Compensatory enlargement of the left main coronary artery: Insights from the PROSPECT study

OBJECTIVES: Glagov proposed that remodeling delayed development of significant coronary artery stenoses until plaque occupied, on average, 40% of arterial area (40% plaque burden). The aim of the current study was to confirm the previously proposed concept of coronary remodeling as first described by Glagov who studied postmortem left main coronary arteries (LMCAs). METHODS: Using the in-vivo intravascular ultrasound data from the Providing Regional Observations to Study Predictors of Events in the Coronary Tree (PROSPECT) study, we evaluated 552 LMCAs in 552 patients. RESULTS: External elastic membrane cross-sectional areas (CSAs) increased in proportion to the increase in plaque and media CSAs (r=0.61, P<0.0001), especially when the plaque burden was 20% or lower (r=0.88, P<0.0001). For more advanced atherosclerosis (>40% plaque burden), there was an inverse relationship between lumen CSA and plaque burden (r=-0.57, P<0.0001), whereas this relationship was weak in the presence of less than 40% plaque burden. The frequency of virtual histology derived thin-cap fibroatheroma increased with increasing plaque burden. In contrast, the frequency of pathological intimal thickening decreased. CONCLUSION: The previously proposed remodeling concept of Glagov was validated in vivo in the PROSPECT study patients. In addition, the present study suggested that plaque phenotype worsened with increasing LMCA plaque growth.