right ventricular wall

The RV wall is abnormally thick for this 5 mo old. Since the aorta is now attached to the RV, the RV has to pump blood to the rest of  the body causing the RV to grow to the same thickness as the LV would traditionally be.  This abnormally RV thick wall leads to the diagnosis of cardiomegaly. 

Left ventricular wall

Text description – The LV wall is of equal thickness to the RV.  Normally the LV should be thicker than the RV since the LV sends blood to the rest of the heart. However, in this case, the aorta is filled with mixed or predominantly deoxygenated blood which will trigger the chemoreceptors which make the heart beat faster and stronger.