Evaluation of Hemodynamics in a Prestressed and Compliant Tapered Femoral Artery Using an Optimization-Based Inverse Algorithm

The important factors that affect the arterial wall compliance are the tissue properties of the arterial wall, the in vivo pulsatile pressure, and the prestressed condition of the artery. It is necessary to obtain the load-free geometry for determining the physiological level of prestress in the arterial wall. The previously developed optimization-based inverse algorithm was improved to obtain the load-free geometry and the wall prestress of an idealized tapered femoral artery of a dog under varying arterial wall properties. The compliance of the artery was also evaluated over a range of systemic pressures (72.5–140.7 mmHg), associated blood flows, and artery wall properties using the prestressed arterial geometry. The results showed that the computed load-free outer diameter at the inlet of the tapered artery was 6.7%, 9.0%, and 12% smaller than the corresponding in vivo diameter for the 25% softer, baseline, and 25% stiffer arterial wall properties, respectively. In contrast, the variations in the prestressed geometry and circumferential wall prestress were less than 2% for variable arterial wall properties. The computed compliance at the inlet of the prestressed artery for the baseline arterial wall property was 0.34%, 0.19%, and 0.13% diameter change/mmHg for time-averaged pressures of 72.5, 104.1, and 140.7 mmHg, respectively. However, the variation in compliance due to the change in arterial wall property was less than 6%. The load-free and prestressed geometries of the idealized tapered femoral artery were accurately (error within 1.2% of the in vivo geometry) computed under variable arterial wall properties using the modified inverse algorithm. Based on the blood-arterial wall interaction results, the arterial wall compliance was influenced significantly by the change in average pressure. In contrast, the change in arterial wall property did not influence the arterial wall compliance.

Download Full-text

In vivo femoropopliteal arterial wall compliance in subjects with and without lower limb vascular disease

Journal of Vascular Surgery ◽

10.1016/s0741-5214(99)70020-0 ◽

1999 ◽

Vol 30 (5) ◽

pp. 936-945 ◽

Cited By ~ 46

Author(s):

Nigel R.M. Tai ◽

Alberto Giudiceandrea ◽

Henryk J. Salacinski ◽

Alexander M. Seifalian ◽

George Hamilton

Keyword(s):

Vascular Disease ◽

Lower Limb ◽

Arterial Wall ◽

Wall Compliance

Download Full-text

132 DIFFERENCES IN RESPIRATION RATES BETWEEN IN VIVO- AND IN VITRO-PRODUCED BOVINE EMBRYOS

Reproduction Fertility and Development ◽

10.1071/rdv18n2ab132 ◽

2006 ◽

Vol 18 (2) ◽

pp. 174

Author(s):

A. S. Lopes ◽

S. E. Madsen ◽

N. B. Ramsing ◽

L. H. Larsen ◽

T. Greve ◽

...

Keyword(s):

