Search results for "Flow velocity"
showing 10 items of 227 documents
Relative sensitivity of four noninvasive methods in assessing systolic cardiovascular effects of isoproterenol in healthy volunteers.
1992
Study objective The study was performed to evaluate the relative sensitivity of various noninvasive methods to detect and describe the systolic cardiovascular effects of stepwise increasing doses of isoproterenol: two-dimensional left ventricular echocardiography (main variable, ejection fraction), ACVF (attenuation compensated volume flow)–dual-beam Doppler echoaortography (time-averaged mean velocity), electrical impedance cardiography [(dZ/dtmax)/RZ index], and systolic time intervals from mechanocar-diography (PEP and QS2c). Methods Isoproterenol was administered by constant rate intravenous infusion in consecutive steps of 0.1, 0.2, 0.4, 0.75, and 1.5 µg/min (each for 15 minutes). Sali…
Loss of the preconditioning effect of rosuvastatin during sustained therapy: a human in vivo study
2011
Studies have demonstrated that the acute administration of 3-hydroxy-3 methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors has protective effects in the setting of ischemia-reperfusion (IR). Previously, we demonstrated that a single dose of rosuvastatin prevented IR-induced endothelial dysfunction in humans through a cyclooxygenase-2-dependent mechanism. Whether the chronic administration of HMG-CoA reductase inhibitors provides similar protection remains controversial and is unknown in humans. Eighteen male volunteers were randomized to receive a single dose of rosuvastatin (20 mg) or placebo. Twenty-four hours later, endothelium-dependent, radial artery flow-mediated dilation (FMD) w…
Transcranial Doppler diagnosis of cerebral vasospasm following subarachnoid haemorrhage: correlation and analysis of results in relation to the age o…
1994
A retrospective analysis was undertaken to determine whether cerebral vasospasm following subarachnoid haemorrhage (SAH) correlates with the age of patients. For at least 3 weeks after bleeding 80 subjects underwent very close follow-up with clinical examination and transcranial Doppler records of the blood velocities within the basal cerebral arteries. Firstly a correlation between measured maximal mean blood flow velocities and age was made. Secondly, according to their age and the maximum of recorded mean velocities (v), the patients were divided into groups as follows: age 55 years or less, age more than 55 years; and maximum velocity v190 cm/s, 90 cm/sv2120 cm/s, 120 cm/sv3160 cm/s, v4…
Exploring metrics for the characterization of the cerebral autoregulation during head-up tilt and propofol general anesthesia
2022
Techniques grounded on the simultaneous utilization of Tiecks' second order differential equations and spontaneous variability of mean arterial pressure (MAP) and mean cerebral blood flow velocity (MCBFV), recorded from middle cerebral arteries through a transcranial Doppler device, provide a characterization of cerebral autoregulation (CA) via the autoregulation index (ARI). These methods exploit two metrics for comparing the measured MCBFV series with the version predicted by Tiecks' model: normalized mean square prediction error (NMSPE) and normalized correlation rho. The aim of this study is to assess the two metrics for ARI computation in 13 healthy subjects (age: 27 & PLUSMN; 8 yr…
Control for carbon dioxide-related changes in flow velocity by transcranial Doppler monitoring.
1994
Transcranial Doppler ultrasonography can monitor changes in intracranial blood flow velocity over time in a variety of experimental and clinical settings with excellent temporal resolution. Alterations in arterial carbon dioxide pressure exert a profound influence on blood flow velocity. Such changes exhibit important individual fluctuation depending on respiratory status. This limits the ability of transcranial Doppler to accurately study subtle changes in blood flow velocity, independent of the respiratory state of the subject. Suggested here is a method to control for the respiration artifact on blood flow velocity. The middle cerebral artery of 7 healthy male volunteers was studied with…
Relationship between albumin excretion rate and aortic stiffness in untreated essential hypertensive patients
2004
. Objectives. To evaluate, in a group of nondiabetic essential hypertensive patients with normal renal function, the relationship between albumin excretion rate (AER) and carotid-femoral pulse wave velocity (PWV), as an index of aortic stiffness. Design. Cross-sectional study. Setting. Outpatient hypertension clinic. Subjects. Seventy patients with mild-to-moderate essential hypertension, aged 42 ± 8 years, never pharmacologically treated. All subjects underwent routine laboratory tests, 24-h ambulatory blood pressure (BP) monitoring, measurement of carotid-femoral PWV, by means of a computerized method, and AER. Results. Microalbuminuric patients (AER ≥ 20 μg min−1; n = 19), when comp…
The preoperative assessment of stroke risk in lesions involving the internal carotid artery.
1995
Patients with vascular or tumourous lesions involving the internal carotid artery are at risk of damage or occlusion of this vessel during surgical or endovascular procedures. To assess the stroke risk transcranial Doppler aided carotid compression tests were performed in 82 patients. Based on changes of blood flow velocity (BFV), pulsatility index, systolic/diastolic ratio and length of transient hyperaemic response three groups could be differentiated. Patients in group A (31%) showed only a slight reaction of BFV and were at minimal risk in case of carotid occlusion. Patients in group B (52%) underwent a distinct decrease of Doppler readings with partial improvement and were considered t…
Dose-dependent effects of decaffeinated coffee on endothelial function in healthy subjects
2009
ackground/Objectives: Coffee is known to contain antioxidant substances whose effects may be blunted because of caffeine that may unfavorably affect the cardiovascular system. This study was designed to investigate the acute dose-dependent effects of decaffeinated coffee (DC) on endothelial function measured by the brachial artery flow-mediated dilation (FMD). Subjects/Methods: A total of 15 (8 men and 7 women) healthy nonobese subjects underwent a single-blind, crossover study. Subjects ingested one and two cups of decaffeinated Italian espresso coffee in random order at 5- to 7-day intervals. Results: In the hour following the ingestion of two cups of DC, FMD increased (mean±s.e.m.): 0 mi…
Noninvasive assessment of pulmonary hemodynamics in patients with chronic thromboembolic pulmonary hypertension by high temporal resolution phase-con…
2013
Background— Right heart catheterization is the gold standard for assessment of pulmonary hemodynamics in patients with chronic thromboembolic pulmonary hypertension. To date, MRI has not been able to produce precise measurements of mean pulmonary arterial pressure (mPAP). The purpose of the study was to create a model for estimating mPAP and pulmonary vascular resistance in patients with chronic thromboembolic pulmonary hypertension by high temporal resolution phase-contrast MRI (PC-MRI) and to correlate the results with simultaneously acquired, invasive catheter-based measurements (simultaneously measured mPAP) and with right heart catheterization measurements. Methods and Results— A tota…
Left ventricular diastolic filling alterations in subjects with mitral valve prolapse: A Doppler echocardiographic study
1993
To assess left ventricular diastolic filling in mitral valve prolapse (MVP), we studied 22 patients with idiopathic MVP and 22 healthy controls matched for sex, age, body surface area and heart rate. A two-dimensional, M-mode and Doppler echocardiographic examination was performed to exclude any cardiac abnormalities. The two groups had similar diastolic and systolic left ventricular volumes, left ventricle mass and ejection fraction. Doppler measurements of mitral inflow were: E and A areas (the components of the total flow velocity-time integral in the early passive period of ventricular filling, E; and the late active period of atrial emptying, A), the peak E and A velocities (cm.s-1), a…