What is Truncus Arteriosus?
Truncus arteriosus is a rare and serious congenital heart defect that occurs at birth, characterized by the presence of a single large blood vessel emerging from the heart instead of the normal two vessels: the aorta and the pulmonary artery. This condition leads to the mixing of oxygen-rich and oxygen-poor blood, significantly reducing the oxygen delivered to the body and often causing increased blood flow to the lungs. As a result, the heart must exert greater effort to manage these altered blood dynamics.
Types and Associated Conditions
Truncus arteriosus is sometimes referred to as a “common arterial trunk.” Most infants with this defect also have a ventricular septal defect (VSD), which is a hole between the two lower heart chambers (ventricles). Additionally, these patients frequently experience issues with the truncal valve—the valve that controls blood flow from the heart into the single vessel—leading to a condition known as truncal valve regurgitation, where blood may flow backward into the heart.
Symptoms of Truncus Arteriosus
Symptoms of truncus arteriosus typically manifest in the first few days of life and may include:
- Cyanosis (blue or gray skin) due to low oxygen levels
- Excessive sleepiness and fatigue
- Poor feeding and inadequate growth
- A rapid heartbeat or pounding heartbeat
- Fast or labored breathing
- Shortness of breath
Causes and Risk Factors
The exact cause of truncus arteriosus is not well understood, although it occurs during the early stages of heart development in the womb. Several factors may increase the risk of this defect, including:
- Viral infections during pregnancy: Infections such as German measles (rubella) can adversely affect heart development.
- Poorly controlled diabetes: Women with diabetes need to manage their blood sugar levels before and during pregnancy to reduce risks.
- Certain medications: Some medications taken during pregnancy may lead to congenital heart defects.
- Chromosomal disorders: Genetic conditions such as DiGeorge syndrome can increase the risk.
- Maternal smoking and alcohol use: Both smoking and drinking during pregnancy are associated with a higher incidence of congenital heart defects.
- Obesity: Maternal obesity has also been linked to an increased risk of heart defects.
Complications
Truncus arteriosus can lead to severe complications affecting the heart, lungs, and overall health of the child:
- Breathing difficulties: Excessive blood flow into the lungs can lead to fluid buildup, making breathing laborious.
- Pulmonary hypertension: This condition occurs when the blood vessels in the lungs narrow, increasing the pressure and making it harder for the heart to pump blood to the lungs.
- Enlarged heart: The increased workload on the heart can cause it to enlarge, leading to potential heart failure over time.
- Heart failure: This serious condition arises when the heart cannot supply adequate blood to the body, resulting in low oxygen levels and fatigue.
Even after successful surgical intervention, long-term complications may develop, including worsening pulmonary hypertension, valve regurgitation, and arrhythmias. Symptoms of these complications can include dizziness, fatigue, and shortness of breath, particularly during physical exertion.
Diagnosis
Truncus arteriosus is usually diagnosed shortly after birth. Signs such as a bluish tint to the skin and respiratory distress prompt further investigation. Diagnostic tools include:
- Pulse oximetry: Measures blood oxygen levels, identifying potential heart or lung issues.
- Chest X-ray: Evaluates heart and lung conditions, providing insight into heart size and fluid accumulation.
- Echocardiogram: This ultrasound-based test is critical for diagnosing truncus arteriosus, revealing blood flow patterns and structural anomalies.
Treatment
Surgery is the primary treatment for truncus arteriosus, typically performed within the first few weeks of life. The surgery aims to create separate pathways for oxygen-rich and oxygen-poor blood. Surgical procedures may include:
- Reconstructing the arterial pathways: Surgeons create a new aorta and separate the pulmonary artery from the single large vessel.
- Closing the ventricular septal defect: A patch is often used to repair the hole between the ventricles.
- Creating a new pulmonary artery: A tube may be used to connect the right ventricle to the pulmonary artery.
In some cases, follow-up surgeries will be necessary as the child grows, particularly to replace non-growing components like tubes or valves. Less invasive options, such as catheter-based procedures, may be available for addressing blockages or valve issues in older children or adults.
Long-Term Care
Children who undergo surgical correction for truncus arteriosus require lifelong follow-up with a congenital cardiologist. Regular checkups are crucial for monitoring heart function, addressing any arising complications, and managing overall health.