Pressure Product Research Articles

Abstract P512: Association Between Resting Rate Pressure Product and All-Cause Mortality Among United States Adults

Background: Rate pressure product (RPP) is a measure of myocardial oxygen consumption and often used to quantify cardiac exercise workload. We sought to determine whether resting RPP was associated with all-cause mortality in healthy U.S. adults. Methods: This was a nationally representative, retrospective cohort study of the 1999-2018 National Health and Nutrition Examination Survey (NHANES), linked to the National Death Index through 2019. We included adult, non-pregnant participants without cardiovascular disease, kidney dysfunction, hypertension, diabetes, or current chronotropic agent use. RPP was calculated as the product of mean systolic BP (of 3 sitting BPs) and resting heart rate, and classified into quintiles (Q1≤7300, Q2 [Ref]: 7300-8250, Q3: 8250-9200, Q4: 9200-10400, Q5: >10400). We used multivariable Cox regression to estimate risk of all-cause mortality, adjusting for demographics, CVD risk factors, and comorbidities, and accounting for the survey design. Results: Among 19,954 participants (mean age 40y; 9,653 [48%] female; 8,056 [66%] non-Hispanic White), 1,013 died over a median follow-up of 10.3 years (IQR, 5.6-15.5). Adults in Q3-Q5 had significantly increased unadjusted risk of all-cause mortality compared to Q2 (HR [95% CI], Q1: 0.89 [0.50,1.58], Q3: 1.69 [1.06,2.72], Q4: 1.97 [1.16,3.34], Q5: 2.69 [1.71,4.22]). Adjustment for covariates attenuated risks of mortality but remained 61% higher for Q5 (Q2 [Ref], Q1: 1.02 [0.77,1.36], Q3: 1.09 [0.85,1.40], Q4: 1.22 [0.93,1.59], Q5: 1.61 [1.25,2.07]). When stratifying by gender, men, but not women, demonstrated increased risk of mortality in Q4 and Q5 (Women, Q4: 0.84 [0.54,1.31], Q5: 1.33 [0.89,1.98]; Men, Q4: 1.53 [1.07,2.18], Q5: 1.79 [1.30,2.46]). Conclusion: Healthy adult participants with a resting RPP greater than 10,400 had 61% higher risk of all-cause mortality compared to a RPP less than or equal to 7,300. This effect seems to be more pronounced in men than women. Further longitudinal studies are needed to understand the independent, predictive value of RPP and factors (e.g. aerobic activity) driving RPP.

More efficient charging of ferroelectrets via tuning of the Paschen breakdown

Charging by means of dielectric barrier discharges (DBDs) is a critical step in the preparation of ferroelectrets (also called piezoelectrets). Triggering of the DBD charging in ferroelectrets is governed by Paschen's law. The Paschen-breakdown voltage Vb of common gases exhibits a U-shaped dependence on the product of gas pressure p and electrode spacing d (internal-cavity height in the present ferroelectret context). This allows for a more efficient charging strategy for ferroelectrets whose pd value at atmospheric pressure is different from the (pd)min value of the Paschen-breakdown curve. For easier triggering of the DBD charging, the pd is adjusted toward (pd)min (corresponding to Vb, min of the Paschen curve) by controlling the gas pressure in the cavity. Subsequently, pd is restored to its value at ambient pressure under the charging voltage in order to obtain a high remanent polarization. The proposed charging scheme is easy to operate and can significantly improve the charging efficiency of ferroelectrets with a wide range of cavity geometries.

Study on the shrinkage mechanism and prediction model of high-strength specified density concrete based on the internal curing micro-pump effect of MSW incineration tailings

