Single Right Ventricle Defects

In the normal heart, blood flows from the left ventricle through the aortic valve to the rest of the body. Aortic valve stenosis is when the aortic valve is more narrow than normal or blocked. This blocks blood flow to the body. Aortic valve stenosis can be mild, moderate, or severe. When a baby has severe aortic stenosis, the left pumping chamber (left ventricle) gets enlarged and weak. This makes less blood flow through the left heart, which causes the left ventricle to stop growing and the left heart to be too small. Aortic stenosis can but doesn’t always cause a condition called hypoplastic left heart syndrome (HLHS).

In DORV, both the pulmonary artery and the aorta start in the lower right pumping chamber (right ventricle). This defect often has a ventricular septal defect (VSD), pulmonary stenosis, or a transposition of the great arteries as well. A VSD is a hole between the bottom chambers. Pulmonary stenosis is when the pulmonary valve is too small. Transposition of the great arteries is when the aorta and pulmonary artery positions are switched. When DORV is combined with a too small (hypoplastic) left ventricle, this heart condition is known as a single ventricle defect.

In HLHS, the parts on the left side of the heart (mitral valve, left ventricle, aortic valve and aorta) do not develop all the way and are too small (hypoplastic). When the left lower pumping chamber (left ventricle) is hypoplastic, it cannot get enough oxygenated blood to the body. When a baby has HLHS, the heart needs a connection between the aorta and pulmonary artery to get the oxygenated blood out to the body and brain. This means the baby needs to have an atrial septal defect (ASD) and a patent ductus arteriosus (PDA) to live.

In rare cases, an unborn baby with severely underdeveloped, left-sided heart chambers (hypoplastic left heart syndrome or ‘HLHS’) can have a blockage within the heart. This is called HLHS with an intact atrial septum. An intact atrial septum is when the wall between the left and right upper chambers of the heart (atria) is closed. Having both HLHS and an intact atrial septum can make the baby very sick right after birth. The blood returning from the lungs into the left upper chamber (left atrium) cannot get out of the chamber. This is because the left side of the heart did not grow (develop) and the atrial septum is closed. This makes blood backup in the lungs, causing lung damage.

An atrioventricular septal defect (AVSD) is a heart defect where there are holes between both the top collecting chambers (atria) and bottom pumping chambers (ventricles). The valves between the atria and ventricles can be two separate valves or combined into one large valve. AVSD is also known as an atrioventricular canal defect (AVC or AVCD).

In an unbalanced, right-dominant atrioventricular septal defect, the right ventricle is larger than the left ventricle. The difference in size between the ventricles can range from small to large. When the left ventricle is too small, it cannot pump blood out to the body and brain. This heart condition is known as a single ventricle defect.

An atrioventricular septal defect (AVSD) is a heart defect where there are holes between both the top collecting chambers (atria) and bottom pumping chambers (ventricles). The valves between the atria and ventricles can be two separate valves or combined into one large valve. AVSD is also known as an atrioventricular canal defect (AVC or AVCD).

In an unbalanced, right-dominant atrioventricular septal defect, the right ventricle is larger than the left ventricle. The difference in size between the ventricles can range from small to large. When the left ventricle is too small, it cannot pump blood out to the body and brain. This heart condition is known as a single ventricle defect. Some combinations of heart defects may include pulmonary stenosis. Pulmonary stenosis is when the pulmonary valve is more narrow than normal and does not open properly. When there is pulmonary stenosis in combination with AVSD, this can be protective, balancing the amount of blood sent to the lungs and the body. However, if the pulmonary stenosis is severe, the blood cannot be pumped into the lungs well and the baby may have low oxygen levels.