REMODELING RATHER THAN NEOINTIMAL FORMATION EXPLAINS LUMINAL NARROWING AFTER DEEP VESSEL WALL INJURY - INSIGHTS FROM A PORCINE CORONARY (RE)STENOSIS MODEL

Background Oversized balloon dilatation of normal porcine coronary art eries usually heals without stenosis formation. Methods and Results Wi th the purpose of developing a stenotic model and examining the mechan isms of luminal narrowing after angioplasty, we produced a circumferen tial deep vessel wall injury by inflating and withdrawing an oversized chain-encircled angioplasty balloon in the left anterior descending c oronary artery (LAD) of 20 pigs. Three pigs died and did not complete the study. In 8 pigs (group 1), serial coronary arteriography was perf ormed. The lumen diameter (mean+/-SD) before dilatation was 3.4+/-0.4 mm; after dilatation, 4.2+/-0.6 mm; and at follow-ups 2 and 4 weeks la ter, 1.6+/-0.4 mm (P<.0001). In 9 pigs (group 2) examined postmortem 3 weeks after dilatation, histology revealed that the injury was deep ( out to adventitia) in all arteries and completely circumferential (360 degrees) in all but two arteries. Adventitia was markedly thickened a s a result of neoadventitial formation. Injury correlated strongly wit h neointimal formation (middle LAD, r=.71, P=.00001), but neither inju ry nor neointima correlated with lumen size (r=.14, P=.46 and r=.34, P =.07, respectively); ie, neointimal formation did not explain late lum inal narrowing. Lumen size, however, did correlate strongly with vesse l size (r=.74, P=.000005). The late loss in lumen diameter observed an giographically in group 1 substantially exceeded that caused by neoint imal formation seen by histology in group 2. Conclusions The chain-enc ircled angioplasty balloon produced a circumferential deep vessel wall injury that healed by luminal narrowing. In this porcine model, arter ial remodeling was more important than neointimal formation in late lu minal narrowing.