Plasma catecholamines in clinical studies of cardiovascular diseases.

This brief review summarizes recent literature about plasma catecholamines as indices of sympathetic nervous and sympathoadrenomedullary activity in clinical cardiologic disease states. Many reports have described high plasma levels of norepinephrine, the neurotransmitter of the sympathetic nervous system, in acute myocardial infarction, congestive heart failure, the mitral valve prolapse syndrome, and early essential hypertension. Fewer studies have reported values for plasma epinephrine, which is the product of sympathoadrenomedullary secretion. The relationship between circulating catecholamine levels and activity of the sympathetic nervous system is obscured by ignorance about catecholamine removal mechanisms and regionalization of sympathetic outflow. Further, whether increased sympathetic outflow increases cardiovascular risk or reflects compensatory recruitment or a non-specific stress response is poorly understood.