Radial Artery Distensibility Research Articles

The Effect of Pregnancy Status on Rat Main Uterine Artery and Radial Uterine Artery Structure and Function

BackgroundHealthy pregnancy is associated with remodeling of the maternal uterine vasculature to meet the metabolic demands of the developing fetus. In contrast to the systemic circulation during pregnancy, it has been suggested that pregnancy decreases radial uterine artery (RUA) distensibility, potentially persisting throughout the postpartum period. The intent of this study is to compare RUA and main uterine artery (MUA) during late pregnancy and the postpartum period to determine whether pregnancy‐related changes in distensibility is similar in both large and small uterine vessels.MethodsMUAs and RUAs from NP (n=7‐9), LP (gestational age: 21±1 d, n=6‐8), and 30±1 days postpartum (PP30; n=4‐6) Sprague‐Dawley rats were isolated, cleaned of connective tissue, cut into 8mm segments, and cannulated in an arteriograph chamber to assess vascular reactivity to the addition of 60 mM KCl and phenylephrine (PE, 1 µM). In addition, passive mechanical properties such as lumen diameter, wall thickness, distensibility and arterial stress/strain were assessed at intraluminal pressures ranging from 10mm Hg to 140mm Hg. Data were analyzed using one‐way ANOVA or two‐way ANOVA. Data were considered significant at P<0.05.ResultsK+‐ induced constriction was similar in RUAs and MUAs from NP, LP, and PP30 rats. PE‐induced constrictions were similar at all pregnancy states in RUAs. In contrast, PE‐induced constriction in LP MUA was greater than NP MUA (P<0.05) and PP30 MUA (P<0.01). Passive LP RUA lumen diameter was greater than PP30 RUA (P<0.05) and trended toward significance in NP RUA (P<0.07). Passive NP MUA lumen diameters were smaller than MUA diameters from LP (P<0.05) and PP30 (P<0.05) rats. There was no difference in arterial wall thickness between NP, LP and PP30 MUAs (P=NS) and NP, LP and PP30 RUAs (P=NS). Distensibility in NP RUA was greater than PP30 RUAs (P<0.05), but there was no statistical difference in distensibility between LP RUA and PP30 RUAs. There was no difference in distensibility in MUAs at all pregnancy states. Stress/strain relationships unmasked vascular remodeling in both RUAs and MUAs. There was a significantly greater leftward shift in stress/strain values in RUAs from PP30 rats than RUAs from LP (P<0.05) and NP (P<0.05) rats. Furthermore, stress/strain values from LP RUAs were different than RUAs from PP30 (P<0.05) and NP (P<0.05) animals. Similar to RUA, the leftward shift in stress/strain values from PP30 MUA were statistically greater than MUA from LP and NP animals.ConclusionsThese preliminary data suggest that significant vascular remodeling occurs with pregnancy which persists 30 days post parturition. Additional studies need to be completed to determine how multiple pregnancies may alter RUA and MUA structure and function.

Arteriovenous fistula and pre-surgery mapping: Potential role of physical exercise on endothelial function.

The success of the construction of an arteriovenous fistula for haemodialysis is related to the vascular function of the vessels involved in the anastomosis, with particular reference to radial artery distensibility after reactive hyperaemia test and to the fall of resistance index. Only few studies have evaluated the impact of exercise protocols on the endothelial and morphological characteristics of the vessels of the upper limb with inconclusive results. In this pilot longitudinal study, we aimed to evaluate the impact of a standardized exercise protocol on the haemodynamic and resistive index of the arteries of the upper limb of uraemic patients. A total of 17 uraemic patients planned to construct arteriovenous fistula at the distal third of the forearm were enrolled and followed up for 30 days. All patients performed repeated handgrips for 30 min/day. The arterial parameters were detected before and after an ischaemic stress of 5 min and radial and brachial artery flow-mediated dilation was evaluated as well as radial artery resistance index. Pre-exercise measurements of radial artery diameter and resistance index and brachial artery diameter were not modified by 30 days hand physical exercise, whereas the post-exercise haemodynamic were improved. Consequently, flow-mediated dilation of the radial artery was improved (21% ± 14% vs 30% ± 19%; p = 0.03) and resistance index of the radial artery was reduced (p = 0.02). Exercise has beneficial effects on endothelial function of the radial artery by resistive index and, potentially, on the outcome of the arteriovenous fistula. Further studies with larger sample size are needed to confirm our preliminary data.

