Heart Defects

We have included the most common types of heart defects. If we are missing one that you want to know more about, please email us and we’ll make sure it gets added to our list.

Aortic stenosis is a narrowing of the aortic valve or a narrowing of the aorta directly above (supravalvar) or below (subaortic) the aortic valve. With aortic stenosis, it makes it very hard for the heart to pump blood to the body.
The septum is the wall that separates the right and left sides of the heart. A hole in the wall between the two upper chambers is called an atrial septal defect, or ASD. When a defect or “hole” is present between the atria (or upper chambers), some oxygen-rich blood leaks back to the right side of the heart. It then goes back to the lungs even though it is already rich in oxygen. Because of this, there is a significant increase in the blood that goes to the lungs.
This complex defect is best described as a large hole in the middle of the heart. It results from a lack of separation of the atria and the ventricles into separate chambers, and a lack of separation of the mitral and tricuspid valves into two separate valves. This results in a large amount of extra blood going to the lungs (through the septal defects) and can lead to enlargement of the heart.
In this defect, the heart’s electrical signal doesn’t pass from the heart’s own natural pacemaker in the atrium to the lower chambers. When this occurs, an independent pacemaker in the lower chambers takes over. The ventricles can contract and pump blood, but at a slower rate than the atrial pacemaker. Congenital heart block is strongly associated with autoantibodies reactive with certain proteins.
Coarctation of the aorta is a constricted segment of the aorta that obstructs blood flow to the body. The left ventricle has to pump harder because the pressure is high. Because of this, the heart may enlarge.
Dextrocardia literally means “heart on the right”. If the developing heart tube bends to the left instead of the right, then the heart is displaced to the right and develops in a mirror image of its normal state. Having dextrocardia does not mean the heart is defective, it just means that it is on the right instead of the left side of the body and can function normally.
The ascending aorta splits into 2 “arches” which pass to the right and left of the trachea and esophagus. The two arches rejoin behind the esophagus to form the descending aorta. There are two types: Type 1 has both arches open and functioning and this type is the most common. Type 2 has both arches intact but one is very narrow, usually the left.
Normally, a ventricle has just ONE outlet. When in addition to DORV, there is narrowing of the pulmonary valve (Pulmonary Stenosis), the condition is similar to Tetralogy of Fallot (ToF). If the VSD is below the pulmonary valve, the features are just like those of Transposition of Great Arteries (TGA).
This defect is a downward displacement of the tricuspid valve (located between the heart’s upper and lower chambers on the right side) into the heart’s right bottom chamber (or right ventricle). It’s usually associated with an atrial septal defect. While there is free flow of blood forward across the tricuspid valve to the right ventricle, the deformed tricuspid valve allows a large amount of blood to flow backwards from the right ventricle to right atrium when the right ventricle contracts. Irregular and fast heartbeats (arrhythmia) frequently accompany this condition.
Endocardial Fibroelastosis is a rare heart disorder that affects infants and children. It is characterized by an abnormal thickening of heart tissue, especially around the valves, causing abnormal enlargement of the heart (cardiac hypertrophy), especially affecting the left ventricle. Endocardial Fibroelastosis may occur for no apparent reason (sporadic) or may be inherited as an X-linked or autosomal recessive genetic trait.
Eisenmenger’s complex is a ventricular septal defect combined with pulmonary high blood pressure, the passage of blood from the right side of the heart to the left (right to left shunt) and an enlarged right ventricle. It may also include a malpositioned aorta that receives blood from both the right and left ventricles (an overriding aorta).
Disorder characterized by distinctive malformations of the bones of the thumbs and forearms (upper limbs) and/or abnormalities of the heart.
Hypoplastic left heart syndrome, or HLHS for short, means that the left side of the heart did not develop normally. Therefore, the mitral and aortic valves are usually tiny or absent, as are the left ventricle and the first part of the aorta. Perhaps the most critical defect in HLHS is the small, underdeveloped left ventricle. When the chamber is small and poorly developed, it will not function effectively and cannot provide enough blood flow to meet the body’s needs.
This defect consists of a complete obstruction of the right ventricle outflow tract due to a hypoplastic (narrowed) pulmonary artery. When the ventricular septum is intact the PDA and / or bronchial collateral arteries provide the only source of pulmonary blood flow. There are two types of this defect: A small right ventricle with a thick wall and a small but working tricuspid valve. This is the most common. The other type is to have a normal right ventricle with a complete but malfunctioning tricuspid valve.
In this defect, part of the aorta is absent and this leads to severe obstruction to blood flow to the lower part of the body.
The left ventricle is made up of embryonic tissue that stopped developing completely in gestation and never finished “forming.”

