Definition

Abnormal communication between a pulmonary artery or arteriole and a pulmonary vein or venule.

Epidemiology

Rare 80–90% occur in the setting of hereditary hemorrhagic telangiectasia (Osler–Weber–Rendu disease).

Etiology, pathophysiology, pathogenesis

Usually congenital, rarely acquired (traumatic) Sporadic, usually solitary Osler–Weber–Rendu disease usually involves multiple lesions An arterial feeder and draining vein are usually present.

Imaging Signs

Modality of choice

CT, CTA.

Radiographic findings

Round or lobulated opacity surrounded by normal-appearing tissue; lesions with larger caliber feeding and draining vessels typically have a vascular pedicle extending toward the hilum.

CT findings

Findings are similar to radiography and include a round or lobulated lesion The vascular relationship is often demonstrated only on cine mode, in which the diagnosis can be made by interactive observation Plain scans show density values Enhancement typical of vascular structures occurs after contrast administration.

Pathognomonic findings

Round or lobulated lesion with a vascular pedicle.

Clinical Aspects

Typical presentation

Usually the lesion is an asymptomatic incidental finding; hypoxemia and signs of heart failure occur only with a high shunt volume One-third of patients have a history of transient ischemic attack or stroke (venous thrombi) or cerebral abscesses (bypassing of the pulmonary capillary filter).

Therapeutic options

Balloon embolization, coiling, or resection.

Course and prognosis

In Osler–Weber–Rendu disease the course and prognosis depend on the underlying disorder.

What does the clinician want to know?

Diagnosis Location In Osler–Weber–Rendu disease it may be advisable to obtain CT scans of carriers in the family for early detection of pulmonary arteriovenous malformation.

Fig. 1.1 AVM in Osler– Weber–Rendu disease. CT (MIP) shows multi-locular tortuous and expanded vascular structures with shunt connections in the periphery that were not visualized on the chest radiograph to this degree of detail.

Differential Diagnosis

Tips and Pitfalls

Can be misinterpreted as a pulmonary nodule or suspected malignancy.

Selected References

Langer R, Langer M. Value of CT in the diagnosis of pulmonary arteriovenous shunts. Cardiovasc Intervent Radiol 1984; 7: 277–279

White RI et al. Pulmonary arteriovenous malformations: diagnosis and transcatheter embolotherapy. J Vasc Interv Radiol 1996; 7: 787–804

Definition

Epidemiology

Most common causes include defect with left-to-right shunt, atrial septal defect, ventricular septal defect, and patent ductus arteriosus.

Etiology, pathophysiology, pathogenesis

Left-to-right shunt increases the volume of blood in the pulmonary circulation Atrial septal defect is a low-pressure shunt with volume overload; it leads to increased vascular resistance in the pulmonary circulation with pulmonary arterial hypertension only after a long time Ventricular septal defect is a high-pressure shunt with rapidly increasing vascular resistance and pulmonary arterial hyper-tension; shunt flow reverses when pressure is equalized (Eisenmenger reaction) Patent ductus arteriosus is a high-pressure shunt with hemodynamic effects similar to ventricular septum defect.

Imaging Signs

Modality of choice

Echocardiography, MRI.

Radiographic findings

Findings are positive only where shunt volume exceeds 40%; the findings then include a prominent pulmonary artery segment as well as prominent lung arteries with a slender aorta Pulmonary vascular structures are enlarged Normal or slightly widened heart silhouette Abrupt changes in vascular caliber and signs of right heart strain only occur with pulmonary arterial hypertension Ventricular septal defect and patent ductus arteriosus are associated with enlargement of the left atrium, and patent ductus arteriosus with a dilated ascending aorta.

MRI findings

Visualizes shunt location and morphology Allows estimation of shunt volume (quantification of blood flow in the ascending aorta and pulmonary trunk).

Pathognomonic findings

Prominent central and peripheral vascular structures.

Clinical Aspects

Typical presentation

Shunts with minimal hemodynamic effects are often asymptomatic or minimally symptomatic Clinically relevant shunts lead to right heart failure in atrial septal defect and left heart failure in ventricular septal defect.

Therapeutic options

Early correction.

Course and prognosis

Prognosis is good with early correction Unfavorable with pulmonary arterial hypertension and Eisenmenger reaction.

Fig. 1.2 Atrial septal defect (ostium secundum) with a 60% left-to-right shunt in a 41-year-old woman. The plain chest radiographs show a widened heart silhouette with signs of right heart strain (prominent pulmonary trunk and broad area of contact between the anterior wall of the heart and the sternum) and a conspicuously narrow aorta. In contrast, the hila are prominent with increased pulmonary vasculature without signs of redistribution.

Shunt location and morphology Shunt volume Valvular and ventricular function Signs of heart failure.

Differential Diagnosis

Tips and Pitfalls

Defects with “small” shunt volume (< 50%) are not detectable on plain radiographs.

Selected References

Baron MG, Book WM. Congenital heart disease in the adult. Radiol Clin North Am 2004; 42: 675–690

Steiner RM, et al. Congenital heart disease in the adult patient: The value of plain film chest radiology. J Thorac Imaging 1995; 10: 1–25

Wang ZJ et al. Cardiovascular shunts: MR imaging evaluation. Radiographics 2003; 23: 181–194

Definition

Anomalous, vertically coursing right pulmonary vein, often associated with other congenital malformations: Pulmonary venolobar syndrome Congenital hypoplastic lung Pulmonary hypoplasia with atypical pulmonary venous drainage Pulmonary sequestration.

Epidemiology

Rare (2 : 100 000).