Objective To analyze the misdiagnosis rate of scimitar syndrome (SS) by transthoracic echocardiography (TTE) and its associated influencing factors, and to explore strategies for optimizing the diagnostic workflow to enhance the accuracy of TTE in diagnosing this disease.Methods Clinical and TTE data of 71 patients diagnosed with SS by surgery and/or computed tomographic angiography (CTA) from January 2008 to December 2025 were retrospectively analyzed, with a particular emphasis on the initial TTE reports. Using surgical and CTA findings as the gold standard, 46 patients with a definite diagnosis or high suspicion of SS on TTE reports were allocated to the confirmed group (Group A), and 25 patients without indications of SS on the initial TTE reports were assigned to the misdiagnosis group (Group B). Exact tests were employed to analyze the correlation between misdiagnosis and factors such as age, routine pulmonary vein scanning, presence of atrial septal defect, degree of right - heart enlargement, and examiner experience. The causes of misdiagnosis were systematically summarized, and methods for optimizing the diagnostic workflow were proposed.Results Among the 71 patients, 46 (64.8%) were correctly identified or suspected of having SS on the initial TTE examination, and 25 (35.2%) were misdiagnosed. The causes of misdiagnosis could be classified into three categories: cognitive and mindset factors (72%, 18/25), primarily manifested as examiners" insufficient knowledge of SS, contentment with diagnosing common malformations like atrial septal defect, lack of awareness for systematic screening of pulmonary veins, and inability to correctly interpret abnormal flow within the inferior vena cava; examination workflow and technical factors (64%, 16/25), including the failure to implement standardized and mandatory scanning sequences for pulmonary veins, especially the neglect of multi - sectional (particularly subxiphoid) tracing of the right pulmonary venous course; case - related challenging factors (12%, 3/25), such as poor image quality or a shifted diagnostic focus due to patient conditions (e.g., obesity, pulmonary gas interference) or concurrent other malformations. There were no statistically significant differences between the misdiagnosis group and the confirmed group in terms of age, gender, or symptoms (P > 0.05). However, statistically significant differences were observed in examiner experience (< 5 years vs. ≥ 5 years), systematic pulmonary vein tracing, systematic subxiphoid scanning, concurrent other intracardiac malformations, and poor image quality (acoustic window limitations) (P < 0.05).Conclusion TTE has a relatively high misdiagnosis rate for SS, mainly attributable to target - oriented cognitive limitations and workflow deficiencies. An enhanced TTE workflow centered on systematic pulmonary vein evaluation should be established. A high level of suspicion should be maintained in patients with indirect clues such as right - ward cardiac displacement, right - heart enlargement, and pulmonary hypertension. Systematic scanning protocols including subxiphoid views should be made mandatory and standardized, and targeted training for junior physicians should be strengthened. For clinically or echocardiographically suspected cases, cardiac CTA is essential for definite diagnosis and comprehensive preoperative evaluation.