HEART-RATE-VARIABILITY IN CHRONIC TRAUMATIC BRAIN INJURY

Heart-rate variability (HRV), a measure of fluctuation around the mean heart rate, reflects the sympathetic and parasympathetic balance of t he autonomic nervous system, and is an excellent technique to study ca rdiovascular tone in patients with neurological injuries. The purpose of this study was to determine whether abnormal HRV is present in pati ents with traumatic brain injury (TBI) during the post-acute recovery phase. Using a prospective, case/control design, we performed 24-h amb ulatory ECG monitoring in seven TBI patients and in seven controls (C) . There was a significant difference in root mean squared successive d ifference of RR intervals (C 40.4 +/- 10.3, TBI 23.3 +/- 16.5, p = 0.0 4) between TBI and C. Four patients with TBI (compared to one control) had abnormal standard deviation of the RR interval. When these four p atients were compared to their matched controls, significant differenc es were found in frequency domain measure (In total po TBI 4.4 +/- 0.9 ms(2), C 7.1 +/- 1.4 ms(2). In low frequency: TBI 3.3 +/- 1.1 ms(2), C 6.4 +/- 1.4 ms(2); In high frequency TBI 2.0 +/- 1.0 ms(2), C 4.8 +/ - 1.3 ms(2), all p < 0.05). Thus, abnormalities in both time and frequ ency domains of HRV are present in TBI during the pose-acute recovery phase.