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- Title
Discordance between direct (microneurographic) and indirect (heart rate variability) estimates of sympathetic activity in patients with pulmonary artery hypertension.
- Authors
McGowan, Cheri L.; Swiston, John; Granton, John T.; Mak, Susanna; Morris, Beverley L.; Notarius, Cathy F.; Picton, Peter E.; Floras, John S.
- Abstract
Low frequency spectral power (PL) may estimate the independent contributions of the sympathetic nervous system to heart rate variability in healthy subjects, but patients with heart failure (HF) due to systolic dysfunction (a state of generalized sympathetic activation) exhibit an inverse rather than direct relationship between muscle sympathetic nerve activity (MSNA) and PL. Patients with pulmonary artery hypertension (PAH) have normal left ventricular (LV) systolic function and low total power (PT) due to right atrial tension secondary to high pulmonary vascular resistance. We therefore tested the hypothesis that PL relates inversely to MSNA in PAH. Heart rate (HR) and MSNA were recorded during 10 min of supine rest in 8 PAH patients (age: 45.6 ± 4.4 yrs, pulmonary capillary wedge pressure: 11 ± 2 mmHg, pulmonary artery mean pressure: 54 ± 4 mmHg, right atrial pressure: 7 ± 1 mmHg; mean ± SE). Coarse-graining spectral analysis was used to determine PL and PT. HR was 87.3 ± 8.4 beats/min and MSNA was 47.9 ± 9.1 bursts/min (mean ± SE). MSNA related inversely to both PL (r = -0.73), and PT (r = -0.72) (p = 0.04). Thus, in PAH patients with normal LV pressures, PT relates inversely to MSNA, i.e., it is the absence of PL that indicates sympathetic activation. As with HF, reductions rather than elevations in low frequency power should be used to infer between-subject differences in sympathetic outflow in PAH.
- Subjects
PULMONARY artery; HYPERTENSION; SYMPATHETIC nervous system; HEART beat; HEART failure
- Publication
FASEB Journal, 2007, Vol 21, Issue 6, pA888
- ISSN
0892-6638
- Publication type
Article