Tetralogy of Fallot (TOF) in Adults Workup

Updated: Nov 18, 2021
  • Author: Shabir Bhimji, MD, PhD; Chief Editor: Yasmine S Ali, MD, MSCI, FACC, FACP  more...
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Approach Considerations

See also the Guidelines section for the 2018 American Heart Association/American College of Cardiology (AHA/ACC) recommendations for the management of adults with tetralogy of Fallot.

Laboratory studies

Laboratory studies that may be helpful in the evaluation of adult patients with tetralogy of Fallot (TOF) include the following:

  • Complete blood cell (CBC) count: Some patients may have a mild anemia, but if cyanosis is absent, polycythemia is rare.

  • Coagulation profile: This may be abnormal in patients with cyanosis and bleeding.

  • Arterial blood gas (including serum lactate, base excess, oxygen partial pressure [PO2]): The patient's oxygenation status, serum lactate levels, and base excess value appear to be prognostic markers for mortality in those undergoing surgical repair of tetralogy of Fallot. [4]

  • Blood cultures: Obtain blood cultures in febrile patients to rule out endocarditis or sepsis.


The electrocardiogram (ECG) will usually show the presence of right ventricular (RV) hypertrophy with a right bundle branch block. The longer the QRS interval, the larger will be the RV mass and volume. Furthermore, when the QRS interval is longer than 180 milliseconds (ms), it is a significant marker for the development of ventricular arrhythmias and sudden death. [23]

Another ECG feature that is also known to predict the risk for ventricular arrhythmias and sudden death is the rate of change in the QRS interval. A relatively fast increase (>3.5 ms/year) is associated with a higher risk of death. A rapid change in the rate of change is also a significant event in the absence of prolongation of the QRS interval. Finally, variation in the heart rate is also a marker for sudden death in these patients. [23]

In other patients, the ECG will reveal atrial tachycardia or atrial fibrillation.

Cardiac catherization

When adults with tetralogy of Fallot (TOF) present, the initial study of choice is usually echocardiography. However, in some cases, cardiac catheterization is needed to assess the pressures in the right ventricle and pulmonary artery, the location and size of the ventricular septal defect, and the status of the pulmonary vessels. Cardiac catheterization is also necessary when the cardiac anatomy cannot be completely defined by echocardiography, when disease in the pulmonary arteries is a concern, and if an anomalous coronary artery or pulmonary hypertension is suspected.


Imaging Studies

Imaging studies used in the evaluation of tetralogy of Fallot (TOF) includechest radiographs, magnetic resonance imaging (MRI), and echocardiography.


The chest x-ray may be normal, or it may show cardiomegaly and prominent right ventricular (RV) shadowing. Although the hallmark of tetralogy of Fallot in infants is the classic boot-shaped heart (coeur en sabot) (see the following image), in which diminished vascularity in the lungs and diminished prominence of the pulmonary arteries become apparent, this classic shape of the heart is not always seen in adults with tetralogy of Fallot.

An uplifted apex and absence of pulmonary artery s An uplifted apex and absence of pulmonary artery segment typifies the "coeur en sabot" (ie, boot-shaped heart) of tetralogy of Fallot.


Color-flow echocardiography is always obtained in adult patients tetralogy of Fallot to assess the overall cardiac function and the status of the valves, and for the presence of any residual ventricular septal defect (VSD), ductus arterosus, or atrial septal defect. Note that although echocardiography can assess the valvular anatomy, it is unable to visualize the coronary anatomy in the adult patient. This imaging modality is also able to reveal the grade and severity of any RV outflow tract (RVOT) obstruction.

Magnetic resonance imaging

MRI has become the gold standard for assessing the RV function and size, as well as for quantifying the pulmonary regurgitant volume. When a problem with the pulmonary valve is suspected, MRI is the first test of choice. This imaging modality can map the velocity of pulmonary regurgitation and provides good delineation of the aorta size as well as assessment of the pulmonary arteries, the status of the RVOT, and the presence of VSDs and/or RV hypertrophy. [5]  MRI can also measure intracardiac pressures, gradients, and blood flows.

MRI is quite sensitive at detecting branch pulmonary artery stenosis, which may be contributing to the increasing pulmonary valve insufficiency and the formation of aortopulmonary collaterals. These findings are more common in those with tetralogy of Fallot who have pulmonary atresia. [24, 25]


Some pediatric cardiology centers specialize in looking after patients with tetralogy of Fallot. They recommend a baseline MRI of the the heart, even in the absence of symptoms. The results can then be used to monitor the patient for any changes every 3-7 years.