ALTERATIONS OF THE AUTONOMIC REGULATION O F HEART-RATE IN PATIENTS WITH BRAIN-STEM LESIONS

The present study investigates the frequency of alterations of autonom ic cardiac innervation in patients with brainstem lesions by testing c ardiovascular reflexes tests. In the neurological ICU, we tested 22 pa tients aged 19 to 78 years (mean age 54 +/- 17 years) suffering from i schemic brain stem lesions. The variability of heart rate was at first evaluated at rest. Mean heart rate, coefficient of variation (VK) and RMSSD (root mean square of successive differences) were calculated. I n addition, a spectral analysis of the heart frequency was computed by a fast fourier transformation and the spectral powers in the frequenc y bands 0.02-0.09 Hz, 0.09-0.15 Hz and 0.20-0.30 Hz, respectively were determined. An atropine test was then carried out. 5 minutes after th e beginning of injection of atropine sulfate, further rate and spectra l analyses were again computed. The VK was pathologically diminished i n 59 % of the patients, the RMSSD in 55 % and both, VK and RMSSD, in 4 5 %. In 32 % of the patients VK and RMSSD were within normal range. Sp ectral power was diminished in all three frequency bands in 4 out of 2 2 patients with pathological heart rate variability. Most abnormal res ults in spectral analysis could be obtained in the frequency band 0.09 -0.15 Hz (73 %), followed by the frequency band 0.20-0.30 Hz (45 %) an d the 0.02-0.09 Hz frequency band (32 %). There were significant corre lations between the heart rate variability; the spectral power in the 0.09-0.15 Hz and 0.20-0.30 Hz frequency bands (p < 0.05; Spearman). 88 % of the patients with abnormal results at rest had diminished heart rate responses to atropine. Five minutes after onset of the atropine t est, VK, RMSSD and spectral power in the frequency bands 0.02-0.09 Hz and 0.20-0.30 Hz were significantly reduced (p < 0.05; Wilcoxon). Impa ired control of heart rate in patients with brain stem lesions may be frequently taken as a sign of autonomic dysregulation. By means of com paring results, alterations of autonomic cardiac innervation could be detected most frequently by heart frequency analysis, corresponding no rmal and pathological results in spectral analysis and atropine test w ere found in most cases.