Evaluation of cardiorespiratory changes during various phases of menstrual cycle in young women before and soon after exercise

Background: Menstruation involves a cyclic expulsion of sanguinous fluid and a sloughing of uterine wall in a female and is a typical feature of the reproductive cycle in humans and subhuman primates. The variations in radial artery distensibility are typical in the natural menstrual cycle. Respiratory function is influenced by female sexual hormones, especially progesterone, which could increase ventilator at rest and soon after exercise. Objective: To study the cardiorespiratory changes during mid-follicular phase and early luteal phases of menstrual cycle before and soon after exercise. Materials and Methods: The samples were collected from young unmarried and nonpregnant women of age group 17 and 25 years from Government General Hospital, Madras Medical College. Blood was drawn during the mid-follicular phase and early luteal phase of menstrual cycle; the serum was separated and stored at 20C. The separated serum was used for quantitative determination of estradiol (E2) concentration by SMAR Test diagnostics and for progesterone determination using hormone kit. Cardiac output, peripheral blood flow, expiratory blast test, performance of isotonic exercise, and cardiac output measurement were performed, and the comparison was made between the different phases of parameters. Result: Cardiac output, peripheral blood flow, and expiratory blast test were performed, and the comparison was made between the parameters. Female subjects show higher ventilatory responses in the luteal phases than in the follicular phase without a change in VO2. Progesterone stimulates respiration and the alveolar PCO2 in women during the luteal phase of menstrual cycle, which is lower than that in men. During exercise, the muscle blood flow can increase a maximum of about 25-fold, the value being 90 mL/100g muscle/min from resting blood flow of 3.6 mL/100 g. In expiratory blast test, a normal subject can increase the mercury column to 55–100 mm or more during a single forceful expiration. Conclusion: The result suggests that cardiovascular parameters were more affected in follicular phase after exercise. Respiratory parameters were more affected in luteal phase after exercise. Change in peripheral blood flow was found to show marked effect than in cardiac output.

Uterine distension differentially affects remodelling and distensibility of the uterine vasculature in non-pregnant rats

During pregnancy the mammalian uterine circulation undergoes significant expansive remodelling necessary for normal pregnancy outcome. The underlying mechanisms are poorly defined. The goal of this study was to test the hypothesis that myometrial stretch actively stimulates uterine vascular remodelling by developing a new surgical approach to induce unilateral uterine distension in non-pregnant rats. Three weeks after surgery, which consisted of an infusion of medical-grade silicone into the uterine lumen, main and mesometrial uterine artery and vein length, diameter and distensibility were recorded. Radial artery diameter, distensibility and vascular smooth muscle mitotic rate (Ki67 staining) were also measured. Unilateral uterine distension resulted in significant increases in the length of main uterine artery and vein and mesometrial segments but had no effect on vessel diameter or distensibility. In contrast, there were significant increases in the diameter of the radial arteries associated with the distended uterus. These changes were accompanied by reduced arterial distensibility and increased vascular muscle hyperplasia. In summary, this is the first report to show that myometrial stretch is a sufficient stimulus to induce significant remodelling of uterine vessels in non-pregnant rats. Moreover, the results indicate differential regulation of these growth processes as a function of vessel size and type.

Elastic properties and structure of the radial artery in patients with type 2 diabetes

Alterations of elastic properties may contribute to the accelerated atherosclerosis in patients with T2D. Little is known, however, about radial artery distensibility in this patient group. A total of 19 patients with T2D and 19 controls were investigated.An echotracking system coupled to a plethysmograph was used to assess the morphologic and elastic properties of radial artery. Distensibility and compliance were evaluated using Langewouters' equations. Distensibility and compliance did not differ significantly in patients with diabetes compared with controls. In contrast, radial IMT and WCSA were significantly higher in patients with T2D than in controls. Multiple regression analyses revealed a significant association between SBP and IMT (r(2) = 0.40, p<0.001) as well as WCSA (r = 0.54; r(2) = 0.30; p<0.001 ) in individuals with diabetes. In conclusion, distensibility and compliance of the radial artery are not reduced in patients with T2D. In contrast, radial IMT and WCSA are significantly higher in patients with T2D than in controls.These modifications are chiefly and positively related to SBP.

