Is acoustic shadowing at intracoronary ultrasound always the marker of intramural calcium accumulation?

Intracoronary ultrasound (ICUs) is increasingly used at catheterization to assess more precisely the severity of luminal narrowing, to delineate the composition of the atherosclerotic plaque, and to select the optimal therapeutic strategy. With this technique, a drop in signal intensity, known as acoustic shadowing, is usually equated with the presence of calcium in the plaque. We report the study of an atherosclerotic coronary artery showing intense acoustic shadowing at ICUS, but in which no calcium deposition could be evidenced at postmortem pathological analysis. This observation suggests a word of caution with regard to considering acoustic shadowing at ICUs as the reflection of superficial calcium deposition within a vessel wall. (C) 1995 Wiley-Liss, Inc.