Why the study?
Does the echogenicity of human carotid plaques correlate with their biochemical composition?
Does the echogenicity of human carotid plaques correlate with their biochemical composition?
Echogenicity of carotid plaques is primarily determined by elastin and calcium content rather than collagen or lipid content, challenging previous histological assumptions.
Echogenicity may reflect carotid plaque elastin and hydroxyapatite content; challenges prior histological assumptions but leaves open clinical risk implications.
BACKGROUND AND PURPOSE: Echolucent carotid plaques have been associated with increased risk for stroke. Histological studies suggested that echolucent plaques are hemorrhage- and lipid-rich, whereas echogenic plaques are characterized by fibrosis and calcification. This is the first study to relate echogenicity to plaque composition analyzed biochemically. METHODS: Echogenicity of human carotid plaques was analyzed by standardized high-definition ultrasound and classified into echolucent, with gray-scale median (GSM) <32 and echogenic with GSM > or =32. The biochemical composition of the plaques was assessed by fast-performance liquid chromotography and high-performance thin-layer chromotography. RESULTS: As assessed biochemically (milligrams per gram [mg/g]), echolucent plaques contained less hydroxyapatite (43.8 [SD 41.2] mg/g versus 121.6 [SD 106.2] mg/g; P=0.018), more total elastin (1.7 [SD 0.4] mg/g versus 1.2 [SD 0.4] mg/g; P=0.008), and more intermediate-size elastin forms (1.2 [SD 0.3] mg/g versus 0.8 [SD 0.4] mg/g; P=0.018). There was no difference in collagen amount between echogenic and echolucent plaques, neither biochemically (15.3 [SD 3.7] mg/g versus 14.4 [SD 3.4] mg/g) nor histologically (13.4 [SD 4.9] % versus 13.0 [SD 5.6] %). Cholesterol esters, unesterified cholesterol, and triglycerides were increased in plaques associated with symptoms (22.5 [SD 23.3] mg/g versus 13.3 [SD 3.2]; P=0.04), but no differences were detected between echolucent and echogenic plaques (13.5 [SD 4.0] versus 20.2 [SD 21.5] mg/g). Similar results were obtained by Oil Red O staining (symptomatic 7.6 [SD 4.7] % versus asymptomatic 4.2 [SD 3.6] %; P=0.03; echolucent 5.9 [SD 4.1] % versus echogenic 5.0 [SD 4.0] % of area). CONCLUSIONS: Echogenicity of carotid plaques is mainly determined by their elastin and calcium but not collagen or lipid content. In addition, echolucency is associated to higher elastin content.
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Gonçalves et al. (2004) studied this question.