This defect consists of having both atrio-ventricular and ventriculo-arterial connections. Note that neither hypertrophic cardiomyopathy nor interrupted aortic arch are considered here. Left ventricular outflow tract obstruction (LVOTO) can occur at several levels:

  • Supravalvar LVOTO seldom occurs in isolation: it is usually part of Williams syndrome.
  • Valvar LVOTO in the adult patient with congenital heart disease is usually due to bicuspid aortic valve.
  • Subvalvar LVOTO is usually a ridge partially or completely encircling the left ventricular outflow tract or a long narrowing beneath the base of the aortic valve. Occasionally, there is a tunnel-like narrowing of the whole left ventricular outflow tract with a small aortic root.

The occurrence of subvalvar LVOTO, coarctation and mitral stenosis (parachute mitral valve and supramitral ring) is known as Shone’s syndrome.

Long QT syndrome (LQTS) is an abnormality of the heart’s electrical system. The mechanical function of the heart is entirely normal. The electrical problem is due to defects in heart muscle cell structures called ion channels. These electrical defects predispose affected persons to a very fast heart rhythm (arrhythmia) called torsade de pointes which leads to sudden loss of consciousness (syncope) and may cause sudden cardiac death.

Children with Marfan syndrome are at risk for serious problems involving the cardiovascular system, including the following:

  • mitral valve prolapse – an abnormality of the valve between the left atrium and left ventricle of the heart that causes backward flow of blood from the left ventricle into the left atrium.
  • arrhythmia – a fast, slow, or irregular heartbeat.
  • aortic regurgitation – backwards leakage of blood from the aorta, through a weakened aortic valve, and into the left ventricle, resulting in stress in the left heart and inadequate blood flow to the body.
  • aortic dissection – weakening of the layers inside the aorta, which can result in tears in the aortic wall and leakage of blood into the chest or abdomen; a medical emergency.
Direct connections (natural shunts) from the aortic system (red blood) to the lungs.
Located in the heart between the left atrium (upper chamber) and left ventricle (lower chamber), the mitral valve consists of two flaps or leaflets, which normally open and shut in coordinated fashion to allow blood to flow only in one direction — from the atrium to the ventricle. In patients with MVP, one or both of the flaps are enlarged, and the leaflets’ supporting muscles are too long. Instead of closing evenly, one or both of the flaps collapse or bulge into the atrium, sometimes allowing blood to flow backwards into the atrium. The condition produces a distinctive “clicking” sound that can be heard when listening to the heart with a stethoscope. Mitral regurgitation can result in the thickening or enlargement of the heart wall, caused by the extra pumping the heart must do to compensate for the backflow of blood.
A PDA, or patent ductus arteriosus, is a connection (called the ductus arteriosus) between the aorta and the pulmonary artery that doesn’t close off after the baby is born. If the ductus remains open, it may cause an excessive amount of blood to go to the lungs.
No pulmonary valve exists, so blood can’t flow from the right ventricle into the pulmonary artery and on to the lungs. The right ventricle may stay small and not well developed.
Pulmonary stenosis is a narrowing of the pulmonary valve. Because of the narrowing, the right ventricle has to pump harder to get past the stenotic valve. This can sometimes lead to enlargement of the right ventricle. With pulmonary stenosis, problems with the pulmonary valve make it harder for the leaflets to open and permit blood to flow forward from the right ventricle to the lungs.
The most common form of RVOTO, is caused by stenosis of the pulmonic valve. It is almost always congenital in origin.
While the normal heart has two ventricles, in some birth defects, one of these ventricles may be absent or poorly developed. The main problem with a single ventricle is the mixing of blood (both oxygenated and unoxygenated) inside the ventricular chamber. The mixed blood flows into the aorta and pulmonary artery.

