Improvement of Myocardial Efficiency

Friday, August 27, 2010

The strength of systolic contraction is increased from direct stimulation of the failing myocardium. The ventricles empty more completely, the cardiac output is increased and the venous pressure is lowered. The work of the heart is more efficient in that relatively less oxygen is used by the myocardium for a given amount of work. In cardiac failure the heart rate is usually increased, especially if there is atrial fibrillation. Digitalis slows the heart by direct depression of the conducting tissues and by vagal stimulation. Improvement of function and slowing of rate are closely related. Digitalis acts as a potent diuretic in patients with edema due to cardiac failure, consequent on the improved blood supply to the kidney which results from its action on the myocardium.