Coronary artery bifurcation lesion is a common lesion subset in PCI accounting for 15-20% of the total number of interventions. Treatment of coronary artery bifurcation lesions represents a challenging area in interventional cardiology. When compared with non-bifurcation interventions, bifurcation interventions have a lower rate of procedural success, higher procedural costs, longer hospitalization and a higher clinical and angiographic restenosis. Factors contributing to this adverse outcome include limitations of angiography in assessment of side-branch (SB) disease severity and the lack of established angiographic predictors of SB patency and lumen compromise. Better understanding of the underlying plaque morphology and plaque composition may facilitate more effective treatment of bifurcation lesions.
Intravascular imaging has provided new understanding of mechanisms associated with SB compromise following bifurcation PCI. Plaque shift has been traditionally considered as the principal mechanism for side-branch compromise after main vessel intervention. Rotational atherectomy(RA) has been advocated for the treatment of bifurcation lesions, since it can effectively remove plaque with minimal injury to adjacent normal arterial segments and potentially reduce plaque shifting, the "snow plow" effect. Intravascular ultrasound (IVUS) has been used for guidance in bifurcation lesions, aiding the visualization of plaque morphology at the main vessel and the side-branches and helping the selection of stent size and length as well as the selection of stenting strategy. However, due to the low spatial resolution of IVUS, all attempts for three-dimensional visualization have only focused on visualization of the luminal contour and not on the vessel morphology or the vessel-stent interaction. Optical coherence tomography (OCT) has \~10 times higher resolution than IVUS, which allows precise evaluation of the microstructure of the vessel wall including lipid pool, fibrous cap, calcification, and thrombus. OCT has been shown to constitute a valuable tool for PCI guidance and also the utility of three-dimensional (3D) renderings for assessing the mechanism of side-branch compromise following intervention in bifurcation lesions. The recent development of OCT with online 3D reconstruction allows the operator to obtain a 3D visualization of the lesion and may provide a unique tool for guidance during complex bifurcation PCI and potentially improve stenting results. 3D OCT has been used to visualize jailed side branches after implantation of bioresorbable scaffolds in the main branch and develop a new classification system based on the number of SB compartments. In addition, its potential clinical application in guiding the rewiring of the distal compartment of the SB ostium (jailed with stent struts after MB stenting) to minimize the risk of floating struts was demonstrated It is important to note that while OCT, 3D-OCT, and 3D-QCA (such as that used in the ORBID trial) are imaging modalities that can be used to answer important research questions, their wide-spread adoption in daily clinical practice has been very limited. Intravascular ultrasound (IVUS) is used more frequently as part of a PCI guidance strategy in daily clinical practice.
Fractional flow reserve (FFR) is a pressure-derived, lesion specific index used to determine the functional significance of coronary artery stenosis. Several studies showed that FFR is a safe and feasible method to assess the significance of an ostial SB stenosis after provisional stenting. Quantitative coronary angiography (QCA) has been shown to be unreliable in assessing the functional significance of SB after stent implantation in MV (the area under the curve 0.64, 41.5% sensitivity and 83.1% specificity) suggesting that treatment decisions for jailed SB should not be based on angiographic findings alone. A recent report demonstrated a better ability of post-PCI 3D-OCT to predict the functional significance for SB ostial lesions caused by a jailed SB outcome.
A previous study (ORBID) of 30 patients was done at Mount Sinai Hospital and aimed to identify the predictors of side branch (SB) ostial stenosis developed after provisional stenting of the main vessel (MV) using Optical Coherence Tomography (OCT). The study Showed that High lipid content of the MV lesion and a contralateral location of lipid in the bifurcation area may contribute to SBOS after provisional stenting.
The objective of this study is to analyze the incidence of SB compromise after provisional main vessel stenting in calcified bifurcation lesions of CAD patients, determine the incidence and OCT predictors of functionally significant SB stenosis defined as FFR ≤ 0.8 and to compare the FFR values with 3D-OCT measurements of jailed SB ostium after MV stenting.
Stable CAD patients with bifurcation lesions in whom provisional stenting strategy is planned, who have moderate or severe calcification in the main vessel lesion identified by angiography, SB stenosis 30-70% and SB reference diameter \> 2mm will be enrolled in the study.
Moderate calcification will be defined as radiopaque density observed only during the cardiac cycle and typically involving only one side of the vascular wall, and severe calcification will be defined as radiopaque density noted without cardiac motion prior to contrast injection and involving both sides of the arterial wall. After completion of diagnostic angiogram and confirmation of subject eligibility, subjects will be randomly assigned to Rotational Atherectomy (RA) or Cutting Balloon Angioplasty (CBA)/Percutaneous Transluminal Coronary Angioplasty (PTCA) group in a 1:1 fashion.
Patients in both groups will undergo PCI with stent implantation according to current standards of care. Lesion preparation including lesion pre-dilation, scoring or sculpting balloon angioplasty, and use of atherectomy and protection devices will be performed at the operator's discretion, followed by MV stenting. The operator will also decide in both groups about the length and size of the implanted stent. Procedural optimization, such as post-dilation or additional stent implantation will be performed based only on the angiographic findings, according to the discretion of the operator.
