Time course of vascular remodeling, formation of neointima and formation of neoadventitia after angioplasty in a porcine model

Background Vascular remodeling is the major cause of restenosis after coron ary balloon angioplasty but the pathophysiology of this process is not know n. Objective To examine the time courses of vascular remodeling, formation of neointima and adventitial changes after coronary angioplasty. Design An experimental study on pigs using coronary angiography, intravascu lar ultrasound (IVUS), and histology. Methods Deep vessel-wall injury was induced by conventional balloon angiopl asty in the circumflex and right coronary arteries, and by retraction of a chain-encircled balloon in the left anterior descending artery. Angiography in all three arteries and IVUS measurements in circumflex and left anterio r descending arteries were performed before and after angioplasty, and at f ollow-up on days 0, 1, 4, 7, 14, 28, and 56 (n = 5 in each group). Serial I VUS measurements were used to determine vascular remodeling, Formation of n eointima and neoadventitia was measured by histomorphometry. Results Angiographically evident loss of lumen and ultrasonographically det ectable constrictive remodeling occurred between day 7 and day 28, IVUS mea surements showed that late loss of lumen (days 28 and 56) was correlated to vascular remodeling but not to the increase in wall area (neointima plus m edia). Histomorphometry revealed that neointima was present from day 7 and that amount of neointima increased up to day 28. Area of adventitia increas ed during the first 4 days and remained unchanged thereafter. Adventitial n eovascularization by vasa vasorum was observed from day 4 onward. Conclusions Formation of neoadventitia precedes late loss of lumen, constri ctive remodeling, and formation of neointima. The time course of vascular r emodeling coincides with growth of neointima rather than with changes in th e adventitia. Coron Artery Dis 12:285-293 (C) 2001 Lippincott Williams & Wi lkins.