Characteristics Of Atherosclerotic Plaque Distribution In Coronary Bifurcation Lesions

Objective: Coronary angiography (CAG) is always be regard as gold standard of coronary heart disease (CHD) diagnosis and therapy. But CAG can only measure stenosis degree of lumen, morphology examination is functional dead zone of CAG Atherosclerosis is pathological changes of vascular wall, but CAG shows information of lumen. We make interventional strategy according to morphological characteristics of lesion which effect long-term outcomes of percuteneous coronary intervention (PCI). Multidetector computer tomography (MDCT) and intravascular ultrasound (IVUS) can provide guidance with interventional therapy of complex coronary lesion. Bifurcation lesion is account for 15-16% of all coronary lesions. Intervention of bifurcation is the most challenging lesion in drug eluting stent (DES) era which associated with low procedural success, more complication and high restenosis rate. According to previous study, plaque in main vascular (MV) removing to ostium of side branch (SB) is also the important reason of SB jailed after PCI, in addition to initial stenosis of SB ostium. Application of MDCT is limited to diagnose CHD now. But MDCT can make qualitative and quantitative analysis with the improvement of time and spatial resolution. We investigated characteristics of plaque distribution in bifurcation by IVUS to know influence of plaque distribution to SB jailed and provide theoretic explanation of interventional strategy. This study is designed for the following objectives: (1) We studied plaque distribution of bifurcation by MDCT, drawed typing of bifurcation lesion by MDCT and evaluated concordance of CAG and MDCT in quantitative analysis, then probed application of MDCT in special lesions; (2)We investigated plaque distribution and remodeling pattern of bifurcation by IVUS and influencing factor of SB jailed, and evaluated outcomes of intervention.Methods: We enrolled 35 lesions with MDCT examination and 52 lesions withIVUS examination. We compared quantitative coronary analysis by MDCT and CAG. MV lumen was quartered according to the site of SB take-off and each quadrant was measured with plaque thickness. CT typing of bifurcation lesions was proposed according to characteristics of plaque distribution. Influential factors of plaque position in distal segment of bifurcation were analyzed by step regression. We made qualitative and quantitative analysis with SB entrance cross-sections and bifurcation crista cross-sections by IVUS. MV lumen was quartered according to the site of SB take-off and each quadrant was measured with plaque area and area percent. We analyzed influential factors of plaque position by step regression. Vessel remodeling was evaluated by remodeling index and vessel compensation ratio. Influential factors of SB jailed after PCI was analyzed by step regression.Results: There was no difference in quantitative analysis of MV between MDCT and CAG, but there was significant different in quantitative analysis of SB. Minimum lumen area (5.22±2.85 vs 3.65±2.94, P=0.027), External elastic member cross-sectional area (7.69±1.69 vs 6.61±2.58, P=0.041), reference vascular area (7.15±2.56 vs 5.95±1.91, P=0.030) and vascular diameter (2.98±0.50 vs 2.72± 0.41,P=0.023) in SB were larger by MDCT than CAG. Stenosis rate of SB was larger by CAG than MDCT (0.44±0.31 vs 0.20±0.14, P=0.041. There was no difference with bifurcational angle between MDCT and CAG (55.24±19.10 vs 54.62±18.35, P=0.891). There was no difference with plaque thickness among each quadrant in proximal segment (0.95±0.65 vs 1.00±0.61 vs 0.99±0.62 vs 0.96±0.65, P>0.05) , but in distal segment, plaque thickness were larger in PT180° than in PT90° and PT270° (1.24±0.49 vs 0.65±0.34, P=0.000), plaque thickness were larger in PT90° and PT270° than PT0° (0.65±0.34 vs 0.08±0.12, P=0.000). We proposed typing of bifurcation lesions as follows: Type A: true bifurcation lesions, there was concentric plaque in proximal segment and eccentric plaque in distal segment of MV, in addition to ostial plaque of SB. Plaque of SB ostium and MV distal segment were all located at opposite wall of bifurcation crista; Type B: there was eccentric plaque in SB ostium which was located at opposite wall of bifurcation crista; Type C: there was eccentric plaque in MV distal segment and SB ostium which were all located at opposite wallof bifurcation crista; Type D: there was concentric plaque in proximal segment and eccentric plaque in distal segment of MV, but no plaque in SB ostium. Plaque of MV distal segment was located at opposite wall of bifurcation crista; Type E: there was concentric plaque in proximal segment of MV; Type F: there was eccentric plaque in distal segment of MV which was located at opposite wall of bifurcation crista. Each type accounted for 22.86%(8/35), 34.28%(12/35%), 14.29%(5/35), 14.29%(5/35), 8.57%(3/35) and 8.57%(3/35), respectively. Qualified analysis with IVUS showed no difference between proximal segment and distal segment of coronary bifurcation. Quantitative analysis showed that external elastic member cross-sectional area(17.83±5.73vs 12.42±3.49 mm~2, P=0.000) and plaque arc (357.15±12.02°vs 233.33±45.91°, P=0.000) were larger in proximal than distal segment, eccentric index were smaller in proximal than distal segment (1.86±0.648 vs 9.52±2.7, P=0.000) , but plaque burden were similar in both segment (52.80±13.21% vs 52.81±12.20%, P=0.997) . Plaque area and area percent were no difference among each quadrant in proximal segment (2.31±1.05 vs 2.46±0.97 vs 2.24±0.98 vs 2.44±1.05 mm~2, P>0.05) , but in distal segment, plaque area and area percent were larger in opposite wall than in the same wall of side branch ostial (2.61±1.20, 2.66±1.85 vs 0.74±0.66, 0.68±0.58 mm~2) . The plaque position related to SB was correlated with the side branch take-off angle positively (R =0.793, R~2=0.628). RI(1.05±0.10 vs 0.94±0.08, p=0.000) and VCR(0.07±0.15 vs -0.17±0.26, p=0.000) were larger in proximal segment than distal segment. Post-procedural plaque burden of SB were correlated with pre-procedural plaque burden of SB and proximal segment plaque burden positively, and were correlated with SB take-off angle and diameter ratio (SB/MV diameter) negatively.Conclusions: Morphology examination including MDCT and IVUS can provide information about atherosclerotic plaque distribution in coronary bifurcation lesions beyond CAG MDCT and IVUS showed significant difference of plaque distribution patterns between proximal and distal segment of bifurcation. Proximal segment demonstrated concentric plaque and negative remodeling. Distal segment demonstrated eccentric plaque and positive remodeling, plaque accumulated oppositeto the flow divider. The side branch take-off angle influenced plaque distribution of distal segment. Plaque accumulated in the opposite wall when side branch took-off with straight angle, then side branch were prone to be jailed for plaque redistribution. Conversely, plaque accumulated in the lateral wall when side branch took-off with acute angle, then side branch were not prone to be jailed for plaque redistribution. Side branch with large pre-procedural plaque burden, large plaque burden in proximal segment of bifurcation, small side-branch take-off angle, small diameter ratio are in high risk of side branch occlusion after PCI. There was good concordance in quantitative analysis of large vascular (>3.0mm) between MDCT and CAG, but poor concordance in quantitative analysis of small vascular (<3.0mm) . There was limitation with MDCT in discriminating mild stenosis. MDCT can made qualitative analysis with plaque according to CT value. CT typing of bifurcation lesion can guide interventional strategy.