Early constriction or expansion of the external elastic membrane area determines the late remodeling response and cumulative lumen loss in transplant vasculopathy: An intravascular ultrasound study with 4-year follow-up

Background: Early constriction of the external elastic membrane (EEM) area has been observed after cardiac transplantation. The aim of this study was to compare the late disease process of transplant vasculopathy between coronary segments with early constrictive and expansive remodeling. Methods: Serial intravascular ultrasound data obtained annually for 4 years after transplantation in 38 transplant recipients was available. In 135 matched segments from 59 coronary arteries ultrasound images were digitized at 1-mm intervals. Mean values of the external elastic membrane (EEM), lumen and intimal areas were calculated. On the basis of a decrease or increase in EEM area within the first year after transplantation, we defined segments with early constrictive remodeling (CR, n = 71) or early expansive remodeling (ER, n = 64). Results: Annual changes in intimal area were similar between segments with early CR and ER throughout the follow-up period. However, during the second and third year, annual increases in EEM area were greater in segments with early CR than in segments with early ER (second year: 1.5 ± 2.7 vs 0.6 ± 2.8 mm², p = 0.052; third year: 1.3 ± 2.5 vs -0.03 ± 2.6 mm², p = 0.003). Despite this late expansion, segments with early CR showed a cumulative decrease in the EEM area and a greater lumen loss than segments with early ER (-2.5 ± 3.4 vs -0.6 ± 2.6 mm², p < 0.001). Conclusions: In transplant vasculopathy, the late remodeling response was different between segments with early constrictive and expansive remodeling, despite similar intimal thickening. Early constriction caused an overall decrease in EEM area and greater loss of lumen during follow-up.