OBJECTIVES: The purpose of this study was to use transesophageal echocardiography (TEE) to define the mechanisms of aortic regurgitation (AR) in acute type A aortic dissection so as to assist the surgeon in identifying patients with mechanisms of AR suitable for valve preservation. BACKGROUND: Significant AR frequently complicates acute type A aortic dissection necessitating either aortic valve repair or replacement at the time of aortic surgery. Although direct surgical inspection can identify intrinsically normal leaflets suitable for repair, it is preferable for the surgeon to correlate aortic valve function with the anatomy prior to thoracotomy. METHODS: We studied 50 consecutive patients with acute type A aortic dissection in whom preoperative TEE findings were considered by the surgeons in planning aortic valve surgery. Six patients did not undergo surgery (noncandidacy or refusal) and one patient had had a prior aortic valve replacement and therefore was excluded from the analysis. RESULTS: Twenty-seven patients had no or minimal AR and 22 had moderate or severe AR. In all, there were 16 with intrinsically normal leaflets who had AR due to one or more correctable aortic valve lesion: incomplete leaflet closure due to leaflet tethering in a dilated aortic root in 7; leaflet prolapse due to disrupted leaflet attachments in 8; and dissection flap prolapse through the aortic valve orifice in 5. Of these 16 patients, 15 had successful aortic valve repair whereas just 1 underwent aortic valve replacement after a complicated intraoperative course (unrelated to the aortic valve). Nine patients underwent aortic valve replacement for nonrepairable abnormalities, including Marfan's syndrome in four, bicuspid aortic valve in four, and aortitis in one. In patients undergoing aortic valve repair, follow-up transthoracic echocardiography at a median of three months revealed no or minimal residual AR, and clinical follow-up at a median of 23 months showed that none required aortic valve replacement. CONCLUSIONS: When significant AR complicates acute type A aortic dissection, TEE can define the severity and mechanisms of AR and can assist the surgeon in identifying patients in whom valve repair is likely to be successful.