Vascular distensibility and compliance in salt-sensitive and salt-resistant borderline hypertension

To gain insight into the relationship between vascular compliance and sodium sensitivity.

Arterial and venous compliance was determined in 17 sodium-sensitive and 28 sodium-resistant, young, borderline hypertensive males and in 10 age-matched normotensive controls, during regular sodium intake.

The carotid, femoral and brachial arteries were studied using a non-invasive ultrasound vessel wall movement detector system, and venous compliance was determined using forearm strain-gauge plethysmography. Cardiac output, plasma volume and hormonal factors, such as plasma renin activity, were also measured to assess their possible influence on vascular compliance.

Large artery compliance was significantly less in the sodium-sensitive than in the sodium-resistant subjects in all arteries studied. Compared with controls, arterial compliance was reduced significantly in the sodium-sensitive group, whereas the sodium-resistant group did not differ significantly from the controls. Venous compliance was reduced equally in the two hypertensive groups compared with the controls, although the differences did not reach statistical significance. Cardiac output, blood pressure, plasma volume and hormonal factors did not differ between sodium-sensitive and sodium-resistant subjects and could not have been responsible for the observed differences in arterial compliance.

The results of this study suggest that sodium-sensitive borderline hypertensives have reduced large artery compliance compared with age-matched sodium-resistant subjects. Since this finding could not be explained by differences in haemodynamic or hormonal factors between the groups, this suggests alterations to the viscoelastic properties of the arterial walls in sodium-sensitive subjects.