Truncus Arteriosus Type 1 is characterized by:

A single large arterial vessel called a Truncus Valve coming out of the heart and overriding a large hole between the two ventricles known as a Ventricular Septal Defect (VSD).

The pulmonary arteries originate from the large vessel.

Note: There are 4 types of Truncus Arteriosus depending on how the pulmonary arteries originate from the single arterial vessel.

The blood enters the heart normally, but freely mixes in the ventricles because of the Ventricular Septal Defect (VSD).

The blood then empties through a common single valve called a Truncus Valve. This freely mixed blood goes to the body, the lungs, and also comes back and supplies the heart itself through the Pulmonary Arteries.

Symptoms:
The baby will be noted to have a characteristic heart murmur at birth. Because there is lots of blood going from a large-pressure artery to the pulmonary arteries, the lungs will be flooded with more blood than they need and your baby's lungs will be very congested.

The baby will be breathing faster, have labored breathing, and sweating excessively. This condition is called Congestive Heart Failure. The baby will be tiring with feedings and will have very little strength to suck.

Treatment:
As a temporary fix your doctor will most likely treat your baby with the following medications:

Lasix
Diuretics such as Lasix, which is a medicine given by mouth, takes away the excessive fluid in the lungs so your baby can breathe easier.

Digoxin
Because the heart has a large amount of fluid in it at one time it is hard for the heart muscles to contract. Digoxin will help the heart muscles contract.