As an effective substitute for high-strength concrete, high-strength specified density concrete can prevent and reduce the autogenous shrinkage cracking of high-strength concrete caused by low water-binder ratio or dry environment. In this paper, the early-stage shrinkage law of high-strength specified density concrete prepared from the lightweight aggregate of municipal solid waste (MSW) incineration tailings was explored through autogenous shrinkage and non-contact dry environment shrinkage tests. Combined with the tests of relative humidity, capillary negative pressure, penetration resistance, mesoporous structure and hydration products, the shrinkage reduction mechanism of internal curing micro-pump effect of incineration tailings in high-strength specified density concrete was revealed systematically and comprehensively. What’s more, the shrinkage prediction model of high-strength specified density concrete was established accordingly. The results show that replacing high-strength concrete with high-strength specified density concrete can effectively reduce the autogenous-shrinkage value by more than 68.5%, and incineration tailings can be widely used as internal curing material in cement concrete. It deserves to be mentioned that incineration tailings have significant internal curing micro-pump effect in high-strength specified density concrete. More importantly, the micro-pump water releases effect before the critical humidity point (RH = 100%) ameliorates the hydration degree of high-strength specified density concrete (SDC-25, SDC-50 and SDC-75) by 34.9%, 69.9% and 103.4%, and the self-expansion effect produced compensates for the volume shrinkage resulted from chemical shrinkage. Nevertheless, after the critical humidity point (RH < 100%), the water release effect of micro-pump lessens the pore negative pressure. The difference between the critical point test results of SDC-25, SDC-50 and SDC-75 relative humidity and the modified predicted shrinkage values of Zhang Jun-Hou Dongwei is 2.4%, 1.8% and 1.3%, respectively. The deviation between the two is within 20%, and the correlation coefficient (R2) is 0.943, which suggests that the modified Zhang Jun-Hou Dongwei model is applicable to the shrinkage prediction of high-strength specified density concrete of the shrinkage reduction type of internal curing. By adjusting the aggregate composition structure of traditional high-strength concrete and introducing internal curing micro-pump effect, it is helpful to improve the shrinkage resistance of high-strength concrete and the technical progress of the resource utilization of bulk solid wastes (incineration tailings) in cement concrete.

Limitations associated with thermoregulation and cardiovascular research assessing laborers performing work in the heat.

To quantify the current literature and limitations associated with research examining thermoregulatory and cardiovascular strain in laborers working in the heat. PubMed, SCOPUS, and SPORTDiscus were searched for terms related to the cardiovascular system, heat stress, and physical work. Qualifying studies included adult participants (18-65 years old), a labor-intensive environment or exercise protocol simulating a labor environment, a minimum duration of 120 min of physical work, and environmental heat stress (ambient temperature ≥26.0°C and ≥30% relative humidity). Studies included at least one of the following outcomes: pre- and peakphysical work, core temperature, heart rate (HR), systolic blood pressure, diastolic blood pressure, HR variability, and rate pressure product. Twenty-one out of 1559 potential studies qualified from our search. There was a total of 598 participants (mean = 28 ± 50 participants per study, range = 4-238 participants per study), which included 51 females (8.5%) and 547 males (91.5%). Of the participants, 3.8% had cardiovascular risk factors (diabetes: n = 10; hypertension: n = 13)and 96.2% were characterized as "healthy". Fifty-seven percentof the included studies were performed in a laboratory setting. Studies were predominantly in men (91.5%), laboratory settings (57%), and "healthy" individuals (96.2%). To advance equity in protection against occupational heat stress and better inform future heat safety recommendations to protect all workers, future studies must focus on addressing these limitations. Employers, supervisors, and other safety stakeholders should consider these limitations while implementing current heat safety recommendations.

Arterial Stiffness is Associated with False-Positive ST-Segment Depression in Supine Bicycle Exercise Stress Echocardiography.

Although exercise stress electrocardiography (ECG) is a popular tool for detecting coronary artery disease (CAD), the induced ST-depression without coronary artery stenosis (FST) remains a challenge for accurate diagnosis. Exercise-induced ST depression is related to poor prognosis even in non-obstructive disease; however, its determinants have not been fully defined. We sought to investigate whether ventriculo-vascular interactional indexes such as arterial stiffness index, exercise hemodynamic parameters and echocardiographic left ventricular (LV) functional parameters were related to FST. In the current study, 609 participants who underwent both supine bicycle exercise echocardiography and brachial-ankle pulse wave velocity (baPWV) measurement without exercise-induced regional wall motion abnormalities (RWMA) were analyzed. Referral reasons for stress test were CAD detection or evaluation of patency of previous revascularization. Stepwise graded supine bicycle exercise was performed with simultaneous ECG recording and echocardiography after full conventional resting echocardiography. The FST was defined as newly developed 1 mm ST depression without RWMA during exercise. The median age of the study participants was 65 (59.0-70.5) years, and 222 (37%) patients were women. Among them, 103 (17%) patients showed FST during the exercise or recovery phase. The prevalence of FST did not differ between sexes. Older age, higher pulmonary arterial systolic pressure (PASP), left atrial volume index, baPWV and ankle brachial index at rest and hypertensive response, higher heart rate and rate-pressure product at peak exercise were significantly associated with FST. In multivariate analysis, higher peak heart rate, PASP, and baPWV were independently related to FST. Stress-induced RWMA in addition to ECG should be evaluated to detect CAD in patients with higher baPWV and PASP. FST might be linked to subclinical myocardial ischemia through arterial stiffness and diastolic dysfunction.

