Sir,—We read with interest the article by von Birgelen and colleagues in which they found both vessel and plaque volume in lesions with inadequate compensatory enlargement to be smaller than in lesions with adequate compensatory enlargement.1 They also found that the eccentricity index (EI)—calculated as minimum wall thickness divided by maximum wall thickness—was higher in lesions with inadequate remodelling than in those with adequate remodelling. Because endothelium dependent arterial dilatation, which has been proposed as a possible mechanism for arterial compensatory remodelling,2 requires a normally functioning endothelium, the higher eccentricity produced by a thick wall with plaque and a thin plaque free wall in lesions with adequate remodelling may support that hypothesis as mentioned by Varnava.3 The EI, however, would decrease in relation to the plaque enlargement with …