The relationship of arterial compliance with endothelial-derived proteins of the hemostatic system

Exercise-induced shear stress is associated with changes in plasma von Willebrand factor in older humans

Shear stress is the frictional force of blood against the endothelium, a stimulus for endothelial activation and the release of von Willebrand factor (vWF). This study tested the hypothesis that the increase in shear stress associated with exercise correlates with plasma vWF. Young (n = 14, 25.7 +/- 5.4 years) and older (n = 13, 65.6 +/- 10.7 years) individuals participated in 30 min of dynamic handgrip exercise at a moderate intensity. Brachial artery diameter and blood flow were measured using ultrasound Doppler and blood samples were collected before, immediately after, and following 30 min of recovery from exercise with plasma levels of vWF. Plasma levels of vWF increased (P < 0.05) by 6 +/- 2% in young individuals and 4 +/- 1% in older individuals immediately after exercise. The change in plasma vWF was linearly correlated with the increase in shear stress during exercise in older individuals (post-exercise: r = 0.78, 30 min recovery: r = 0.77, P < 0.01), but no association was found in the young individuals. These changes in plasma levels of vWF in humans suggest that aging influences endothelial activation and hemostasis.

Valsartan improves arterial stiffness in type 2 diabetes independently of blood pressure lowering

Increased arterial stiffness, as estimated from aortic pulse wave velocity (Ao-PWV), and albuminuria are independent predictors for cardiovascular disease in type 2 diabetes mellitus (T2DM). Whether angiotensin receptor blockers (ARBs), drugs with cardio-renal protective effects, improve Ao-PWV to a greater extent than other equipotent antihypertensive medications remains unclear. After a 4-week washout phase, we compared the effects of valsartan (n=66), an ARB, with that of amlodipine (n=65), a calcium channel blocker on Ao-PWV in 131 T2DM patients with pulse pressure (PP) >or=60 mm Hg and raised albumin excretion rate (AER) in a 24-week randomized, double-blind, parallel group study. Hydrochlorothiazide (HCTZ) 25 mg/d was added to valsartan 160 mg and amlodipine 5 mg/od uptitrated to 10 mg/od after 4 weeks to ensure equivalent BP control. After 24 weeks brachial and central aortic PP had fallen to a similar extent with attained mean (SD) brachial and central PP of 61.6 (13.6) and 47.3 (14.1) mm Hg in the valsartan/HCTZ group and 61.5 (12.2) and 47.3 (9.9) mm Hg in the amlodipine group, respectively. Ao-PWV showed a significantly greater reduction, mean (95% CI), -0.9 m/s (-1.4 to -0.3) for valsartan/HCTZ compared to amlodipine (P=0.002). AER fell significantly only with Val/HCTZ from 30.8(20.4, 46.5) to 18.2(12.5, 26.3) mcg/min, (P=0.01) with between treatment difference in favor of Val/HCTZ of -15.3mcg/min (P<0.001). Changes in AER and Ao-PWV were not correlated. Valsartan/HCTZ improves arterial stiffness and AER to a significantly greater extent than amlodipine despite similar central and brachial BP control. These 2 effects, which appear independent of each other, may explain the specific cardio-renal protective properties of ARBs.

Effects of enhanced counterpulsation on vascular cell release of coagulation factors

BACKGROUND

Enhanced external counterpulsation (EECP), a noninvasive treatment for patients with angina pectoris, provides long-term benefits of decreased anginal frequency and improved exercise tolerance. Previous studies have suggested that shear stress may result in angiogenesis and alter endothelial hemostatic factor release. Whether EECP therapy effects an alteration in endothelial cell proliferation and function remains unclear. The level of vascular endothelial growth factor (VEGF) and four other endothelial hemostatic factors (tissue plasminogen activator, plasminogen activator inhibitor-1, von Willebrand factor, and D-dimers) were measured in patients before and after 35 hours of EECP treatment.

METHODS

Plasma levels of endothelial growth and hemostatic factors were assessed using the standard enzyme-linked immunosorbent method.

