Truncus arteriosus is a rare type of congenital heart disease characterized by a single blood vessel arising from the right and left ventricles, instead of the normal two (pulmonary artery and aorta).

There are three subtypes of truncus arteriosus, depending on the specific anatomy of the single vessel.

In normal circulation, the pulmonary artery arises from the right ventricle and the aorta arises from the left ventricle, which are separate from each other. Coronary arteries, which supply the heart muscle, arise from the aorta, just above the valve at the entrance of the aorta.

In truncus arteriosus, a single arterial trunk arises from the ventricles. A large ventricular septal defect (hole between the two ventricles) is usually present along with a truncus defect, essentially making the right and left ventricles into a single chamber, with the blue (unoxygenated) and red (oxygenated) blood mixing completely.

Some of this mixed blood goes to the lungs, some to the coronary arteries, and the rest to the body. Whether more blood goes to the body versus the lungs is determined by the pressures in the two places. Generally the pressure is much lower in the lungs than in the body, so too much blood gets pumped to the lungs, flooding them with fluid.

If left untreated, this increased blood flow causes two problems. First, the lungs are filled with fluid, making it difficult to breathe. The second problem is more long term. When the lungs get too much blood, the vessels there become narrowed and are permanently damaged, to the point where they are so narrow the heart can no longer force blood into them. This is called pulmonary hypertension and it can be life-threatening.

• lethargy
• poor feeding
• shortness of breath (dyspnea)
• rapid breathing (tachypnea)
• fatigue
• sometimes cyanosis (blue discoloration of skin)
• delayed growth or growth failure
• broadening of the finger tips (clubbing)

The cardiologist or pediatrician usually hears a murmur when listening to the heart with a stethoscope.

• An ECG shows signs of enlargement of the heart (ventricular hypertrophy).
• An X-ray of the chest shows heart enlargement and fluid-filled lungs.
• An echocardiogram shows a ventricular septal defect (VSD) and a single truncal artery -- definitive diagnosis.
• Rarely, a heart catheterization is necessary to help with the diagnosis or planning of a treatment strategy.

Complete repair usually affords good results, although re-operation is sometimes necessary as the patient grows. Untreated cases have a poor outcome, usually leading to death between the first and second years of life. Sometimes the diagnosis is missed until early adulthood; these patients generally need a heart and a lung transplant.

• heart failure
• pulmonary hypertension (high blood pressure in the lungs)

Call your health care provider if your infant or child appears lethargic, does not eat well, appears excessively tired or mildly short of breath, or does not seem to be growing or developing normally.

If the child's skin, lips, or nail beds appear blue or if the child seems significantly short of breath, take the child to the emergency room or have the child examined promptly.