Imaging description

Congenital absence of the pericardium is most easily diagnosed on axial CT or MR images. The heart appears rotated into the left hemithorax (Figure 22.1). Lung can be seen interposed between the aorta and the pulmonary artery, where normally there is fat covered by a layer of pericardium (Figure 22.2). In some cases, pericardium will be clearly visible along the right heart but not along the left heart (Figure 22.3). If the pericardial defect is small, focal herniation of a portion of the heart or great vessels may occur, increasing the risk for strangulation.

Importance

Distinguishing between complete and partial absence of the pericardium can be difficult when the normal, thin pericardium is generally difficult to visualize. Identifying absence of the pericardium is particularly important when the defect is partial, as this can result in herniation and strangulation of a portion of the heart or adjacent great vessels, which necessitates surgical correction.

Typical clinical scenario

Congenital absence of the pericardium occurs in approximately 0.002–0.004% of individuals. Partial absence of the left pericardium only (the most common form) results from atrophy of the left common cardinal vein, which interferes with development of the pericardium on that side.

It is most commonly incidentally detected during thoracic imaging ordered for unrelated reasons. Additionally, most cases are asymptomatic, although positional dyspnea and non-exertional chest pain have been reported, as has right bundle branch block. In 30% of patients, it is associated with congenital heart disease, such as tetralogy of Fallot, atrial septal defect, bicuspid aortic valve or patent ductus arteriosus.

Differential diagnosis

The differential diagnosis falls within two major categories: causes of levoposition of the heart or focal outpouchings from the heart. Volume loss in the left hemithorax due to atelectasis, prior lobectomy or left-sided bronchial atresia can also lead to levoposition of the heart in the setting of an intact pericardium. Enlargement of the right heart due to valvular disease or other causes can displace the heart into the left hemithorax.