Nitroglycerin reduces augmentation index and central blood pressure independent of effects on cardiac preload

Objective To determine whether reduction in central pressure augmentation and central systolic blood pressure by nitroglycerine (NTG) results from effects on pre-load or is due to arterial dilation. Methods We compared effects of NTG with those of lower body negative pressure (LBNP). Hemodynamic measurements were made at rest,during LBNP (10,20 and 30 mmHg,each for 15 min) and after NTG (10,30 and 100 μg/min,each dose for 15 min) in ten healthy volunteers. Cardiac pre-load,stroke volume and cardiac output were assessed by echocardiography. Central pressure augmentation and central systolic pressure were obtained by radial tonometry using a transfer function. Results LBNP (20 mmHg) and NTG (30 μg/min) reduced pre-load (as measured by the peak velocity of the S wave in the superior vena cava) to a similar degree [by (26.8±3.8)% and (23.9±3.4)%,respectively]. Compared to LBNP,NTG reduced systemic vascular resistance [by (32.9±7.5)%,P<0.01],decreased peripheral and central pressure augmentation [by (20.8±3.4)% units and (12.9±2.9)% units,respectively,each P<0.01]. Conclusion These results suggest that a reduction in pre-load does not explain reduction in pressure augmentation and central systolic blood pressure by NTG and that these effects are mediated through arterial dilation.

Sex modification of the association of the radial augmentation index and incident hypertension in a Chinese community-based population

BACKGROUND Arterial stiffness,as assessed by aortic ultrasound and pulse wave velocity,is associated with incident hypertension.However,there is still no consensus on whether the augmentation index(AI)affects new onset of hypertension.This study investigated the relationship of radial AI(r AI)and incident hypertension in a Chinese community-based population without hypertension at baseline.METHOD A total of 1,615 Chinese non-hypertensive participants from an atherosclerosis cohort in Beijing,China were included in our analysis.Baseline r AI normalized to heart rate of 75 beats/min(r AIp75)was obtained using HEM-9000 AI.New-onset hypertension was defined as blood pressure≥140/90 mm Hg or self-reported hypertension or taking anti-hypertensive medications at the follow up survey.Multivariate regression models were used to evaluate the impact of r AIp75 on the risk of new-onset hypertension.RESULTS After a mean 2.35-year follow-up,213(13.19%)participants developed incident hypertension.No significant relation between r AIp75 and incident hypertension was observed in the whole population after adjustment for possible confounders(adjusted odds ratio(OR)and 95%confidence interval(CI):1.09[0.95-1.27];P=0.2260).However,r AIp75 was significantly associated with incident hypertension in women,but not in men(adjusted OR and 95%CI:1.29[1.06-1.56],P=0.0113 for women;0.91[0.72-1.15],P=0.4244 for men;P for interaction=0.0133).CONCLUSIONS Sex modified the effect of the r AI on incident hypertension in a Chinese,community-based,non-hypertensive population.Screening of the r AI could be considered in women with a high risk of hypertension for the purpose of primary intervention.

Trees with Given Diameter Minimizing the Augmented Zagreb Index and Maximizing the ABC Index

Let G be a simple connected graph with vertex set V（G） and edge set E（G）.The augmented Zagreb index of a graph G is defined asAZI（G） =∑uv∈E（G）(d;d;/（d;+ d;-2）);,and the atom-bond connectivity index（ABC index for short） of a graph G is defined asABC（G） =∑uv∈E（G）(（d;+ d;-2）/d;d;),where d;and d;denote the degree of vertices u and v in G,respectively.In this paper,trees with given diameter minimizing the augmented Zagreb index and maximizing the ABC index are determined,respectively.

On Augmented Zagreb Index of Molecular Graphs

The augmented Zagreb index displays a good correlation with the formation heat of octanes and heptanes. The augmented Zagreb index of catacondensed hexagonal systems and molecular trees was discussed. By using the methods of analysis of graph structure and mathematical induction,the catacondensed hexagonal systems with extreme augmented Zagreb index were characterized.The lower bound for augmented Zagreb index of molecular trees with fixed numbers of pendent vertices was given,and the extremal trees were characterized. From these results,we can compare the formation heat of catacondensed hexagonal systems and molecular trees.

Increased Risk of Arterial Stiffness in Rhumatoid Arthritis Patients in a Sub-Saharan African Setting

Background: Analysis of arterial stiffness (AS) is a good marker of early arterial disease and an important determinant of cardiovascular risk, independent of other traditional cardiovascular risk factors. Carotid-femoral pulse wave velocity (CfPWV) is the gold standard to evaluate arterial stiffness. There is evidence that patients with rheumatoid arthritis (RA) have a higher arterial stiffness than their age-matched healthy counterparts and thus have higher cardiovascular (CV) risk. However, data on arterial stiffness in African rheumatoid arthritis patients is scarce. Objectives: To determine the patterns of arterial stiffness in rheumatoid arthritis patients in a sub-Saharan African setting, using CfPWV and Augmentation index (AIx). Method: We conducted a case-control study, at the Douala general hospital over four months (February to May 2018) on 63 subjects among which 31 RA patients matched for age and sex with 32 healthy subjects. AIx and CfPWV were determined non-invasively by radial pulse wave analysis and carotid femoral wave analysis respectively, using a sphygmocor Atcor device (SphygmoCor, PWV Medical, Sydney, Australia). Results: The mean age of RA patients was 47 ± 14 years with most of them being females (n = 26, 83.9%). CfPWV was significantly higher in RA patients compared to the control group (mean: 8.85 ± 2.1 vs 7.45 ± 1.38;p ≤ 0.01) as well as was AIx (Median: 33 [26 - 43] vs 26 [20 - 31];p = 0.01). RA (OR: 6.105;95% CI: 1.52 - 24.54;p 1.34;95% CI: 1.14 - 5.17;p = 0.05), elevated CRP levels (OR: 4.01;95% CI: 1.16 - 13.68;p = 0.03) and Hypertension (OR: 5.75;95% CI: 1.24 -11.60;p Conclusion: Arterial stiffness, a well-recognized marker of cardiovascular risk is increased among patients suffering from rheumatoid arthritis when compared to a healthy control group.

