The purpose of this study is to stimulate the circuits in the spinal cord that are directly responsible for hemodynamic control to restore hemodynamic stability in participants with chronic cervical or high-thoracic spinal cord injury. The ultimate objective of this study is to provide preliminary safety and efficacy measures on the ability of the hemodynamic Targeted Epidural Spinal Stimulation (TESS) to ensure the long-term management of hemodynamic instability and reduce the incidence and severity of orthostatic hypotension and autonomic dysreflexia episodes in individuals with chronic cervical or high-thoracic spinal cord injury. In addition, the long-term safety and efficacy of TESS on cardiovascular health, respiratory function, and quality of life in participants with chronic spinal cord injury will be evaluated.