Glagov, in autopsy study of 136 hearts, concluded that coronary arteries (see left panel with a cross section and corresponding contour of the left main coronary artery, magnification×7.4) enlarge in relation to plaque area and functionally important lumen stenosis may be delayed until the lesion occupies 40 per cent of the internal elastic lamina area. The lumen area did not decrease in relation to the percentage of stenosis (lesion area/internal elastic membrane area×100) for values between zero and 40 per cent (see right top panel), but did diminish markedly and in close relation to the percentage of stenosis for values above 40 per cent (r=-0.73, p value <0.001).The artery initially enlarges (see right bottom panel)in association with plaque accumulation to maintain an adequate, if not normal, lumen area. Early stages of lesion development may be associated with overcompensation. At more than 40 per cent stenosis, however, the plaque area continues to increase to involve the entire circumference of the vessel, and the artery no longer enlarges at a rate sufficient to prevent narrowing of the lumen. Le–lesion, Lu–lumen. Figure Adapted from reference [17].