Heart rate variability power spectrogram as a potential noninvasive signature of cardiac regulatory system response, mechanisms, and disorders.

This paper attempts to provide evidence that the heart rate variability power spectrum (HRVPS) reflects the presence of neural control of cardiac regulation. A normal individual is seen to have a characteristic HRVPS (comprising a 0.1-Hz peak and a respiratory peak at 0.25-0.34 Hz), which is altered in a predictable manner in response to orthostatic stress and exercise, while in two patients with autonomic neuropathy, the HRVPS failed to demonstrate such a characteristic alteration in response to orthostatic stress. Postinfarct HRVPS signatures were studied in two patients with anterior and inferior infarcts so as to lend insight using non-invasive means into both the healing process and the dominant deliterious sympathetic or protective vagal tone due to the infarct. When subjects with transplanted hearts were studied, their HRVPS did not exhibit the characteristic pattern of a normal individual; rather, the HRVPS energy was spread over a wider and higher frequency range. However, one of the transplanted patients surprisingly but consistently revealed the characteristic HRVPS; the post-transplant time at the time of the study was 33 months and the patient had the typically high resting heart rate of a transplant recipient but a wide standard deviation like that of a normal individual. This could be the first noninvasively demonstrated evidence in humans of reinnervation of a transplanted heart. Thus, the HRVPS constitutes a simple non-invasive method to assess cardiac neuroregulatory response and disorders and it is proposed that it be referred to as the heart rate variability cardiogram (HRVC).