Deleterious effects of digitalis on newborn rabbit myocardium after simulated cardiac surgery.

We studied the effect of the digitalis glycoside ouabain on isolated blood-perfused neonatal (4- to 6-day-old) rabbit hearts during 60 minutes of hypothermic/ischemic arrest (at 15 degrees C), simulating conditions during cardiac surgery. Compared with a control (no ouabain) group, both low- and high-dose ouabain groups had increased left ventricular diastolic chamber stiffness ("contracture") during and after the arrest period. The high-dose ouabain group also showed less recovery of contractile function than did the control group. We conclude that digitalis glycosides have the potential to impair recovery of myocardial function in the newborn infant after hypothermic/ischemic arrest; myocardial relaxation and diastolic function appear more sensitive to this manifestation of digitalis toxicity than does contractile function.