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Arterial Compliance (arterial + compliance)

Distribution by Scientific Domains

Medical Sciences	91%

Distribution within Medical Sciences

Cardiovascular Disease	23%
Diabetes	18%

Selected Abstracts

Experimental and clinical study of the combined effect of arterial stiffness and heart rate on pulse pressure: Differences between central and peripheral arteries

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2005
Theodoros G Papaioannou
SUMMARY 1.,Pulse pressure (PP) constitutes an independent predictor of cardiovascular events and mortality in various populations. Heart rate (HR) and arterial stiffness, in addition to their independent predictive value for cardiovascular complications, seem to interact with regard to the modification of PP. The aim of the present study was to investigate the association of PP with HR under different levels of arterial compliance (AC), revealing their synergistic effects. 2.,Seventy-one normotensive and untreated hypertensive subjects were examined. Arterial compliance was measured by the ,area' method, whereas central blood pressures and wave reflections were evaluated using the Sphygmocor® system (AtCor Medical, Sydney, NSW, Australia). A hydraulic Windkessel model was also used to evaluate the independent effect of HR and AC on PP. Peripheral PP was associated only with mean pressure and AC. In contrast, central PP was further related to HR (20 b.p.m. decrease in HR resulted in central PP augmentation by 5.6 mmHg) regardless of mean pressure, stroke volume, age and gender. However, this association was statistically significant only for subjects with lower AC (< 1.1 mL/mmHg) and not for those with more compliant arteries. These findings are also in accordance with the experimental data. 3.,Aortic PP is affected to a greater degree by HR changes compared with peripheral PP. This response was observed only at high levels of arterial stiffness. 4.,The present study provides the first evidence regarding the combined effect of AC and HR on aortic PP, which may lead to larger clinical or epidemiological studies aiming to optimization of drug treatment and to a possible reduction of cardiovascular risk. [source]

Atherosclerosis measured by whole body magnetic resonance angiography and carotid artery ultrasound is related to arterial compliance, but not to endothelium-dependent vasodilation , the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study

CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2009
Lars Lind
Summary Background:, Arterial compliance and endothelium-dependent vasodilation are two characteristics of the vessel wall. In the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study, we studied the relationships between arterial compliance and endothelium-dependent vasodilation versus atherosclerosis as measured with two imaging modalities. Methods:, In the population-based PIVUS study (1016 subjects aged 70), arterial compliance was determined by ultrasound in the carotid artery and the stroke volume to pulse pressure ratio by echocardiography, while endothelium-dependent vasodilation was assessed by the invasive forearm technique with acetylcholine and brachial artery ultrasound. Intima-media thickness was evaluated by ultrasound in the carotid artery (n = 954). Stenosis in the carotid, aorta, renal, upper and lower leg arteries were determined by magnetic resonance angiography in a random subsample of 306 subjects. Results:, After adjustments for gender, Framingham risk score, obesity, myocardial infarction and stroke, distensibility in the carotid artery and the stroke volume to pulse pressure ratio were both significantly related to a weighted index of stenosis in the five arterial territories evaluated by magnetic resonance angiography (p<0·02 for both). Distensibility in the carotid artery (P = 0·021), but not the stroke volume to pulse pressure ratio (P = 0·08), was also significantly related to intima-media thickness. Conclusion:, In the elderly population, atherosclerosis is mainly related to arterial compliance, but not to endothelium-dependent vasodilation in peripheral conduit or resistance vessels. [source]

Acute and Chronic Oral Magnesium Supplementation: Effects on Endothelial Function, Exercise Capacity, and Quality of Life in Patients With Symptomatic Heart Failure

CONGESTIVE HEART FAILURE, Issue 1 2006
Johanna C. Fuentes MD
Endothelial dysfunction is an important pathophysiologic mechanism in the progression of heart failure. The objective of the present study was to determine the effects of acute and chronic oral magnesium supplementation on endothelial function in patients with symptomatic heart failure. Twenty-two symptomatic chronic heart failure patients were randomized to receive 800 mg oral magnesium oxide daily or placebo for 3 months. Data collected included large and small arterial elasticity/compliance, hemodynamic parameters, exercise capacity, and quality-of-life score at baseline, 1 week, and 3 months. Patients who received magnesium had improved small arterial compliance at 3 months from baseline compared with placebo. This study suggests that chronic supplementation with oral magnesium is well tolerated and could improve endothelial function in symptomatic heart failure patients. [source]

Subclinical vascular alterations in young adults with type 1 diabetes detected by arterial tonometry

DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 8 2009
I. Barchetta
Abstract Background Diabetes mellitus is characterized by a very high prevalence of atherosclerotic disease. Aims of this study were to determine arterial compliance parameters in type 1 diabetes (T1D) patients as an expression of early pre-clinical endothelial dysfunction and to evaluate the impact of glucose exposure parameters such as the duration of diabetes and glycosylated haemoglobin (HbA1c) on the risk of developing alterations in vascular compliance. Methods 23 patients with uncomplicated type 1 diabetes (mean age: 32.78 ± 9.06 years, mean disease duration: 10.78 ± 7.51 years, mean HbA1c levels: 7.7 ± 1.9) and 26 age- and sex-matched healthy subjects (mean age: 32.3 ± 8.51 years) were recruited. In these subjects, we evaluated arterial compliance by calibrated tonometry (HDI/PulsewaveÔ CR-2000). Parameters included the following: large artery elasticity (C1), small artery elasticity (C2), systemic vascular resistance (SVR) and total vascular impedance (TVI). Results Patients with longer duration of T1D (>10 years) showed significant alterations in C2 (4.97 ± 2.7 mL/mmHg × 100) and in SVR (1464.67 ± 169.16 dina × s × cm,5) when compared with both healthy individuals (C2: 8.28 ± 2.67 mL/mmHg × 100, p = 0.001; SVR: 1180.58 ± 151.55 dina × s × cm,5, p = 0.01) and patients with recent-onset disease (,10 years) (C2: 10.02 ± 3.6 mL/mmHg × 100, p < 0.001; SVR: 1124.18 ± 178.5 dina × s × cm,5, p < 0.000). Both disease duration and HbA1c independently predicted impaired arterial compliance. Conclusions Young adult T1D patients with no signs of disease complication have detectable vessel wall abnormalities, particularly of small arteries, suggestive of hyperglycaemia-related early endothelial dysfunction. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Effect of long-term treatment with rosiglitazone on arterial elasticity and metabolic parameters in patients with Type 2 diabetes mellitus: a 2-year follow-up study

DIABETIC MEDICINE, Issue 11 2007
M. Shargorodsky
Abstract Aims, Thiazolidinediones may influence the atherogenic process by improving cardiovascular risk factors. The present study was designed to determine the long-term effect of rosiglitazone on arterial compliance and metabolic parameters in patients with Type 2 diabetes. Methods, In an open-label, prospective study, 65 diabetic patients received rosiglitazone orally (4,8 mg/day) for 6 months. After 6 months, the patients continued an open follow-up study and were divided into two groups: group 1 included patients continuing rosiglitazone for 2 years, group 2 included patients discontinuing rosiglitazone and receiving other oral glucose-lowering agents. Lipid profile, glycated haemoglobin (HbA1c), insulin, C-peptide, fibrinogen, high-sensitivity-CRP and homeostasis model assessment,insulin resistance were measured. Arterial elasticity was assessed using pulse wave contour analysis. Results, In patients treated with rosiglitazone for 2 years: the large artery elasticity index (LAEI) increased from 10.0 ± 4.6 to 13.9 ± 4.7 ml/mmHg × 100 after 2 years (P = 0.003). The small artery elasticity (SAEI) index increased significantly from 3.2 ± 1.2 to 5.1 ± 1.9 (P < 0.0001). In patients who discontinued rosiglitazone: LAEI did not change after 6 months, but decreased from 12.1 ± 5.4 to 8.9 ± 3.9 ml/mmHg × 10 (P < 0.0001) at the end of 2 years. SAEI increased during the first 6 months of treatment, from 3.9 ± 1.8 to 5.1 ± 1.5 ml/mmHg × 100 (P < 0.0001) and decreased after discontinuation of rosiglitazone (P = 0.042). Conclusions, Prolonged treatment with rosiglitazone improved arterial elasticity. However, significant deterioration in LAEI and SAEI was observed in patients who discontinued rosiglitazone. The beneficial vascular effect of rosiglitazone on arterial elasticity was independent of glycaemic control. [source]

The Effects of Antihypertensive Treatment on the Doppler-Derived Myocardial Performance Index in Patients with Hypertensive Left Ventricular Hypertrophy: Results from the Swedish Irbesartan in Left Ventricular Hypertrophy Investigation Versus Atenolol (SILVHIA)