The effect of acute aerobic exercise on central arterial stiffness,wave reflections,and hemodynamics in adults with diabetes:A randomized cross-over design

Background:Individuals with diabetes have greater central arterial stiffness,wave reflections,and hemodynamics,all of which promote the accelerated cardiovascular pathology seen in this population.Acute aerobic exercise has been shown to be an effective strategy for reducing central arterial stiffness,wave reflections,and hemodynamics in healthy individuals;however,the effects of acute aerobic exercise in reducing these outcomes is not well established in people with diabetes.Recently,implementation of high-intensity interval exercise(HIIE)has shown superior improvements in cardiovascular health outcomes when compared to traditional aerobic exercise.Yet,the effect of HIIE on the aforementioned outcomes in people with diabetes is not known.The purpose of this study was to(i)describe the central arterial stiffness,wave reflections,and hemodynamic responses to a bout of HIIE and moderate-intensity continuous exercise(MICE)in adults with diabetes;and(ii)compare the effects of HIIE and MICE on the aforementioned outcomes.Methods:A total of 24 adult men and women(aged 29-59 years old)with type 1(n=12)and type 2(n=12)diabetes participated in a randomized cross-over study.All participants completed the following protocols:(i)HIIE:cycling for 4×4 min at 85%-95%of heart rate peak(HR_(peak)),interspersed with 3 min of active recovery at 60%-70%HR_(peak);(ii)MICE:33 min of continuous cycling at 60%-70%HR_(peak);and(iii)control(CON):lying quietly in a supine position for 30 min.Results:A significant group￡time effect was found for changes in central systolic blood pressure(F=3.20,p=0.01)with a transient reduction for the HIIE group but not for the MICE or CON groups.There was a significant group￡time effect for changes in augmentation index at a heart rate of 75 beats/min(F=2.32,p=0.04)with a decrease following for HIIE and MICE but not for CON.For all other measures of central arterial stiffness and hemodynamics,no significant changes were observed(p>0.05).Conclusion:A bout of HIIE appears to lead to a greater transient reduction in central systolic blood pressure than the reduction observed following MICE;however,both HIIE and MICE improved augmentation index at a heart rate of 75 beats/min in people with diabetes.There was no significant difference in response to HIIE and MICE in all outcomes.This provides preliminary evidence on the role of HIIE on such outcomes in people with diabetes.

Non-invasive cuffless blood pressure and heart rate monitoring using impedance cardiography

Background Continuous blood pressure(BP)monitoring provides additional information about how changes in BP may correlate with daily activities and sleep patterns.Recommendations from the American Heart Association and American College of Cardiology strongly suggest confirming a diagnosis of hypertension with continuous BP monitoring.Non-invasive and non-intrusive detection of haemodynamic parameters is emerging as a norm,based on self-monitoring wearable medical devices.Researchers have carried out several studies using non-invasive and continuous BP measurements as an alternative to conventional cuff-based measurements.In this work,we proposed a novel method for cuffless estimation of BP using impedance cardiography(ICG).Methods We conducted a single-centre,cross-sectional study of 104 subjects(of whom 30 were categorized as controls and the remaining 74 as the disease group)at the Medical College and Hospital,Kolkata.The disease group consisted of patients with confirmed coronary artery disease,while the individuals in the control group were deemed to be healthy.All subjects underwent electrocardiogram recording by on-duty doctors in order to determine their health status.A custom-made device based on the principle of impedance plethysmography was designed to record impedance changes due to subjects’peripheral blood flow.The device was used to record ICG signals.In this study,we developed a novel auto-adaptive algorithm based on ICG signals for non-invasive,cuffless,continuous monitoring of BP and heart rate.Separate mathematical models were developed for all the estimated parameters(BP and heart rate)for both the study groups(control and disease).The developed models were auto-adaptive and did not require subject-specific calibration.Performance indicators including,𝑟2,error percentage,standard deviation,and mean difference were used to quantify the performance of the models.Results The ICG signal recorded by the device was used to extract features and compute the augmentation index.The calculated augmentation index values showed strong correlations with systolic BP(𝑟=0.99,𝑃<0.05),diastolic BP(𝑟=0.95,𝑃<0.05),and heart rate(𝑟=0.78,𝑃<0.05).The models were also shown to have a high degree of accuracy for systolic and diastolic BP.Error margins were in the range±2.33 and±1.79 mmHg for systolic BP in disease and control subjects,respectively,and±3.60 and±1.82 mmHg for diastolic BP.However,the accuracy was lower in the prediction of heart rate in disease subjects,with a reported𝑟2 value of 0.72 and an error margin of±2.88 beats per min;for healthy subjects,the results were marginally better,with an error margin of±1.82 beats per min.All statistical analyses were performed using MATLAB(R2017a,MathWorks R○,USA).Conclusion In this study,we developed a non-invasive cuffless approach for estimation of systemic peripheral BP and heart rate using ICG.The proposed methodology eliminated any discomfort to patients caused by inflation of the cuff(in the case of cuff-based BP monitoring)or the need to constantly wear a fingertip photoplethysmography device(in the case of cuffless BP monitoring).The results obtained appeared promising and increased the potential scope of ICG for monitoring other haemodynamic parameters related to heart function.