730-5 Why Do Aorto-Ostial Lesions Behave Differently than Non-ostial Lesions? Histologic Findings in Directional Atherectomy Specimens of Aorto-Ostial vs. Non-ostial Lesions

Conventional angioplasty of aorto-ostial lesions (≤3 mm from aorta) is frequently associated with suboptimal results, high procedural complications, and increased restenosis rate compared to non-ostial lesions. To gain insight into the differences between aorto-ostial and non-ostial lesions, directional atherectomy (DCA) samples of de novo native aorto-ostial lesions from 32 patients (64 ± 11 years; 22 men) were compared to randomly selected DCA samples of de novo native non-ostial lesions from 34 patients (61 ± 11 years; 23 men). Results (1) The amount of tissue removed was similar between the two groups (6.4 ± 3.6 μm 2 vs. 6.2 ± 3.8 μm 2 ). with predominantly fibrosclerotic plaque (59% vs. 68%): (2) The aorto-ostial group had significantly more areas of high cellularity vs. non-ostial group (0.73 ± 0.74 μm 2 vs. 0.41 ± 0.49 μm 2 ; p l 0.05): (3) The aorto-ostial group tended to contain more thrombus (0.61 ± 0.79 μm 2 vs. 0.29 ± 0.35 μm 2 ; p l 0.08); and (4) the aorto-ostial DCA samples more frequently had adventitial tissue (0.1 0 ± 0.14 μm 2 vs. 0.04 ± 0.06 μm 2 ; p = 0.07). We conclude that: (1) The aorto-ostiallesions seem to experience greater spontaneous trauma and stimulus for proliferation, as evidenced by the more abundant reactive cellular component. This histologic confirmation of the known rheologic effect on aorto-ostial regions may explain the increased restenosis rate observed with these lesions.: (2) The aorto-ostiallesions are more unstable, with a trend for more thrombotic component. This may explain the high procedural complications during angioplasty of the aorto-ostiallesions.: and (3) DCA specimens from the aortoostial lesions tended to have greater amount of adventitia, another potential source for procedural complication and increased restenosis. These findings suggest that there are biologic explanations for observed suboptimal acute and chronic results after angioplasty of aorto-ostial lesions, and further suggest a need for an improved strategy, such as minimization of the aorto-ostial turbulent flow possibly with stenting combined with local pharmacologic treatment.