RESULTS

No significant difference in the hemostatic factors and VEGF after EECP treatment was revealed; there was a trend toward an increase in VEGF levels posttreatment.

CONCLUSIONS

Vascular endothelial cells play a critical role in the regulation of coagulation because they control the expression of tissue plasminogen activator, plasminogen activator inhibitor-1, von Willebrand factor, and D-dimers. Our results suggest EECP may not play a role in controlling coagulation in patients with coronary artery disease through release of endothelial hemostatic factors. Although there was a tendency for increased VEGF release, larger studies are necessary to confirm these observations.

Relationship between arterial elasticity indices and carotid artery intima-media thickness

Functional and structural changes of the arterial wall appear to serve as early hallmarks of the hypertensive disease process. Structural vascular changes can be studied by the determination of the intima-media wall thickness (IMT) at the carotid artery. The elastic behavior of the proximal and distal parts of the arterial tree can be assessed from noninvasively recorded radial artery waveforms. The aim of the study was to compare large (proximal, C1) and small (distal, C2) artery elasticity indices in two age-matched study groups with high- and low-normal blood pressure (BP) and to assess the relation between elasticity indices and IMT. A total number of 22 subjects with high-normal BP (40 +/- 2 years; BP, 147 +/- 2.5/84 +/- 1.5 mm Hg) and 22 matched controls with low-normal BP (40 +/- 2 years; BP, 123 +/- 1.9/69 +/- 1.5 mm Hg) were enrolled. The IMT was echographically determined at the common carotid artery by the leading-edge technique. Large artery (C1) and small artery (C2) elasticity indices were calculated from a third-order, four-element model of the arterial circulation. In the group with high-normal BP large and small artery elasticity indices were significantly decreased versus controls with low-normal BP (C1: 1.63 +/- 0.08 v 1.99 +/- 0.09 mL/mm Hg, P < .01; C2: 0.059 +/- 0.005 v 0.076 +/- 0.007 mL/ mm Hg, P < .05) and IMT increased significantly (0.607 +/- 0.039 v 0.516 +/- 0.027 mm, P < .05). Moreover, there was an inverse relationship between IMT and small artery elasticity index (r = -0.60, P = .004). In subjects with a high-normal BP there is already a change in the IMT of the carotid artery versus normotension. The IMT is related to the small artery elasticity index (C2).

Arterial geometric abnormalities produce two-dimensional compliance disturbances

PURPOSE

This study describes the two-dimensional compliance changes that develop in low-grade hemodynamically insignificant stenoses.

METHODS

Twenty-four male Sprague-Dawley rats were used in the study. In 14 rats, balloon injury and endothelial denudation of the common carotid artery was followed by the application of a ligature, which produced a 20% narrowing of the outer diameter; five other rats were similarly injured without creating a stenosis, and five were stenosed without injury. The latter two groups served as control. Two-dimensional measures of arterial wall motions were obtained 30 minutes and 3 days after surgery by use of a video motion analyzer. Subsequently, circumferential (Cc) and longitudinal (Cl) compliance values were calculated and analyzed.

RESULTS

At 30 minutes, in the injured stenosed arteries, overall Cc was significantly greater than in the nonstenosed injured arteries at all measured points along the artery. Both stenosed injured and stenosed noninjured arteries also displayed increased Cc both proximal and distal to the stenoses compared with Cc values furthest from the stenosis. Cl values in the stenosed arteries, both injured and noninjured, became negative across the stenosis. All two-dimensional compliance changes occurred within the area of arterial narrowing and gradually resolved approaching the nonstenotic region of the artery. At systole, in the adjacent to the stenosis arterial segments, circumferential distension was accompanied by simultaneous longitudinal compression. Three days after surgery, although Cc increased proximal and distal to the stenosis and Cl decreased in the areas adjacent to the stenoses, no statistically significant difference was found.

CONCLUSIONS

Low-grade stenosis results in a longitudinal compression accompanied by a relatively increased circumferential distension of arterial segments adjacent to the stenotic region. This pattern is not initiated or influenced by the presence or absence of endothelial cells.