Changes in left ventricular ejection fraction (LVEF) between apelin-13 (A13) infusion (n = 16, black) and 0.9% saline infusion (n = 16, white). A. Although LVEF of 0.9% saline infusion group was significantly decreased, A13 infusion group showed preserved LVEF through 4 weeks (weeks 1–5) of infusion (21.9 ± 3.2% to 23.1 ± 1.7%* vs. 23.5 ± 1.7% to 16.9 ± 2.8%, *p = 0.02) and B. In the extended group, infusion was stopped at the end of week 5 for 4 weeks from weeks 6–9. A13 group consistently demonstrated preservation of LVEF while the saline group showed reduction of LVEF during both the 4 weeks of infusion (weeks 1–5) and the 4 weeks of extended period without infusion. LVEF change at week 9 between A13 vs. control demonstrated significant increase in A13 group (+1.4%* vs. −9.4%, *p = 0.03).