ECHOCARDIOGRAPHY, Issue 7 2009
Stefan Liljedahl M.D.
Objectives: To investigate the effects of antihypertensive treatment on the Doppler-derived myocardial performance index (MPI) in patients with hypertensive left ventricular hypertrophy. Methods: The MPI was measured at baseline and after 48 weeks of antihypertensive treatment in 93 participants of the SILVHIA trial, where individuals with primary hypertension and left ventricular hypertrophy were randomized to double blind treatment with either irbesartan or atenolol. Results: Antihypertensive treatment lowered MPI (mean difference ,0.03 ± 0.01, P = 0.04). Changes in MPI by treatment were associated with changes in left ventricular ejection fraction (,-coefficient ,0.35 P = 0.005), stroke volume/pulse pressure (reflecting arterial compliance, ,-coefficient ,0.39 P < 0.001) and peripheral vascular resistance (,-coefficient 0.28 P < 0.04). Furthermore, there was a borderline significant association between changes in MPI and changes in E-wave deceleration time (reflecting diastolic function, ,-coefficient 0.23, P = 0.06). No associations were found between changes in MPI and changes in blood pressure, E/A-ratio, left ventricular mass index, relative wall thickness or heart rate. A stepwise multivariable regression model confirmed the association between changes in MPI and changes in ejection fraction and stroke volume/pulse pressure (all P < 0.05), as well as the trend for E-wave deceleration time (P = 0.08), but not in the case of peripheral vascular resistance. Conclusion: The MPI exhibited a modest decrease after 48 weeks of antihypertensive treatment in patients with hypertensive left ventricular hypertrophy. Changes in MPI were associated with changes in left ventricular function and vascular compliance, rather than with changes in left ventricular remodeling or blood pressure. [source]

Echo-Tracking Assessment of Carotid Artery Stiffness in Patients with Aortic Valve Stenosis

ECHOCARDIOGRAPHY, Issue 7 2009
Francesco Antonini-Canterin M.D.
Background: There is little information about mechanical properties of large arteries in patients (pts) with aortic stenosis (AS). Methods: Nineteen patients with AS (aortic valve area: 0.88 ± 0.29 cm2) and 24 control subjects without AS but with a similar distribution of risk factors were recruited. , index, pressure-strain elastic modulus (Ep), arterial compliance (AC), augmentation index (AIx), and local pulse-wave velocity (PWV) were obtained at the level of right common carotid artery (CCA) by a real time echo-tracking system. Time to dominant peak of carotid diameter change waveform, corrected for heart rate (tDPc), and maximum rate of rise of carotid diameter (dD/dt) were measured. Systemic arterial compliance (SAC) was also calculated. Parameters of AS severity (mean gradient, valve area, stroke work loss [SWL]) were determined. Results: tDPc was higher in patients with AS than in controls (7.9 ± 0.6 vs. 6.6 ± 0.7, P < 0.0001) while dD/dt was lower (5.3 ± 3.6 mm/s vs. 7.8 ± 2.8 mm/s, P = 0.01). AIx was significantly higher in AS group (32.5 ± 13.6% vs. 20.6 ± 12.2%, P = 0.005) and had a linear correlation both with tDPc (r = 0.63, P < 0.0001) and with dD/dt (r =,0.38, P = 0.01). There was a significant correlation between carotid AC and SAC (r = 0.49, P = 0.03), but only carotid AC was related to SWL (r = 0.51, P = 0.02), while SAC was not (P = 0.26).Conclusions: AIx was the only parameter of arterial rigidity found to be higher in patients with AS than in controls. Carotid AC showed a significant correlation with SAC and it seemed to be more closely related to AS severity than to SAC. [source]

Variations in carotid arterial compliance during the menstrual cycle in young women

EXPERIMENTAL PHYSIOLOGY, Issue 2 2006
Koichiro Hayashi
The effect of menstrual cycle phase on arterial elasticity is controversial. In 10 healthy women (20.6 ± 1.5 years old, mean ±s.d.), we investigated the variations in central and peripheral arterial elasticity, blood pressure (carotid and brachial), carotid intima,media thickness (IMT), and serum oestradiol and progesterone concentrations at five points in the menstrual cycle (menstrual, M; follicular, F; ovulatory, O; early luteal, EL; and late luteal, LL). Carotid arterial compliance (simultaneous ultrasound and applanation tonometry) varied cyclically, with significant increases from the values seen in M (0.164 ± 0.036 mm2 mmHg,1) and F (0.171 ± 0.029 mm2 mmHg,1) to that seen in the O phase (0.184 ± 0.029 mm2 mmHg,1). Sharp declines were observed in the EL (0.150 ± 0.033 mm2 mmHg,1) and LL phases (0.147 ± 0.026 mm2 mmHg,1; F= 8.51, P < 0.05). Pulse wave velocity in the leg (i.e. peripheral arterial stiffness) did not exhibit any significant changes. Fluctuations in carotid arterial elasticity correlated with the balance between oestradiol and progesterone concentrations. No significant changes were found in carotid and brachial blood pressures, carotid artery lumen diameter, or IMT throughout the menstrual cycle. These data provide evidence that the elastic properties of central, but not peripheral, arteries fluctuate significantly with the phases of the menstrual cycle. [source]

