Superficial femoral artery endothelial responses to a short-term altered shear rate intervention in healthy men

Abstract

In animal and in-vitro models, increased oscillatory shear stress characterized by increased retrograde shear-rate (SR) is associated with acutely decreased endothelial cell function. While previous research suggests a possible detrimental role of elevated retrograde SR on endothelial-function in the brachial artery in humans, little research has been conducted examining arteries in the leg. Examinations of altered shear pattern in the superficial femoral artery (SFA) are important, as this vessel is both prone to atherosclerosis and leg exercise is a common form of activity in humans. Seven healthy men participated; bilateral endothelial-function was assessed via flow-mediated-dilation (FMD) before and after 30-minute unilateral inflations of a thigh blood pressure cuff to either 75 mmHg or 100 mmHg on two separate visits. Inflation of the cuff induced increases in maximum anterograde (p<0.05), maximum retrograde (p<0.01), and oscillatory shear index (OSI) (p<0.001) in the cuffed leg at both inflation pressures. At 100 mmHg the increases in SR were larger in the retrograde than the anterograde direction evidenced by a decrease in mean SR (p<0.01). There was an acute decrease in relative FMD in the cuffed leg alone following inflation to both pressures. These results indicate that in the SFA, altered SR profiles incorporating increased retrograde and OSI influence the attenuation in FMD after a 30-minute unilateral thigh-cuff inflation intervention. Novel information highlighting the importance of OSI calculations and assessments of flow profiles add to current body of knowledge regarding the influence of changes in SR patterns on FMD. Findings from the current study may provide additional insight when designing strategies to combat impaired vascular function in the lower extremity where blood vessels are more prone to atherosclerosis in comparison to the upper extremity.

Figure 1. Superficial Femoral Artery Cuff-Inflation Intervention (Doppler Screen Capture).

Screen capture of the Doppler velocity profile before and at 30-minute of the (A) 75 mmHg and (B) 100 mmHg cuff inflation in the cuffed leg.

Figure 2. Superficial Femoral Artery 75 mmHg Cuff-Inflation Intervention.

On the left (A): mean, anterograde (+ ve), and retrograde (-ve) SR patterns pre- and during the intervention in the cuffed leg. On the right (B): relative FMD before and after the intervention in the cuffed and non-cuffed leg; mean and individual data are presented (n = 7). Error bars represent SD.

Figure 3. Superficial Femoral Artery 100 mmHg Cuff-Inflation Intervention.

On the left (A): mean, anterograde (+ ve), and retrograde (-ve) SR patterns pre- and during the intervention in the cuffed leg. On the right (B): relative FMD before and after the intervention in the cuffed and non-cuffed leg; mean and individual data are presented (n = 7). Error bars represent SD.