HISTOLOGIC CORRELATES OF ANGIOGRAPHIC CHRONIC TOTAL CORONARY-ARTERY OCCLUSIONS - INFLUENCE OF OCCLUSION DURATION ON NEOVASCULAR CHANNEL PATTERNS AND INTIMAL PLAQUE COMPOSITION

Objectives. Age-related changes in histologic composition and neovascu lar channel (NC) pattern of angiographic chronic total coronary artery occlusions (CTOs) were studied to define histologic correlates of age -related revascularization profiles and neovascular channel formation. Background. Revascularization of CTOs is frequently characterized by inability to cross or dilate the lesion and a high incidence of reoccl usion or restenosis but low periprocedural ischemic complication rates . Little is known about the histopathologic basis of these observation s. Methods. Ninety-six angiographic CTOs from autopsy studies in 61 pa tients who had undergone coronary angiography within 3 months of death were studied. Abrupt plaque rupture was excluded. Occlusion segments were analyzed for 1) histologic composition as a function of lesion ag e; and 2) NC pattern as a function of lesion age and intimal plaque OF ) composition. Results. Cholesterol and foam cell-laden IP was more fr equent in younger lesions (p = 0.0007), whereas fibrocalcific IP incre ased with CTO age (p = 0.008). IP NCs arose directly from adventitial vasa vasorum and were anatomically and quantitatively related in terms of number and size (p = 0.0001) to the extent of IP cellular inflamma tion. IP cellular inflammation exceeded that found in the adventitia ( p < 0.001) or media (p = 0.0001) across all CTO ages. In CTOs <1 year old, the adventitia was associated with a larger number and size of NC s relative to the IP (p = 0.0006 and p 0.009), media (p = 0.0001 and p = 0.002) and recanalized lumen (p = 0.0001 and p = 0.001). In CTOs >1 year old, the adventitia and IP NC numbers were similar and exceeded NC numbers found in the media (p = 0.0001) and recanalized lumen (p 0. 0001 and p = 0.003). Conclusions. Angiographic CTO frequently correspo nds to less than complete occlusion by histologic criteria. Age-relate d changes in IP composition from cholesterol laden to fibrocalcific ma y explain the adverse revascularization profile of older CTOs. IP NC g rowth derived from the adventitia increases with age and is strongly a ssociated with IP cellular inflammation. IP NC formation may protect a gainst the flow-limiting effects of IP growth.