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Denervated heart: exercise physiology

Donor heart, which is completely denervated, does not respond to manipulations of the parasympathetic nervous system (including reductions in parasympathetic outflow, ex. anticholinergics, anticholinesterases, or increases on PNS outflow, ex. phenylephrine), or neuronal SNS outflow (ex. cardioaccelerator fibers, although systemic epinephrine may still affect the heart). Furthermore, denervation impairs the response to changes in cardiac filling pressures as well as the renin-angiotensin-aldosterone system. Resting heart rate is increased, the heart rate does not respond to hypovolemia, vasodilation, or exercise. Diabetes is the most common cause of denervation in the non-cardiac surgery population.

Denervated Heart

  • Resting HR 90-110
  • No response to hypovolemia, vasodilation, or exercise
  • Impaired response to changes in cardiac filling pressures
  • Impaired renin-angiotensin-aldosterone system
  • Normal resting inotropic state

Despite these changes, inotropic state and myocardial blood flow are normal at rest. Beta receptors may be upregulated, leading to an exaggerated response to systemic catecholamines. Afferent sensation is absent (and thus subsequent myocardial disease is asymptomatic).

Cardiac transplantation surgery results in postganglionic denervation. Note that preganglionic denervation (as occurs during spinal cord injury, Shy-Drager syndrome, etc.) will leave some reflexes intact.