Incidence of compensatory enlargement and paradoxical shrinkage of coronary arteries in presence of atherosclerotic lesions: an intracoronary ultrasound study based on multiple cross-section analysis per artery.

BACKGROUND: The aim of the study was to evaluate with intravascular ultrasound (IVUS) the incidence of compensatory enlargement and paradoxical shrinkage in 50 de novo coronary lesions, using two different approaches: 1) a single cross-section analysis and 2) a multiple cross-section analysis per artery. A 3-D IVUS system based on contour detection of lumen and plaque was applied (image acquisition speed: 0.5 mm/s, digitization rate: 5 images/s). In each cross section, we determined: 1) the lumen area (LA), 2) the external elastic membrane area (EEMA), 3) the plaque+media complex (p+m), 4) the relative EEMA = cross section EEMA/reference EEMA, 5) the relative p+m area = cross-section p+m area/reference p+m area, 6) the lumen area stenosis: 1-(cross-section LA/reference LA). In the single cross-section analysis, compensatory vessel enlargement was defined as narrowest EEMA > reference EEMA, and paradoxical vessel constriction as narrowest EEMA < reference EEMA. In the multiple cross-section analysis, compensatory vessel enlargement was defined as the presence of a significant positive correlation between relative EEMA and relative p+m area and paradoxical vessel constriction as a significant negative correlation between relative EEMA and lumen area stenosis. RESULTS: In the single cross-section analysis, compensatory vessel enlargement and paradoxical constriction occurred in 58 and 42% of cases respectively. The multiple cross-section per artery analysis showed compensatory vessel enlargement in 80% of cases and paradoxical constriction in 36% of cases and revealed the combination of compensatory enlargement with paradoxical constriction in 22% of the analyzed segments. CONCLUSIONS: Compensatory enlargement of coronary arteries was underestimated by the single cross-section analysis and was observed in 80% of cases when a multiple cross-section per artery analysis was applied. Paradoxical shrinkage was less common and often occurred in combination with compensatory enlargement within the same analyzed segment.