Tetralogy of Fallot

Anatomy

The heart, a muscular organ, consists of four chambers: the right atrium and ventricle and the left atrium and ventricle. The atria sit above the ventricles. A partition (septum) separates the right and left sides of the heart, including between the atria and ventricles. Normally, venous blood rich in carbon dioxide flows from the right atrium to the right ventricle and then the heart pumps it into the pulmonary artery. This artery branches into smaller vessels that supply the lungs, where the blood oxygenates. Oxygenated blood then moves from the lungs into the left atrium, then the left ventricle, and the heart pumps it into the aorta, the body’s main artery which distributes oxygen to tissues throughout the body.

Description of the Disease

Tetralogy of Fallot is a congenital heart defect comprising pulmonary trunk stenosis (narrowing), a high ventricular septal defect, aortic dextroposition (the aorta positioned above the ventricular septum), and right ventricular hypertrophy. The anatomical features of this condition allow venous blood from the right ventricle to flow not only to the lungs but also to the left side of the heart, getting pumped into the aorta. Thus, the body receives mixed, oxygen-poor blood, categorizing it as cyanotic heart disease.

Tetralogy of Fallot represents 5-8% of all congenital heart defects and occurs more frequently in boys than in girls.

Causes of the Disease

Genetic factors, specifically certain gene mutations, are most closely linked to the development of Tetralogy of Fallot. Other factors that may trigger the disease include infectious diseases during pregnancy (like rubella), alcohol consumption during pregnancy, and advanced maternal age (>40 years).

Symptoms

Symptoms usually present between the ages of 2-5 and include:

• An inability to tolerate physical exertion, evident as shortness of breath during physical activity;
• Cyanosis, marked by blueness of the lips, fingers, and toes;
• Clubbed fingers and nails shaped like watch glass, stemming from chronic oxygen deficiency.

Episodes of breathlessness can also occur at rest, causing the child to become restless, cry, and possibly experience seizures. Older children often squat during an episode to enhance blood flow to the lungs.

Diagnosis

Doctors assess clinical symptoms and conduct a physical examination. Key laboratory tests include a chest X-ray, which may show a boot-shaped heart shadow in children, and echocardiography, which identifies all four components of this condition.

Treatment

Surgical intervention is the primary treatment, performed early in childhood to improve life expectancy; without surgery, children typically survive only until around 12-14 years of age. Surgical treatment restores normal heart function, leading to a good prognosis, though there may be a persisting reduced tolerance for physical exertion.

Source | Author Doctor Nikas Samuolis, reviewed by Prof. Virginijus Šapoka | Vilnius University | Faculty of Medicine | Head of the Department of Internal Medicine, Family Medicine, and Oncology