Solid-State Fermentation of Distiller’s Dried Grains with Solubles Improves Digestibility for European Seabass (Dicentrarchus labrax) Juveniles

Aquaculture requires new, economical, and eco-friendly protein sources to replace traditional fisheries and plant ingredients. Using agriculture by-products as protein sources would reduce land-based feed production pressure and waste production, promoting a circular economy and sustainable aquaculture. Distiller’s dried grains with solubles (DDGS) is the main by-product of bioethanol production. Corn DDGS has a high protein level, but its high fiber content limits its use as a feed ingredient, particularly for carnivorous fish. Solid-state fermentation (SSF) uses lignocellulosic-rich substrates, such as DDGS, for microbial growth in the near absence of water, promoting enzyme production that degrades the lignocellulosic matrix, increasing free reducing sugars, protein, and antioxidant levels of the substrate. In the present work, the SSF of corn DDGS with Aspergillus carbonarius, A. ibericus, and A. uvarum was tested. Then, the digestibility of the most promising fermented DDGS (in terms of upgraded nutritional composition) was tested by including it in a reference diet (70% of a reference diet; 48% crude protein; 15% crude lipids) for European seabass (Dicentrarchus labrax) juveniles (171 g averaged weight; trial duration of 52 days). Among the fungi tested, Aspergillus ibericus led a generally higher upgrading of the DDGS nutritional composition, leading to a high amount of protein (from 42.7 to 49.7 g N/kg DM), phenolic compounds (1.49 to 4.86 mg/g caffeic acid equivalents), free sugars (9.5 to 31.9 mg/g), and enzyme production (45 U/g and 68 U/g of cellulase and xylanase, respectively), and a high reduction in acid detergent fiber and neutral detergent fiber content (up to 29 and 43%, respectively). Compared to the unfermented DDGS, fermented DDGS presented increased protein, lipids, starch, and energy digestibility, while phosphorous digestibility was similar. Compared to the reference diet, dietary inclusion of unfermented or fermented DDGS increased trypsin and chymotrypsin activities. The activity of digestive enzymes was not affected by the inclusion of fermented DDGS, except for amylase activity, which was lower with the fermented DDGS than with the unfermented DDGS diet. In conclusion, SSF of DDGS enhanced its nutritional value, increasing DDGS digestibility when included in diets for European seabass juveniles.

Multiple In-Mold Sensors for Quality and Process Control in Injection Molding.

The simultaneous improvement of injection molding process efficiency and product quality, as required by Industry 4.0, is a complex, non-trivial task that requires a comprehensive approach, which involves a combination of sensoring and information techniques. In this study, we investigated the suitability of in-mold pressure sensors to control the injection molding process in multi-cavity molds. We have conducted several experiments to show how to optimize the clamping force, switchover, or holding time by measuring only pressure in a multi-cavity mold. The results show that the pressure curves and the pressure integral are suitable for determining optimal clamping force. We also proved that in-channel sensors could be effectively used for a pressure-controlled SWOP. In the volume-controlled method, only the sensors in the cavity were capable of correctly detecting the end of the filling. We proposed a method to optimize the holding phase. In this method, we first determined the integration time of the area under the pressure curve and then performed a model fit using the relationship between the pressure integral and product mass. The saturation curve fitted to the pressure data can easily determine the gate freeze-off time from pressure measurements.

