scholarly journals Modeling of Hemodynamics in a Vascular Bioprosthesis

2021 ◽  
Vol 16 (1) ◽  
pp. 15-28
Author(s):  
P. Onishchenko ◽  
Yu. Zakharov ◽  
V. Borisov ◽  
K. Klyshnikov ◽  
E. Ovcharenko ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Flow Velocity ◽  
Flow Structure ◽  
Numerical Comparison ◽  
Vascular Bed ◽  
Inner Surface ◽  
Implantation Method ◽  
Complicated Task

The study of blood flow in vascular bioprostheses is a rather complicated task, since the shape of the inner surface of the bioprosthesis is variable, due to xenogenic origin. Because of this, vortex zones can occur inside the vascular bioprosthesis. In addition, the flow structure may contain sections where the flow velocity is abnormally high. It is all the more difficult to assess the nature of the course when using this vascular bioprosthesis as a shunt. A numerical comparison of the blood flow in a bioprosthesis connected to the main vascular bed using the «end-to-end» and «end-to-side» methods (bypass) taking into account the heart rate and blood pressure was performed. It is shown that, due to the nonlinearity of the initial bioprosthesis geometry, the implantation method affects the blood flow. Because of this, vortex zones arise and, with certain combinations of parameters, the effects of «separation» of vortices.

scholarly journals Assessment of Functional Hemispheric Asymmetry by Bilateral Simultaneous Cerebral Blood Flow Velocity Monitoring

1997 ◽  
Vol 17 (5) ◽  
pp. 577-585 ◽  
Author(s):  
Jürgen Klingelhöfer ◽  
Gernot Matzander ◽  
Dirk Sander ◽  
Jens Schwarze ◽  
Henning Boecker ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Flow Velocity ◽  
Transcranial Doppler ◽  
Spatial Task ◽  
Hemispheric Dominance ◽  
Left And Right ◽  
End Tidal ◽  
Overt Speech

The aim of this study was to investigate side-to-side differences of simultaneously measured middle cerebral artery (MCA) blood flow velocities during various hemisphere-specific tasks. Using a transcranial Doppler device, flow velocity changes of 24 healthy, right-handed subjects were monitored simultaneously in the left and right MCA during different hemisphere-specific tasks. Mean flow velocity (MFV) curves were averaged for each individual subject and task. Simultaneously, heart rate, blood pressure and end-tidal carbon dioxide (CO2) were measured in a subgroup of six subjects. When compared with the resting state, all stimuli produced significant ( p < 0.001) bilateral MFV increases, ranging from 2.5–9.2%. A lateralization of MFV increases with a significantly ( p < 0.001) more pronounced increase in MFV in the hemisphere contralateral to the performing hand was observed both during simple sequential finger movements and a complex spatial task. During the complex spatial task, consistently higher MFV increases were observed in the right MCA ( p < 0.001), regardless of the side of task performance. Recognition of pictorial material presented as part of a memory task, also resulted in a side-to-side difference of respective MFV increases (right > left, p < 0.001), whereas memorization did not. Whereas bilateral MFV elevations observed during stimulation with white noise were only discrete and not lateralized, exposure to overt speech produced significantly higher ( p < 0.001) MFV increases in the left MCA. The time course of the MFV reaction showed a rapid increase with an initial maximum after 4–5 s. Heart rate, blood pressure, and end-tidal CO2 showed only subtle changes during the stimulation periods. In conclusion, the observed side-to-side differences of MFV reaction in the left and right MCA concur with current functional imaging data. Bilateral simultaneous repetitive transcranial Doppler monitoring is a sensitive method to detect cerebral perfusion asymmetries caused by hemisphere-specific activation, and thus may be helpful for noninvasive assessment of hemispheric dominance for language.

Case 16: Autonomic Failure or Postural Tachycardia Syndrome?

2019 ◽  
pp. 120-124
Author(s):  
Peter Novak
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Cerebral Blood Flow Velocity ◽  
Postural Tachycardia Syndrome ◽  
Postural Tachycardia ◽  
Transient Elevation

Small fiber neuropathy is associated with adrenergic failure. Anxiety is common and occasionally can be identified as a transient elevation of heart rate, blood pressure, and cerebral blood flow velocity.

Case 31: Hypocapnic Cerebral Hypoperfusion with an Artifact

2019 ◽  
pp. 194-197
Author(s):  
Peter Novak
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Cerebral Blood Flow Velocity ◽  
Cerebral Hypoperfusion ◽  
Autonomic Functions ◽  
Raw Data

In this patient, the initial decline in blood pressure at the tilt onset was physiologic since it was accompanied by the decline in cerebral blood flow velocity and heart rate responses. The testing revealed normal autonomic functions. It is important always to check the raw data. Blood pressure from the finger cuff is not always accurate.

