Relationship between endogenous concentrations of vasoactive substances and measures of peripheral vasodilator function in patients with coronary artery disease

The aim of the present study was to determine the relationship between plasma concentrations of nitrite/nitrate (NO_x) and endothelin (ET)-1 and non-invasive measures of peripheral vasodilator function in patients with coronary artery disease (CAD). Twenty-two patients with angiographic CAD underwent non-invasive measurement of peripheral vasodilator function in the brachial conduit artery (flow-mediated dilation (FMD) testing via ultrasound) and in the forearm resistance arteries (via venous occlusion plethysmography) during reactive hyperaemia after 5 min ischaemia. In addition, plasma NO_x and ET-1 concentrations were determined. The plasma concentration of NO_x was related to the peak brachial FMD response when expressed as either the relative (%) or absolute (mm) change in diameter (r = 0.73, P < 0.001; and r = 0.64, P < 0.01, respectively). Moreover, plasma concentrations of NO_x demonstrated a relationship with forearm vasodilation estimated by total forearm blood flow following 5 min ischaemia (r = 0.63, P < 0.01) and the flow debt repayment of the forearm (r = 0.54, P < 0.01). Finally, ET-1 concentrations were inversely related to FMD% (r = -0.45, P < 0.05). The findings of the present study demonstrate a relationship between the plasma concentrations of NO_x and measures of vascular reactivity in conduit and resistance arteries in patients with CAD. Therefore, measurement of plasma NO_x may serve as a reliable marker for peripheral vasodilator dysfunction in patients with CAD.