Brachial artery diameter

The effects of raloxifene on the vascular endothelium have been studied in 19 subjects who underwent endothelial function testing at baseline and after treatment with placebo or raloxifene (60 mg/day for 6 weeks) (27). The findings in this small short-term study were entirely positive. Brachial artery diameter change (flow-mediated dilatation) increased 5.0% with placebo and 8.6% with raloxifene in response to a hyperemic stimulus. The ratio of AUC response to AUC reference with the use of laser Doppler measures was 1.18 for placebo and 1.28 for raloxifene. Flow-mediated dilatation and AUC ratio correlated significantly. The authors concluded that raloxifene enhanced endothelial-mediated dilatation in brachial arteries and digital vessels in these women, and they discussed the drug s possible cardioprotective effect. 

Approximately half of randomized clinical trials demonstrated a beneficial effect of soy supplementation on endothelial function, shown either by increased brachial artery diameter or flow-mediated dilation, or decreased peak flow velocity. Of the studies reporting a positive effect, four reported an improvement in endothelial function after 4-6 weeks of supplementation with 20—25 g/d soy protein (Cuevas et al., 2003 Cupisti et al., 2007 Steinberg et al., 2003 Yildirir et al., 2001). The study populations in these four studies consisted of renal transplant patients and postmenopausal women. Three studies ranging from 6 weeks to 1 year also demonstrated an improvement in endothelial function in postmenopausal women following daily supplementation with soy isoflavones (54—90 mg/d) (Colacurci et al., 2005 Lissin et al., 2004 Squadrito et al., 2003). In addition, Azadbakht et al. (2007a) reported a decrease in E-selectin, a biomarker of endothelial function, after 8 weeks of soy-nut consumption in postmenopausal women. However, insufficient evidence is available to determine differential effects of soy protein dose or type of soy products on changes in endothelial function (Balk et al., 2005). 

In vivo vasodilation Two methods observe the release of NO by the endothelium by measuring changes in blood flow in humans. In flow-mediated dilatation, the diameter of the brachial artery is measured with ultrasound. The vasodilation is induced by the increase of arterial shear stress after the release of an inflatable cuff around the arm. Plethysmography measures the blood flow via the volume changes of the forearm after venous occlusion. Quantification of NO is not possible in either method and the diagnostic value is limited as individuals show considerable variations in systemic response. 

Several epidemiological studies have linked a protective effect against cardiovascular diseases and regular consumption of either red wine [7, 8, 98] or polyphenol-rich sources such as green tea [14,15,99], cocoa, or chocolate [16,17]. Since many cardiovascular diseases are associated with an impaired endothelial function, the evaluation of the endothelial function is of great importance. In humans, the endothelial function is often assessed by the flow-mediated dilatation (FMD). For this purpose, reactive hyperemia is induced after a transient ischemia in the upper arm using an inflatable cuff like that used for the measurement of blood pressure, while the diameter of the brachial artery is monitored continuously at the elbow level by ultrasound. The cuff is inflated tmtil the occlusion of the brachial artery, which is maintained for 5 min before the blood flow is released. The reperfusion then induces an endothelium-dependent dilatation of the brachial artery due to the increased shear stress, the most important physiological activator of eNOS. Impaired endothelial function, assessed by FMD, has been reported as an independent predictor of cardiovascular outcome in subjects with cardiovascular risk factors or established cardiovascular diseases [18]. 

This procedure involves ligation of the fistula at its origin followed by reestablishment of the fistula via a saphenous vein bypass from a more distal arterial source to the fistula (fig. 2). By using a smaller distal artery as inflow, RUDI lengthens the fistula, decreases the diameter, and preserves antegrade flow in the brachial artery. In contrast to DRIL, it is the fistula, not the native arterial supply that is placed at risk by ligation and revascularization. However, the overall success rate for radial artery-based access procedures is fairly poor in the elderly and diabetics. 

Two authors have reported their experience with the PAVA or PAI technique that consists of performing proximal anastomosis to a more proximal mid-brachial or axillary artery by using a small-caliber (4 or 5 mm) or a 4-7 tapered expanded PTFE graft as feeder [28, 29]. The more proximal artery has a larger diameter, and theoretically the arterial pressure drop distal to the AVF should be significantly lower. The absence of reversed flow in the forearm arteries... 

---