Imaging description

Partial anomalous pulmonary venous return (PAPVR) is characterized by the inappropriate drainage of one or more pulmonary veins into the systemic venous circulation. Anomalous drainage of the left superior pulmonary vein to the left brachiocephalic vein or the right superior pulmonary vein to the superior vena cava (Figures 23.1 and 23.2) are the most common incidentally encountered forms of PAPVR in adults undergoing chest CT exams. Right upper lobe PAPVR is associated with a sinus venosus type atrial septal defect in 42% of patients (Figure 23.2). Scimitar syndrome is a specialized form of PAPVR that predominantly involves the right-sided pulmonary veins (Figure 23.3). In this scenario, the right inferior pulmonary vein drains below the diaphragm to join the IVC just distal to the hepatic vein confluence (Figure 23.1). Scimitar syndrome is often associated with right-sided thoracic anomalies, such as a hypoplastic right lung (Figure 23.2). PAPVR is a left-to-right shunt, and depending on the volume of shunting, right-sided cardiac chamber enlargement and pulmonary artery enlargement may be present (Figure 23.1).

Importance

PAPVR occurs in many forms, which together have a prevalence of less than 1%. Although rare, PAPVR can be detected incidentally in asymptomatic patients, which may prompt further evaluation to assess need for repair. In addition, in patients being evaluated for an occult shunt due to right-sided chamber enlargement, PAPVR is an important subtype of shunt that may be missed by echocardiography. Cross-sectional imaging becomes important for characterization of the anatomy, particularly in patients who are symptomatic and are undergoing preoperative evaluation. Surgical therapy is generally considered if the Qp:Qs is at least 1.5:1, because of the risk of pulmonary hypertension and right ventricular failure.

Typical clinical scenario

The timing of diagnosis of PAPVR is closely related to the degree of symptoms and number of associated anomalies. Patients who are incidentally found to have PAPVR as adults are rarely symptomatic and have few associated anomalies, while those who are diagnosed earlier in life typically have more severe symptoms and a higher number of associated congenital malformations.