Inclusion Criteria:  acute HF patients with reduced ejection fraction (left ventricular ejection fraction, LVEF <=40%) and discharged alive from the hospital patients with age >= 20 years of age patients who performed cardiopulmonary exercise test (CPET) within one month after discharge patients with serum B-type natriuretic peptide (BNP) level >100 pg/mL.  Exclusion Criteria:  patients with estimated survival time < 6 months patients who could not tolerate exercise test due to muscular-skeletal disorder or other reason patients who had severe valvular heart disease.