[Influence of spirolactone on the myocardial potassium balance following strophanthin in man (author's transl)].

In order to examine the question, whether improved digitalis tolerance by Spirolactone may be partially a result of antagonism on myocardial potassium balance, 6 patients without clinical signs of heart failure were given 400 mg, 3 were given 200 or 300 mg Spirolactone orally daily and 6 patients received placebo during a 5 to 7 days period. During cardiac catheterization hemodynamics and serum potassium concentrations were determined repeatedly prior to and following intravenous administration of 0,375 to 0,625 mg Strophanthin. Injection of Strophanthin resulted in a significant drop in left ventricular enddiastolic pressure and a rise in dp/dt max. In the control group a significant increase in arterial and coronary sinus potassium concentration was observed. Myocardial potassium balance was definitely negative from the third to the eighth minute. Values in the group receiving Spirolactone did not differ significantly from the placebo group. It is suggested that therapeutic doses of Strophanthin resllt in a loss of potassium from the myocardium by inhibition of the Na+, K+ membrane ATPase not influenced by pretreatment with Spirolactone.