A description of two morphologic patterns of aortic fatty streaks, and a hypothesis of their pathogenesis

Two morphologic patterns of fatty streak were identified on examination of 74 aortas from the Pathobiological Determinants of Atherosclerosis in Youth study. Pattern 1, which predominated in 78% of aortas, is characterized by broad bands of intense stain which extend to the proximal edge of ostia. P attern 2, which predominated in 11%, is characterized by less intense stain ing which is concave to the associated ostium. Pattern 1 predominated in ol der subjects and smokers. Aging and smoking decrease arterial elasticity, t hereby decreasing the volume and duration of retrograde blood flow in diast ole. Doppler ultrasonography of the posterior intercostal arteries and aort a in 42 healthy subjects revealed that retrograde blood flow in late systol e/early diastole is normal in subjects in the 15-34 age group. Transition f rom retrograde to antegrade flow was associated with transient blood stasis . This stasis should prolong the residence time of lipid-rich particles, en hancing diffusion into the vessel wall. A region of lower flow velocity was noted in the periostial region in all patients during diastole. The anatom ic, hemodynamic, and risk factor data suggest that the morphology of fatty streaks is determined by interaction of retrograde with antegrade blood flo w as modulated by arterial elasticity. (C) 1998 Elsevier Science Ireland Lt d. All rights reserved.