Changes in left main bifurcation geometry after a single-stent crossover technique: an intravascular ultrasound study using direct imaging of both the left anterior descending and the left circumflex coronary arteries before and after intervention.

BACKGROUND We assessed geometric changes responsible for acute lumen loss at the left circumflex coronary artery (LCX) ostium after crossover stenting from the left anterior descending coronary artery (LAD) to the left main artery. METHODS AND RESULTS Twenty-three left main artery bifurcation lesions with a preprocedural angiographic diameter stenosis <50% at the LCX ostium were evaluated using prestenting and poststenting intravascular ultrasound pullbacks from both the LAD and the LCX. At the minimal lumen area (MLA) sites within the LCX ostium and at the LCX carina, the lumen, stent, plaque+media (P+M), and external elastic membrane (EEM) areas were measured; the EEM eccentricity was calculated at the LCX carina. The change in MLA within the LCX ostium (ΔL), the change in EEM area at the MLA site (ΔV), and the change in P+M area at the MLA site (ΔP) were calculated. The MLA within the LCX ostium significantly decreased from 5.4 mm(2) (first and third quartiles, 4.3 mm(2), 7.2 mm(2)) prestenting to 4.0 mm(2) (3.0 mm(2), 4.8 mm(2)) poststenting (P<0.001). The percent change in MLA within the LCX ostium correlated with changes in EEM eccentricity (r=-0.414, P=0.049) and percent change in EEM area at the MLA site (r=0.626, P=0.001). A smaller distal carina angle between the LAD and the LCX before stenting was associated with a greater percent reduction in lumen (r=0.472, P=0.023) and EEM (r=0.402, P=0.048) after stenting. In 18 lesions with >10% reduction of MLA within the LCX ostium despite the lack of direct relationship between ΔL and ΔP at the MLA site, ΔP closely correlated with the ratio of ΔV to ΔL (r=-0.953, P<0.001), suggesting that an increase in plaque at the LCX ostium contributed to the MLA loss relative to the decrease in EEM area. CONCLUSIONS Lumen loss at the LCX ostium frequently occurred after crossover stenting from the distal LM to the LAD. The main mechanism was carina shift that was associated with a narrow angle between the LAD and LCX.