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.