Clinical significance of echo signal attenuation on intravascular ultrasound in patients with coronary artery disease.

BACKGROUND Atherosclerotic plaque that shows echo signal attenuation (EA) without associated bright echoes is sometimes observed by intravascular ultrasound but its clinical significance remains unclear. We investigated the impact of EA on coronary perfusion and evaluated the pathological features of plaque with EA. METHODS AND RESULTS We studied 687 native coronary lesions in 687 consecutive patients (336 with acute coronary syndrome and 351 with stable angina pectoris) who underwent intravascular ultrasound before percutaneous coronary intervention. By subgroup analysis, 60 lesions (30 lesions with EA) treated with directional coronary atherectomy underwent pathological examination. The Thrombolysis in Myocardial Infarction (TIMI) flow grade and myocardial blush grade after percutaneous coronary intervention were compared between lesions with and without EA in 627 lesions except directional coronary atherectomy subgroup. EA was observed in 245 lesions (35.7%), and coronary flow after percutaneous coronary intervention was worse for lesions with EA than without (final TIMI grade of 0 to 2: 15.4% versus 2.4%, P<0.001; final myocardial blush grade of 0 to 2: 45.6% versus 21.4%, P<0.001). Multivariate analysis revealed a significant association between no reflow (TIMI grade 0 to 2) and EA (odds ratio, 5.59; 95% CI, 2.64 to 11.85; P<0.001), a baseline TIMI grade of 0 to 2 (odds ratio, 5.91; 95% CI, 2.79 to 12.5; P<0.001), and a large reference area (odds ratio, 3.08; 95% CI, 1.40 to 6.76; P=0.005) after controlling for other associated factors. Pathological examination revealed a significantly higher frequency of lipid-rich plaque with microcalcification in lesions with EA. CONCLUSIONS Atherosclerotic plaque with EA showed a significant association with no reflow after percutaneous coronary intervention, suggesting the existence of fragile components susceptible to distal embolization.