Pulse wave velocity (PWV) was measured by means of transcutaneous Doppler techniques in the aorta, right arm, and right leg of 480 normal subjects of both sexes in urban Beijing, China (age range 3 to 89 years, mean age 41 +/- 20.8 SD); supine blood pressure was recorded in the brachial artery of each subject with standard sphygmomanometric procedures. Serum cholesterol was determined in a subgroup of 79 subjects (age 17 to 85 years, mean 47 +/- 26 SD). PWV (y in cm/sec) was found to vary with age (x, years) at each of the three locations according to the following regression equations: aorta, y = 9.2x + 615, r = .673 (p less than .001); right arm, y = 4.8x + 998, r = .453 (p less than .001); right leg, y = 5.6x + 791, r = .630 (p less than .001). Systolic, diastolic, mean, and pulse pressures were found to increase with age. PWV also increased with mean supine blood pressure but was not related to serum cholesterol (average 4.49 +/- 0.11 [SEM], mmol/l). Compared with that of Western populations, serum cholesterol tended to be lower at all age groups, systolic pressure higher at ages over 35 years, and PWV higher at all ages. Because change in PWV is directly related to change in arterial compliance, these results indicate that aging and not concomitant atherosclerosis (known to be rare in Asian populations) is the dominant factor associated with reduced arterial compliance and increased left ventricular load in these subjects.

Effects of aging on changing arterial compliance and left ventricular load in a northern Chinese urban community.

Arterial pulse wave velocity, an established index of arterial distensibility, was measured together with arterial pressure in a group of 524 normal subjects of both sexes 2 months to 94 years old (mean age 45.6 +/- 15.3 years [SD]) in rural Guangzhou, China, an area with known low prevalence of hypertension. Fasting serum lipid levels and overnight Na+ and K+ urinary excretion levels were determined in a subgroup of 104 subjects (ages 8 to 88 years). Comparisons were made with data obtained similarly from normal subjects in urban Beijing, an area with known high prevalence of hypertension. Serum cholesterol levels were similar and low in each group (Guangzhou, 4.34 +/- 0.12 mmol/liter [SE]; BEijing, 4.49 +/- 0.11 mmol/liter). Prevalence of hypertension (WHO criteria) was 4.9% (Guangzhou) and 15.6% (Beijing). In Guangzhou subjects pulse wave velocity was consistently lower in the aorta, arm, and leg, and increased to a lesser degree with age compared with Beijing subjects. Regression equations (x = pulse wave velocity [cm/sec], y = age [years]) were as follows: (1) aorta, Guangzhou: y = 5.1x + 533, r = .552, p less than .05; Beijing: y = 9.2x + 615, r = .673, p less than .001; (2) arm, Guangzhou: y = 0.61x + 817, r = .121, p less than .05; Beijing: y = 4.8x + 998, r = .453, p less than .001; (3) leg, Guangzhou: y = 4.43x + 718, r = .512, p less than .05; Beijing: y = 5.6x + 791, r = .630, p less than .001.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of aging on arterial distensibility in populations with high and low prevalence of hypertension: comparison between urban and rural communities in China.

The static elastic properties of arterial tree (abdominal aorta and common carotid artery) were studied in 19 normal subjects and in 49 patients with myocardial infarction with an ultrasonic phase-locked echo-tracking system that allows continuous transcutaneous measurement of the arterial diameter. The stiffness index beta, which represented the mechanical properties in the arterial wall, was calculated from the relation between systemic blood pressure and the diameter of the artery. Patients with myocardial infarction underwent coronary angiography in their convalescent period to determine involved vessels. In 11 patients, coronary artery was patent; 15 patients had one-vessel disease, 12 had two-vessel disease, and the remaining 11 patients had three-vessel disease. In normal subjects, increasing age was associated with an increase in arterial stiffness. An average value of the stiffness index of the abdominal aorta was 8.58 +/- 3.02 (mean +/- SD) and that of common carotid artery was 9.17 +/- 2.22. In patients with three-vessel disease, these values were significantly higher (22.37 +/- 4.29 in abdominal aorta and 13.17 +/- 4.56 in common carotid artery) than those in normal subjects. Stiffness index of patients with two- or one-vessel disease was also increased but lower than those in patients with three-vessel disease (p less than 0.05). Forty-four of 49 patients with infarction had an arterial stiffness index of abdominal aorta higher than the 95% confidence limits of the normal data (p less than 0.05). Twenty-eight patients were outside the nomogram of common carotid artery (p less than 0.05). The mechanical properties of these elastic arteries provided sufficiently reliable information on changes caused by atherosclerosis.

Stiffness of systemic arteries in patients with myocardial infarction. A noninvasive method to predict severity of coronary atherosclerosis.

