Background: The principal roles of the pericardium include protection from microorganisms, prevention of cardiac friction, and restriction of unlimited dilation of the heart. In the case of a congenital pericardial defect in which structural, electrophysiological, and haemodynamic abnormalities manifested during postural changes, we propose another indispensable pericardial function of cardiac central anchorage. Case summary: A 29-year-old man with atypical chest pain was referred to our hospital. Electrocardiography revealed fluctuations in the QRS transitional zone, electrical axis, and atrial polarity with body posture. Echocardiography revealed a far dorsally displaced heart, paradoxical motion of the interventricular septum (IVS), and hyperdynamic motion of the posterior wall in the left lateral decubitus position, which normalized to the right lateral decubitus position, along with significant haemodynamic alterations. Multidetector-row computed tomography revealed a complete absence of the left pericardium. Discussion: When pericardial fixation is impaired, the heart falls dorsally owing to gravity in the left lateral decubitus position, resulting in right ventricular overstretch and enlargement, which, in turn, results in compression of the left ventricle via a leftward shift of the IVS and a consequent reduction in cardiac output. Moreover, the energy generated by the myocardium, which should normally be concentrated only on blood ejection, would be distributed between the energy used for ejection and that used for the leap-up movement of the heart, reducing its energy efficiency. Through detailed observation of the congenital pericardial defect, haemodynamic insights into the important functions of the pericardium, which were not visible through static observation, were obtained.