Coronary luminal shape and the arc of disease-free wall: morphologic observations and clinical relevance.

Variation in the distribution of atherosclerotic plaque along the circumference of coronary arteries results in two major types of cross-sectional luminal shapes: concentric and ec• centric. If the atherosclerotic plaque is distributed along the entire vessel circumference, the cross-sectional coronary lumen is located centrally and is called a central or con• centric type lumen (1). If, however, the plaque fails to involve the entire coronary artery circumference leaving a variable arc of normal wall, the residual cross-sectional lumen is called eccentric (1). The eccentric lumen has been further subdivided into slit-like and polymorphous or semi• lunar types (1,2). Although the polymorphous type of ec• centric lumen may be observed with variable degrees of obstruction, the slit-like eccentric lumen is always associ• ated with severe (>75%) cross-sectional area narrowing. More than 10 years ago, Vlodaver and Edwards (1) re• ported the incidence of the various types of coronary luminal shapes. On the basis of examination of 200 atherosclerotic coronary artery sections, the frequency of the three types of coronary lumen was: concentric, 30%; eccentric poly• morphous, 41 % and eccentric slit-like, 29%. Thus, in 70% of the cross sections studied, the residual lumen was ec• centric and in only 30% was the lumen concentric. In a recent study, Baroldi (2) examined 1,069 sites of severe (> 70%) diameter reduction and found that 46% of the coro• nary luminal shapes were concentric, 24% eccentric (lateral lumen position but still encircled by plaque) and 30% "semilunar" (a variable arc of free wall). Continually changing and evolving diagnostic and ther• apeutic procedures in the evaluation and treatment of symp• tomatic coronary atherosclerosis have stimulated new in• terest in morphologic aspects of atherosclerotic plaque. In