Bezold-Jarisch reflex

The Bezold–Jarisch reflex involves a variety of cardiovascular and neurological processes which cause hypopnea (overly shallow breathing or an abnormally low respiratory rate) and bradycardia (abnormally low resting heart rate).

Physiology
Prolonged upright posture results in some degree of pooling of blood in the lower extremities that can lead to diminished intracardiac volume.

This phenomenon is accentuated if the individual is dehydrated.

The resultant arterial hypotension is sensed in the carotid sinus baroreceptors, and efferent fibers from these receptors trigger autonomic signals that increase cardiac rate and contractility.

However, pressure receptors in the wall and trabeculae of the underfilled left ventricle may then sense stimuli, indicating high-pressure C-fiber afferent nerves from these receptors.

They may respond by sending signals that trigger paradoxical bradycardia and decreased contractility, resulting in additional and relatively sudden arterial hypotension.

It usually occurs in nitrate therapy and use of serotonin agonists.

History
It is named for Albert von Bezold and Adolf Jarisch Junior.