P21 REDUCTION OF CARDIAC PRE-LOAD HAS ANTITHETICAL EFFECTS ON BLOOD PRESSURE AND ARTERIAL STIFFNESS: IS BLOOD PRESSURE THE MAIN DETERMINANT OF WITHIN-SUBJECT VARIATION IN PULSE WAVE VELOCITY?

Abstract

Objective: Blood pressure (BP) is considered the most important determinant of within-subject variation in pulse wave velocity (PWV) and the possibility of altering arterial stiffness independently of BP is still a matter of debate. When investigating acute effects of a reduction in cardiac pre-load, we hypothesised that this would decrease BP and PWV. Design and methods: Hypertensive patients (mean±SD age 44±14 years, n = 45) had brachial BP measurements (OMRON), central BP recorded by radial pulse wave analysis (SphygmoCor) and estimation of aortic PWV (aoPWV) by trans-thoracic echocardiography. Carotid-femoral PWV (cfPWV) was also evaluated by SphygmoCor in n = 17. Measurements were performed before and after (>5 minutes) supra-diastolic, sub-systolic pressure inflation of thigh cuffs in order to decrease venous return from the lower limbs. Evaluation of inferior vena cava (IVC) diameter was used to assess pre-load. Results: Leg cuff-inflation was effective in reducing cardiac pre-load (change in IVC diameter (mean±SE) from 1.6±0.4 cm to 1.3±0.4 cm, p < 0.01) and decreased both brachial and central SBP (−3±0.9 mmHg and −3.6±1.2 mmHg respectively, both p < 0.05) while change in DBP (0.8±0.9 mmHg) and heart rate (−0.1±0.6 bpm) were not significant. By contrast, aoPWV increased by 0.8±0.35 m/s (p < 0.01) and cfPWV by 1.05±0.33 m/s (p = 0.014). Conclusions: Contrary to our hypothesis, acute reduction of cardiac pre-load significantly decreased BP but had an opposite effect on PWV. This could be mediated by an increase in sympathetic tone triggered by reduction in circulating blood volume; sympathetic tone might affect PWV independently of BP.