Which effect does a lesion above T6 have on cardiac performance?

Lesions above T6 have significant implications for cardiac performance due to the autonomic nervous system's regulation of heart function. The thoracic spinal cord contains sympathetic nerves that facilitate the heart's response to stress, such as an increased heart rate and enhanced cardiac output during physical demand.

When a lesion occurs above T6, it disrupts the ascending and descending pathways for sympathetic nervous system control. This disruption can impair the heart's ability to increase its rate and contractility in response to both daily physiological demands and stressors. The inability to appropriately increase heart rate and cardiac output means that the heart might not sufficiently meet the body's needs, especially during exertion, leading to impaired cardiac performance.

This concept underscores the importance of sympathetic innervation in maintaining robust cardiovascular function. The changes in autonomic control can result in a range of symptoms, including orthostatic hypotension and exercise intolerance, highlighting the connection between spinal cord lesions and cardiac performance.