(Table 2) shows the number of bypass grafts, the aortic cross-clamp time, and the CPB time. There were no significant differences in these variables between the hANP and placebo groups. The post-operative hospital mortality rate was 1.6% (n = 4) in the hANP group and 2.4% (n = 6) in the placebo group, and there was no significant difference between the 2 groups. The cause of death was cardiac failure in 2 patients and pneumonia in 2 patients from the hANP group, whereas it was cardiac failure in 3 patients, cerebral infarction in 1, pneumonia in 1, and hepatic failure in 1 patient from the placebo group. Complications occurred in 8 patients (3.2%) from the hANP group and 20 patients (7.9%) from the placebo group, so significantly more patients from the latter group developed complications (p = 0.0208). In the hANP group, cardiac failure, respiratory failure, and mediastinitis occurred in 4, 3, and 1 of the patients, respectively. In the placebo group, the complications were cardiac failure, acute renal failure requiring hemodialysis, respiratory failure, cerebral infarction, severe arrhythmia, and hepatic failure in 7, 4, 3, 3, 2, and 1 of the patients, respectively. No patient discontinued hANP administration due to reduced blood pressure, and no rebound was observed after discontinuation of infusion. The hospital stay was significantly shorter in the hANP group (p = 0.0002).