Tetralogy patients after surgical repair usually have a murmur of pulmonary insufficiency (diastolic murmur) and residual pulmonary stenosis (systolic). There may also be a murmur of a residual VSD. Besides the evaluation of the murmur, if present, diagnosis is based on an electrocardiogram (ECG), chest x-ray, MRI (Magnetic Resonance Imaging), echocardiogram, and/or angiography.

The chest x-ray will usually reveal a normal-sized heart with a distinctive shape, which is caused by right ventricular hypertrophy. The ECG also shows signs of right ventricular hypertrophy, as well as distinctive conduction abnormalities. The overall anatomy of the heart and the defect itself may be seen on the echocardiogram. Angiograms of the two ventricles and aorta will show important details of blood flow.

In addition to these non-invasive tests, a cardiac catheterization procedure is often performed to accurately determine the anatomy of the pulmonary artery and coronary arteries so that a repair strategy can be devised. If a shunt was inserted during childhood, the pulmonary artery anatomy may have become distorted, which could affect the operation procedure.

Before the development of open-heart surgical techniques, this defect was treated by the insertion of shunts (connecting tubes between heart chambers and/or blood vessels) that increased pulmonary blood flow. Some of these procedures (e.g. the Potts and Waterston shunts) were abandoned because they resulted in excessive pulmonary blood flow that caused various complications. Adults who received these treatments in childhood may have distorted pulmonary arteries or have developed pulmonary vascular obstructive disease (PVOD).

Other patients received the original Blalock-Taussig shunt. As it was composed of the patient's own tissue, this shunt would often enlarge over time and also result in PVOD. Nevertheless, the benefits of the surgical repair of Tetralogy of Fallot make it far superior to all of the shunt procedures, which tend to cause pulmonary hypertension, overload of the left ventricle, and other side effects. Therefore, a repair operation is often performed later in life, resulting in increased tolerance for exercise, the elimination of cyanosis, and other benefits.

Though the prospects for long life are excellent after primary repair, there is a small risk of sudden death. This occurs in between 2 and 6 percent of cases (with resuscitation often possible), and usually seems to be caused by ventricular arrhythmias. The risk of sudden death is linked to normalcy of the right ventricular pressure, size and function.

Patients after primary surgical repair of Tetralogy in childhood will often require further surgical repairs, especially replacement of the pulmonary valve as a young adult to minimize right ventricular volume overload as a result of the complete pulmonary insufficiency that is a consequence of the Tetralogy repair.