Metabolic Stress ◽

Average Diameter ◽

Blastocyst Stage ◽

Culture Conditions ◽

Outer Diameter ◽

Bovine Embryos ◽

Physiological Level ◽

Respiration Rates

In vitro-produced (IVP) bovine embryos differ (e.g. morphology and physiology) from their in vivo counterparts. Oxygen consumption is an indicator of the overall metabolic activity of a single embryo. Therefore, the aim of this study was to determine and compare respiration rates of in vivo- and in vitro-produced bovine day 7 embryos. Diameters of these two embryo types were also compared. In vivo embryos (n = 28) were recovered from 8 superovulated Holstein Frisian cows on day 7 following AI, while IVP embryos (n = 160; Holm et al. 1999 Theriogenology 52, 683-700) were used on day 7 after fertilization. Embryos were measured (outer diameter) and morphologically evaluated (Quality 1 to 4, IETS Manual, 1998). Only transferable in vivo embryos were used (i.e. excluding Quality 4). Respiration rates were measured on each embryo by Nanorespirometer technology (Lopes et al. 2005 Reprod. Fertil. Develop. 17, 151). Data were analyzed using Proc Mixed, and values are presented as mean � SEM. Values with different superscripts differ significantly (P < 0.05). The average respiration rates were 0.82 � 0.06a nL/h for in vivo vs. 1.37 � 0.06b nL/h for IVP embryos. The average respiration rates for the different morphological qualities were as follows (nL/h, numbers in brackets): IVP: 2.1 � 0.08a (38), 1.37 � 0.07b (55), 1.08 � 0.07c (48) and 0.62 � 0.11d (19) for Quality 1, 2, 3, and 4, respectively. In vivo: 1.17 � 0.21b,c,e (6), 0.80 � 0.15c,d,e (12), and 0.64 � 0.16d,f (10) for Quality 1, 2, and 3, respectively. The average diameter (mm) of in vivo and IVP embryos was 0.157 � 0.002a and 0.176 � 0.002b, respectively. Respiration rates were directly related to embryo diameter; larger embryos were associated with higher respiration rates (y = 17.55 � 1.32 nL/h � mm, n = 188). Respiration rates of in vivo embryos were significantly lower than those of IVP embryos, regardless of quality. This difference could reflect an effect of the culture conditions on IVP embryos because media components affect embryo metabolism. Moreover, the different ages (day 7 for IVP vs. approximately Day 6.5 for in vivo embryos, because in vivo embryos are less than 7 days after fertilization at recovery) and stages (IVP: up to expanded blastocyst stage; in vivo: morula or early blastocyst stage) could have influenced the results and also partly explain the smaller diameter of the in vivo embryos. Finally, respiration rates decreased proportionately to the morphological quality within embryo type, indicating that morphological differences are reflected at the physiological level. In conclusion, this study further outlines metabolic differences between in vivo and IVP bovine embryos. Whether such differences are a manifestation of metabolic stress associated to the separation from the natural environment or reflect suboptimal culture conditions is yet to be determined. ASL is supported by FCT, Portugal.

Download Full-text

Time Invariance Mechanical Arterial-Wall Properties: In-Vitro and In-Vivo Studio

IFMBE Proceedings - World Congress on Medical Physics and Biomedical Engineering May 26-31, 2012, Beijing, China ◽

10.1007/978-3-642-29305-4_102 ◽

2013 ◽

pp. 383-386

Author(s):

F. Pessana ◽

D. Bia ◽

Y. Zocalo ◽

L. Cymberknop ◽

R. Armentano

Keyword(s):

Arterial Wall ◽

Wall Properties ◽

Time Invariance

Download Full-text

Female sex Hormones do not Influence Arterial wall Properties during the Normal Menstrual Cycle

Clinical Science ◽

10.1042/cs0920487 ◽

1997 ◽

Vol 92 (5) ◽

pp. 487-491 ◽

Cited By ~ 32

Author(s):

Christine Willekes ◽

Henk J. Hoogland ◽

Hans A. Keizer ◽

Arnold P. Hoeks ◽

Robert S. Reneman

Keyword(s):

Menstrual Cycle ◽

Carotid Artery ◽

Femoral Artery ◽

Common Carotid Artery ◽

Arterial Wall ◽

Common Femoral Artery ◽

Cross Sectional ◽

Wall Properties ◽

Normal Menstrual Cycle ◽

The Common

1. In previous studies, the elastic properties of the common carotid artery were found to differ between men and women. In these studies, however, the phase of the menstrual cycle was not taken into consideration. It was the aim of the present study to investigate the effect of changing ovarian hormone levels during the normal menstrual cycle on the arterial wall properties of female large arteries. 2. We investigated the elastic right common carotid artery and the muscular right common femoral artery of normotensive young (18–35 years) female subjects (n = 12). The arterial distensibility and cross-sectional compliance coefficients were determined by the use of a specially designed ultrasonic wall-tracking device and measurements of automatic brachial artery cuff blood pressure. The phase of the menstrual cycle was assessed by ultrasonographic evaluation and measurement of 17β-oestradiol and progesterone blood plasma levels. 3. The distensibility coefficient and the cross-sectional compliance coefficient of both the common carotid and the common femoral artery did not change significantly during the normal menstrual cycle despite evidently changing ovarian hormone levels. 4. We conclude that the menstrual cycle does not influence the arterial wall properties of either the elastic common carotid artery or the muscular common femoral artery.

