Hemodynamic impact of changes in bifurcation geometry after single-stent cross-over technique assessed by intravascular ultrasound and fractional flow reserve

Background Angiographic stenosis of a sidebranch (SB) ostium is common after single-stent cross-over, but it is usually not hemodynamically significant. We evaluated the relationship between the mechanisms of SB stenosis and its hemodynamic significance. Methods and Results We used preinterventional and post-interventional intravascular ultrasound (IVUS) of the main branch (MB) and the SB and post-intervention fractional flow reserve (FFR) of the SB to assess 40 nonleft main bifurcation lesions after a single stent cross-over. Although post-stenting angiographic diameter stenosis >50% was seen in 19 (48%) SB lesions, only 6 (15%) showed FFR < 0.80. Carina shift was seen in all but one lesion; and plaque shift superimposed on the carina shift was found in 18 (45%) lesions. The change in plaque area at the SB ostium positively correlated with preprocedural plaque burden at the carina of distal MB r = 0.341, P = 0.031). Plaque shift was more common in lesions with FFR < 0.80 vs. ≥0.80 (83% vs. 38%, P = 0.041); and FFR < 0.80 was more frequent in lesions with plaque shift superimposed on carina shift versus isolated carina shift (28% vs. 5%, P = 0.041). Conclusions Although carina shift was the main mechanism of SB lumen loss after a single stent cross-over technique, plaque shift superimposed on carina shift appeared to be necessary to cause a hemodynamically significant stenosis (FFR < 0.80). However, post-procedural IVUS assessment did not accurately predict the functional significance.