Abstract:
The current classification system for spinal cord injury (SCI) considers only somatic
information and neglects autonomic damage after injiuy. Heart rate variability (HRV) has
the potential to be a valuable measure of cardiac autonomic control after (SCI). Five
individuals with tetraplegia and four able-bodied controls underwent 1 min continuous
ECG recordings during rest, after Metoprolol administration (max dose=3x5mg) and after
Atropine administration (0.02mg/kg) in both supine and 40° head-up tilt. After
Metoprolol administration there was a 61.8% decrease in the LF:HF ratio in the SCI
participants suggesting that the LF:HF ratio is a reflection of cardiac sympathetic
outflow. After Atropine administration there was a 99.1% decrease in the HF power in
the SCI participants suggesting that HF power is highly representative of cardiac
parasympathetic outflow. There were no significant differences between the SCI and
able-bodied participants. Thus, HRV measures are a valid index of cardiac autonomic
control after SCI.
