Erythrocyte Na+, K+-ATPase activity in patients with congestive heart failure

In order to determine if the Na+, K+-ATPase activity in erythrocyte membranes is altered in congestive heart failure, and to examine its clinical significance with respect to other clinical variables, erythrocyte Na+, K+-ATPase activity was measured in 51 patients with left ventricular ejection fractions <40% (coronary artery disease, n=26; dilated cardiomyopathy, n=25) and 24 control patients. Na+, K+-ATPase activity was lower in both coronary artery disease and dilated cardiomyopathy groups than control group even in the absence of digitalis use. There was a significant inverse correlation between Na+, K+-ATPase activity and plasma norepinephrine. The presence of non-sustained ventricular tachycardia was associated with a lower Na+, K+-ATPase activity in both groups with congestive heart failure without digitalis use than those without ventricular tachycardia. Plasma norepinephrine was higher in patients with non-sustained ventricular tachycardia than those without in the coronary artery disease group, but not in the dilated cardiomyopathy group. Na+, K+-ATPase activity may be helpful in predicting electrophysiologic instability in patients with heart failure.