Abnormal Heart Rate Variability in Adults with Growth Hormone Deficiency1
King S. Leong,
Paul Mann,
Maureen Wallymahmed,
Ian A. MacFarlane and
John P. H. Wilding
Address all correspondence and requests for reprints to: Dr. John P. H. Wilding, University Clinical Departments, University Hospital Aintree, Longmoor Lane, Liverpool, United Kingdom L9 7AL. E-mail: j.p.h.wilding{at}liv.ac.uk
GH-deficient (GHD) patients have increased risk of cardiovasculardeath
and may have cardiac structural abnormalities. In non-GHDpatients
these are associated with cardiac autonomic dysfunction,and it is
possible that autonomic dysfunction is also presentin GHD patients.
Power spectral analysis (PSA) of heart ratevariability (HRV)
indirectly measures cardiac autonomic toneand generates peaks at 3
frequency bands, very low frequency(VLF), low frequency (LF) and high
frequency (HF). The areaunder the LF curve is considered to reflect
predominantly cardiacsympathetic activity, whereas HF indicates
parasympathetic activity.PSA of HRV was performed in 14 normotensive
GHD patients (5men and 9 women; mean age, 35.2 yr) and 19 healthy
controls(9 men and 10 women; mean age, 38.3 yr). GHD patients had 26%
lowernormalized LF power (P < 0.004), 39% higher
normalized HFpower (P < 0.001), 28% lower
normalized VLF power (P <0.046), and 51% lower
LF/HF ratio (an index of sympathovagalbalance; P
< 0.001) compared to controls. These data indicatethat heart rate
variability is abnormal in patients with GHD.The decreased sympathetic
tone could be a consequence of reducedcentral sympathetic tone or
altered cardiac responsiveness toautonomic control and may contribute
to the increased cardiovascularrisk in GHD patients.
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