Tetralogy of Fallot is a cyanotic congenital heart disease. TOF is the most common cyanotic congenital heart disease, 10-15 % of the total.
Tetralogy implies four anatomical abnormalities of heart:
Ventricular Septal Defect: defect between the two bottom chambers(ventricles) of the heart
Pulmonary Stenosis: Narrowing of the outflow tract from the right ventricle , the lower compartment of heart
Overriding Aorta: usually the Aorta arises from the left ventricle but here, the aortic inlet is open to both the ventricles
Right Ventricular Hypertrophy: The right ventricle becomes more muscular, due to handling of enormous amount of blood from the left side of heart.
TOF may manifest with spells of cyanosis – bluish discoloration of skin, difficulty in feeding, failure to gain weight, retarded growth and physical development, shortness of breath on exertion, clubbing of the fingers and toes – thickening at the nail skin junction, and polycythemia – manifested as congestion of the eyes. Cyanotic spells are characterized by a sudden, marked increase in cyanosis followed by syncope – loss of consciousness, and may result in brain injury and death, due to lack of oxygen for the brain. Older children will often squat during a spell, which cuts off circulation to the legs and therefore improves blood flow to the brain and vital organs.
Diagnosis of TOF if made using clinical findings combined with minimal investigations of Chest x-ray, echocardiography and electrocardiography. Chest X-ray gives a boot shaped heart, also known as “coeur-en-sabot”.
Management of TOF involves the following:
- Treatment of emergency cyanotic spells
- Palliative surgery
- Definitive surgery
Emergency cyanotic spells can be treated by using oxygen and drugs such as Beta blocker – Propranolol, morphine, epinephrine etc. Making the patient squat in knee chest position is an important first aid that can be advocated to the care taker.
nitially TOF was considered an untreatable condition until palliative surgeries evolved. Palliative surgeries involve Blalock Taussig shunt (BT Shunt), where a vascular anastomosis improves the blood supply to the lungs. Others in palliative approach are Pott’s shunt and Waterston’s shunt. These are no longer the first line management in TOF.
The definitive surgeries involve the surgical correction of the anatomical defects described earlier. Surgery is now often carried out in infants 1 year of age or younger, and the mortality chance due to surgery has significantly, decreased over years. The surgery generally involves making incisions into the heart muscle, relieving the obstruction to the out flow of right ventricle, by careful resection of muscle, and repairing the VSD usingan artificial graft of taken elsewhere from body. Additional reparative or reconstructive work may be done on patients as required by their particular anatomy. Antibiotic prophylaxis is indicated during dental treatment or other minor surgical procedures in order to prevent infective endocarditis.
Untreated, tetralogy of Fallot rapidly results in progression to heart failure. Actual survival for untreated tetralogy of Fallot is approximately 75% after the first year of life, 60% by four years, 30% by ten years, and 5% by forty years. Long-term follow up studies show that patients with total repair of TOF are at risk for sudden cardiac death and for heart failure. Therefore, lifetime follow-up care by an adult cardiologist is recommended to monitor these risks and to recommend treatment, such as interventional procedures or re-operation, if it becomes necessary.