|Image courtesy of the American Heart Association|
What truncus arteriosus?
Truncus arteriosus is a rare congenital heart defect characterized by a large ventricular septal defect over which a large, single great vessel (truncus) arises. It occurs when the two large arteries carrying blood away from the heart don’t form properly and one large artery is present instead. This single great vessel carries blood both to the body and to the lungs. This artery (the truncus) sits over a large opening or hole in the wall between the two pumping chambers (ventricular septal defect).
In Layman's terms, this basically means that there is hole in the septum separating the lower ventricles of the heart (this is what the ventricular septal defect entails). Additionally, when the pulmonary artery and aorta form correctly, they create separate connections to the heart. Lukas' heart did not form this way and instead his aorta and pulmonary artery essentially are one large artery.
What causes it?
In most cases, the cause is unknown. Every once in a great while truncus arteriosus is thought to be caused by a genetic condition called DiGeorge Syndrome. We only really know it occurs during the early stages of fetal development (within the first 8 weeks).
How does this affect the heart?It affects the heart and body in a number of ways. Essentially, the blood leaving the heart can go to either the heart or lungs. Early in life this results in quite a bit of extra blood going to the lungs, which makes the heart work very hard. Over time the extra blood flow damages the blood vessels in the lungs, resulting in pulmonary hypertension. When this happens (often before one year of life) the patient becomes blue, and it’s often too late to do successful surgery. The valve leading to the main blood vessel can have blockage or leakage, which can also make the heart work harder.
What problems can truncus arteriosus cause in the future?
There are a number of factors truncus arteriosus can affect. Among these are:
In the long-term period after the operation to correct truncus, the heart muscle’s ability to contract may decrease. After repair, a patient may need medication including diuretics, agents to help the heart pump better and drugs to control blood pressure.
Heart Rhythm Disturbances
Patients with repaired truncus arteriosus have a higher risk for heart rhythm disturbances called arrhythmias. These can originate from the atria (the heart’s two upper chambers) or the ventricles (the two lower chambers). Sometimes they may cause dizziness or fainting. Medication may be required to control them. In rare cases, a procedure in the cardiac catheterization laboratory or the operating room may be required to eliminate these arrhythmias and control symptoms.
High Blood Pressure in the Lungs (Pulmonary Hypertension)
Sometimes, even when the defect is repaired early, pulmonary hypertension becomes progressively worse. Patients may experience shortness of breath, decreased exercise endurance and sometimes headaches and dizziness.
What about ongoing care?
Patients with truncus arteriosus need regular follow-up with a cardiologist with special training in congenital heart defects. The cardiologist will monitor a patient with a variety of tests including electrocardiograms, Holter monitors, exercise stress tests and echocardiograms to determine when another procedure may be needed.
What about activity restrictions or limitations?
Of course, our little Lukas will never be a hockey or football player simply because it is just too risky after such an extensive operation. According to the American Heart Association, further limitations can come about if you have decreased heart function or rhythm disturbances. Likewise, if valve obstruction and leakage is mild and tests show good heart function and no abnormal heart rhythms, you can usually participate in some sports. Your cardiologist may recommend avoiding certain intense competitive sports. As always, you should consult your own cardiologist to determine which activities are appropriate.
How about surgery? Is there only one operation?
I only wish little Lukas would have to undergo one operation. Lukas will have an artificial conduit and valve placed during his initial operation. Essentially, this will create a new pathway separate of his aorta. The conduit connecting the right ventricle to the pulmonary artery conduit may become obstructed (stenotic) over time and may need to be replaced at some point in the future. Timing of this replacement varies greatly from patient to patient. The peripheral pulmonary arteries also may become narrowed and require treatment as well. Likewise, the new valve they place will need to replaced as he grows and his heart has different needs. The first of these changes will occur around 5-6 years of age when an adult size valve will be placed. This valve sometimes becomes leaky over time and may need to be replaced, usually after 10-15 years.