The relation of membrane-ATPase activity with congestive heart failure.

By the use of the phosphate method the activity of the (Na+ + K+)-ATPase system (E. C. 3.1.6.1.) of human left ventricle was measured in one tissue sample each obtained from 47 autopsied patients. The subjects between the ages of 20 and 79 years had suffered from congestive heart failure of different functional classes NYHA), from diseases of the heart and circulation, or from tumors. Only 23 of the patients of the entire group took digitalis glycosides. With the exception of one sample (8.58 mumol Pi.mg-1.h-1), the enzyme activity amounted from 0.45 to 4.84 mumol Pi.mg-1. The ATPase activity depends on the age (A), the functional classes of congestive heart failure (CF; CF greater than A), and the time between death and autopsy. Chronic hypoxic alterations decreased the enzyme activity. Digitalization did not influence the post-mortem enzyme activity. Due to the small therapeutic range of digitalis glycosides and a distinctly reduced ATPase activity of the ageing patient, enhanced glycoside maintenance doses will not improve myocardial contractility, but provoke arrhythmias.