Unprotected vs. protected left main PCI outcomes: a meta-analysis of reconstructed time-to-event data

Background Percutaneous coronary intervention (PCI) is an established revascularization strategy for selected patients with left main coronary artery disease (LMCAD). However, outcomes differ depending on whether the left coronary system is protected by prior CABG. While unprotected PCI is clinically recognized to carry a higher risk, the extent of this risk difference has not been comprehensively quantified. Purpose This study aimed to quantify the difference in all-cause mortality and adverse cardiovascular outcomes between unprotected and protected left main PCI. Methods A systematic review and meta-analysis were conducted in accordance with PRISMA guidelines. We searched PubMed, Embase, Scopus, and Web of Science through April 2025. Eligible studies included patients with LMCAD undergoing PCI, stratified by prior CABG status. The primary outcome was all-cause mortality. We calculated pooled odds ratios using a random-effects model with Paule–Mandel variance estimation. For studies reporting Kaplan–Meier curves on all-cause mortality, individual patient data (IPD) were reconstructed to derive a pooled hazard ratio using Cox regression. Results Individual patient data reconstructed from Kaplan–Meier curves involving 3,022 patients showed a significantly higher risk of all-cause mortality in unprotected patients (HR: 1.86; 95% CI: 1.55–2.23), with 1-year survival rates of 88% in the protected group versus 71% in the unprotected group. The proportional hazards assumption was not violated. Meta-analysis of 11 studies comprising 4,786 patients further demonstrated increased all-cause mortality in the unprotected group (OR: 5.56; 95% CI: 2.56–12.50; I² = 57.3%), including in-hospital mortality (OR: 5.88; 95% CI: 1.79–20.00) and 1-year mortality (OR: 6.25; 95% CI: 1.85–20.00). Major adverse cardiovascular events were also more frequent in unprotected patients (OR: 2.08; 95% CI: 1.32–3.23; I² = 48.5%), particularly at 1 year (OR: 2.04; 95% CI: 1.27–3.33). Revascularization rates were similar overall (OR: 1.22; 95% CI: 0.64–2.33), although in-hospital revascularization was significantly more common in the unprotected group (OR: 10.00; 95% CI: 1.27–100.00). Conclusion Unprotected left main PCI is associated with significantly worse outcomes compared to protected PCI, including a 17% absolute reduction in 1-year survival and a higher risk of major adverse cardiovascular events.