Congenital absence of anterior pericardium at left ventricular assist device implantation

The present case includes the extremely rare finding of anterior CAP and an abnormally large heart as seen preoperatively on MRI and intraoperatively. Both the preoperative MRI findings and the intraoperative findings raised the question of whether there was any association between the patient’s cardiomyopathy and the loss of the structural support and stabilization that an intact pericardium would have provided.

Congenital absence of the pericardium is a rare but well documented clinical phenomenon. ¹ It represents not a single entity but a spectrum of abnormalities ranging from very small pericardial defects to complete agenesis occurring as a result of perturbations in the development of the common cardinal veins during embryogenesis. Normally, the left common cardinal vein develops into the left pleuropericardial membrane, and the right common cardinal vein forms the superior vena cava with concomitant closure of the right pleuropericardial membrane. Congenital pericardial defects can occur alone or in association with other congenital anomalies. ² Reports of right-sided pericardial defects in the literature are few, but some of them suggest that the superior vena cava may persist on the left side but be absent on the right. ⁵

Patients who have CAP may show no symptoms, mild symptoms, or intractable symptoms requiring surgery. ¹ In asymptomatic patients, CAP is usually diagnosed incidentally on a chest radiograph performed for other reasons. Symptomatic patients often describe a sharp, stabbing, left-sided chest pain that may be postural. ⁶ Although its cause is unclear, the pain may be due to tension on pleuropericardial adhesions in the presence of partial defects.

With or without symptoms, CAP is often difficult to diagnose. However, certain characteristic features can be identified by various imaging techniques. On the chest radiograph, left-sided CAP is often indicated by a cardiac silhouette that is displaced to the left with a right heart border that is lost to view by superimposition of the vertebral column. A “tongue” of lung tissue may also be seen between the pulmonary artery and the aorta. ¹ Frequently, however, the chest radiograph is not diagnostic. Echocardiography may rule out other structural defects. It may also allow visualization of paradoxical ventricular septal motion and other subtle findings, such as bulging of the inferior left ventricular wall during diastole. ⁷ Computed tomography ⁸ and MRI ⁹ are especially useful. Both techniques can reveal levoposition of the heart, interposition of lung tissue between the inferior aspect of the heart and the diaphragm, and abnormal extension of the main pulmonary artery and the left atrial appendage beyond the margins of the mediastinum.

In our patient, the diagnosis of CAP was confounded by the abnormally dilated cardiac chambers seen on cine MRIs. Although the displaced apex and enlarged left atrial appendage may have prompted us to consider a diagnosis of CAP, they did not enable us to make a definitive diagnosis until surgery, since the chamber dilatation could also have caused the distortion and malposition of nearby anatomic structures visible on the chest radiograph.

Because CAP is rare and most of the published literature consists of case reports, treatment options are unclear. In asymptomatic patients, observation alone is adequate. However, because the heart and great vessels tend to move within the mediastinum, some clinicians have advocated repair in such cases, if thoracotomy is being performed for other reasons. ³ When symptoms are debilitating or if the atrial appendage has herniated through a pericardial defect, corrective procedures, such as left atrial appendectomy, pericardioplasty, or extension of the pericardial defect, might also be beneficial. ¹ The presence of cardiomyopathy in our patient suggests that some benefit might also be gained by earlier diagnosis and treatment with innovative—although as yet unproven—techniques such as passive containment with a cardiac support device. ^10,11

Herein, we describe the case of a patient with symptoms of congestive heart failure in whom congenital absence of the pericardium was confirmed during surgical implantation of a left ventricular assist device. No attempt was made to repair the large defect during surgery, because it was assumed, correctly, that the left ventricular assist device would adequately stabilize the heart.