Temporal analysis of cardiovascular control and function following incomplete T3 and T10 spinal cord injury in rodents

Abstract

Spinal cord injury (SCI) is a devastating condition that results in whole‐body dysfunction, notably cardiovascular (CV) disruption and disease. Injury‐induced destruction of autonomic pathways in conjunction with a progressive decline in physical fitness contribute to the poor CV status of SCI individuals. Despite the wide use of exercise training as a therapeutic option to reduce CV dysfunction, little is known about the acute hemodynamic responses to the exercise itself. We investigated CV responses to an exercise challenge (swimming) following both high and low thoracic contusion to determine if the CV system is able to respond appropriately to the challenge of swimming. Blood pressure (BP) telemetry and echocardiography were used to track the progression of dysfunction in rodents with T3 and T10 SCI (n = 8 each) for 10 weeks postcontusion. At 1 week postinjury, all animals displayed a drastic decline in heart rate (HR) during the exercise challenge, likely a consequence of neurogenic shock. Furthermore, over time, all groups developed a progressive inability to maintain BP within a narrow range during the exercise challenge despite displaying normal hemodynamic parameters at rest. Echocardiography of T10 animals revealed no persistent signs of cardiac dysfunction; T3 animals exhibited a transient decline in systolic function that returned to preinjury levels by 10 weeks postinjury. Novel evidence provided here illustrates that incomplete injuries produce hemodynamic instability that only becomes apparent during an exercise challenge. Further, this dysfunction lasts into the chronic phase of disease progression despite significant recovery of hindlimb locomotion and cardiac function.

Markers of susceptibility to cardiac arrhythmia in experimental spinal cord injury and the impact of sympathetic stimulation and exercise training

“…Interestingly, the vulnerability to sympathetic stimulation in rodents with contusive SCI using this injury model was shown to be associated with adverse changes in left ventricular function and blunted responses to DOB based on echocardiographic markers of cardiac dysfunction at 1week after injury, but with an exaggerated response 5 weeks after SCI (Harman et al, 2018). In the present study, we observed changes to ECG parameters with DOB as early as 1-week post injury, suggesting that cardiac electrical remodeling occurs prior to structural remodeling.…”

Effects of early exercise training on the severity of autonomic dysreflexia following incomplete spinal cord injury in rodents

“…Unlike arm ergometry, swimming involves a significant need for trunk stability/orientation to ensure that the rodent swims in the appropriate direction during each lap. Previous studies in our lab showed that 4 min of swim exercise significantly challenges the CV system following incomplete T3 contusion in female rats (Harman et al, 2018). The current results suggest that intensive swimming exercise rehabilitation may tend to normalize resting hemodynamic parameters in animals with severe T2 contusions.…”

Trihydroxyethyl Rutin Provides Neuroprotection in Rats With Cervical Spinal Cord Hemi-Contusion

“…Spinal cord injury results from central nervous system trauma and seriously endangers human health. This major cause of disability imposes a heavy economic and social burden ( Jain et al, 2015 ; Harman et al, 2018 ; Zhou et al, 2018 ). Various drugs and cell therapies have shown some potential in the treatment of spinal cord injury, and some clinical trials have shown promising results.…”