndrome (CCS) is informed by studies predominantly including men. This study investigated the relationship between patients sex and different endotypes of CCS, including sex-specific clinical outcomes. Methods: In patients with CCS undergoing coronary angiography, invasive Fractional Flow Reserve (FFR) and Coronary Flow Reserve (CFR) were measured. Patients were stratified into groups: 1) obstructive coronary artery disease (oCAD) (FFR≤0.80, no revascularization), 2) undergoing revascularization, 3) non-obstructive coronary artery disease with coronary microvascular dysfunction (CMD) (FFR>0.80, CFR≤2.5), and 4) non-obstructive coronary artery disease without CMD (FFR>0.80 and CFR>2.5). Results: 1836 patients (2335 vessels) were included, comprising 1359 (74.0%) men and 477 (26.0%) women. oCAD was present in 14.1% and was significantly less prevalent in women than in men (10.3% vs 15.5%, respectively p < 0.01). Revascularization was present in 30.9% and was similarly prevalent in women and men (28.2% vs. 31.9%, respectively p = 0.13). CMD was present in 24.2% and was significantly more prevalent in women than men (28.6% vs 22.6%, respectively p < 0.01). Normal invasive measurements were found in 564 patients (33.0% women vs 30.0% men, p = 0.23). Male sex was associated with an increased risk of target vessel failure compared to women (HR.1.89, 95% CI 1.12–3.18, p = 0.018), regardless of CCS-endotype. Conclusions: Sex differences exist in the prevalence and outcomes of different endotypes of CCS in symptomatic patients undergoing invasive coronary angiography. In particular, oCAD (and subsequent revascularization) were more prevalent in men. Conversely, CMD was more prevalent in women. Overall, men experienced a worse cardiovascular outcome compared to women, independent of any specific CCS endotype

Estimating global injuries morbidity and mortality : methods and data used in the Global Burden of Disease 2017 study

Background: While there is a long history of measuring death and disability from injuries, modern research methods must account for the wide spectrum of disability that can occur in an injury, and must provide estimates with sufficient demographic, geographical and temporal detail to be useful for policy makers. The Global Burden of Disease (GBD) 2017 study used methods to provide highly detailed estimates of global injury burden that meet these criteria. Methods: In this study, we report and discuss the methods used in GBD 2017 for injury morbidity and mortality burden estimation. In summary, these methods included estimating cause-specific mortality for every cause of injury, and then estimating incidence for every cause of injury. Non-fatal disability for each cause is then calculated based on the probabilities of suffering from different types of bodily injury experienced. Results: GBD 2017 produced morbidity and mortality estimates for 38 causes of injury. Estimates were produced in terms of incidence, prevalence, years lived with disability, cause-specific mortality, years of life lost and disability-adjusted life-years for a 28-year period for 22 age groups, 195 countries and both sexes. Conclusions: GBD 2017 demonstrated a complex and sophisticated series of analytical steps using the largest known database of morbidity and mortality data on injuries. GBD 2017 results should be used to help inform injury prevention policy making and resource allocation. We also identify important avenues for improving injury burden estimation in the future