To analyze the cases of missed and misdiagnosis of unroofed coronary sinus syndrome (UCSS) by ultrasound to improve the accuracy of preoperative diagnosis.

Thirteen cases of UCSS examined by preoperative echocardiography and undergoing cardiac surgery at Union Hospital, Tongji Medical College, Huazhong University of Science and Technology were retrospectively analyzed from January 2013 to January 2021. The ultrasound images and image description, including imaging quality, the display of important sections of the coronary sinus (CS) and persistent left superior vena cava (PLSVC), and the key image features, were reviewed and compared with the surgical results.

Four UCSS cases were missed, including 3 type Ia and 1 type IIa. Nine cases were misdiagnosed, among which UCSS was misdiagnosed as primary foramen atrial septal defect (ASD) in 2 cases, as secondary foramen ASD in 2, and as inferior vena cava ASD in 1. In addition, 4 cases, including 1 case of inferior vena cava ASD, 2 cases of intracardiac anomalous right pulmonary venous drainage, and 1 case of CS widening caused by PLSVC, were misdiagnosed as UCSS. In patients with a missed diagnosis, the relevant sections of the CS and PLSVC were not scanned completely in two cases, 1 case stored partial sections were stored and the septal defect of the CS was not identified in 1, and PLSVC was missed due to poor acoustic window in 1. In 5 cases with UCSS misdiagnosed as other malformations, special CS and PLSVC sections were not closely observed but only some sections were stored unintentionally. What's more, the position of defect, abnormal blood flow, and the course and shape of shunt bundle were misinterpreted. In 4 cases with other cardiovascular malformations misdiagnosed as UCSS, the CS and PLSVC were scanned before operation. However, the CS was ignored and misjudged as complete absence due to its expansion and displacement, or misinterpreted as sinus wall defect with its shunt under the influence of echo loss due to its tortuous and weak sinus wall and nearby blood flow signals.

Missed diagnosis and misdiagnosis of UCSS by ultrasound are mainly related to the lack of vigilance or unskilled scanning of the examiners, and wrong interpretation of the defect on the sinus wall or atrial septum and relevant abnormal blood flow. The accuracy of preoperative ultrasound diagnosis can be significantly improved by more vigilance of UCSS and more differential diagnostic knowledge between UCSS and ASD or intracardiac anomalous pulmonary venous drainage.