The Scientific Principles and Causes of Congenital Heart Disease
By Thierry Chiu and Rick Liu, March 2026
Congenital heart disease (CHD) refers to structural heart problems present at birth and is the most common type of birth defect worldwide, affecting approximately 1 in every 100 newborns (Heartfoundation.org.au, 2019). While some defects are mild and do not significantly impact an individual’s lifestyle, more than half of all children with CHDs require medical treatment.
Understanding the causes of CHD is essential for accurate diagnosis, effective treatment, and reducing the risk of occurrence.
What causes congenital heart defects? (www.nhlbi.nih.gov, 2022) (Services, 2024)
Congenital heart defects result from mutations in a child’s DNA, which may or may not have been inherited from the parents. Although it is rare for CHD to be directly inherited, certain factors can increase the risk, including:
Family history and genetics – While CHD is usually not passed down directly, families with a history of the condition have a higher risk of recurrence.
Smoking during pregnancy
Use of certain medications during pregnancy
Pre-existing maternal health conditions, such as diabetes or viral infections
Other birth defects, such as Down syndrome, which can include heart malformations
Symptoms and impacts of congenital heart disease (Heartfoundation.org.au, 2019) (Services, 2024)
Congenital heart defects can significantly disrupt the lives of both patients and their caregivers. More severe symptoms are often present from birth and may include:
Irregular, shallow, or rapid breathing
A blue tinge to the skin, lips, or fingernails (cyanosis)
Swelling in the limbs and torso
Shortness of breath while feeding
Less severe symptoms, which may be diagnosed later in life, include:
Extreme fatigue and shortness of breath during exercise
Fainting during physical activity
Swelling in the hands, ankles, or feet
Although most congenital heart defects cannot be completely cured, they can be treated, managed, or surgically corrected to improve the individual’s quality of life.
Understanding the anatomy of the heart and how it functions (Services, 2024)
The heart consists of two halves and four chambers: the right atrium, right ventricle, left atrium, and left ventricle. Deoxygenated blood returns to the right atrium, is squeezed into the right ventricle, and then pumped through the pulmonary artery to the lungs to become oxygenated. From the lungs, oxygenated blood flows into the left atrium, then into the left ventricle, and is finally pumped into the aorta. From there, it circulates throughout the body, delivering oxygen to cells before returning to the heart.
Five common heart defects (Services, 2024)
Ventricular septal defect: A hole exists in the wall between the two lower ventricles, allowing oxygenated and deoxygenated blood to mix. This can lead to increased heart rate, failure to grow at the expected rate, congestive heart failure, and a higher risk of pneumonia.
Transposition of the great vessels: The pulmonary artery is attached to the left ventricle, and the aorta to the right ventricle. As a result, oxygenated blood is pumped back to the lungs instead of throughout the body, causing cyanosis (bluish skin due to lack of oxygen).
Coarctation of the aorta: The aorta is narrowed or pinched in the upper chest, leading to lower-than-normal blood pressure in the lower body and causing breathlessness and difficulty breathing.
Tetralogy of Fallot: This condition involves four main defects: a ventricular septal defect, blockage of blood flow out of the right ventricle, thickening of the right ventricular wall, and displacement of the aorta toward the right ventricle. These abnormalities allow oxygenated and deoxygenated blood to mix, resulting in cyanosis.
Hypoplastic left heart syndrome: The entire left side of the heart (including valves and blood vessels) is underdeveloped, leading to a greyish complexion and severe breathing difficulties.
This Article is written by our volunteer student research team at Feel Every Beat, and is intended for educational purposes only. It is not a substitute for professional medical advice.
References
https://www.nhlbi.nih.gov/health/congenital-heart-defects/causes
https://www.heartfoundation.org.au/your-heart/congenital-heart-conditions
https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/congenital-heart-disease
