Reconstruction of the right common carotid artery has been shown to be feasible in neonates after extracorporeal membrane oxygenation (ECMO). However, the long-term outcome after carotid artery reconstruction (CAR) remains unknown. The purpose of this study was to evaluate the natural progression of the anastomotic site after CAR. Between February 1990 and June 1993, 201 patients received ECMO. All veno-arterial (VA) ECMO patients (n = 172) were considered candidates for reconstruction unless a significant neurological event (ie, intracranial hemorrhage, stroke) had occurred; the duration of ECMO exceeded 10 days, making carotid mobilization difficult; or the patient's prognosis was deemed poor. Reconstruction was performed by excising the arteriotomy site, followed by primary end-to-end anastomosis. Reconstruction was abandoned and the artery ligated if an intimal flap, arterial thrombosis, or excessive tension was encountered. After reconstruction all patients had early carotid ultrasonography and either head computed tomography (CT) or magnetic resonance imaging (MRI). Subsequent ultrasound examinations were performed at approximately 6-month intervals. Diameter index (DI) (a measure of anastomotic narrowing) was calculated using ultrasound by dividing the anastomotic diameter by the diameter of the carotid artery 5 mm proximal to the anastomosis. Forty-three of 172 VA ECMO patients (25%) had successful reconstruction. Long-term follow-up data were available on 27 patients. These 27 patients had 39 ultrasound examinations, with an average follow-up time of 7.3 months (range, 4 days to 29 months). All carotid arteries were patent. Linear regression analysis showed significant improvement in the DI with time (P = .0001, r2 = .382).(ABSTRACT TRUNCATED AT 250 WORDS)