In babies who are too small, a temporary surgery may be done with plans for a second surgery when the baby is bigger. With proper care, most people who are affected live to be adults. Long-term problems may include an irregular heart rate and pulmonary regurgitation.The prevalence of TOF is estimated to be anywhere from 0.02 to 0.04%. Though males and females were initially thought to be affected equally, more recent studies have found males to be affected more than females. It is the most common complex congenital heart defect, accounting for about 10 percent of cases. It was initially described in 1671 by Niels Steensen. A further description was published in 1888 by the French physician Étienne-Louis Arthur Fallot, after whom it is named. The first total surgical repair was carried out in 1954. Signs and symptoms
Tetralogy of Fallot results in low oxygenation of blood. This is due to a mixing of oxygenated and deoxygenated blood in the left ventricle via the ventricular septal defect (VSD) and preferential flow of the mixed blood from both ventricles through the aorta because of the obstruction to flow through the pulmonary valve. The latter is known as a right-to-left shunt.Infants with TOF – a cyanotic heart disease – have low blood oxygen saturation. Blood oxygenation varies greatly from one patient to another depending on the severity of the anatomic defects. Typical ranges vary from 60% to around 90%. Depending on the degree of obstruction, symptoms vary from no cyanosis or mild cyanosis to profound cyanosis at birth.
: 153 Timing of surgery in asymptomatic patients is usually between the ages of two months to one year. : 201–2  However, in symptomatic patients showing worsening blood oxygen levels, severe tet-spells (cyanotic spells), or dependence on prostaglandins from early neonatal period (to keep the ductus arteriosus open) need to be planned fairly urgently: 201–2 Potential surgical repair complications include residual ventricular septal defect, residual outflow tract obstruction, complete atrioventricular block, arrhythmias, aneurysm of right ventricular outflow patch, and pulmonary valve insufficiency. : 59  Long-term complications most commonly include pulmonary valve regurgitation, and arrhythmias.Total repair of tetralogy of Fallot initially carried a high mortality risk, but this risk has gone down steadily over the years. Surgery is now often carried out in infants one year of age or younger with less than 5% perioperative mortality. : 205  Post surgery, most patients enjoy an active life free of symptoms. : 205  Currently, long-term survival is close to 90%. : 167  Today the adult TOF population continues to grow and is one of the most common congenital heart defects seen in adult outpatient clinics. : 100–101

Palliative surgery
Initially surgery involved forming a side to end anastomosis between the subclavian artery and the pulmonary artery -i.e. a systemic to pulmonary arterial shunt. : 57  This redirected a large portion of the partially oxygenated blood leaving the heart for the body into the lungs, increasing flow through the pulmonary circuit, and relieving symptoms.