Atherosclerotic coronary lesions with inadequate compensatory enlargement have smaller plaque and vessel volumes: observations with three dimensional intravascular ultrasound in vivo

Abstract

Objective: To compare vessel, lumen, and plaque volumes in atherosclerotic coronary lesions with inadequate compensatory enlargement versus lesions with adequate compensatory enlargement.

Design: 35 angiographically significant coronary lesions were examined by intravascular ultrasound (IVUS) during motorised transducer pullback. Segments 20 mm in length were analysed using a validated automated three dimensional analysis system. IVUS was used to classify lesions as having inadequate (group I) or adequate (group II) compensatory enlargement.

Results: There was no significant difference in quantitative angiographic measurements and the IVUS minimum lumen cross sectional area between groups I (n = 15) and II (n = 20). In group I, the vessel cross sectional area was 13.3 (3.0) mm2 at the lesion site and 14.4 (3.6) mm2 at the distal reference (p < 0.01), whereas in group II it was 17.5 (5.6) mm2 at the lesion site and 14.0 (6.0) mm2 at the distal reference (p < 0.001). Vessel and plaque cross sectional areas were significantly smaller in group I than in group II (13.3 (3.0) v 17.5 (5.6) mm2, p < 0.01; and 10.9 (2.8) v 15.2 (4.9) mm2; p < 0.005). Similarly, vessel and plaque volume were smaller in group I (291.0 (61.0) v 353.7 (110.0) mm3, and 177.5 (48.4) v 228.0 (92.8) mm3, p < 0.05 for both). Lumen areas and volumes were similar.

Conclusions: In lesions with inadequate compensatory enlargement, both vessel and plaque volume appear to be smaller than in lesions with adequate compensatory enlargement.

Figure 1

Principle of automated three dimensional intravascular ultrasound image analysis. Detection of the contours corresponding to the lumen-tissue and media-adventitia interfaces is first performed on two perpendicular longitudinal sections (A, B), reconstructed from the image data of the entire three dimensional "stack" of images. Edge information of the longitudinal contours are represented as points on the planar images, defining there the centre and range of the final contour detection process.

Figure 2

Analysis of a 20 mm long mid-right coronary segment with inadequate compensatory vascular enlargement (group I). The vessel cross sectional area is smallest at the target lesion site. Markers indicate that site on the longitudinal sections (right upper panels) and the display of the cross sectional area measurements (right lower panel). Linear functions of the vessel and lumen cross sectional area form the upper and lower boundaries of the greyish area, which represents the plaque cross sectional area. Alternatively, the values of plaque cross sectional area can be derived directly from a linear function (single black line), which here partly overlaps the greyish area.

Figure 3

Adequate compensatory vascular enlargement, as observed in one of the lesion of group II. The vessel cross sectional area is larger at the target lesion site (upper panel) than at the reference site (left mid panel). The lower panel illustrates and underlines the principle of compensatory vascular enlargement.