Tetralogy of Fallot is one of the most common forms of complex congenital heart defects that causes cyanosis, or a blue baby. Tetralogy of Fallot is comprised of four separate components.

  • Ventricular septal defect (VSD).
  • Pulmonary stenosis (PS).
  • Right ventricular hypertrophy (an increase in the size of the right ventricle).
  • Overriding aorta (the aorta lies directly over the ventricular septal defect).

The ventricular septal defect is usually large, because of the resistance of blood flow through the pulmonary valve. Once the blood flows into the left ventricle, it is ejected into the aorta and delivers de-oxygenated blood into the body. Because there is de-oxygenated blood being delivered to the body, these babies may appear cyanotic, or “blue”.

In this congenital heart defect, the aorta (the main artery that carries blood to the body) originates from the right ventricle and the pulmonary artery (the artery that carries low-oxygen blood to the lungs) from the left ventricle. Because of this reversal, the aorta carries low-oxygen blood from the right ventricle to the body. The pulmonary artery carries oxygen-rich blood back to the lungs.
Pulmonary veins normally bring oxygenated blood back from the lungs to the left atrium. In TAPVR all the pulmonary veins drain into the right atrium.
In this defect, only one artery originates from the heart and forms both the aorta and the pulmonary artery. The truncus arises above a VSD. The truncus receives low-oxygen blood from the right ventricle and oxygen-rich blood from the left ventricle. This mix of high and low-oxygen blood is sent out to the body and to the lungs.
In tricuspid atresia, there’s no tricuspid valve so no blood can flow from the right atrium to the right ventricle. As a result, the right ventricle is small and not fully developed. There’s often an opening in the wall between the atria (atrial septal defect) and usually an opening in the wall between the two ventricles (ventricular septal defect) associated with tricuspid atresia, resulting in a mixing of oxygenated and unoxygenated blood.
A ventricular septal defect, or VSD, is the most common kind of congenital heart defect. A defect or “hole” is present between the ventricles (or lower chambers), where blood from the left side of the heart is forced through the defect to the right side every time the heart beats. It then goes back to the lungs even though it is already rich in oxygen. Because of this, blood that is not yet oxygen-rich can’t get to the lungs. The most common signs and symptoms are trouble eating and gaining weight, breathlessness and easy fatigability. A baby with a large VSD tires quickly after not eating very much, falls asleep, wakes us in a short while quite hungry, tries to eat again, tires easily, and the cycle is repeated. Because the heart has to pump extra blood, it may enlarge. Many, if not most, of all VSDs will close on their own. Those that close on their own are usually small and do so in the first year of life. Large VSDs, especially those that don’t close in the first year of life, will usually need to be closed surgically. VSD closure is one of the most commonly performed congenital heart operations. The child would be expected to have virtually normal growth, development, and life expectancy following repair.
Bereavement Photo


Mended Little Angels is a program of Mended Little Hearts (a program of The Mended Hearts, Inc), which is a special program offered to parents and family members who have lost a child or loved one to a congenital heart defect (CHD).

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Visit Request

Our Visiting Program serves heart families while they are inpatient. It can be a very emotional and difficult time while your child is in the hospital. MLH’s accredited visitors are there to listen, empathize and offer support to families. Our visitors are Heart parents, who can relate and understand the concern of other parents during their time in the hospital. Being inpatient can be an overwhelming experience and we hope that a friendly face and a listening ear over a cup coffee can offer some comfort during this time.