The effect of severe brainstem injury on heart rate and blood pressure oscillations

To determine whether an intact brainstem is essential for the generation of neurogenically mediated fluctuations of R—R intervals and blood pressure, three patients with cerebellar lesions causing severe brainstem compression or death, one patient with a large pontine infarct and one patient with a pontine haemorrhage, were studied. Time—frequency maps (based on a modified Wigner distribution) were constructed from blood pressure and R—R interval signals in these patients with brainstem injury and were compared with maps of normal control subjects. Low frequency sympathetically mediated rhythms (0.01–0.12 Hz) in systolic and diastolic pressure remained detectable but attenuated in patients with brainstem injury whereas there was an almost complete loss of normal R—R intervals rhythmicity over 0.01 to 0.5 Hz range. These data suggest that fluctuations in R—R intervals require an intact brainstem, whereas low frequency ∼0.06 ± 0.02 Hz blood pressure rhythms may be preserved by spinal sympathetic circuitry.