Impact of Nonobstructive Left Main Coronary Artery Atherosclerosis on Long-Term Mortality

Background: Although the presence of severe stenosis in the left main coronary artery (LMCA) is a well-established predictor of mortality, whether this extends to nonobstructive atherosclerosis in the LMCA is unknown.

Objectives: The aim of this study was to evaluate the association between LMCA disease by intravascular ultrasound (IVUS) and long-term mortality.

Methods: Between 2005 and 2013, 3,239 patients with LMCA IVUS imaging without LMCA revascularization (either before angiography or scheduled based on index angiography or IVUS) were included. The primary and secondary endpoints were all-cause and cardiac mortality at a minimum of 5 years obtained from the National Death Index.

Results: The IVUS-measured LMCA minimum lumen area (MLA) and plaque burden were 13.1 ± 5.0 mm² and 41.7% ± 15.6%, respectively. The median follow-up was 8.2 years. The Kaplan-Meier estimated 12-year all-cause and cardiac death rates were 37.5% and 17.0%, respectively. Greater plaque burden (unadjusted HR per 10%: 1.17; 95% CI: 1.12-1.22; P < 0.0001) and smaller IVUS MLA (unadjusted HR per 1 mm²: 0.98; 95% CI: 0.96-0.99; P = 0.0008) were associated with all-cause death. After adjusting for clinical, angiographic, and IVUS factors, plaque burden (adjusted HR per 10%: 1.12; 95% CI: 1.04-1.21; P = 0.003) but not MLA (adjusted HR per 1 mm²: 1.02; 95% CI: 0.99-1.04; P = 0.18) was associated with long-term all-cause death. These findings were also consistent for long-term cardiac mortality.

Conclusions: In the present large-scale study with a 12-year follow-up, increasing LMCA plaque burden was associated with long-term all-cause and cardiac mortality in patients not undergoing LMCA revascularization, even when the lumen area was preserved.