[Observations on serum digoxin-like immunoreactive substances in patients with cor-pulmonale]

The level of endogenous digoxin-like immunoreactive substances (DLIS) was determined with RIA in 27 patients with cor-pulmonale and 10 normal subjects as controls. The results showed that the concentration of serum DLIS was 0.51 +/- 0.18 ng/ml in the controls, 0.82 +/- 0.24 (P < 0.05), 1.45 +/- 0.51 (P < 0.001), and 2.31 +/- 1.22 ng/ml (P < 0.001) in the patients groups with cardiac function grade II (9 cases), III (10 cases) and IV (8 cases) respectively. It has been reported that both endo- and exogenous digoxin-like substances have the same function. Cor-pulmonale patients with heart failure who are treated with digoxin tend to have toxic reactions. We consider the increase in serum endogenous DLIS as the cause. It is suggested that the dosage of digoxin, if it must be used, should be individualized and the serum level monitored if possible, so as to achieve best therapeutic effects with smaller doses.