Background:Percutaneous coronary intervention (PCI) for bifurcation lesions has been associated with a high incidence of procedural complications, including side branch occlusion (SBO) and peri-procedural myocardial infarction. It remains controversial whether preintervention intravascular ultrasound (IVUS) can help to predict SBO for bifurcation lesions. Methods:We analyzed volumetric IVUS parameters(EEM,Lumen, and P&M) in 66 bifurcation lesions without side branch ostial stenosis before and after PCI. Lesions were classified into two groups according to the occurrence of SBO (SBO vs non-SBO). Cross sections were analyzed at 1-mm intervals in segments that were 5 mm proximal and distal to the side branch ostium and analyzed seperately (proximal portion vs. distal portion). Results:Baseline clinical and angiographic charateristics were comparable between groups. Before intervention, distal portion of SBO group showed significantly smaller lumen and EEM volume than non-SBO group (19.80±6.78mm3 vs. 28.42±10.96mm3, 43.83±11.06mm3 vs. 53.33±13.35mm3, p<0.01), whereas the P&M volume did not differ between groups (24.04±11.76mm3 vs. 25.13±11.15mm3, p=ns). None of the parameters regarding the proximal portion did not differ between groups. After intervention, the lumen volume of the distal portion increased significantly in SBO group compared with non-SBO group (+16.65±10.00mm3 vs. +10.95±8.45mm3, p<0.05). This is mainly derived from EEM volume increase (66.58±15.43mm3 to 75.70±13.70mm3 at proximal portion, 49.49mm3 to 60.42mm3 at distal portion, p<0.001) rather than P&M volume reduction (34.92±12.58mm3 to 33.58±10.40mm3 at proximal portion, 24.67mm3 to 22.27mm3 at distal portion, p=ns). At the proximal portion, there were no significant differences in mean changes of EEM, lumen, and P&M volume between groups. Conclusion:Over-expansion of distal portion of bifurcation relative to proximal portion may be the main mechanism for SBO, rather than plaque shifting. Consequently, pre-PCI small vessel dimension at distal portion of bifurcation was associated with SBO.
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