Background: We sought to investigate the mechanism of geometric changes after main branch (MB) stent implantation and to identify the predictors of functionally significant "jailed" side branch (SB) lesions.
Methods and results: Seventy-seven patients with bifurcation lesions were prospectively enrolled from 8 centers. MB intravascular ultrasound was performed before and after MB stent implantation, and fractional flow reserve was measured in the jailed SB. The vessel volume index of both the proximal and distal MB was increased after stent implantation. The plaque volume index decreased in the proximal MB (9.1+/-3.0 to 8.4+/-2.4 mm(3)/mm, P=0.001), implicating plaque shift, but not in the distal MB (5.4+/-1.8 to 5.3+/-1.7 mm(3)/mm, P=0.227), implicating carina shifting to account for the change in vessel size (N=56). The mean SB fractional flow reserve was 0.71+/-0.20 (N=68) and 43% of the lesions were functionally significant. Binary logistic-regression analysis revealed that preintervention % diameter stenosis of the SB (odds ratio=1.05; 95% CI, 1.01 to 1.09) and the MB minimum lumen diameter located distal to the SB ostium (odds ratio=3.86; 95% CI, 1.03 to 14.43) were independent predictors of functionally significant SB jailing. In patients with > or =75% stenosis and Thrombolysis In Myocardial Infarction grade 3 flow in the SB, no difference in post-stent angiographic and intravascular ultrasound parameters was found between SB lesions with and without functional significance.
Conclusions: Both plaque shift from the MB and carina shift contribute to the creation/aggravation of an SB ostial lesion after MB stent implantation. Anatomic evaluation does not reliably predict the functional significance of a jailed SB stenosis.
Trial registration: ClinicalTrials.gov NCT00553670.