Abnormal heart rate variability reflecting autonomic dysfunction in brainstem infarction

Objectives - Brainstem infarctions frequently cause disturbances of cardiovascular and other autonomic functions, but the pathophysiologic mechanisms of these prognostically unfavourable complications are not well-known. Material & methods - In order to evaluate the effects of ischemic brainstem infarction on autonomic cardiac regulation, we analyzed the power spectrum of heart rate variability in 15 consecutive patients with brainstem infarction and in 15 age- and sex-matched healthy control subjects. The components of the power spectrum which reflect quantitatively both sympathetic and parasympathetic cardiovascular regulatory functions were measured from 24-hour electrocardiogram in the acute phase and at 1 month and 6 months after the infarction. Results - All the measured components of heart rate variability, i.e. total power (p<0.01), very-low-frequency power (p<0.001), low-frequency power (p<0.01), and high-frequency power (p<0.05), were significantly lower in the patients with medullary brainstem infarction than in the control subjects in the acute phase of the infarction. By 6 months, these abnormalities had been reversed. On the contrary, heart rate variability in pontine brainstem infarct patients did not differ significantly from that in the control subjects. Conclusions - These results suggest that brainstem infarction located in the medulla oblongata causes cardiovascular autonomic dysregulation manifesting as impaired heart rate variability. Medullary brainstem infarction seems to cause both sympathetic and parasympathetic dysfunction, which may contribute to the occurrence of cardiac complications in stroke.