Temperature-Transient Analysis for Matrix Linear Flow Toward Infinite-Conductivity Hydraulically Fractured Wells

SummaryThis work presents novel analytical temperature-transient solutions for matrix linear flow toward an infinite-conductivity hydraulically fractured well producing under specified constant rate (CR) or constant bottomhole pressure (CBHP) production. The solutions apply to the single-phase flow of a slightly compressible fluid with constant viscosity (e.g., undersaturated oil reservoirs with irreducible water saturation or liquid-dominated geothermal reservoirs). They include the effects of conduction, convection, the Joule-Thomson (J-T) expansion of fluids and adiabatic expansion of the total rock and fluid system, and fluid loss fracture damage and assume constant rock and fluid physical and thermophysical properties with pressure and temperature. They are obtained by using Laplace (for CR) and Boltzmann (for CBHP) transformations. To validate the analytical solutions, an in-house numerical solution is also developed. It solves the mass and thermal energy balance equations coupled simultaneously and accounts for the variation of rock and fluid properties with pressure and temperature. The in-house simulator was validated by using a commercial reservoir simulator. Results indicate that the fracture surface temperature is decreasing with a square root of time for CR production but is constant for CBHP production. The temperature responses for both modes of production are controlled by the adiabatic expansion of the rock and fluid properties and the thermal diffusivity of the rock. The effect of thermal conductivity plays a significant role in both production modes as the matrix permeability decreases. The fracture damage has different signatures on temperature transients depending on the mode of production. The approximate analytical solutions show the information content of temperature-transient data acquired from an infinitely conductive hydraulically fractured well under matrix linear flow. They are simple and can be used to perform matrix linear-flow analysis jointly with pressure and rate transient data to estimate the physical and thermophysical properties of the rock and fluids. We also propose a simple correction to fluid viscosity variation as input for the analytic solutions to accurately estimate the physical and thermophysical parameters in case drawdowns are significant.

The impact of diabetes mellitus on improvement of resting rate pressure product in patients with refractory angina undergone external counter pulsation

Abstract Funding Acknowledgements Type of funding sources: None. Background The management of coronary artery disease (CAD) has developed significantly in the last few decades. One of the therapeutic modalities that could be considered to patients with refractory angina caused by CAD is external counter pulsation (ECP). Rate pressure product (RPP) is a determinant of cardiac oxygen consumption and heart workload. It is a simple parameter that could be calculated easily by multiplying systolic blood pressure and heart rate. Increased resting RPP is associated with higher myocardial oxygen consumption and decreased cardiac efficiency. Studies that discuss factors that influence the decrease of resting RPP due to ECP procedure as a possible mechanism underlying the improvement of clinical symptoms in patients with refractory angina are still very limited. Purpose This study aimed to determine the impact of diabetes mellitus (DM) as one of most common risk factors for complex CAD and refractory angina on the decremental of resting RPP in refractory angina patients who have undergone standard 35 sessions of ECP. Methods This is a cohort retrospective study that collected data from registry of all patients who have completed 35 sessions of ECP procedures from 2018 until 2021. We compared the improvement of resting RPP after program completion and evaluated the effect of DM and blood glucose levels on the difference in resting RPP. Statistical test was performed by SPSS software for windows. Results A total of 16 patients were enrolled in this study with mean age of 65.4 years old. Subjects in this study were predominantly male (87.5%) and most of the subjects (68.8%) were diagnosed with CAD/3-vessels disease (3VD). The main risk factors found in the subjects were hypertension (75%) and DM (62.5%). All subjects underwent random blood sugar examination before starting ECP procedure with mean 122.7 mg/dL. Paired samples T-test analysis found that there was a decrease in resting RPP in subjects after undergoing ECP compared to before the procedure (7046.1 ± 1515.3 vs 8572.5 ± 1915.7; p-value &amp;lt;0.001). Independent samples T-test showed that the presence of DM reduced the mean decrease of resting RPP in study subjects (1034.8 ± 1122.2 vs 2345.7 ± 1167.5; p-value 0.043). Pearson correlation analysis showed that there was no significant correlation between blood sugar levels and decrease in resting RPP after ECP completion in study subjects (correlation coefficient -0.049; p-value: 0.869). Conclusion Standard 35 ECP sessions could decrease resting RPP in refractory angina patients. The improvements may contribute to the clinical benefit of ECP. However, the presence of DM can reduce the effectiveness of ECP in improving resting RPP, regardless of the blood sugar levels. These findings were probably related to cardiovascular autonomic neuropathy that were commonly found among diabetics. Further research is needed to elucidate the exact underlying mechanisms of these outcomes.

