Objectives: To study coronary artery (CA) perfusion and myocardial performance after patent ductus arteriosus (PDA) ligation. The postoperative course in premature infants undergoing surgical ligation of PDA is often complicated by cardiorespiratory instability secondary to impaired left ventricular performance. Methods: Serial echocardiography was performed before and after (1, 8, and 24 hours) PDA ligation to assess systolic (left ventricular output [LVO]) and diastolic (isovolumic relaxation time, E and A wave peak velocity) myocardial performance, and CA diastolic flow (CA velocity time integral and flow). The ratio of CA flow to LVO was calculated as a surrogate of coronary flow. Results: A total of 20 infants (gestational age at birth, 26.3 ± 0.7 weeks) requiring PDA ligation at a median of 28.5 days (range, 9-40) after birth and weight of 780 g (range, 570-2840) were studied. A postoperative increase in the CA flow/LVO ratio was demonstrated. An early decrease in E and A wave peak velocity (P < .05) and increase in isovolumic relaxation time (P < .05) were demonstrated at 1 hour, before any clinical deterioration. A low baseline CA velocity time integral was associated with a low E/A ratio (r = 0.63, P = .01) at 1 hour and lower systolic blood pressure at 8 hours (r = 0.5, P = .05). The postoperative need for inotropes (n = 8) was associated with a low baseline CA velocity time integral at 1 hour (r = 0.52, P < .05), low LVO at 1 and 8 hours (P < .05), and increased oxygen requirement at 24 hours (P < .05). Conclusions: PDA ligation is followed by altered CA perfusion. Perioperative evaluation of the CA perfusion can help identify neonates at risk of impaired myocardial performance, systolic hypotension, and the need for inotropes.