In this double-blind , randomized , placebo-controlled , multicenter study , patients with New York Heart Association Class II to III chronic heart failure , left ventricular ejection fraction 45 % , and estimated glomerular filtration rate ( GFR ) 30 to 89 mL/min per 1.73 m ( 2 ) received intravenous serelaxin 30 g/kg per day or placebo for 24 hours .