Rapid measurement of aortic wave velocity: In vivo evaluation

MAGNETIC RESONANCE IN MEDICINE, Issue 1 2001
Kenneth A. Kraft
Abstract A 1D MR sequence has been developed for determining aortic flow wave velocity (WV), a metric of arterial compliance, within a single cardiac cycle. Studies were carried out on the thoracic aortas of 10 normal volunteers. Correlative WV data were also acquired from each subject using a conventional phase-velocity 2D mapping technique. Aortic WV in this cohort was found to range from 411 to 714 cm/s and was highly correlated (R = 0.95) between the two methods. Peak blood velocity was also measured using both methods and found to agree closely. The reproducibility of WV measurements using the rapid 1D method averaged 7.6%, which is comparable or better than that achieved using existing noninvasive techniques. Magn Reson Med 46:95,102, 2001. © 2001 Wiley-Liss, Inc. [source]

Relationship between vascular calcification, arterial stiffness and bone mineral density in a cross-sectional study of prevalent Australian haemodialysis patients

NEPHROLOGY, Issue 1 2009
NIGEL D TOUSSAINT
SUMMARY Background: Cardiovascular disease in dialysis patients is associated with increased vascular calcification (VC) and arterial stiffness, both inversely correlated with bone mineral density (BMD). Few studies have correlated VC in the dialysis population with measurements of BMD and arterial compliance. Methods: We report cross-sectional data on 45 haemodialysis (HD) patients assessing the prevalence of VC and its associations. Patients had computed tomography scans through abdominal aorta and superficial femoral arteries (SFA) to determine VC, pulse wave velocity (PWV) using SphygmoCor device measuring arterial stiffness, and dual-energy X-ray absorptiometry (DXA) to determine BMD. Results: Patients, 64% male, 38% diabetic, had median age 58 years. Mean PWV was 8.7 ± 3.5 m/s and median aortic VC score 488.1 ± 298 Hounsfield units, with 91% having aortic VC present. In univariate linear regression analysis, aortic VC correlated positively with length of HD (P = 0.03) and diabetes (P = 0.06). Increasing PWV was positively associated with age (P = 0.001), diabetes (P = 0.05) and VC (aortic P = 0.08, SFA P = 0.01). In multivariate regression analysis, length of HD and diabetes were significantly associated with aortic VC, whereas age and diabetes were associated with SFA VC and PWV. Mean lumbar spine and femoral neck T-scores on DXA were 0.14 and ,1.66 respectively. Conclusion: Increased VC and reduced arterial compliance, both closely related, are common in Australian HD patients. Both are associated with diabetes and increasing age, and greater aortic VC is seen with longer duration of dialysis. [source]

Increased arterial stiffness in children and adolescents with type 1 diabetes: no association between arterial stiffness and serum levels of adiponectin

PEDIATRIC DIABETES, Issue 1 2010
Angela Galler
Galler A, Heitmann A, Siekmeyer W, Gelbrich G, Kapellen T, Kratzsch J, Kiess W. Increased arterial stiffness in children and adolescents with type 1 diabetes: no association between arterial stiffness and serum levels of adiponectin. Objective: Type 1 diabetes is associated with an increased risk of atherosclerosis. Adiponectin serum levels correlate inversely with cardiovascular disease in adults. The aim of this study was to examine associations between arterial stiffness indices and serum adiponectin concentrations in children and adolescents with type 1 diabetes and to study the impact of metabolic control. Subjects and methods: We evaluated arterial stiffness, distensibility, and compliance in 93 children and adolescents with type 1 diabetes and correlated the data with clinical parameters and HbA1c levels. The control group comprised 85 matched healthy children. Serum levels of adiponectin in children with diabetes were measured by enzyme-linked immunoassay and correlated with arterial stiffness indices. Results: Arterial stiffness was significantly increased in children and adolescents with type 1 diabetes (aged 13.0 ± 3.8 yr) compared with matched healthy children (p = 0.03). Arterial stiffness was elevated in males with type 1 diabetes compared with females (p = 0.023). Arterial distensibility was significantly lower in children with diabetes compared with healthy controls (p = 0.025). Arterial stiffness, distensibility, and compliance did not correlate with diabetes duration, level of HbA1c, or serum cholesterol. Adiponectin concentrations in children and adolescents with diabetes were significantly elevated compared with normal values based on gender, age, and body mass index. We found no significant associations between arterial stiffness indices and adiponectin levels in children with type 1 diabetes. Conclusions: Children and adolescents with type 1 diabetes had increased arterial stiffness and reduced arterial distensibility and arterial compliance. However, no associations between arterial functional alterations and adiponectin concentrations were seen. [source]