Abstract 13868: Effects of Chronic Electronic Cigarette Vapor Exposures on the Cardiovascular Function in Rats

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Wangde Dai ◽  
Jianru Shi ◽  
Juan Carreno ◽  
Lifu zhao ◽  
Michael T Kleinman ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Flow Velocity ◽  
Femoral Artery ◽  
Blood Flow Velocity ◽  
Cardiovascular Function ◽  
Artery Occlusion ◽  
Left Ventricular

Background: We investigated the effects of chronic electronic cigarettes with nicotine (E-Cig) exposure on cardiovascular function in rats. Methods: Adult Sprague Dawley rats were exposed to either pure air (n=10) or E-Cig (n=14) for 12 weeks. After 12 weeks of exposure, flow-mediated vasodilation was measured in anesthetized rats with ultrasound to measure femoral artery diameter. Femoral artery flow velocity was measured before and 5 minutes after reperfusion of a 5-minute femoral artery occlusion. Cardiac function was assessed by echocardiogram. A Millar catheter was used to record systemic arterial and LV pressures. Cardiac output was measured using a themodilution catheter. Results: The femoral artery internal diameter and blood flow velocity were comparable between the 2 groups before and after artery occlusion. However, in the E-cig group, blood flow velocity significantly decreased from 55.5 ± 5.2 cm/s prior to occlusion to 41.3 ± 4.1 cm/s after reperfusion (p = 0.005); it remained similar prior to (47.8 ± 3.4 cm/s) and after (47.8 ± 5.5 cm/s) occlusion in the air group. There were no statistically significant differences in left ventricular diastolic and systolic dimensions, LV fractional shortening, heart rate or mean blood pressure (80 ± 3 mmHg in air and 79 ± 5 mmHg in E-cig group) , LV end-diastolic pressure (Ped), end-systolic pressure (Pes), peak -dP/dt, Tau, or cardiac output (48.3 ± 3.3 ml/min in air and 47.6 ± 3.9 ml/min in E-cig group) between the E-Cig and the pure air group. There was a trend toward a reduction in peak LV +dP /dt in the E-Cig group (5574 ± 341 mmHg/s) compared to the air group (6166 ± 238 mmHg/s). LV weight and wall thickness were similar between groups. Conclusions: Twelve weeks of E-Cig exposure did not affect heart rate or blood pressure; but did tend to reduce contractility. E-cigarette exposure slowed the flow-mediated blood flow velocity probably at a microvascular level, possibly by altering endothelial function.

scholarly journals Endurance training reduces renal vasoconstriction to orthostatic stress

2010 ◽  
Vol 298 (2) ◽  
pp. F279-F284 ◽  
Author(s):  
Erin E. Conboy ◽  
Amy E. Fogelman ◽  
Charity L. Sauder ◽  
Chester A. Ray
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Flow Velocity ◽  
Endurance Training ◽  
Renal Blood Flow ◽  
Blood Flow Velocity ◽  
Vascular Conductance ◽  
Renal Vasoconstriction ◽  
Arterial Blood

Endurance training has been associated with increased orthostatic intolerance. The purpose of the present study was to test the hypothesis that endurance training reduces renal vasoconstriction to orthostatic stress. Blood pressure, heart rate, and renal blood flow velocity were measured during a 25-min 60° head-up tilt (HUT) test before and after 8 wk of endurance training in eight healthy sedentary subjects (26 ± 1 yrs). Training elicited a 21 ± 3% increase in peak oxygen uptake (V̇o2peak) and a reduction in heart rate at rest of 8 ± 2 beats/min. During HUT, heart rate progressively increased (∼20 beats/min) over the 25-min HUT trial both before and after training. Systolic arterial blood pressure during HUT was unchanged with training, whereas diastolic arterial blood pressure was lower at the end of HUT after training. Before training renal blood flow velocity (Δ14 ± 5 cm/s) and renal vascular conductance (Δ22 ± 7%) decreased during HUT, whereas after training renal blood flow velocity (Δ2 ± 5 cm/s) and renal vascular conductance (Δ1 ± 12%) did not change significantly during HUT. Renal blood flow velocity and vascular conductance responses to HUT did not change in control subjects during the 8-wk period. These results demonstrate that endurance training reduces renal vasoconstriction during an orthostatic challenge and may contribute to training-induced orthostatic intolerance.

Blood pressure, heart rate, and adrenal catecholamines prior to ventricular fibrillation

1961 ◽  
Vol 201 (1) ◽  
pp. 109-111 ◽  
Author(s):  
Noel M. Bass ◽  
Vincent V. Glaviano
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Ventricular Fibrillation ◽  
Coronary Occlusion ◽  
Marked Decrease ◽  
Mean Blood Pressure ◽  
Plasma Adrenaline ◽  
Acute Coronary Occlusion ◽  
Before And After

Heart rate, mean blood pressure, adrenal blood flow, and adrenal plasma adrenaline and noradrenaline were compared before and after ligation of the anterior descending coronary artery in dogs anesthetized with chloralose. One group of 12 dogs responded to acute coronary occlusion with a sudden and marked decrease in mean blood pressure (mean, 31%) and heart rate (mean, 18%) followed by an early onset (mean, 227 sec) of ventricular fibrillation. Another group of nine dogs responded with slight decreases in mean blood pressure (mean, 13%) and heart rate (mean, 5%), during which time ventricular fibrillation occurred late (mean, 30 min) or not at all. While the two groups were statistically different in mean blood pressure and heart rate, the minute output of adrenal catecholamines in either group was not found to be related to the early or late occurrence of ventricular fibrillation.

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