First-in-man prospective evaluation of temporal changes in coronary plaque composition by in vivo intravascular...

The composition of atherosclerotic coronary plaque is a major determinant of future clinical events. Spectral analysis of IVUS radiofrequency data has demonstrated potential to provide detailed quantitative information on plaque composition. We prospectively assessed plaque composition in matched coronary segments at a six-month interval and sought to explore correlations between temporal changes in plaque composition and circulating biomarkers.

Twenty coronary segments (mean baseline length, 29.9+/-14.1mm) with non-significant angiographic (<50 % diameter) stenosis, in non-culprit vessels of patients (n=20) referred for percutaneous intervention, were studied at baseline and six-month follow-up. Spectral analysis of IVUS radiofrequency data, obtained with a 30 MHz catheter in segments matched on predefined anatomic landmarks, was performed with IVUS-Virtual Histology software. After 6 months, an overall decrease in the level of different biomarkers of instability was present. There were no significant changes in absolute values (mm2) of plaque components; calcium (0.036+/-0.05 vs. 0.033+/-0.04), fibrous (2.68+/-1.5 vs. 2.90+/-1.5), fibrolipidic (0.77+/-0.4 vs. 0.73+/-0.4), and lipid core (0.42+/-0.4 vs. 0.52+/-0.5), between baseline and six-months. Nor did any conventional IVUS variable (lumen, vessel, or plaque cross-sectional area, or percent area stenosis). Change in lipid core area (r=0.51, p=0.024), fibrous area (r=0.49, p=0.033) and calcium area (r=0.63, p=0.004), were significantly correlated with change in Lp-PLA2 activity.

Routine medical care does not result in significant overall changes in IVUS-derived plaque size or composition over a 6-month period. This study provides indication of quantifiable boundaries beyond which modifications in tissue composition might be interpreted as statistically significant.