Primarily, the degree of right ventricular outflow tract obstruction varies between patients and generally determines clinical symptoms and disease progression.Presumably, this arises from an unequal growth of the aorticopulmonary septum (aka pulmonary outflow septum). : 199  The aorta is too large, thus "overriding," and this "steals" from the pulmonary artery, which is therefore stenosed. This then prevents ventricular wall closure, therefore VSD, and this increases the pressures on the right side, and so the R ventricle becomes bigger to handle the work. : 199

Additional anomalies
In addition, tetralogy of Fallot may present with other anatomical anomalies, including:: 66–8 
stenosis of the left pulmonary artery, in 40%
a bicuspid pulmonary valve, in 60%
right-sided aortic arch, in 25%
coronary artery anomalies, in 10%
a patent foramen ovale or atrial septal defect, in which case the syndrome is sometimes called a pentalogy of Fallot
an atrioventricular septal defect
partially or totally anomalous pulmonary venous returnTetralogy of Fallot with pulmonary atresia (pseudotruncus arteriosus) is a severe variant in which there is complete obstruction (atresia) of the right ventricular outflow tract, causing an absence of the pulmonary trunk during embryonic development. : 67–8  In these individuals, blood shunts completely from the right ventricle to the left where it is pumped only through the aorta. The lungs are perfused via extensive collaterals from the systemic arteries, and sometimes also via the ductus arteriosus. : 67–8

Diagnosis
There are three different useful diagnostic tests used for the diagnosis of tetralogy of Fallot. These include a chest radiograph, electrocardiogram, and echocardiogram. The echocardiography determines the final diagnosis and typically offers enough information for surgical treatment planning.
There are also simple procedures such as squatting and the knee chest position which increase systemic vascular resistance and decrease right-to-left shunting of deoxygenated blood into the systemic circulation. : 18, 201 If the spells are refractory to the above treatments, people are usually intubated and sedated. The treatment of last resort for tet spells is extracorporeal membrane oxygenation (ECMO) along with consideration of Blalock Taussig shunt (BT shunt). : 18, 201

Total surgical repair
Total surgical repair of TOF is a curative surgery. Different techniques can be used in performing TOF repair. However, a transatrial, transpulmonary artery approach is used for most cases. : 153  The repair consists of two main steps: closure of the VSD with a patch and reconstruction of the right ventricular outflow tract.This open-heart surgery is designed to relieve the right ventricular outflow tract stenosis by careful resection of muscle and to repair the VSD. : 154 The right ventricle outflow tract can be reconstructed using mainly 2 procedures: a transannular patch (TAP) or a pulmonary valve-sparing procedure (PVS). The decision on the type of the procedure depends on individual anatomy (especially the size of the pulmonary valve). PVS showed better overall survival, event-free survival and less pulmonary regurgitation at 10, 20 and 30 years after the operation. PVS  can be performed with or without ventriculotomy. A study found similar overall and event-free survival and pulmonary regurgitation rate between patients who underwent PVS with ventriculotomy and the ones who did not.Additional reparative or reconstructive surgery may be done on patients as required by their particular cardiac anatomy.