LOW-FREQUENCY ARTERIAL-PRESSURE FLUCTUATIONS DO NOT REFLECT SYMPATHETIC OUTFLOW - GENDER AND AGE-DIFFERENCES

Low-frequency arterial pressure oscillations (Mayer waves) have been p roposed as an index of vascular sympathetic outflow. However, cross-se ctional differences in these pressure oscillations may not reflect dif ferent levels of sympathetic nervous outflow in humans. Three groups o f healthy subjects with characteristically different sympathetic nervo us 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 i nterval, arterial pressures, and systolic pressure variability at the Mayer wave frequency (0.05-0.15 Hz) did not differ among the three gro ups. Diastolic pressure Mayer wave variability was similar in young fe males vs. young males (39 +/- 10 vs. 34 +/- 5 mmHg(2)) and lower in ol der males vs. young males (14 +/- 2 mmHg(2); P < 0.05). In contrast, m uscle sympathetic activity was lowest in young females (892 +/- 249 to tal activity/min) and highest in older males (3,616 +/- 528 total acti vity/min; both P < 0.05 vs. young males: 2,505 +/- 285 total activity/ min). Across the three groups, arterial pressure Mayer wave variabilit y did not correlate with any index of sympathetic activity. Our result s demonstrate that arterial pressure Mayer wave amplitude is not a sur rogate measure of vascular sympathetic outflow.