The purpose of this exploratory study is to assess the efficacy and safety of nesiritide in participants with acute (a quick and severe form of illness in its early stage) heart failure (when the heart inadequately pumps blood through the body) including acute exacerbation of chronic (lasting a long time) heart failure, administered intravenous (into a vein) bolus (a large amount) followed by intravenous infusion (a fluid or a medicine delivered into a vein by way of a needle).