METHODS	Patients in the multicenter , randomized , double-blind , placebo-controlled , parallel treatment study will be randomized to 1 of 3 treatment arms : ( 1 ) low-dose milrinone ( 25 microg/kg intravenous bolus over 60 minutes followed by a 0.25 microg/kg/min infusion for 35 hours ) , ( 2 ) high-dose milrinone ( 75 microg/kg intravenous bolus over 60 minutes followed by a 0.75 microg/kg/min infusion for 35 hours ) , or ( 3 ) placebo .\