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Criss-cross heart is a type of congenital heart defect where the right atrium is closely associated with the left ventricle in space, and the left atrium is closely associated with the right ventricle.

Although it is classified as a defect, the criss-cross is more of a spatial anomaly than a functional one, and it is possible for the heart to have relatively normal functioning. Less than 0.1% of all congenital heart defects are criss-cross heart conditions.

History
The congenital disease was first described by Lev and Rowlatt in 1961. However, it wasn’t until 1974 that doctors started diagnosing patients with this disease.

Causes
There is no known cause for criss-cross hearts. The disease may form due to a combination of genetic, epigenetic and environmental reasons.

Classic form
With criss-cross hearts, the base of the heart remains, in the same spatial position, as normal hearts. But the ventricles appear in a different position. In normal hearts the chambers are parallel. The right atrium is above the right ventricle, and the left atrium is above the left ventricle.

In criss-cross hearts there is a spatial change with the location of the ventricles. Each ventricle is in the opposite position with respect to their corresponding atrium. Therefore, the right atrium is above the left ventricle, while the left atrium is above the right ventricle.

The ventricles have been rotated along their major longitudinal axis which is why they appear in the opposite position.

Initially there was a false impression that each atrium was associated with the opposite ventricle. However, it was noted that this condition promotes a change in blood flow in the circulatory system. Blood flows across the chambers into their respective ventricles, rather than directly below as seen in normal hearts. Criss-cross hearts bring about structural changes rather than functional changes in terms of how the atriums and ventricles are connected.

Patients with criss-cross hearts have other heart malformations due to errors in embryonic heart development. These can include defects with the mitral valves, sizing of the ventricles or septal defects.

Since this condition involves changes in the coronary circulation, magnetic resonance imaging (MRI) and angiography tools are used in the diagnosis of the disease.

Treatment
Children with criss-cross hearts undergo surgery to improve their quality of life. Without surgery, 50% of patients die in the neonatal period and 64% of patients die by childhood.

Surgery does not revert the anatomical positions of the ventricles. Surgery aims to repair the malformations found with the disease. These include defects with the mitral valves, sizing of ventricles or septal defects. Septal defects can affect the ventricles or atria. They are holes between the walls of the atria or ventricles of the heart. The holes lead to uncontrolled blood flow.

Surgery will be specific to each patient. It will include different procedures that target the malformed cardiac segments.

Establishing the presence or absence of pulmonary stenosis (the obstruction of blood flow from the right ventricle to the pulmonary artery) and its severity is required before surgical treatment can begin. When pulmonary blood flow is lower than normal, patients are prescribed prostaglandin E1. Prostaglandin E1 is a powerful vasodilator that maintains the opening of the ductus arteriosus tube. This ensures the body has sufficient oxygenated blood, before surgery can begin.

The surgery starts above the right atrium. Once the body cavity is open, the surgeon reverts the cardiac malformations. For example, if a patient has a criss-cross heart and ventricle septal defect, surgeons will repair the septal defect. They will perform biventricular repairs. These repairs close the hole between the ventricles so blood flow is controlled. For patients who cannot undergo biventricular repairs, treatment to maintain and improve quality of life is proposed using the Glenn and Fontan technique. With this technique, venous blood flows from the veins to the arteries without passing through the right ventricle.