An independent relationship between muscle sympathetic nerve activity and pulse wave velocity in normal humans.

Objective: Carotid-femoral pulse wave velocity (PWV) has been shown to be a powerful predictor of cardiovascular morbidity and mortality. Sympathetic neural mechanisms may have a stiffening influence on arterial mechanical properties. The relationship between direct measures of sympathetic traffic and PWV in healthy humans has not been previously studied. We, therefore, tested the hypothesis that PWV is independently linked to muscle sympathetic nerve activity (MSNA) in normal individuals.

Methods: We measured MSNA (microneurography), PWV (Complior device), heart rate and blood pressure in 25 healthy male participants (mean age 43 +/- 10 years).

Results: PWV correlated significantly with age (r = 0.63, P < 0.001), SBP (r = 0.43, P < 0.05) and MSNA (r = 0.43, P < 0.05) but not with BMI, waist circumference, waist-to-hip ratio, heart rate, pulse pressure or DBP. Robust multiple linear regression analysis revealed that only age and MSNA were linked independently to PWV (r2 = 0.62, P < 0.001), explaining 39 and 25% of its variance, respectively. After adjustment of PWV for age and SBP, we further divided individuals into 'excessive' PWV (i.e. higher than expected from age and SBP) and 'optimal' PWV (i.e. lower than expected). BMI and blood pressure were similar in both subgroups. Individuals with excessive PWV had significantly greater MSNA than individuals with optimal PWV (30 +/- 10 vs. 18 +/- 11 bursts/min, P = 0.01).

Conclusion: This study provides the first evidence that PWV is linked to MSNA in normal humans. The relationship between MSNA and PWV is independent of age, BMI, waist circumference, waist-to-hip ratio, heart rate, pulse pressure or blood pressure.