Contemporary Cardiovascular Concerns after Spinal Cord Injury: Mechanisms, Maladaptations, and Management

Abstract

Cardiovascular (CV) issues after spinal cord injury (SCI) are of paramount importance considering they are the leading cause of death in this population. Disruption of autonomic pathways leads to a highly unstable CV system, with impaired blood pressure (BP) and heart rate regulation. In addition to low resting BP, on a daily basis the majority of those with SCI suffer from transient episodes of aberrantly low and high BP (termed orthostatic hypotension and autonomic dysreflexia, respectively). In fact, autonomic issues, including resolution of autonomic dysreflexia, are frequently ranked by individuals with high-level SCI to be of greater priority than walking again. Owing to a combination of these autonomic disturbances and a myriad of lifestyle factors, the pernicious process of CV disease is accelerated post-SCI. Unfortunately, these secondary consequences of SCI are only beginning to receive appropriate clinical attention. Immediately after high-level SCI, major CV abnormalities present in the form of neurogenic shock. After subsiding, new issues related to BP instability arise, including orthostatic hypotension and autonomic dysreflexia. This review describes autonomic control over the CV system before injury and the mechanisms underlying CV abnormalities post-SCI, while also detailing the end-organ consequences, including those of the heart, as well as the systemic and cerebral vasculature. The tertiary impact of CV dysfunction will also be discussed, such as the potential impediment of rehabilitation, and impaired cognitive function. In the recent past, our understanding of autonomic dysfunctions post-SCI has been greatly enhanced; however, it is vital to further develop our understanding of the long-term consequences of these conditions, which will equip us to better manage CV disease morbidity and mortality in this population.

Emergency management of autonomic dysreflexia with neurologic complications

“…Individuals with high-thoracic or cervical complete spinal cord injury commonly experience dramatic hypertensive episodes known as autonomic dysreflexia, 1 which likely contribute to their 300%-400% increased risk of stroke. 2 Autonomic dysreflexia is reported in 90% of patients with high-thoracic or cervical spinal cord injury…”

“…[6][7][8] Clinical evidence suggests that episodes of autonomic dysreflexia with systolic blood pressure exceeding 180 mm Hg can lead to cerebral vascular insult and death. 1 Furthermore, posterior reversible encephalopathy syndrome is associated with cerebral hemorrhage in 15%-65% 4,9 of cases (and has previously been reported in an individual with spinal cord injury 6 ). Therefore, our patient, who presented with decreased level of consciousness related to autonomic dysreflexia, as well as seizures, was at high risk of progression to a life-threatening outcome.…”

“…1 Most autonomic dysreflexia is a direct result of urogenital complications (e.g., urinary tract infection, bladder distension or catheter blockage). 1 We have presented a case of severe autonomic dysreflexia that resulted in profound clinical complications (i.e., blurred vision, headache, tonic-clonic seizures) and subtle posterior T2 and fluid-attenuated inversion recovery abnormalities consistent with posterior reversible encephalopathy syndrome. We outline here the critical steps in the clinical management of this complex and rare presentation of autonomic dysreflexia.…”

“…Without descending supraspinal control, these sympathetic pre ganglionic neurons become susceptible to bouts of hyperactivity resulting from stimuli below the level of injury, which ultimately constrict the corresponding vasculature and dangerously elevate blood pressure (Figure 2). 1 Although it is life-threatening, some individuals with spinal cord injury may selfelicit autonomic dysreflexia in an effort to combat low resting blood pressure (i.e., "boosting"); 1 this practice is not clinically recommended.…”

“…5 The first step typically involves moving the patient to an upright position to elicit an orthostatic reduction in blood pressure; this reduction can be quite dramatic in those with spinal cord injury because of disrupted supraspinal regulation of blood vessel tone. 1 This manoeuvre is followed by identification and elimination of possible triggers for the elevated blood pressure (e.g., bladder distension, kinked Foley catheter, urinary tract infection, bowel impaction), with specific emphasis on the bladder and bowel. If, despite these steps, systolic blood pressure does not drop below 150 mm Hg, oral antihypertensive medications with a short onset of action (e.g., nifedipine, captopril) are recommended to reverse the hypertension.…”