Teaching Case

A 30-year-old male patient with recent onset chest pain on exertion and palpitation presented. His stress ECG was normal, echocardiography revealed a subtle abnormality of the cardiac axis with apical hypermobility. The patient was referred to perform CT coronary angiography which was unremarkable.

The CT chest revealed an abnormal cardiac axis with exaggerated levocardia and rotation of the longitudinal axis in the clockwise direction and subsequently both right and left ventricles were on the same axial level. Also a partial absence of the pericardium over the ventricles level with residual pericardial linings still covering the atria was noted. Subsequent to this pericardial absence, the left lung tissues were seen interposed between the pulmonary trunk and the ascending thoracic aorta through the absent pericardium at the aorto-pulmonary window.

Congenital absent pericardium is a rare congenital anomaly, with an estimated prevalence of around 0.002: 0.004% of the population. In these cases, there will be either complete absence of the pericardium or only partial absence, which is rather called the congenital pericardial defect [1].

The pathogenesis of the pericardial absence is related to the premature atrophy of the common cardinal vein with ischemic agenesis of the pericardium. Six categories of pericardial defects are recognised: right-sided (partial or complete), left-sided (partial or complete), total absence, and absent pericardium with diaphragmatic defects [2, 3]. The most common variant is the left-sided partial defect. 30 to 50% percent of defects are associated with other cardiopulmonary anomalies as ASD, PDA, bicuspid aortic valve, tetralogy of Fallot, pulmonary sequestration and bronchogenic cysts [2, 3].

The majority of patients with an absent pericardium are asymptomatic, with only a few cases presenting with symptoms possibly related to the mechanical impairment of the cardiac function as fatigue. None with exertional chest pain and a few cases with cardiac conductivity related abnormalities [3, 4].

Plain radiography may reveal elevated cardiac apex, excessive levocardia and lucency related to lung tissues interposed between the pulmonary trunk and aorta. Echocardiography can detect pericardial absence with marked lateral displacement of the apical, parasternal long- and short-axis windows, cardiac hypermobility with swinging motion.
At CT, thin pericardial linings around the heart will be partially or totally absent with excessive levocardia. Lung tissues can also be seen extending to the aortopulmonary window, which doesn't occur normally due to the covering pericardial reflections. At MRI, cine sequences may also reveal excessive apical motion with an outward bulge [5 ].

Rarely, a congenital absent pericardium may result in complications as valvular mechanical dysfunction due to ventricular traction and papillary muscle dysfunction. Also coronary artery compression may occur against the edges of pericardial defects resulting in critical myocardial ischaemia. Myocardial herniation with possible incarceration through small partial pericardial defects were also reported and may result in life-threatening myocardial dysfunction or ischaemia and requires proper diagnosis and differentiation, notably from ventricle true and pseudoaneurysms. The main differentiation is that herniated myocardium through pericardial defects will demonstrate normal thickness and contractility, compared to aneurysms which are likely sequel to ischaemia and MI, with subsequent myocardial thinning and loss of function [2, 6].

Most cases of an absent pericardium are asymptomatic and require no treatment, symptomatic or complicated cases may require pericardioplasty, which in rare occasions can be carried out on emergency basis [7].