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Vascular Compliance (vascular + compliance)
Selected AbstractsRegulatory processes interacting to maintain hepatic blood flow constancy: Vascular compliance, hepatic arterial buffer response, hepatorenal reflex, liver regeneration, escape from vasoconstrictionHEPATOLOGY RESEARCH, Issue 11 2007W. Wayne Lautt Constancy of hepatic blood flow (HBF) is crucial for several homeostatic roles. The present conceptual review focuses on interrelated mechanisms that act to maintain a constant HBF per liver mass. The liver cannot directly control portal blood flow (PF); therefore, these mechanisms largely operate to compensate for PF changes. A reduction in PF leads to reduced intrahepatic distending pressure, resulting in the highly compliant hepatic vasculature passively expelling up to 50% of its blood volume, thus adding to venous return, cardiac output and HBF. Also activated immediately upon reduction of PF are the hepatic arterial buffer response and an HBF-dependent hepatorenal reflex. Adenosine is secreted at a constant rate into the small fluid space of Mall which surrounds the terminal branches of the hepatic arterioles, portal venules and sensory nerves. The concentration of adenosine is regulated by washout into the portal venules. Reduced PFreduces the washout and the accumulated adenosine causes dilation of the hepatic artery, thus buffering the PF change. Adenosine also activates hepatic sensory nerves to cause reflex renal fluid retention, thus increasing circulating blood volume and maintaining cardiac output and PF. If these mechanisms are not able to maintain total HBF, the hemodynamic imbalance results in hepatocyte proliferation, or apoptosis, by a shear stress/nitric oxide-dependent mechanism, to adjust total liver mass to match the blood supply. These mechanisms are specific to this unique vascular bed and provide an excellent example of multiple integrative regulation of a major homeostatic organ. [source] Subclinical vascular alterations in young adults with type 1 diabetes detected by arterial tonometryDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 8 2009I. 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] 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 2009Stefan 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] Acute Stent Thrombosis in the Setting of Cocaine Abuse Following Percutaneous Coronary InterventionJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 1 2009JOHN N. MAKARYUS M.D. The treatment of acute coronary syndrome (ACS) in patients with documented cocaine abuse has always presented significant challenges. Issues related to medication compliance, the potential risks of beta adrenergic blockade, and possible continued cocaine abuse postmyocardial infarction necessitate a unique, individualized approach to these patients. Recent data in the era of extensive percutaneous coronary interventions (PCI) and intracoronary stent (ICS) implantation have raised questions regarding the safety of ICS in patients who may revert to cocaine abuse postacute coronary syndrome as a result of the potentially higher risk of stent thrombosis in these patients. While the precise reason as to why cocaine use may increase the risk of stent thrombosis is not fully understood, it is likely the result of a confluence of factors, including coronary vessel vasoconstriction, impaired vascular compliance, as well as the platelet-activating effect of cocaine. We present the case a 46-year-old male with a history of cocaine abuse who presented with an acute stent thrombosis 2 days post-PCI likely as a result of cocaine abuse on the day of discharge following initial stent implantation for a non-ST-elevation myocardial infarction (NSTEMI). We also review the literature regarding the safety of PCI in cocaine abusers. [source] Aldosterone receptor antagonists , how cardiovascular actions may explain their beneficial effects in heart failureJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 2 2010P. OVAERT Ovaert, P., Elliott, J., Bernay, F., Guillot, E., Bardon, T. Aldosterone receptor antagonists , how cardiovascular actions may explain their beneficial effects in heart failure. J. vet. Pharmacol. Therap.33, 109,117. Historically, aldosterone receptor antagonists (ARA) have been classified as ,potassium sparing diuretics'. However, the positive effect of spironolactone, the most extensively studied ARA, on morbidity and mortality observed in humans suffering cardiac insufficiency could not be explained by the renal effect of the drug alone, and a pivotal clinical study has led to extensive research. Many experimental studies have demonstrated that ARA have previously unexpected beneficial effects on the cardiovascular system including reduction in remodelling of the vascular smooth muscle cells and myocytes and improvement of endothelial cell dysfunction in heart failure. These effects improve vascular compliance and slow down the progression of left ventricular dysfunction and end-organ damage. Furthermore, aldosterone receptor blockade also restores the baroreceptor reflex, improving heart rate variability in heart failure in humans. Some of these effects have been demonstrated in dog models of cardiac disease and so justified further investigation of the potential benefit of ARA in dogs with congestive heart failure (CHF). Positive effects of spironolactone on morbidity and mortality appear to have been seen in studies conducted in dogs suffering from naturally occurring CHF. In addition, eplerenone has been shown to have benefits in canine models of heart failure. The precise mechanisms by which ARA produce these beneficial effects in dogs remain to be determined but this group of drugs clearly provide therapeutic actions out-with their diuretic effects. [source] Low plasma volume following pregnancy complicated by pre-eclampsia predisposes for hypertensive disease in a next pregnancyBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 11 2003Robert Aardenburg Objective A large number of women with a history of pre-eclampsia/HELLP have a low plasma volume at least six months postpartum. The objective of this study was to determine whether a low plasma volume in formerly pre-eclamptic women and HELLP patients is associated with an increased risk for recurrent hypertensive complications in a next pregnancy. Design Prospective observational study. Setting Tertiary obstetric centre. Sample Formerly pre-eclamptic women and controls. Methods In 316 women with a history of pre-eclampsia and/or HELLP, we measured, plasma volume along with haemodynamic, metabolic and haemostatic variables at least six months postpartum. A group of 22 healthy parous controls was used as a reference. After standardising plasma volume for body mass index, women were subdivided into normotensive and normal plasma volume (n = 199), normotensive and low plasma volume (n = 76) and hypertensive (n = 41) subgroups, which were compared for demography, clinical parameters and course of a next pregnancy. Main outcome measures Recurrent hypertensive disease of pregnancy. Results Relative to the normal plasma volume subgroup, normotensive women in the low plasma volume subgroup have a higher body mass index, a lower total vascular compliance and a shorter estimated systemic circulation time. They have a higher HOMA index and higher fasting triglyceride levels. In normotensive and hypertensive former patients alike, low plasma volume is associated with a higher recurrence of hypertensive complications in a next pregnancy compared with normotensive women with normal plasma volume. Conclusion Low plasma volume in normotensive women with a history of pre-eclampsia and/or HELLP is associated with overweight, reduced vascular compliance and insulin resistance and a predisposition for recurrent pre-eclampsia and HELLP syndrome in a next pregnancy. [source] | ||||||||||