Screening for atherosclerosis in patients with rheumatoid arthritis: Comparison of two in vivo tests of vascular function

ARTHRITIS & RHEUMATISM, Issue 1 2003
S. Van Doornum
Objective Inflammation appears to play a central role in atherosclerosis, and endothelial damage mediated by systemic inflammation may contribute to the increased cardiovascular mortality in rheumatoid arthritis (RA). Brachial artery flow-mediated dilatation (FMD) and pulse wave analysis (PWA) are measures of vascular function. The aim of this study was to determine if FMD and PWA are abnormal in patients with RA. Methods Twenty-five RA patients and 25 matched healthy controls were studied. All were free of traditional cardiovascular risk factors. FMD was measured in all subjects. PWA was performed in 18 RA patients and 18 controls, with results expressed as large and small artery compliance (C1 and C2). Modified Sharp scores were calculated in 13 RA patients. Results Results (mean ± SD) in RA patients and controls, respectively, were as follows: FMD 107.6 ± 4.6% versus 108.5 ± 4.1% (P = 0.49), C1 14.8 ± 2.8 ml/mm Hg × 10 versus 17.9 ± 3.1 ml/mm Hg × 10 (P = 0.0033), C2 4.5 ± 2.3 ml/mm Hg × 100 versus 7.7 ± 3.7 ml/mm Hg × 100 (P = 0.0039). There was an inverse correlation between C2 and modified Sharp scores in the RA patients (Spearman's rho ,0.69, P = 0.0085). Conclusion FMD was normal in these RA patients, whereas arterial compliance was markedly reduced. PWA appears to be a more sensitive measure of vascular dysfunction than FMD in RA and may be the preferred surrogate marker of vascular dysfunction in longitudinal studies of RA patients. The inverse correlation between C2 and the modified Sharp score, a measure that reflects disease activity over time, supports the notion that chronic inflammation plays a role in RA-associated atherosclerosis. [source]

RELATIONSHIP BETWEEN ARTERIAL STIFFNESS AND GLUCOSE METABOLISM IN WOMEN WITH METABOLIC SYNDROME

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 9 2006
Paul Nestel
SUMMARY 1Cardiovascular risk factors associated with the metabolic syndrome affect vascular functions adversely. The aim of the present study was to assess the relationship between parameters of glucose homeostasis and arterial stiffness in women with characteristics of the metabolic syndrome. 2Twenty post-menopausal women participated in a cross-sectional study in which systemic arterial compliance (SAC) and plasma glucose, lipids and glycosylated haemoglobin (HbA1c) were measured while subjects were maintained on a diet high in fibre, raised in protein and reduced in saturated fat. 3Regression analysis suggested that mean ( SD) fasting glucose of 5.9 ± 1.7 mmol/L, glucose levels 2 h after a 75 g glucose load of 6.8 ± 3.6 mmol/L, systolic blood pressure of 131 ± 12 mmHg and HbA1c of 5.3 ± 1.7% predicted SAC negatively. The following correlations were obtained between SAC and: (i) fasting glucose: R = -0.49, P = 0.028; (ii) 2 h glucose level post-glucose load: R = -0.42, P = 0.064; (iii) HbA1c: R = -0.42, P = 0.056; and (iv) systolic blood pressure: R = -0.55, P = 0.012. 4Relationships between SAC and fasting glucose and systolic blood pressure were significantly independent of each other. There was no evidence of relationships between SAC and any plasma lipid parameter (other than a trend in relation to plasma triglyceride), bodyweight or waist circumference. 5In conclusion, in post-menopausal women with metabolic syndrome, fasting plasma glucose and systolic blood pressure, and possibly HbA1c and the 2 h glucose post-glucose load, predicted increased arterial stiffness. [source]