Download Full-text

Absence of Flow-Mediated Vasodilation in the Rabbit Femoral Artery

Physiological Research ◽

10.33549/physiolres.931672 ◽

2010 ◽

pp. 331-338

Author(s):

P S Clifford ◽

J A Madden ◽

J J Hamann ◽

J B Buckwalter ◽

Z Valic

Keyword(s):

Blood Flow ◽

Femoral Artery ◽

Outer Diameter ◽

Solution Ph ◽

Physiological Range ◽

In Vivo Experiments ◽

Exercise Hyperemia ◽

Femoral Artery Blood Flow ◽

Flow Mediated Vasodilation

The purpose of this study was to determine if there is flowmediated vasodilation of the femoral artery in response to progressive increases in flow within a physiological range observed in the in vivo experiments. Femoral artery blood flow was determined in conscious rabbits (n=5) using chronically implanted flowprobes. Resting blood flow was 8.3±0.6 ml/min and increased to 39.9±5.4 ml/min during high intensity exercise. Femoral arteries (n=12, 1705±43 µm outer diameter) harvested from a separate group of rabbits were mounted on cannulas and diameter was continuously monitored by video system. Functional integrity of the endothelium was tested with acetylcholine. The arteries were set at a transmural pressure of 100 mm Hg and preconstricted with phenylephrine to 73±3 % of initial diameter. Using a roller pump with pressure held constant, the arteries were perfused intraluminally with warmed, oxygenated Krebs' solution (pH=7.4) over a physiological range of flows up to 35 ml/min. As flow increased from 5 ml/min to 35 ml/min, diameter decreased significantly (p<0.05) from 1285±58 µm to 1100±49 µm. Thus, in vessels with a functional endothelium, increasing intraluminal flow over a physiological range of flows produced constriction, not dilation. Based on these results, it seems unlikely that flow-mediated vasodilation in the rabbit femoral artery contributes to exercise hyperemia.

Download Full-text

Remodeling of the zero-stress state of femoral arteries in response to flow overload

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2001.280.4.h1547 ◽

2001 ◽

Vol 280 (4) ◽

pp. H1547-H1559 ◽

Cited By ~ 41

Author(s):

X. Lu ◽

J. B. Zhao ◽

G. R. Wang ◽

H. Gregersen ◽

G. S. Kassab

Keyword(s):

Blood Flow ◽

Stress State ◽

Blood Vessel ◽

Femoral Artery ◽

Quantitative Description ◽

Step Change ◽

Outer Diameter ◽

Operative Trauma ◽

Unit Step

The goal of this study is to quantitatively describe the remodeling of the zero-stress state of the femoral artery in flow overload. Increased blood flow, approximately as a unit step change, was imposed on the femoral artery by making an arteriovenous (a-v) fistula with the epigastric vein. The a-v fistula was created in the right leg of 36 rats, which were divided equally into six groups (2 days and 1, 2, 4, 8, and 12 wk after the fistula). The vessels in the left leg were used as controls without operative trauma. The in vivo blood pressure, flow, and femoral outer diameter and the in vitro zero-stress state geometry were measured. The in vivo shear rate at the endothelial surface increased approximately as a step function by ∼83%, after 2 days, compared with the control artery. The arterial luminal and wall area significantly increased postsurgically from 0.15 ± 0.02 and 0.22 ± 0.02 mm2 to 0.28 ± 0.04 and 0.31 ± 0.05 mm2, respectively, after 12 wk. The wall thickness did not change significantly over time ( P > 0.1). The opening angle decreased to 82 ± 4.2 degrees postsurgically when compared with controls (102 ± 4.4) after 12 wk and correlated linearly with the thickness-to-radius ratio. Histological analysis revealed vascular smooth muscle cell growth. The remodeling data are expressed mathematically in terms of indicial functions, i.e., change of a particular feature of a blood vessel in response to a unit step change of blood flow. The indicial function approach provides a quantitative description of the remodeling process in the blood vessel wall.

Download Full-text