Lumen loss in transplant coronary artery disease is a biphasic process involving early intimal thickening and late constrictive remodeling - Results from a 5-year serial intravascular ultrasound study

Background-Coronary artery disease is the major cause of late cardiac allog raft failure. However, few data exist regarding the natural history of chan ges in intimal and external elastic membrane (EEM) areas after heart transp lantation. Methods and Results-In 38 transplant recipients, serial intravascular ultra sound examinations were performed 3.7 +/-2.2 weeks after transplantation an d annually thereafter for 5 years. In 59 coronary arteries, we compared 135 matched segments among serial studies. In each segment, intravascular ultr asound images were digitized at 1-mm intervals, and mean values of EEM and lumen and intimal areas were analyzed. In the first year after transplantat ion, the intimal area increased significantly from 1.8 +/-1.6 to 3.0 +/-2.1 mm(2) (P <0.001). Subsequently, the annual increase in intimal area decrea sed. EEM area did not change during the first year; however, between years 1 and 3, significant expansion of EEM area occurred (15.4 +/-4.6 to 17.2 +/ -5.4 mm(2)-, P <0.001). Thereafter, EEM area decreased significantly from 1 7.2 +/-5.4 mm(2) (year 3) to 15.1 +/-4.9 min. (year 5, P=0.01). Different r nechanisms of lumen loss were observed during 2 phases after transplantatio n: early lumen loss primarily caused by intimal thickening and late lumen l oss caused by EEM area constriction. Conclusions-This serial ultrasound study revealed that most of the intimal thickening occurred during the first year after heart transplantation. Chan ges in the EEM area showed a biphasic response, consisting of early expansi on and late constriction. Thus, different mechanisms of lumen loss were obs erved during the early and late phases after transplantation.