BACKGROUND: Complete revascularization with PCI is not always achieved in patients with ischemic HF. Therefore, this study aimed to elucidate the prognostic impact of residual coronary stenosis (RS) after percutaneous coronary intervention (PCI) in patients with ischemic heart failure (HF). METHODS: We analyzed a total of 1307 patients with symptomatic HF and a history of PCI registered in our Chronic Heart Failure Analysis and Registry in the Tohoku District-2 (CHART-2) Study. RS that was defined as the presence of ≥70% luminal stenosis in major coronary arteries at the last coronary angiography. RESULTS: Among the study population, 851 patients (65.1%) had RS. During a median follow-up period of 3.2 years, patients with RS had higher all-cause mortality than those without it even after propensity score matching (21.9 vs. 11.6%, log-rank P = 0.027). Multivariable Cox hazard analysis also showed the negative impact of RS on all-cause death in ischemic HF patients [hazard ratio (HR):1.62, 95% confidence interval (CI): 1.07-2.46, P = 0.024]. Importantly, when divided all subjects into three subgroups by left ventricular ejection fraction (LVEF) [LVEF < 40% (HFrEF), LVEF 40-49% (HFmrEF), and LVEF ≥ 50% (HFpEF)], inverse probability of treatment weighted method provided a similar result that RS after PCI was an independent risk factor for death in the HFpEF [HR(95%CI); 1.94(1.22-3.09), P < 0.01] and HFmrEF [4.47(1.13-14.98), P < 0.01] groups, but not in the HFrEF group [1.20(0.59-2.43), P = 0.62]. CONCLUSIONS: These results indicate that RS after PCI could aggravate long-term prognosis of ischemic HF patients with moderate- to well-preserved EF, but not those with reduced EF.