BackgroundAlthough consistent clinical data support intravascular ultrasound (IVUS) use during complex percutaneous coronary intervention (PCI), long-term follow-up outcomes on differential effects of IVUS according to operator experience are scarce. ObjectivesThe current study aimed to evaluate the influence of operator experience on lesion complexity, long-term clinical outcomes, and the interactions of IVUS guidance in patients undergoing complex PCI. MethodsA total of 6,005 patients who underwent PCI with drug-eluting stents for complex lesions were recruited from the institutional registry of Samsung Medical Center. The study population was stratified by the use of IVUS and operator experience (less experienced operator [lifetime independent experience with PCI ≤5 years] vs experienced operator). The primary endpoint was a composite of cardiac death or target vessel myocardial infarction (TVMI) up to 10 years. ResultsCompared with less experienced operators, experienced operators used IVUS more frequently (29.6% [1,128/3,805] vs 24.8% [546/2,200]; P < 0.001) and achieved a lower risk of cardiac death or TVMI (experienced vs less experienced, adjusted HR: 0.779; 95% CI: 0.663-0.915; P = 0.002). IVUS use was associated with a significantly lower risk of cardiac death or TVMI than angiography alone for less experienced operators (23.5% vs 11.4%; adjusted HR: 0.477; 95% CI: 0.337-0.673; P < 0.001) as well as experienced operators (18.0% vs 13.5%; adjusted HR: 0.747; 95% CI: 0.559-0.998; P = 0.048). There were significant interactions for the risk of cardiac death or TVMI between IVUS use and operator experience (P = 0.037). ConclusionsPCI by experienced operators and the use of IVUS during complex PCI were independently associated with lower long-term risks of cardiac death or TVMI. The beneficial effects of IVUS were more prominent for less experienced operators. (Prospective Percutaneous Coronary Intervention Registry [SMC-PCI]; NCT05624905)