A new semi-analytical flow model for multi-branch well testing in natural gas hydrates

This paper presents a new semi-analytical solution and the related methodology to analyze the pressure behavior of multi-branch wells produced from natural gas hydrates. For constant bottom-hole pressure production, the transient flow solution is obtained by Laplace transforms. The interference among various branches is investigated using the superposition principle. A simplified form of the proposed model is validated using published analytical solutions. The complete flow profile can be divided into nine distinct regimes: wellbore storage and skin, vertical radial flow, linear flow, pseudo-radial flow, composite flow, dissociated flow, transitional flow, improvement flow and stress-sensitive flow. A well’s multi-branch structure governs the vertical radial and the linear flow regimes. In our model, a dynamic interface divides the natural gas hydrates deposit into dissociated and non-dissociated regions. Natural gas hydrates formation properties govern the compositeeffect, dissociated, transitional, and improvement flow regimes. A dissociation coefficient governs the difference in flow resistance between dissociated and non-dissociated natural gas hydrates regions. The dissociated-zone radius affects the timing of these flow regimes. Conversion of natural gas hydrates to natural gas becomes instantaneous as the dissociation coefficient increases. The pressure derivative exhibits the same features as a homogeneous formation. The natural gas hydrates parameter values in the Shenhu area of the South China Sea cause the prominent dissociated flow regime to conceal the later transitional and improvement flow regimes. Due to the maximum practical well-test duration limitation, the first five flow regimes (through composite flow) are more likely to appear in practice than later flow regimes. Cited as: Chu, H., Zhang, J., Zhang, L., Ma, T, Gao Y., Lee, W. J. A new semi-analytical flow model for multi-branch well testing in natural gas hydrates. Advances in Geo-Energy Research, 2023, 7(3): 176-188. https://doi.org/10.46690/ager.2023.03.04

Comparison of the Results of Cardiopulmonary Exercise Testing between Healthy Peers and Pediatric Patients with Different Echocardiographic Severity of Mitral Valve Prolapse

Patients with mitral valve prolapse (MVP) have been reported to have exercise intolerance. However, the underlying pathophysiological mechanisms and their physical fitness remain unclear. We aimed to determine the exercise capacity of patients with MVP through the cardiopulmonary exercise test (CPET). We retrospectively collected the data of 45 patients with a diagnosis of MVP. Their CPET and echocardiogram results were compared with 76 healthy individuals as primary outcomes. No significant differences regarding the patient's baseline characteristics and echocardiographic data were found between the two groups, except for the lower body mass index (BMI) of the MVP group. Patients in the MVP group demonstrated a similar peak metabolic equivalent (MET), but a significantly lower peak rate pressure product (PRPP) (p = 0.048). Patients with MVP possessed similar exercise capacity to healthy individuals. The reduced PRPP may indicate compromised coronary perfusion and subtle left ventricular function impairment.

A New Interpretation of Gas Viscosity for Flow through Micro-Capillaries and Pores.

The Hagen-Poiseuille equation for gas flowhad never been derived theoretically; it is rather a simple analogy of the same for liquid flow, and "gas viscosity" is a measure for overall resistance to flow. In this work, experimental flow data for different gases through capillaries and porous media, reported in literature by different groups, including those measured and treated by Knudsen are treated with Hagen-Poiseuille equation, but taking "gas viscosity" as an adjustable parameter. It is found that, at constant temperature, there exists an unambiguous relation between the viscosity (µ) of a given gas, and the product of average pressure (Pav ) and capillary diameter (D). In addition, for Pav * D<0.01, a universal linear relation exists between µ/M0.5 (where M is molecular mass) for different gases and the parameter Pav * D. The new interpretation of gas viscosity avoids the differentiation of regimes into "Knudsen" and "viscous" flow as it is frequently done in literature. The concept can be applied to obtain a reliable data base for gas viscosities in different fields of applications, for example in microfluidic systems or the analysis of pore size distributions of filters and membranes by gas flow porometry.

Numerical investigation of a 1MW full-loop chemical looping combustion unit with dual CFB reactors

Chemical looping combustion (CLC) is a novel carbon capture technology with inherent advantage of CO2 separation and less energy penalty. The oxygen carrier circulates between the reactors realizing the transportation of oxygen and heat and preventing the mixing of air with flue gas. Currently, it lacks researches on the industrial scale system which operates autothermal. In this work, three-dimensional simulations of 1MW chemical looping combustion unit with gaseous fuel are presented in the frame of Eulerian approach. The configuration with dual circulating fluidized bed reactors is built according to the experimental construction, including air reactor, fuel reactor, loop seals, cyclones and L-valve. The time-averaged and local pressure, temperature and gaseous products are predicted numerically and compared with experimental measurements. Simulation results show that the reduction level changes by 0.08 between reactors corresponding to the oxygen transfer. Due to the exothermic process in air reactor, the difference of outlet temperature between air reactor and fuel reactor is 63 °C. Moreover, the higher operating temperature and solid inventory are beneficial for raising the performance of system. Results turn out that the numerical models developed in this work can be used for investigating detailed characteristic or scale-up of CLC system with high accuracy, high efficiency and low cost.

