Relationship between coronary function by positron emission tomography and temporal changes in morphology by intravascular ultrasound (IVUS) in transplant recipients

Background: Transplant coronary vasculopathy is one of the major causes of graft failure and death in cardiac transplant recipients. A non-invasive test of coronary function to predict the course of this disease would be desirable. Methods: To determine whether the degree of abnormalities in endothelial dependent coronary vasomotion (cold presser testing) or endothelial independent vasodilatory capacity (intravenous dipyridamole) as determined by positron emission tomography (PET) one to two years after heart transplantation is correlated with the course of transplant vasculopathy. Nineteen patients had baseline PET and intravascular ultrasound studies (IVUS) at 18 +/- 6 months after cardiac transplantation and a follow up IVUS study 15 +/- 5 months later. Results: Myocardial blood flow was higher in patients than in healthy controls (p < 0.002) but increased during cold presser testing only in controls (p < 0.005). Myocardial blood flow normalized to the rate pressure product declined in patients (p < 0.001). Dipyridamole-induced hyperemic blood flow and the flow reserve normalized to the resting rate pressure product were lower in patients than in controls (p < 0.001 and p < 0.01). The normalized flow reserve was correlated with changes in total vessel area (r = 0.55; p = 0.02) and lumen diameter (r = 0.52; p < 0.05). Conclusion: These findings suggest that the degree of abnormalities in endothelial independent myocardial flow as detected by PET one to two years after transplantation is associated with morphological indices of disease progression by IVUS.