Abstract
Spinal cord injury (SCI) leads to autonomic nervous system damage, resulting in loss
of sympathetic control to the vasculature and the heart proportional to injury level.
Given maintained cardiac parasympathetic control, we hypothesized that SCI demonstrates
a compensatory, higher baroreflex gain compared to able-bodied that relates to injury
level (neurological and/or sensory). We compared baroreflex gain (average and across
10–20, 20–30, and 30–40 mmHg input stimuli) derived from neck chamber technique in
SCI (N = 29; neurological level C1-T10, sensory zone of partial preservation C4–S4/5;
≤2 yrs since injury) and able-bodied (N = 14). Average gain tended to be higher in
able-bodied compared to SCI (p = 0.06), primarily due to higher gains at 10–20 and
20–30 mmHg (p = 0.03, p = 0.06). In SCI, although gain was not related to neurological
level, average gain and gain at 10–20 mmHg was related to sensory zone of partial
preservation and resting RR-interval (all p < 0.02). Multiple regression showed that
both sensory level and RR-interval were strongly predictive of average baroreflex
gain (r2 = 0.41, p < 0.01) and gain at 10–20 mmHg (r2 = 0.51, p < 0.01); gain decreased with higher sensory zone of partial preservation
and lower resting RR-interval. Moreover, gain was significantly lower in those with
high sensory level compared to both able-bodied (average gain and gain at 10–20 and
20–30 mmHg p < 0.01) and those with low level injury (all p < 0.05). In SCI, sensory
zone of partial preservation is more predictive of gain than neurological level. This
might reflect that those with high level sensory injuries may have the lowest likelihood
of intact cardiac sympathetic innervation and therefore lesser cardiac vagal responsiveness
due to vagal-sympathetic interactions.
Keywords
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References
- Effects of noradrenaline on human vagal baroreflexes.Ann. Med. 2001; 33: 193-200
- Mechanisms of blood pressure and heart rate variability: an insight from low-level paraplegia.Am. J. Physiol. Regul. Integr. Comp. Physiol. 2007; 292: R1502-R1509
- Clinical correlates of frequency analyses of cardiovascular control after spinal cord injury.Am. J. Physiol. Heart Circ. Physiol. 2008; 294: H668-H678https://doi.org/10.1152/ajpheart.00869.2007
- Impairment of carotid-cardiac vagal baroreflex in wheelchair-dependent quadriplegics.Am. J. Phys. 1991; 260: R576-R580https://doi.org/10.1152/ajpregu.1991.260.3.R576
- Respiratory and baroreceptor reflex interactions in man.J. Clin. Invest. 1977; 59: 780-785https://doi.org/10.1172/JCI108699
- Autonomic control of the heart and renal vascular bed during autonomic dysreflexia in high spinal cord injury.Clin. Auton. Res. 2002; 12: 457-464https://doi.org/10.1007/s10286-002-0068-0
- Effects of azepexole and clonidine on baroreceptor mediated reflex bradycardia and physiological tremor in man.Br. J. Clin. Pharmacol. 1985; 20: 431-436
- Autonomic consequences of spinal cord injury.Compr. Physiol. 2014; 4: 1419-1453https://doi.org/10.1002/cphy.c130045
- Baroreflex buffering is reduced with age in healthy men.Circulation. 2003; 107: 1770-1774https://doi.org/10.1161/01.CIR.0000057811.86187.88
- International standards for neurological classification of spinal cord injury (revised 2011).J. Spinal Cord Med. 2011; 34: 535-546https://doi.org/10.1179/204577211X13207446293695
- Reference for the 2011 revision of the International Standards for Neurological Classification of Spinal Cord Injury.J. Spinal Cord Med. 2011; 34: 547-554https://doi.org/10.1179/107902611X13186000420242
- Pressure-diameter relationship in the common carotid artery of conscious man.Pflugers Arch. 1970; 314: 27-39
- Human autonomic rhythms: vagal cardiac mechanisms in tetraplegic subjects.J. Physiol. Lond. 1994; 474: 483-495
- Pressor dose responses and baroreflex sensitivity in quadriplegic spinal cord injury patients.J. Hypertens. 1992; 10: 245-250
- Sympathetic-parasympathetic interactions in the heart.Circ. Res. 1971; 29: 437-445
- Cardiac sympathetic-parasympathetic interactions.Fed. Proc. 1984; 43: 2598-2602
- Spontaneous indices are inconsistent with arterial baroreflex gain.Hypertension. 2003; 42: 481-487https://doi.org/10.1161/01.HYP.0000091370.83602.E6
- Altered Mayer wave and baroreflex profiles in high spinal cord injury.Am. J. Hypertens. 2001; 14: 141-148
- Autonomic nervous system influence on arterial baroreflex control of heart rate during exercise in humans.J. Physiol. Lond. 2005; 566: 599-611https://doi.org/10.1113/jphysiol.2005.084541
- Impaired baroreflex function during orthostatic challenge in patients after spinal cord injury.J. Neurotrauma. 2017; 34: 3381-3387https://doi.org/10.1089/neu.2017.4989
- Spontaneous cardiac baroreflex in humans. Comparison with drug-induced responses.Hypertension. 1995; 25: 1058-1068
- Increased central arterial stiffness explains baroreflex dysfunction in spinal cord injury.J. Neurotrauma. 2014; 31: 1122-1128https://doi.org/10.1089/neu.2013.3280
- The action of clonidine on the baroreflex control of heart rate in conscious animals and man, and on single aortic baroreceptor discharge in the rabbit.Arch. Int. Pharmacodyn. Ther. 1975; 214: 4-11
- Device for rapid quantification of human carotid baroreceptor-cardiac reflex responses.J. Appl. Physiol. 1986; 60: 727-732https://doi.org/10.1152/jappl.1986.60.2.727
- Sympathetic-parasympathetic interaction and accentuated antagonism in conscious dogs.Am. J. Phys. 1991; 260: H335-H340https://doi.org/10.1152/ajpheart.1991.260.2.H335
- Cardiovascular consequences of loss of supraspinal control of the sympathetic nervous system after spinal cord injury.Arch. Phys. Med. Rehabil. 2000; 81: 506-516https://doi.org/10.1053/mr.2000.3848
- Accentuated antagonism in the control of human heart rate.Clin. Auton. Res. 2000; 10: 107-110
- Combined medical and surgical treatment after acute spinal cord injury: results of a prospective pilot study to assess the merits of aggressive medical resuscitation and blood pressure management.J. Neurosurg. 1997; 87: 239-246https://doi.org/10.3171/jns.1997.87.2.0239
Article info
Publication history
Published online: March 23, 2020
Accepted:
March 21,
2020
Received in revised form:
February 28,
2020
Received:
August 9,
2019
Identification
Copyright
© 2020 Elsevier B.V. All rights reserved.
