The pathogenesis of IPA is based on abnormal embryologic development of the pericardium resulting from a premature atrophy of the left duct of Cuvier. This implies a compromised vascular circulation to the left pleuropericardial membrane, which would eventually become the left pericardium. This theory is supported by post-mortem studies showing that congenital pericardial defects almost invariably involve the entire left side of the heart[7]. Detectable anomalies on chest X-rays often include displacement of the cardiac silhouette to the left, a lucent area between the aorta and pulmonary artery secondary to lung interposition, irregular left heart border, loss of the right heart border through its superimposition on the spine, prominence of the main pulmonary artery, and presence of lung tissue between the heart and diaphragm[8]. Common ECG records include right axis deviation, incomplete right bundle branch block, left displacement of the transition zone in the precordial leads, poor R wave progression, and prominent P waves[9]. Concerning echocardiography, the presence of IPA commonly requires a lateral probe position for the apical four-chamber view[10].

Although in our case, no further cardiac malformations were detected, according to the literature, about one-third of all IPA cases can be associated with other cardiac lesions, as patent arterial duct, mitral stenosis or tetralogy of Fallot[11]. Other possible echocardiographic findings include right ventricular dilation and paradoxical septal motion, usually associated with normal ventricular function. Further radiological investigations such as heart MRI are necessary to confirm the suspected diagnosis and determine the extent of the agenesis or to highlight the eventual evidence of herniation of the cardiac chambers through the defect. Typical findings detectable on cardiac MRI include heart levoposition, left atrial appendage/main pulmonary artery beyond the mediastinum, lung between the main pulmonary artery and aorta, lung between the heart and diaphragm, and elevated apex[12].

Fig. 2. Axial black blood fast spin echo (FSE) magnetic resonance imaging showing the prominence (arrow) of the pulmonary trunk in the left hemithorax due to herniation through the pericardial defect.

Most of the described cases of IPA deal with adult patients, and only a few descriptions exist in relationship with childhood. In our pediatric patient, presenting with spontaneously remitting abdominal pain unrelated to the IPA, the diagnosis was established following the investigation of bradycardia, which represented an occasional finding, since no coexisting symptoms were present on the child’s arrival or had ever been detected in the past.

The therapeutic approach of IPA consists of different strategies, which should be adopted according to the large spectrum of clinical presentations. Surgical reconstruction of the absent pericardium may represent a safe intervention in case of debilitating symptoms and lead to symptomatic improvement; on the other hand, a conservative approach including only clinical follow-up is recommended in case of well-compensated clinical pictures and complete absence of symptoms.

In conclusion, our report is aimed both to underline that IPA can be diagnosed early in childhood, even in completely asymptomatic patients, and to familiarize clinicians and radiologists to this uncommon condition. In fact, although IPA may not significantly alter cardiac function, as in our case, the potential development of sudden and severe complications should always be carefully taken into consideration.