Non-invasive assessment of unstimulated forearm arterial compliance in human subjects. Impaired vasoreactivity in hypercholesterolaemia

A study was carried out in order to determine the feasibility and reproducibility of a direct plethysmographic assessment of unstimulated forearm arterial compliance (FAC) in hypercholesterolaemic and normocholesterolaemic subjects. Simultaneous recordings of forearm pulse volume and blood pressure over the whole cardiac cycle are used to establish the pulse volume-blood pressure relationship. FAC was measured on-line by computing the ratio of dV/dP. The area under the curve (FAC(AUC)) of FAC/blood-pressure curve was determined in a standard range of blood pressure (70-130 mmHg). The method was validated by demonstrating its capacity to detect changes in FAC(AUC) induced by nitrate and by muscarinic stimuli. The results show a reduced FAC(AUC) in hypercholesterolaemic patients vs. controls (2.28 +/- 0.8 x 10(-3) vs. 4.12 +/- 1.06 x 10(-3) (mL 100 mL-1 forearm mmHg-1) mmHg; P = 0.0001). The method appears to be highly sensitive to nitrate and muscarinic stimuli. The new technique provides a potentially useful tool to detect and monitor in vivo, without stimulating arterial dilatation, e.g. by acetylcholine infusion, the functional arterial changes in subjects with a major risk factor for arterial disease as well as the effects of dietary/drug treatments.