Influence of Acute, Sympathetic Nervous Activity‐Independent Changes in Blood Pressure on Forearm Arterial Stiffness

Abstract

Several studies have demonstrated the relationship between acute changes in blood pressure and arterial stiffness utilizing perturbations that alter sympathetic nervous activity (SNA), which influences vascular tone. The purpose of the current study was to elicit changes in blood pressure without altering SNA to thus observe the isolated influence of local changes in blood pressure on arterial stiffness. In this scenario, myogenic responses and changes in elastic reserve may contribute to changes in stiffness. Eleven young and healthy adults (age 20± 2 years) participated in this study. Left forearm blood pressure was acutely manipulated by elevating the forearm above heart level (AHL; reduced blood pressure) or lowering the forearm below heart level (BHL; increased blood pressure). Using applanation tonometry at the wrist and antecubital fossa, arterial stiffness was assessed via pulse wave velocity (PWV) after 5 min of rest in three positions: heart level (HL), AHL and BHL. To determine myogenic response involvement, forearm vascular conductance (VC; forearm blood flow/forearm mean blood pressure) was also assessed with duplex ultrasound. Results are mean ± SD. Forearm mean blood pressure was significantly different between arm positions (p<0.001): BHL 99 ± 6 mmHg; HL 80 ± 5 mmHg; AHL 60 ± 4 mmHg. PWV was higher in the BHL (13.4 ± 7.6 m/s) and HL (10.8 ± 4.5 m/s) positions compared to the AHL position (7.4 ± 3.6 m/s) (p<0.001 and 0.01 respectively). Including all positions, blood pressure and PWV were positively correlated (r2=0.4, p=0.002). Forearm VC was significantly lower in the BHL position compared to the HL and AHL positions (p=0.002 and 0.001 respectively). AHL and HL VC were not significantly different (p=1.0). There was no correlation between PWV and VC (r2=0.04, p=0.78). In conclusion, these results indicate that increasing blood pressure results in increases in local arterial stiffness, independent of changes in SNA. The absence of correlation between VC and PWV suggests that changes in elastic reserve played a larger role than myogenic tone in determining changes in stiffness with acutely altered forearm blood pressure.