Preoperative left ventricular dysfunction is a risk factor for postoperative mortality and morbidity in cardiovascular surgeries with cardiopulmonary bypass, including thoracic aortic surgery. Using a retrospective study design, this study aimed to clarify the short- and mid-term outcomes of patients who underwent acute type A aortic dissection (ATAAD) repair with reduced left ventricular function.Between July 2007 and February 2018, a total of 510 adult patients underwent surgical repair of ATAAD in a single institution. The patients were classified as having left ventricular ejection fraction (LVEF) <50% (low EF group, n = 86, 16.9%) and LVEF ≥50% (normal group, n = 424, 83.1%) according to transesophageal echocardiographic assessment at the operating room. Preoperative demographics, surgical information, and postoperative complication were compared between the two groups. Three-year survival was analyzed using the Kaplan-Meier actuarial method. Serial echocardiographic evaluations were performed at 1, 2, and 3 years postoperation.Demographics, comorbidities, and surgical procedures were generally homogenous between the 2 groups, except for a lower rate of aortic arch replacement in the low EF group. The averaged LVEFs were 44.3 ± 2.5% and 65.8 ± 6.6% among the low EF and normal groups, respectively. The patients with low EF had higher in-hospital mortality (23.3% versus 13.9%, P = .025) compared with the normal group. Multivariate analysis revealed that intraoperative myocardial failure requiring extracorporeal membrane oxygenation support was an in-hospital mortality predictor (odds ratio, 16.99; 95% confidence interval, 1.23-234.32; P = .034), as was preoperative serum creatinine >1.5 mg/dL. For patients who survived to discharge, the 3-year cumulative survival rates were 77.8% and 82.1% in the low EF and normal groups, respectively (P = .522). The serial echocardiograms revealed no postoperative deterioration of LVEF during the 3-year follow-up.Even with a more conservative aortic repair procedure, the patients with preoperative left ventricular dysfunction are at higher surgical risk for in-hospital mortality. However, once such patients are able to survive to discharge, the midterm outcome can still be promising.