Beneficial Cardiac Structural and Functional Adaptations After Lumbosacral Spinal Cord Epidural Stimulation and Task-Specific Interventions: A Pilot Study

Abstract

Cardiac myocyte atrophy and the resulting decreases to the left ventricular mass and dimensions are well documented in spinal cord injury. Therapeutic interventions that increase preload can increase the chamber size and improve the diastolic filling ratios; however, there are no data describing cardiac adaptation to chronic afterload increases. Research from our center has demonstrated that spinal cord epidural stimulation (scES) can normalize arterial blood pressure, so we decided to investigate the effects of scES on cardiac function using echocardiography. Four individuals with chronic, motor-complete cervical spinal cord injury were implanted with a stimulator over the lumbosacral enlargement. We assessed the cardiac structure and function at the following time points: (a) prior to implantation; (b) after scES targeted to increase systolic blood pressure; (c) after the addition of scES targeted to facilitate voluntary (i.e., with intent) movement of the trunk and lower extremities; and (d) after the addition of scES targeted to facilitate independent, overground standing. We found significant improvements to the cardiac structure (left ventricular mass = 10 ± 2 g, p < 0.001; internal dimension during diastole = 0.1 ± 0.04 cm, p < 0.05; internal dimension during systole = 0.06 ± 0.03 cm, p < 0.05; interventricular septum dimension = 0.04 ± 0.02 cm, p < 0.05), systolic function (ejection fraction = 1 ± 0.4%, p < 0.05; velocity time integral = 2 ± 0.4 cm, p < 0.001; stroke volume = 4.4 ± 1.5 ml, p < 0.01), and diastolic function (mitral valve deceleration time =-32 ± 11 ms, p < 0.05; mitral valve deceleration slope = 50 ± 25 cm s −1 , p < 0.05; isovolumic relaxation time = −6 ± 1.9 ms, p < 0.05) with each subsequent scES intervention. Despite the pilot nature of this study, statistically significant improvements to the cardiac structure, systolic function, and diastolic function demonstrate that scES combined with task-specific interventions led to beneficial cardiac remodeling, which can reverse

Effects of a Tailored Physical Activity Intervention on Cardiovascular Structure and Function in Individuals With Spinal Cord Injury

“…14,15,40 Alternatively, the inability to activate the sympathetic nervous system and/or lower-limb motor function during exercise may preclude an effective stimulus for measurable cardiovascular effects, given the growing evidence that sympathetic activation may be necessary for cardiac and vascular adaptation. 56,57 To specifically address the important role of the autonomic system, future studies should consider the influence of “autonomic completeness” on the cardiac and vascular adaptations to PA interventions in individuals with SCI.…”

Epidural stimulation with locomotor training ameliorates unstable blood pressure after tetraplegia. A case report

“…Recent reports have demonstrated the efficacy and the mechanisms of spinal cord epidural stimulation (SCES) in enhancing motor recovery, 4 and restoration of standing and volitional overground stepping 5–7 . Furthermore, multiple reports show that SCES is effective in modulating lumbosacral neural circuits to regulate BP in persons with complete SCI 8–10 . Potential mechanisms of SCES‐induced regulation of orthostatic hypotension and cardiovascular function have been proposed 11,12 .…”

“… 5 , 6 , 7 Furthermore, multiple reports show that SCES is effective in modulating lumbosacral neural circuits to regulate BP in persons with complete SCI. 8 , 9 , 10 Potential mechanisms of SCES‐induced regulation of orthostatic hypotension and cardiovascular function have been proposed. 11 , 12 This may include increasing the resting membrane potential of the sympathetic circuitry via the stimulation of dorsal afferent relays, modulating local efferent outflow of spinal sympathetic neurons, changes in hormonal and inflammatory profiles, or vasodilation induced by antidromic stimulation of the afferent terminals.…”

Targeting bladder function with network-specific epidural stimulation after chronic spinal cord injury

“…Lumbosacral spinal cord epidural stimulation (scES) combined with intensive activity-based recovery training is one such neuromodulatory approach that re-engages existing spinal circuits below the level of injury, challenging the novel postinjury circuitry to reorganize in functionally and physiologically signi cant ways [12][13][14][15][16][17]. Capitalizing on the inherent functional capacity that comprises these systemic circuits, scES enables autonomic circuits to recover signi cant levels of function [18][19][20][21][22][23][24][25][26][27]. We have previously shown that scES can be used to augment the lumbosacral neural circuitry below the level of injury su cient to potentiate gains in bladder function [21] achieved through activity-based recovery interventions alone [8,28].…”