Experimental and clinical study of the combined effect of arterial stiffness and heart rate on pulse pressure: Differences between central and peripheral arteries

Large Artery Stiffness: Implications For Exercise Capacity And Cardiovascular Risk

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 3 2002
Bronwyn A Kingwell
SUMMARY 1. Large artery stiffness, or its inverse, compliance, determines pulse pressure, which, in turn, influences myocardial work capacity and coronary perfusion, both of which impact on exercise capacity and cardiovascular risk. 2. In support of a role for arterial properties in exercise performance, aerobically trained athletes (aged 30,59 years) have lower arterial stiffness than their sedentary counterparts. Furthermore, in healthy older subjects (aged 57,80 years), time to exhaustion on treadmill testing correlated positively with arterial compliance. 3. Arterial stiffness is more closely linked to exercise capacity and myocardial risk in patients with coronary disease where, independently of degree of coronary disease, those with stiffer proximal arteries have a lower exercise-induced ischaemic threshold. 4. Moderate aerobic training elevates resting arterial compliance by approximately 30%, independently of mean pressure reduction, in young healthy individuals but not in isolated systolic hypertensive patients. Rat training studies support a role for exercise training in structural remodelling of the large arteries. 5. High-resistance strength training is associated with stiffer large arteries and higher pulse pressure than matched controls. 6. Large artery stiffness is an important modulator of the myocardial blood supply and demand equation, with significant ramifications for athletic performance and ischaemic threshold in coronary disease patients. Moderate aerobic training, but not high-resistance strength training, reduces large artery stiffness in young individuals whereas older subjects with established isolated systolic hypertension are resistant to such adaptation. [source]

Atherosclerosis measured by whole body magnetic resonance angiography and carotid artery ultrasound is related to arterial compliance, but not to endothelium-dependent vasodilation , the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study

Cardiovascular changes induced by cold water immersion during hyperbaric hyperoxic exposure

CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 5 2007
Alain Boussuges
Summary The present study was designed to assess the cardiac changes induced by cold water immersion compared with dry conditions during a prolonged hyperbaric and hyperoxic exposure (ambient pressure between 1·6 and 3 ATA and PiO2 between 1·2 and 2·8 ATA). Ten healthy volunteers were studied during a 6 h compression in a hyperbaric chamber with immersion up to the neck in cold water while wearing wet suits. Results were compared with measurements obtained in dry conditions. Echocardiography and Doppler examinations were performed after 15 min and 5 h. Stroke volume, left atrial and left ventricular (LV) diameters remained unchanged during immersion, whereas they significantly fell during the dry session. As an index of LV contractility, percentage fractional shortening remained unchanged, in contrast to a decrease during dry experiment. Heart rate (HR) significantly decreased after 5 h, although it had not changed during the dry session. The changes in the total arterial compliance were similar during the immersed and dry sessions, with a significant decrease after 5 h. In immersed and dry conditions, cardiac output was unchanged after 15 min but decreased by almost 20% after 5 h. This decrease was related to a decrease in HR during immersion and to a decrease in stroke volume in dry conditions. The hydrostatic pressure exerted by water immersion on the systemic vessels could explain these differences. Indeed, the redistribution of blood volume towards the compliant thoracic bed may conceal a part of hypovolaemia that developed in the course of the session. [source]

The obligatory role of the kidney in long-term arterial blood pressure control: extending Guyton's model of the circulation

ANAESTHESIA, Issue 11 2009
K. L. Dorrington
Summary We describe a model for the essential role of the kidney in long-term blood pressure regulation. We begin with a simple hydraulic model for the circulation, with a constant circulating volume. We show, with the help of a modification of Guyton's classic diagram, that cardiac output and mean arterial pressure are functions of circulating volume, peripheral resistance, venous and arterial compliances, and the cardiac Starling curve. This approach models only acute changes in a ,closed' circulation , one where there is no intake or excretion of fluid. The model is then adapted to ,open' the circulation, include a role for the kidney, and represent more chronic changes. Arterial pressure is then a sole function of renal behaviour and daily sodium (and liquid) intake, and becomes independent of other cardiovascular variables. As well as generating specific hypotheses for further investigation, these models can be used for the purpose of education in cardiovascular control and the treatment of hypertension. [source]

Acute and Chronic Oral Magnesium Supplementation: Effects on Endothelial Function, Exercise Capacity, and Quality of Life in Patients With Symptomatic Heart Failure