Assessment of fractal ratio of vessel diameters in coronary bifurcation lesions by angiography and intravascular ultrasound

Physiological coronary branching at the bifurcation has a constant fractal ratio (FR) of the diameter of the mother vessel to the sum of daughter vessels on quantitative coronary angiography (QCA). We sought to investigate the FR of diseased coronary bifurcations using QCA and intravascular ultrasound (IVUS) and its impact on late lumen loss after percutaneous coronary intervention (PCI). In multicentre prospective studies of the J-REVERSE and 3D OCT Bifurcation Registry, 402 and 109 bifurcations treated with stenting that completed QCAs and IVUS examinations, respectively were analysed. FR was investigated at the reference sites pre-PCI and the minimum lumen diameter (MLD) post-PCI. In the QCA analysis, constant FR was observed in the pre-PCI reference (0.62 +/- 0.08) and in the post-PCI MLD site (0.74 +/- 0.10), which was greater (p < 0.05). In the IVUS analysis, the constant FR in the post-PCI MLD site (0.67 +/- 0.06) was similar to that in the pre-PCI reference (0.66 +/- 0.06) and close to the physiological FR value (0.678). The fourth quintile of pre-PCI reference FR in the IVUS analysis showed numerically least late lumen loss in proximal main vessel (MV) (0.16 +/- 0.22 mm) and distal MV (0.13 +/- 0.32 mm) and significantly less in the side branch compared to higher FR quintile (- 0.14 +/- 0.27 mm vs. 0.10 +/- 0.19 mm, p = 0.004), while no relationship was found in the QCA analysis. FR in the diseased coronary bifurcation was more accurately assessed on IVUS than on QCA, and the accomplishment of physiological FR might lead to less late lumen loss after bifurcation PCI.