Hemitruncus is a rare congenital heart defect (CHD). With this condition, the largest artery leading to the lungs (the pulmonary artery) and usually the left branch are in the correct position, but the right branch is coming off the aorta, which is the main artery supplying blood to the body.
Another heart defect, a hole in the wall separating the bottom chambers of the heart, is usually also present.
The hemitruncus causes too much blood to be pumped to the lungs, leading to fluid overload and high blood pressure in the lungs. In addition, the hole in the heart allows oxygen-rich blood from the lungs and oxygen-depleted blood from the body to mix, leading to less oxygen reaching the body's cells.
Healthy heart structure and function
In a healthy heart, two main arteries come off the top of the heart.
The right side of the heart receives blood that has just circulated through the body and pumps it to the lungs via the pulmonary artery. The pulmonary artery comes off the top of the heart and branches into two large blood vessels, one going to the left lung and one to the right.
After the blood absorbs oxygen from the lungs, it returns to the left side of the heart. The left side of the heart pumps this oxygen-rich blood to the body via a large artery (the aorta), which also comes off the top of the heart.
Then the blood returns to the right side of the heart to begin the entire circuit again.
The oxygen-rich blood and the oxygen-depleted blood never mix.
Hemitruncus is also known as hemitruncus arteriosus, pulmonary artery coming from the aorta, or truncus arteriosus.
The defect is present at birth
Hemitruncus is a heart defect that is present at birth. While the infant is developing in the womb, the wall separating the two large arteries coming off the top of the heart does not close and seal properly.
The main artery to the lungs and usually the left branch are in their proper places, but the right branch is attached to the aorta, the large artery supplying the body with oxygen-rich blood.
The properly connected artery branch receives all the blood pumped to the lungs from the right side of the heart, causing increased pressure on the artery. The improperly positioned artery receives blood from the aorta. The extra force from the pumping in the left side of the heart causes extra pressure in the lungs. Too much blood flows to the lungs, and the heart must work harder to get oxygenated blood out to the body.
Also, instead of two separate valves regulating the flow of blood to the aorta and the pulmonary artery, only one valve is present; this valve is often not formed correctly. It may be thick and narrow, preventing blood from leaving the heart efficiently, or it may allow blood to leak back into the heart.
In addition, the infant also usually has a VSD (a ventricular septal defect), a hole in the wall between the two sides of the heart. This hole allows oxygen-rich blood from the lungs to mix with oxygen-depleted blood from the body. As a result, blood with little oxygen goes out to the body through the aorta.
Hemitruncus is a congenital heart defect, meaning the heart does not form properly as the infant grows in the womb. In most cases, the exact cause is unknown.
Hemitruncus is a very rare congenital heart defect comprising only 0.1% of all congenital heart diseases.
Although finding an exact cause is not always possible, a few factors present during your pregnancy can increase the risk of your child developing hemitruncus.
- Certain viral illnesses, such as rubella (German measles)
- Poorly controlled diabetes
- Taking certain medications
- Alcohol use
An infant with DiGeorge's or velocardiofacial syndrome also has an increased risk of developing hemitruncus.
An infant with hemitruncus will generally show distress in the first few days of life. Symptoms may include:
- Cyanosis (bluish hue to the lips, nails, or skin)
- Poor feeding and weight gain
- Difficulty breathing
- Extreme sleepiness
- Rapid heart rate
- Weak pulse
- Ashen skin
Doctors can sometimes detect heart defects before an infant is born with prenatal screening tests. If the screening test reveals the potential for a CHD, your doctor will probably order a fetal echocardiogram. This test allows the doctor to see the heart's structure and functioning.
A newborn pulse oximetry test can sometimes reveal a problem if the defect remains undetected before birth.
A pediatrician will listen to your baby's heart and lungs and may order a chest x-ray or echocardiogram.
At first, a pediatric cardiologist may give you medicine for your child. This medicine may improve heart function, eliminate extra fluid in the lungs, or lower the blood pressure in your baby's lungs.
They may also advise you to feed your baby a high-calorie formula to increase their weight if they are not growing and gaining weight. If your baby becomes too tired too quickly while eating, your doctor may recommend a feeding tube until surgery.
Hemitruncus is considered a critical congenital heart defect. Your baby will probably need surgery within the first few months of life. During the surgery, the surgeon will:
- Reconstruct the one large artery into a single aorta
- Construct a new, artificial pulmonary artery with an artificial valve connected to the lung
- Close the hole in the heart if needed
Surgery is typically successful, especially when performed within one month of birth.
Since the artificial artery and valve will not grow with your child, they may need additional procedures or surgeries as they grow.
An untreated hemitruncus could lead to some long-term complications, such as:
- Respiratory problems
- Pulmonary hypertension (high blood pressure in the lungs)
- Enlarged heart
- Heart failure
- Premature death
After surgical repair, complications that may arise later in life include:
- Pulmonary hypertension
- Irregular heart rhythms
- Leaky heart valves
With these complications, you may experience symptoms such as:
- Heart palpitations
- Shortness of breath when exercising
- Swelling in the feet, legs, and abdomen
Hemitruncus can be fatal if left untreated.
After surgery to repair the defect, most children will need procedures or surgeries to increase the size of the artificial tube as the child grows.
Your child will need regular follow-up care from a cardiologist.
In some situations, a person may survive to adulthood without surgery, but they will most likely develop Eisenmenger syndrome, a condition characterized by pulmonary hypertension and heart failure.
Call your child's pediatrician if they are exhibiting symptoms of a heart defect, including:
- Ashen or bluish skin (cyanosis)
- Excessive sleepiness
- Poor feeding
Call 9-1-1 if your infant or child has:
- Difficulty breathing
- Worsening cyanosis (the blue color of the lips, nail beds, or skin)
Talk to your cardiologist if you have had surgery to repair a hemitruncus and are pregnant or plan to become pregnant.