ObjectiveWe sought to investigate whether long-term clinical outcomes differ following percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) in patients with three-vessel disease (3VD) and lesions in the proximal left anterior descending artery (P-LAD).MethodsThis post-hoc analysis of the Synergy between PCI with Taxus and Cardiac Surgery (SYNTAX) Extended Survival study included patients with 3VD who were classified according to the presence or absence of lesions located in the P-LAD. Ten-year all-cause death and 5-year major adverse cardiac or cerebrovascular events (MACCE) were assessed.ResultsAmong 1088 patients with 3VD, 559 (51.4%) had involvement of P-LAD and their 10-year mortality was numerically higher following PCI versus CABG (28.9% vs 21.9%; HR: 1.39, 95% CI 0.99 to 1.95). Although patients without P-LAD lesions had significantly higher 10-year mortality following PCI compared with CABG, there was no evidence of a treatment-by-subgroup interaction (28.8% vs 20.2%; HR: 1.47, 95% CI 1.03 to 2.09, p_interaction=0.837). The incidence of MACCE at 5 years was significantly higher with PCI than CABG, irrespective of involvement of P-LAD (with P-LAD: HR: 1.86, 95% CI 1.36 to 2.55; without P-LAD: HR: 1.54, 95% CI 1.11 to 2.12; p_interaction=0.408). Individualised assessment using the SYNTAX Score II 2020 established that a quarter of patients with P-LAD lesions had significantly higher mortality with PCI than CABG, whereas in the remaining three-quarters CABG had similar mortality.ConclusionsAmong patients with 3VD, the presence or absence of a P-LAD lesion was not associated with any treatment effect on long-term outcomes following PCI or CABG.Trial registration numberSYNTAXES:NCT03417050; SYNTAX:NCT00114972.