Age and Blood Pressure Levels Modify the Functional Properties of Central but Not Peripheral Arteries

The effect of age and blood pressure on the carotid and the radial artery distensibilities was investigated. Patients referred to the outpatient clinic of the Department of Internal Medicine and Geriatric Medicine were asked to participate in the study. The carotid and radial artery distensibility coefficients were measured. Linear regression analyses were performed to investigate the associations between determinants and arterial distensibility. The mean age of the participants was 72.3 years, and 41.5% were men. Carotid distensibility decreased with age in adjusted models (beta = -0.317; 95% confidence interval [CI], -0.241, -0.055), whereas the radial distensibility did not decrease. Levels of systolic blood pressure and mean arterial pressure were associated with decreasing levels of carotid distensibility, whereas the diastolic blood pressure and pulse pressure were not associated (beta = -0.571; 95% CI, -0.404, -0.007; beta = -0.410; 95% CI, -0.308, -0.101, respectively). In conclusion, age and blood pressure levels are associated with the distensibility of the central arteries but not with that of the peripheral arteries.

Different relation between 24-h blood pressure and distensibility at different peripheral arteries. Data from the European Lacidipine Study on Atherosclerosis (ELSA)

The European Lacidipine Study on Atherosclerosis (ELSA) has been planned to investigate the effect of reduction in office and ambulatory blood pressure by lacidipine versus atenolol on carotid artery wall thickness in mild to moderate essential hypertensive patients with no metabolic abnormalities. One prespecified sub-study of ELSA focused on measurements of arterial distensibility in the carotid as well as in the radial artery to determine the relationship of functional arterial properties with office versus ambulatory blood pressure (BP) values as well as the correspondence between functional and structural arterial alterations. The sub-study was conducted on 124 patients recruited in four centres (Monza-Milan, Paris, Grenoble and Glasgow). BP was measured both by a mercury sphygmomanometer and by 24-h ambulatory monitoring. Common carotid artery wall thickness was measured by certified sonographers as described in the main study. Common carotid and radial artery distensibility were obtained by echotracking techniques, which allowed to relate changes in arterial diameter with systo-diastolic BP changes. Carotid artery wall distensibility showed (1) a negative correlation with office and more so 24-h average systolic BP (r = -0.45 and -0.58, P < 0.008 and 0.001) but not with office or 24-h diastolic BP) and (2) a negative correlation with the corresponding wall thickness (r = -0.47, P < 0.005). In contrast, at the radial artery level distensibility and thickness showed no correlation with each other and with BP. Carotid (but not radial) artery distensibility also correlated with ambulatory systolic BP variability but the correlation was lost after adjustment for age and mean BP values. These data suggest that stiffening of large elastic artery is reflected more by ambulatory than office BP elevations, systolic BP being much more important than diastolic. Alterations of large elastic arteries function is related to structural wall changes. Functional and structural properties of middle-size muscle arteries are independent of BP.

Arterial Stiffening Influence of Sympathetic Nerve Activity

Studies in animals and humans suggest that sympathetic activity exerts a stiffening influence on large and middle-sized artery walls. We sought to obtain further evidence on this issue by measuring radial artery distensibility in an allotransplanted and thus denervated hand using the contralateral artery as control. In 2 men, blood pressure was measured by a semiautomatic device (Dinamap). Diastolic diameter, systo-diastolic diameter excursion (ultrasound Wall Track system), and distensibility (Reneman formula) of both radial arteries were measured at a level corresponding to 4 cm below the suture of the transplanted hand 40 days after surgery and every 4 weeks for the next 6 months. After surgery, systo-diastolic diameter excursion and distensibility were much greater in the transplanted radial artery than in the contralateral vessel, reaching values similar to the contralateral ones after 4 months, when signs of reinnervation of the transplanted hands had appeared. Radial deinnervation was accompanied by an increased arterial distensibility, which provides further evidence of the sympathetic stiffening effect on arterial wall in humans.

