Comparison of vessel geometry in bifurcation between normal and diseased segments: intravascular ultrasound analysis.

Objective: To investigate the geometry in bifurcation using intravascular ultrasound (IVUS) analysis.

Methods: We performed quantitative three-dimensional IVUS analysis of 31 true bifurcation lesions and 30 angiographically normal bifurcation segments including the main and side branches as well as parent vessel.

Results: The external elastic membrane (EEM) area changed significantly according to distance from bifurcation in the parent vessel and main branches of the lesion group while there was no significant change in the EEM area in the normal group. Vessel size of bifurcation segments obeyed the principle of minimum work (Murray's law). The cube of the mean EEM diameter of parent vessel nearly equaled the sum of the cubes of the mean EEM diameters of main and side branches (95.5 +/- 38.9 mm(3) versus 90.7 +/- 36.1 mm(3) for the lesion group and 93.4 +/- 49.6 mm(3) versus 85.3 +/- 47.3 mm(3) for the normal group). However, the deviation from the optimal relationship of lumen size was noted more frequently in bifurcation lesion than normal bifurcation segments (71% versus 43%, P=0.03).

Conclusions: The EEM pattern may differ between bifurcation lesions and normal bifurcating segments. Although human coronary artery system obeys the principle of minimum work, the geometry may deviate from the optimal relationship in bifurcation lesions.