Normal and sinoaortic baroreceptor-denervated dogs were monitored continuously (24 hours a day) to quantify the role of the baroreceptors in determining the average level and the variability of arterial blood pressure, heart rate, cardiac output, and total peripheral resistance. The frequency of occurrence over 24-hour periods was obtained for each variable using a fiber optic curve-scanning system to read the variables from continuously recorded charts and a digital computer system to plot curves. The results indicate that the degree of hypertension previously reported for this preparation has been highly exaggerated, presumably due to the methods of study. The average 24-hour mean arterial blood pressure was 101.6 mm Hg in normal dogs and only 112.7 mm Hg in baroreceptor-denervated dogs. The normal dogs exhibited narrowly distributed 24-hour frequency distribution curves for blood pressure; in contrast the denervated dogs exhibited curves with twice the 24-hour standard deviation. Similar analysis indicated that the baroreceptors exerted less influence on the daily stabilization of heart rate than they did on arterial blood pressure and that they had very little if any influence on the daily stabilization of cardiac output and total peripheral resistance. Hemodynamic variables during postural changes were studied along with diurnal rhythms. We concluded that the primary function of the baroreceptor reflex is not to set the chronic level of arterial blood pressure but, instead, to minimize variations in systemic arterial blood pressure, whether these variations are caused by postural changes of the animal, excitement, diurnal rhythm, or even spontaneous fluctuations of unknown origin.

Role of the Baroreceptor Reflex in Daily Control of Arterial Blood Pressure and Other Variables in Dogs

In this review, we compare the reported values of Young's modulus (YM) obtained from indentation and tensile deformations of soft biological tissues. When the method of deformation is ignored, YM values for any given tissue typically span several orders of magnitude. If the method of deformation is considered, then a consistent and less ambiguous result emerges. On average, YM values for soft tissues are consistently lower when obtained by indentation deformations. We discuss the implications and potential impact of this finding.

http://chemotaxis.semmelweis.hu/CHTXhpg/Durotaxis/DT2/McKeeCT_TissueEng_2011.pdf

Indentation versus tensile measurements of Young's modulus for soft biological tissues.

Aortic pulse wave velocity was determined in Macaca fascicularis monkeys fed either atherogenic or control diets for 36 months. The foot-to-foot velocity and apparent phase velocities of the second through seventh Fourier harmonics at a given diastolic pressure in the atherosclerotic monkeys were 1.5 to 2.0 times the values for the control animals. More than 80% of the aortic intimal surface of the atherosclerotic monkeys was covered with fibrous or fatty plaque, which approximately doubled wall thickness and wall thickness to radius ratio. Angiochemical evaluations showed no difference in collagen or elastin concentration (as a fraction of lipid and mineral-free dried aorta), but the atherosclerotic aortas were 1.5 to 2.0 times that of control in collagen and elastin content (defined as the absolute quantity beneath a square centimeter of intimal surface). Total cholesterol and calcium concentrations in the atherosclerotic aortas were more than 10 times the values for the control aortas. The static circumferential distensibility of the excised atherosclerotic aortas was significantly less than control, but there was no difference in incremental (Young's) modulus of elasticity. The in vitro pressure-strain elastic modulus of the atherosclerotic aortas was more than twice that of control, which was predicted from the enhanced wave velocity. The significantly increased stiffness of the atherosclerotic arteries appeared to be due mainly to the increased wall thickness caused by the atherosclerotic plaques rather than to material changes described by Young's modulus. Extensive medial damage, however, also was present and could have had a major influence on stiffness. Atherosclerosis therefore can result in increased aortic stiffening, detectable by pulse wave velocity, even if there is no change in the overall Young's modulus of elasticity.

Aortic pulse wave velocity, elasticity, and composition in a nonhuman primate model of atherosclerosis.

SUMMARY Subclavian-to-femoral artery pulse wave velocity, as a measure of aortic stiffness, was determined in 31 rhesus monkeys (Macaca mulatto) which were divided into three groups on atherogenic progression or regression diets: nine monkeys (IIA) were fed a high cholesterol diet for 38 months, resulting in an average plasma cholesterol concentration of 638 mg/dl; and 10 (IIBi) and 12 (IICi) monkeys were fed the same progression diet followed by 24-month regression diets which were manipulated to maintain plasma cholesterol concentrations as close as possible to 300 and 200 mg/dl, respectively. Average pulse wave velocity at a diastolic blood pressure of 70 mm Hg was significantly greater (9.4 ± 1.0 (mean ± SEM) m/sec) in the IIA group than in the IIBi (6.3 ± 0.3) or IIC, (6.6 ± 0.3) groups, although four of the IIA monkeys had pulse wave velocities that were not significantly higher than the regression monkeys. Total thoracic plus abdominal aortic cholesterol concentration was significantly reduced from 10.2 ± 1.4 mg/g wet weight in the IIA group to 5.7 ± 0.6 (IIBi) and 4.6 ± 0.6 m g/ S wet weight (IIC2). The total percentage of thoracic plus abdominal aortic intimal surface covered with fibrous plus fatty plaque averaged 56.9 ± 9.2% (IIA) vs. 33.5 ± 6.7 (IIBi) and 35.0 ± 7.4% (IICi). Collagen content beneath a given intimal square surface significantly increased from 4.59 ± 0.31 mg/ cm 2 (IIA) to 6.46 ± 0.33 (HB,) and 6.49 ± 0.48 mg/cm 2 (IICi), whereas elastin content decreased from 9.47 ± 1.56 (IIA) to 6.58 ± 0.73 (IIBi) and 6.01 ± 0.39 mg/cm 2 (IIC,). There was no significant difference in any parameter between the two regression groups. These studies suggest a functional improvement of aortic elastic properties with regression of atherosclerosis. When comparing groups, the improvement appears to follow the reductions in total aortic cholesterol concentrations and in the extent of total atherosclerotic plaque rather than alterations in the collagen: elastin ratio which, in fact, increased when arterial stiffness decreased with regression. Circ Res 47: 425-432, 1980.