Effects of Heart Rate Changes on Arterial Distensibility in Humans

To the Editor: Dependence of arterial stiffness on heart rate, claimed by Giannattasio et al,1 runs counter to classic studies, which were previously discussed in relation to conflicting data obtained with one method used to measure aortic pulse wave velocity.2 There is a potential flaw in the method applied by Giannattasio et al in their determination of carotid and radial artery distensibility at different heart rates. They measured diameter change of the target artery, but pressure pulsation at a distal site (brachial pressure for carotid, finger pressure for radial artery). Errors inherent in distal pressure measurement have been stressed in a recent consensus document3 but were considered by authors1 to be minimal. We disagree. In similar studies by Wilkinson et al,4 there was an …

Arterial remodeling and stiffness in patients with pseudoxanthoma elasticum.

Proteoglycans organize the extracellular matrix, act as signaling molecules, and are involved in cell migration and proliferation. They may play an important role in arterial geometric and elastic properties. The aim of the present study was to determine large artery phenotype in patients with pseudoxanthoma elasticum (PXE), a genetic disease characterized by proteoglycan accumulation and fragmented elastic fibers in connective tissues. In 27 patients with PXE (25 females and 2 male) and 27 control subjects matched by age, sex, and blood pressure, we noninvasively determined the common carotid and radial artery diameter, intima-media thickness (IMT), and distensibility with high-definition echo-tracking systems and applanation tonometry. Patients with PXE had a significantly higher carotid IMT (611+/-106 versus 520+/-76 microm, P<0.001) independently of body surface area, age, and mean blood pressure. The increase in carotid IMT predominated in older patients with PXE at the time of examination. No significant difference in carotid elastic properties was observed between patients with PXE and control subjects. At the site of the radial artery, distensibility was significantly higher in patients with PXE than in control subjects (11.6+/-11.4 versus 5.9+/-3.4 kPa(-1) x 0.10(-3); P=0.02) and internal diameter was lower (1.66+/-0.51 versus 2.07+/-0.36 mm; P<0.01) without change in intima-media thickness and Young's elastic modulus. Phenotypic changes of superficial arteries in patients with PXE were represented by a thickening of the carotid artery and a reduced stiffness of the radial artery and predominated in older female patients.

Arterial remodelling in Fabry disease.

The enzymatic defect in Fabry disease results in the slow systemic deposition of uncleaved glycosphingolipids in the lysosomes of vascular endothelium and smooth muscle cells, leading to ischaemic strokes, cardiomyopathy and renal failure. Whereas it is known that Fabry disease affects small blood vessels, little is known about its effects on peripheral large arteries. We therefore set out to compare parameters of arterial wall structure and function in a cohort of patients with Fabry disease and an age-matched control group. Large artery phenotype was non-invasively investigated in 21 hemizygous patients with Fabry disease and 24 age-matched male controls. Common carotid and radial artery diameter, intima-media thickness (IMT) and distensibility were determined with high-definition echotracking systems and aplanation tonometry. Patients with Fabry disease had a significant twofold increase in radial artery IMT and distensibility, independent of body surface area, age and mean blood pressure. In both groups, older age at the time of examination was significantly associated with larger radial artery IMT. The relationship between age and radial IMT was 2.3-fold higher in patients with Fabry disease than in controls (p < 0.01). Carotid IMT was mildly but significantly increased in patients with Fabry disease (+18%), whereas distensibility was unchanged. This study presents evidence of a major increase in arterial wall thickness and distensibility, measurable at the site of a medium-sized artery, in a cohort of patients with classic Fabry disease.

Fluctuations of radial artery distensibility throughout the menstrual cycle.

