Objective: To investigate the plasma concentrations and cardiac effects of endogenous digitalis-like substance (EDLS) before and after cardiopulmonary bypass (CPB).
Methods: 29 adults patients with NYHA II - IV, who suffered from congenital and acquired heart diseases, were included in this study. The plasma EDLS levels were determined by radioimmunoassay before and at the end of CPB, 2 h, 6 h, 24 h and 3 days after operation.
Results: The plasma EDLS concentrations in NYHA IV patients [(403 +/- 27) pg/mL] were significantly higher than those in II [(221 +/- 98) pg/mL] and III patients [(296 +/- 71 pg/mL), P < 0.01] before CPB. CPB could induce the release of EDLS. The EDLS concentrations in plasma increased to (683 +/- 371) pg/mL and (577 +/- 274) pg/mL at 2 h and 6 h respectively after CPB, and went back to normal at 24 h after operation. However, there was no relationship between plasma EDLS concentration and the time of ascending aorta blocked at 2 h or 6 h after operation (r = 0.0748 and 0.0393 respectively). Over 50% patients in the higher EDLS (> 1000 pg/mL) group are NYHA IV, and the ratio was significantly higher than that in lower EDLS group (< 999 pg/ mL, P < 0.05). There was no difference between higher and lower EDLS groups in respect of the requirement of inotropic support and blood pressure.
Conclusions: The EDLS release can be induced by heart failure and CPB. The plasma EDLS concentrations increase up to climax in 2-6 h after CPB. The higher plasma EDLS concentration may improve the cardiac function.