Objectives The aim of this study was to assess the volume–outcome relationship for PCI within the nationwide registration system in Japan. Background The effect of site and operator case load for percutaneous coronary intervention (PCI) on outcomes has not been investigated thoroughly in non-Western regions. Methods In the present study, PCI procedural data recorded between January 2014 and December 2015 in the Japanese PCI registry, a nationwide registration system, were analyzed. Institutions and operators were categorized into deciles based on the number of PCIs performed per year. Odds ratios (ORs) for in-hospital mortality and the composite endpoint (in-hospital death and periprocedural complications) were estimated for each decile (with the lowest volume group as a reference group). Results A total of 323,322 PCIs (at 625 hospitals [median PCI cases/year: 216; quartiles: 121 to 332] by 4,211 operators [median PCI cases/year: 28; quartiles: 10 to 56]) were analyzed, of which 2,959 patients (0.9%) and 7,205 patients (2.2%) experienced in-hospital mortality and the composite endpoint after PCI, respectively. The adjusted risk for in-hospital mortality and the composite endpoint was significantly higher in hospitals included in the lowest decile (<150 PCIs/year); the risk remained consistently low across the remaining deciles. Contrastingly, no significant volume–outcome relationship was observed between operator volume and outcomes. A similar trend was observed when the analysis was confined to emergency/urgent PCI cases. Conclusions In contemporary Japanese PCI practice, lower institutional volume was related inversely to in-hospital outcomes, but the association of annual operator volume with outcomes was less clear.
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