Acute cardiovascular responses to unilateral bicep curls with blood flow restriction

Background/ObjectivesA consensus on the acute cardiovascular responses to low intensity (LI) resistance exercise (RE) combined with blood flow restriction (BFR) has not yet been reached. This study was designed to compare acute cardiovascular responses to a single bout of LIRE, high intensity (HI) RE, and LIRE with BFR in physically active young males. MethodsParticipants completed 3 RE sessions in random order, where each session consists of 4 sets of unilateral dumbbell bicep curls. Cardiovascular hemodynamics were measured at baseline and right after each set of RE. ResultsAortic augmentation index (AIx) was significantly higher after set 2,3,4 of RE in LI + BFR session compared to LI session (P < 0.05). Brachial systolic blood pressure (SBP), heart rate (HR), brachial rate pressure product (RPP), and central RPP responses did not differ between LI and LI + BFR sessions (P > 0.05). HI session had a higher central SBP, brachial RPP, central RPP, and aortic AIx compared to LI session after each set of RE (P < 0.05), but not brachial SBP (P > 0.05). ConclusionsTaken together, this study showed that LIRE combined with BFR acutely augmented aortic stiffness, as also observed in HI session, but myocardial oxygen consumption was only higher in HI session when compared to LI session. Thus, although BFR did not exaggerate cardiovascular responses nor cause extra myocardial oxygen consumption, it should be prescribed with caution when control of acute aortic stiffening is necessary during RE.

Responsibility in Universal Healthcare

Responsibility in Universal Healthcare

Responsibility in Universal Healthcare

Responsibility in Universal Healthcare

TO OBSERVE EFFECTS OF MELATONIN PREMEDICATION ON HAEMODYNAMIC RESPONSES TO LARYNGOSCOPY AND INTUBATION

Laryngoscopy using rigid metal blade produces noxious stimuli that causes stimulation of sensory receptors which in turn causes release of endogenous catecholamines, which in turn provokes hemodynamic changes called stress response. Due to its inhibitory action on CNS which causes sedation and anxiolysis as well as suppression of catecholamine release, we hypothesized that oral melatonin tablet 10 mg, administered orally about 120 minutes before the procedure should provide hemodynamic stability and blunt this response. The primary objective of the study was to observe magnitude and duration of changes in vital parameters before, during and after laryngoscopy and intubation, in a group of patients who were premedicated with 10 mg mouth dispersible tablet melatonin 120 min anesthesia. Continuous numeric data on pulse rate, blood pressure, SPO2 were analyzed as mean and standard deviation. Signicance of observation was derived by applying student's t-test. Non parametric data on complication of study drug was reported as number of patients exhibiting the complication and also as percentage. One group of 35 patients received 10 mg of oral melatonin as mouth dispersible tablet 120 minutes before conduct of anesthesia and other group did not received the study drug and acted as control group for comparison. Pre induction hemodynamic parameters after 120 minutes of oral melatonin administration were recorded and after induction of anesthesia and intubation hemodynamic parameters were recorded. In group of patients who received melatonin the magnitude of rise of heart rate, systolic, diastolic and mean arterial pressure was less returning to pre induction value within 3 minutes. .In control group patients we observed a statistically signicant rise in magnitude of heart rate and blood pressure that remained elevated till 10 minutes after laryngoscopy and intubation. The rate pressure product, an indicator of myocardial oxygen demand and consumption was signicantly higher in control group and lasted for longer time. While in melatonin treated patients insignicant rise of RPP occurred. The clinical observations made in the present study allow us to conclude that oral melatonin administered 120 minutes before induction of anesthesia effectively controlled the stress response to laryngoscopy and endotracheal intubation and shown cardio-protective effect.

