Background.Transplant coronary artery disease (TxCAD) is a major cause of long-term mortality after heart transplantation. Although vascular remodeling has been implicated in the pathophysiology of TxCAD, its determinants remain unknown.Methods.Twenty-nine consecutive heart-transplant recipients prospectively received intravascular ultrasound (IVUS) of the left-anterior descending artery 1 and 12 months after transplant, with volumetric reconstruction of the proximal 30 mm.Results.Overall, patients exhibited intimal volume increase (+83%,P<0.001), wheras vessel volume remained largely unchanged (+4%,P=0.270); consequently, overall lumen volume decreased (−6%,P=0.058). Among the clinical and laboratory variables, cytomegalovirus (CMV) infection requiring treatment (occurring in 12 patients), as assessed by pp65 antigenemia, was independently associated with the impaired ability of the vessel wall to enlarge in response to intimal volume increase, ultimately resulting in lumen loss (OR [95% CI]=0.098 [0.010–0.920];P=0.042). However, adequate vessel response to intimal hyperplasia with consequent lumen preservation was observed in the remaining 17 patients who did not present CMV infection requiring treatment.Conclusions.The present study demonstrates that either adequate or inadequate coronary remodeling may occur during the first year after transplantation. Moreover, for the first time, it strongly suggests that remodeling modalities may be negatively influenced by the occurrence of clinically relevant CMV infection. Randomized prospective trials are warranted to investigate whether aggressive treatment of CMV infection may help prevent TxCAD.