Estrogen administration has a number of favorable cardiovascular effects, and recent evidence suggests that these include an increase in arterial distensibility. Whether this is also the case for the physiological changes in estrogen production during the menstrual cycle has never been determined, however. In 21 premenopausal healthy women, we continuously measured radial artery diameter and blood pressure by an echo-tracking device and a beat-to-beat finger device, respectively. Arterial distensibility was calculated as distensibility/blood pressure curve. The measurements were made during the follicular, ovulatory, and luteal phases of the menstrual cycle. As expected, compared with the follicular phase, plasma estradiol, follicle-stimulating hormone, luteinizing hormone, and prolactin were increased in the ovulatory phase, whereas progesterone was increased in the luteal phase, together with antidiuretic hormone. Radial artery distensibility was increased in the ovulatory and reduced in the luteal phase, the changes being independent of the small, concomitant blood pressure changes. The arterial wall stiffening seen in the luteal phase was associated with a reduction in the flow-dependent endothelial dilatation of the radial artery as assessed by the hyperemia after short-term ischemia of the hand. Thus, the natural menstrual cycle is characterized by alterations in radial artery distensibility. The mechanisms responsible for this phenomenon remain to be clarified. It is possible, however, that the greater arterial distensibility of the ovulatory phase is due to an estrogen-dependent reduction in vascular smooth muscle tone, whereas the arterial stiffening of the luteal phase depends on vascular smooth muscle contraction due to more complex hormonal phenomena, ie, an endothelial impairment due to estrogen reduction but also to an increase in progesterone and antidiuretic hormone levels.

Sympathetic tone restrains arterial distensibility of healthy and atherosclerotic subjects.

Sympathetic activation induced by cold pressor test or cigarette smoking is accompanied by a marked reduction of radial artery distensibility. It is not known, however, whether arterial distensibility is under tonic sympathetic restraint, or whether this restraint involves arteries greater than the radial one in both normal and pathological conditions. We studied the distensibility of radial artery by continuous ultrasonographic assessment of the changes in arterial diameter over the diasto-systolic pressure range (finger pressure measurement) in eight patients with a Dupuytren disease before and 20 min after ipsilateral brachial plexus anaesthesia. We also studied ultrasonographic distensibility of femoral artery in seven subjects before and 20 min after ipsilateral subarachnoid anaesthesia, performed before arthroscopic surgery, and in five patients with claudicatio intermittens before and 1 month after ipsilateral removal of the lumbar sympathectomy chain. In all three conditions, the contralateral artery served as control. The three interventions did not cause any significant alteration in blood pressure and heart rate. Radial artery distensibility was markedly increased by ipsilateral anaesthesia of the brachial plexus (+36%, P<0.01). This was the case also for femoral artery distensibility both following ipsilateral subarachnoid anaesthesia in healthy subjects (+47%, P<0.05) or ipsilateral sympathetic gangliectomy in patients with peripheral artery disease (+26%, P<0.05). In all three instances, the distensibility of the contralateral artery remained unaffected. These data indicate that the sympathetic nervous system exerts a marked tonic restraint of arterial distensibility. This restraint involves medium-size and large muscular arteries and can also be seen in subjects with peripheral artery disease. This stiffening influence may increase the traumatic effect of intravascular pressure on the vessel wall and favour atherosclerosis.

Relationship between low-frequency oscillations of blood pressure and changes in arterial diameter

To study spontaneous variations in radial artery compliance. Compliance was evaluated non-invasively by an echo-tracking system, and variations in sympathovagal tone were analysed by a spectral analysis of continuous blood pressure recordings using a Fast Fourier algorithm. We studied 23 healthy volunteers, aged 25 +/- 4 years (mean +/- SD), at rest, on two occasions at least one day apart (5 +/- 3 days). There were no significant differences between the means of the arterial compliance measurements and those of the corresponding spectral analysis. However, the magnitude of change in the low-frequency periods (4-66 mHz) was significantly related (P less than 0.01) to a significant and inverse change in compliance for the same level of blood pressure. While it is possible to use spectral analysis to measure the effect of autonomic nervous regulation on radial artery properties, low-frequency periods cannot be safely ascribed to sympathetic effects alone. Other effects must also be taken into account in measurements of radial artery distensibility.