Low-frequency arterial pressure fluctuations do not reflect sympathetic outflow: gender and age differences.

Low-frequency arterial pressure oscillations (Mayer waves) have been proposed as an index of vascular sympathetic outflow. However, cross-sectional differences in these pressure oscillations may not reflect different levels of sympathetic nervous outflow in humans. Three groups of healthy subjects with characteristically different sympathetic nervous outflow were studied: young females (n = 10, 18-28 yr), young males (n = 11, 18-29 yr), and older males (n = 13, 60-72 yr). Average R-R interval, arterial pressures, and systolic pressure variability at the Mayer wave frequency (0.05-0.15 Hz) did not differ among the three groups. Diastolic pressure Mayer wave variability was similar in young females vs. young males (39 +/- 10 vs. 34 +/- 5 mmHg2) and lower in older males vs. young males (14 +/- 2 mmHg2; P < 0.05). In contrast, muscle sympathetic activity was lowest in young females (892 +/- 249 total activity/min) and highest in older males (3,616 +/- 528 total activity/min; both P < 0.05 vs. young males: 2,505 +/- 285 total activity/min). Across the three groups, arterial pressure Mayer wave variability did not correlate with any index of sympathetic activity. Our results demonstrate that arterial pressure Mayer wave amplitude is not a surrogate measure of vascular sympathetic outflow.