Imatinib attenuates reperfusion injury in a rat model of acute myocardial infarction

Following an acute myocardial infarction, reperfusion of an occluded coronary artery is often accompanied by microvascular injury, leading to worse long-term prognosis. Experimental studies have revealed the potential of tyrosine-kinase inhibitor imatinib to reduce vascular leakage in various organs. Here, we examined the potential of imatinib to attenuate microvascular injury in a rat model of myocardial reperfusion injury. Isolated male Wistar rat hearts (n = 20) in a Langendorff system and male Wistar rats (n = 37) in an in vivo model were randomly assigned to imatinib or placebo and subjected to ischaemia and reperfusion. Evans-blue/Thioflavin-S/TTC staining and Cardiac Magnetic Resonance Imaging were performed to assess the extent of reperfusion injury. Subsequently, in vivo hearts were perfused ex vivo with a vascular leakage tracer and fluorescence and electron microscopy were performed. In isolated rat hearts, imatinib reduced global infarct size, improved end-diastolic pressure, and improved rate pressure product recovery compared to placebo. In vivo, imatinib reduced no-reflow and infarct size with no difference between imatinib and placebo for global cardiac function. In addition, imatinib showed lower vascular resistance, higher coronary flow, and less microvascular leakage in the affected myocardium. At the ultrastructural level, imatinib showed higher preserved microvascular integrity compared to placebo. We provide evidence that low-dose imatinib can reduce microvascular injury and accompanying myocardial infarct size in a rat model of acute myocardial infarction. These data warrant future work to examine the potential of imatinib to reduce reperfusion injury in patients with acute myocardial infarction.

Assessment of Vascular and Valvular Calcification Improves Screening for Coronary Artery Disease Before Liver Transplantation

Coronary artery disease (CAD) is common in patients with cirrhosis who underwent orthotopic liver transplantation (OLT) evaluation and stress echocardiogram (echo) has a low sensitivity in these patients. This study aimed to assess the impact of vascular and valvular calcification on the ability to identify CAD before OLT. We performed a case-control study of 88 patients with and 97 without obstructive CAD who underwent OLT evaluation. All patients had a preoperative stress echo, abdominal computed tomography, and cardiac catheterization. A series of nested logistic regression models of CAD were fit by adding independent variables of vascular (including coronary) calcification, aortic and mitral valve calcification, age, gender, and history of diabetes mellitus requiring insulin to a baseline model of abnormal stress echo. Compared with stress echo alone, identification of the presence or absence of vascular and valvular calcification on routine preoperative computed tomography and echo improved the diagnostic performance for the detection of CAD based on coronary angiogram when combined with stress echo in patients with cirrhosis who underwent OLT evaluation (area under the curve 0.58 vs 0.73, p <0.001), which is even further improved when age, gender, and history of diabetes mellitus requiring insulin are considered (area under the curve 0.58 vs 0.80, p <0.001). Achieving target heart rate (p=0.92) or rate-pressure product >25,000 (p=0.63) did not improve the ability of stress echo to identify CAD. In conclusion, the use of abdominal vascular, coronary artery, and valvular calcification, along with stress echo, improves the ability to identify and rule out obstructive CAD before OLT compared with stress echo alone.

The Presence of Wind Worsens the Effect of Cold Temperature on Time to Ischemia in Patients with Stable Angina.

This study tested the hypothesis that the combination of cold temperature and wind further reduces time to ischemia during treadmill stress testing compared with cold temperature alone. Eighteen participants (56 ± 9 yr) with stable angina performed four treadmill stress tests in a randomized crossover design at +20°C and -8°C, with and without a 24-km·h -1 headwind. Time to ischemia (≥1-mm ST-segment depression) and angina, rate pressure product, and total exercise duration were determined. At -8°C, time to ischemia was reduced by 22% (-58 s (-85 to -31 s), P < 0.01) compared with +20°C. The addition of wind at -8°C reduced time to ischemia by a further 15% (-31 s (-58 to -4 s) vs -8°C without wind, P = 0.02). The addition of wind did not affect time to ischemia at +20°C ( P = 0.38). Cold temperature and wind did not affect time to angina ( P = 0.46 and P = 0.61) or rate pressure product ( P = 0.46 and P = 0.09). Total exercise time was reduced in the presence of wind at -8°C (-29 s (-51 to -7 s), P = 0.01), but not at +20°C ( P = 0.09). The presence of wind reduces time to ischemia when exercise stress testing is performed in a cold environment. These results suggest that wind should be considered when evaluating the risks posed by cold weather in patients with coronary artery disease and exercise-induced ischemia.