DISCUSSION

Situs describes the position of the cardiac atria and abdominal viscera relative to midline. Situs solitus is the normal position while situs inversus refers to mirror-image placement of those organs. Situs inversus is almost always associated with dextrocardia (right-sided apex beat) and is linked to a 3-5% incidence of CHD. Situs inversus with levocardia (left-sided apex beat) is rare and almost always associated with CHD.^{1, 2} The cause, however, is not fully known.^{3, 4}

In this case, the diagnosis of situs inversus with levocardia was made clinically and based upon a set of imaging done. The erect chest X-ray clearly demonstrated the opposing orientation of the cardiac apex towards the left and the gastric fundal bubble to the right. An abdominal ultrasound revealed the placement of the liver in the left hypochondrium while that of the spleen in the right hypochondrium. The electrocardiogram and echocardiogram done further suggests cardiac situs inversus. A cardiac magnetic resonance imaging (MRI) or cardiac computed tomography (CT) scan may be useful to further delineate the cardiac anatomy.

Cyanotic CHD is associated with secondary polycythaemia. This is a physiological response to tissue hypoxia, stimulating erythropoietin production and subsequent erythropoiesis.⁵ It results in improved oxygen carrying capacity. However, this is offset by an increase in serum viscosity that impairs blood flow and tissue perfusion. In the setting of background cyanotic heart disease, the body regulates the degree of erythropoiesis to balance the detrimental effect of increased blood viscosity in order to optimise tissue oxygen perfusion and delivery. However, this balance can be tipped off in the presence of infection, dehydration, or failure of compensatory mechanisms, leading to hyperviscosity syndrome. Hyperviscosity syndrome may manifests as headache, visual disturbance, dyspnoea, angina, paraesthesia, lethargy or thrombosis.

This patient had developed symptomatic hyperviscosity syndrome precipitated by pneumonia and dehydration. The treatment is intravenous hydration and venesection, which results in reduced red cell mass and peripheral vascular resistance. This improves blood flow and tissue oxygen delivery.

Currently there are no studies recommending routine venesection as a long term treatment of polycythaemia in patients with cyanotic CHD. Regular venesection results in iron deficiency, leading to the production of microcytic red cells that are more viscous than normocytic red cells, paradoxically increasing the risk of thrombosis.⁶ These microcytic red cells are more rigid and less malleable in the microcirculation.⁶ Therefore, venesection is recommended only in the setting of acute hyperviscosity to avoid chronic iron deficiency.

Contemporary advances in medical care has resulted in increasing number of patients with CHD entering adulthood. Nevertheless, mortality is this patient sub group is still higher compared to the general population. The primary cause of death in adults with complex CHD remains cardiac origin, of which progressive heart failure (27%) and sudden cardiac death (23%) are the leading causes.^{7, 8} Extracardiac complications such as malignancy and infections are also more prevalent in this group. Pneumonia has been identified as a second leading cause of death after cardiac causes in a population study. This is postulated to be related to the associated genetic abnormality, immune system compromise or congenital lung anomaly.⁹ Some CHD patients with heterotaxy syndrome (abnormal arrangement of internal organs) have absence or hypofunctioning spleen, rendering them susceptible to infection with encapsulated bacteria.

CONCLUSION

This case report highlights a rare case of situs inversus with levocardia and concomitant cyanotic CHD. With the advancement in the field of paediatric cardiology, there will be an increase in adult survivors with complex CHD. Potential long term complications should be anticipated and treated accordingly.

ACKNOWLEDGEMENT
We would like to thank the Director General of Health Malaysia for his permission to publish this article

DECLARATION OF INTERESTS
The authors have no conflict of interest to declare

FUNDING
This study did not receive external funding