Numerical study of stenotic side branch hemodynamics in true bifurcation lesions

Coronary bifurcation lesions are complex. Whether a critical condition exists in the stenotic side branch (SB) of bifurcation lesions, according to the Medina classification, is unassessed. Computational models of coronary bifurcations were developed with different stenosis severities and locations, in order to study the flow distribution and wall shear stress (WSS) in the SB. It was found that bifurcation lesion type (1,0,1) had a flow ratio of 0.25, much less than the corresponding normal ratio of 0.47, and the 0.46 and 0.39 ratios computed for lesion types (0,1,1) and (1,1,1), respectively. Bifurcation type (1,0,1) was associated with a 47% reduction from normal coronary flow, resulting in coronary branch steal. Blood flow to the SB decreased as the stenosis severity increased and approached the carina, in the proximal, distal, and side branches. Similarly, WSS values decreased with increasing stenosis severity. Bifurcation type (1,0,1) had the lowest WSS values in the SB, and were below the 0.5 Pa threshold for atherosclerotic growth. In conclusion, the results suggest that lesion type (1,0,1) is at the greatest risk of coronary branch steal, leading to potential ischemia, as well as further atherosclerotic growth. This is counterintuitive to the Medina classification, where bifurcation type (1,1,1) is usually considered the most severe.