Reduction in Pulse Wave Velocity and Improvement of Aortic Distensibility Accompanying Regression of Atherosclerosis in the Rhesus Monkey

A new type electromagnetic flowmeter which utilizes an alternating square wave magnetic field applied to the unopened blood vessel is described. It attains stability of baseline and sensitivity not possible with older D.C. and A.C. meters and therefore puts measurement of blood flow through the unopened vessel on a practical basis.

A square wave electromagnetic flowmeter for application to intact blood vessels.

To determine the time course of changes in arterial stiffness and corresponding morphology during atherosclerosis progression, we determined pulse wave velocity (PWV) in cynomolgus monkeys fed atherogenic (test) and control diets over an 18-month period. At 6-month intervals, thoracic and abdominal aortic PWVs were determined with a pressure transducer retracted down the aorta in 5 cm increments. Iliac artery PWV was determined from the abdominal aortic pressure to a noninvasive femoral pulse. Groups of individual cardiac cycles, triggered by the ECGs, were sampled on a computer and the velocities (PWV) of the pulse wave fronts were calculated. There was no significant difference between groups until 18 months when test animal PWVs in the thoracic (7.44±0.83 m·s−1) and abdominal (8.52±0.67 m·s−1) aorta were significantly greater than those of controls (5.02±0.51 and 6.24±0.53 m·s−1, respectively), indicating increased arterial stiffness. There was no change in iliac PWV, 10.96±0.74 m·s−1 for 18-month test compared with 9.44±0.89 m·s−1 for controls. Constant infusion of nitroprusside and noradrenaline lowered and raised blood pressure and PWV in all groups, and PWV changes due to drug-induced pressure changes were greater in atherosclerotic than in control arteries. Systolic pressure of 18-month test and pulse pressure of 12- and 18-month test groups were significantly greater than controls under all drug conditions, also indicating increased vessel stiffness. Morphometric evaluation of histological aortic cross sections revealed early, noncomplicated atherosclerosis showing gradual increases in the ratio of intimal to medial cross-sectional area in the thoracic (1.24±0.30 after 18 months) and abdominal (1.70±0.42 after 18 months) aortas, compared with control ratios of essentially zero. The fraction of the internal elastic lamina covered with atherosclerotic lesions, and maximal intimal thickness also showed significant increases during the test diet period. These data show that early atherosclerosis resulted in aortic but not iliac stiffening which was detected by increased PWV before development of significant stenotic lesions.

Pulse wave velocity and morphological changes associated with early atherosclerosis progression in the aortas of cynomolgus monkeys

Cerebral venous outflow was measured in anesthetized dogs at the confluence of the sagittal and straight sinuses, with the lateral sinuses occluded. Denervation of the carotid bifurcation increased systemic arterial pressure (+25.8; SE±7.7 mm Hg) and decreased cerebral vascular conductance (-0.018; SE±0.005 ml/min · mm Hg); stimulation of the carotid sinus nerve decreased systemic arterial pressure and increased cerebral vascular conductance. Graded constrictions of the common carotid arteries induced transient responses of the cerebral blood flow that were characteristic of an autoregulatory process. Plots of the steady-state pressures and flows during the decreases of perfusion pressure were concave toward the pressure axis, were similar before and after denervation of the carotid bifurcation, and were indicative of autoregulation. We conclude that pressoreceptors in the carotid bifurcation or other pressoreceptors in systemic vessels upstream from the carotid bifurcation are not necessary for the contr...

Harold D. Green

Papers

Aortic pulse wave velocity, elasticity, and composition in a nonhuman primate model of atherosclerosis.

Reduction in Pulse Wave Velocity and Improvement of Aortic Distensibility Accompanying Regression of Atherosclerosis in the Rhesus Monkey

A square wave electromagnetic flowmeter for application to intact blood vessels.

Pulse wave velocity and morphological changes associated with early atherosclerosis progression in the aortas of cynomolgus monkeys

Baroreceptor Reflexes and Autoregulation of Cerebral Blood Flow in the Dog