NURS 5315 Factors Which Affect Myocardial Contractility

Factors Which Affect Myocardial Contractility (p1103) 1. Analyze factors which affect cardiac contractility. In healthy persons, three major factors determine the force of contraction: (1) Changes in the stretching of the ventricular myocardium caused by variations in ventricular volume (preload) (2) Alterations in nervous system input to the ventricles, (3) Adequacy of myocardial oxygen supply a. Evaluate the effects of the catecholamines on the cardiovascular system. Catecholamine Effect on the CV system Epinephrine (p1106,1117, lecture) Released by adrenal cortex; causes vasoconstriction in most vascular beds except the coronary, liver and skeletal muscle circulations. It dilates the coronary, liver and skeletal vessels, thus causing and increase in myocardial contractility; stimulates Beta 1 receptors of the heart which results in an increase myocardial contractility and heart rate. It also has some effect on Beta 2 and Alpha 1 receptors; enhances cardiac output. Norepinephrine (1106,1117, lecture) Released from the sympatheti