Overview 

An overriding Aorta is one of the four conditions found in Tetralogy of Fallot. It is rarely present on its own. There is a difference in the position of the aorta that affects the blood flow in the body, hence it is important to understand this condition. 

Tetralogy of Fallot includes:

• Overriding aorta
• Ventricular septal defect 
• Pulmonary stenosis
• Right ventricular hypertrophy

In a healthy person, the aorta is positioned at the left ventricle, where it ascends to form an arch and then descends to give rise to multiple arteries supplying various body parts.

An overriding aorta is a congenital heart defect (a structural anomaly present by birth) in which the aorta is present above a ventricular septal defect (another type of congenital heart defect in which the heart wall between the right and the left side is damaged). 

About 1% infants get a congenital heart defect and 10% of which have Tetralogy of Fallot (including overriding aorta).

In this article, we will talk about Tetralogy of Fallot as overriding aorta is a part of this condition.¹

Causes and Risk Factors 

• Gender: More common in males.
• Family history: A greater risk is present if one or both the parents have had this condition.
• Down syndrome: Babies who have down syndrome have a higher chance of having Tetralogy of Fallot. 

Also see:

• Pregnancy related factors
• Gestational diabetes (diabetes during pregnancy)
• Phenylketonuria
• Rubella 
• Smoking or secondhand smoke exposure during pregnancy
• Alcohol consumption during pregnancy 
• Using drugs like: ACE inhibitors and/ or retinoic acids during pregnancy
• Other conditions that are associated with Tetralogy of Fallot: Fallot complex, Irons Bhan syndrome, Williams syndrome, Aortic arch anomaly-peculiar facies-intellectual disability syndrome, Steinfeld syndrome and Apert syndrome.²

Symptoms 

There are variations in symptoms depending on severity.

In adults, these clinical features can be seen:

• Reduced exercise endurance
• Feeling your own heart beat (palpitations)
• Bluish discolouration of skin (cyanosis)
• Loss of consciousness (syncope)
• Abnormal heart rhythm (cardiac arrhythmias)
• Heart murmur 
• Blood clotting defects
• Minimal appetite
• Anemia
• Cardiac arrest⁸

Clinical features in infants:

• Failure to thrive (delayed development)
• Tet spells (episodes of pale and blue skin while feeding or crying)
• Loss of consciousness (syncope)
• Minimal appetite
• Heart murmur 
• Seizures
• Cardiac arrest 
• Anemia 
• Blood clotting defects
• Abnormal heart rhythm (cardiac arrhythmias)³

Diagnosis 

Newborn babies are examined by the healthcare provider for tetralogy of Fallot as early detection is the key to good prognosis. For adults many tests can be done to diagnose this condition, most of these tests are performed on newborns as well.

These include:

• Physical examination: A general physical examination is performed. Certain parameters like: pulse, blood pressure, temperature, pulse oximetry, jugular venous pressure would also be measured. Both physical examination and imaging is necessary to help create a diagnosis of this condition. 
• Complete blood count/ whole blood count: In most cases a mild anemia is found.
• Coagulation profile test: A blood test is done to check the blood’s ability to clot.
• Blood culture: In patients with fever, a blood culture is done to check for infective endocarditis. 
• Arterial blood gas: Normally done in patients who are undergoing a surgical management for Tetralogy of Fallot. Used as a prognostic marker.
• Cardiac auscultation: A stethoscope is used to listen to the heart sounds. Various types of murmurs can be heard in both adults and infants.
• Cardiopulmonary Exercise Testing (CPET): This test is done using a bicycle or a treadmill to test for exercise tolerance. 
• Electrocardiogram (ECG): This is a standard test conducted when a cardiac anomaly is suspected. It detects the electrical impulses generated throughout a cardiac cycle, measuring them through sensors placed on the body.
• Chest radiographs: A chest X-ray shows a boot shaped heart (coeur en sabot) in infants but the case in adults can be different. An enlarged heart is present in adults.
• Cardiac echocardiography: It involves utilizing high-frequency sound waves to generate an image of the heart, capturing its internal structure and the surrounding vessels. This test is also performed on infants and is a crucial test to get a confirmation of the disease. It also assesses the overall heart function.
• Cardiac MRI: This generates a 3 dimensional image of the heart which is necessary to visualize it.
• Cardiac catheterization: This intricate procedure is done to conduct a range of tests on the heart. It is invasive in nature and requires the expertise of a specialist, typically a cardiologist. Normally done when an echocardiography is not enough.
• Cardiac Computed Tomography: A 3D X ray of the heart. Another important imaging technique.^3,8

Treatment 

There is no medical cure for Tetralogy of Fallot hence overriding aorta cannot be fixed either. Instead, medications can be used to manage symptoms for both adults and infants. They’re given on a case by case basis. 

Which include:

• Beta blockers: For ‘tet’ spells and to manage heart rate and rhythm abnormalities
• Antibiotics: For infective endocarditis present with this condition
• Diuretics: To remove the excess water during heart failure
• Pulmonary vasodilator drugs: To dilate the pulmonary vessels and reduce the symptoms. The drugs used are Sildenafil and nitrous oxide
• Painkillers

Surgical management 

Since Tetralogy of Fallot cannot be cured through medical management, corrective surgeries are essential. Corrective surgery isn’t curative but it can improve the function of the heart significantly. Without surgery, the mortality in infants is about 50% by the age of 6. Timely cardiac surgery can provide a good prognosis and a great quality of life.

There are many types of surgeries for Tetralogy of fallot.

A cardiopulmonary bypass is performed and the structural defects of the heart are fixed. Complex techniques are used to provide the best possible outcome for the patient. 

In some cases mechanical and bioprosthetic valves are used.

Percutaneous valve replacement is one of the new surgeries for Tetralogy of Fallot and related complications.

Automatic implantable cardioverter defibrillators are used in patients who have continued irregular heart rhythm even after the surgery. 

Reoperation and revision surgery is advised if the symptoms persist.

Most surgeries in infants are performed by 6 months of age for better prognosis.^3,4,8

Surgical complications^5,8

Prognosis 

The outlook for individuals with an overriding aorta with early detection is excellent. Most patients can survive up to 15-20 years after their first surgery. Many get pulmonic valve regurgitation and eventually require pulmonic valve replacement. A lot of patients can live to see their 70s and 80s due to advancement in cardiac surgeries. Without the surgery most can only live up to 20-30 years of age. 

Your healthcare provider can tell you about the prognosis for your unique case.^3,6,8

Strategies for prevention

Tetralogy of Fallot can be prevented during pregnancy by controlling the modifiable risk factors. 

• No amount of alcohol consumption or smoking should be done during pregnancy. 
• Rubella vaccine can prevent rubella infection during pregnancy.
• During pregnancy, diabetes should be well managed.
• Make sure you avoid the list of medications harmful to the baby provided by your doctor. 
• In patients with phenylketonuria, a low protein diet can help.

Certain prenatal tests can be performed to detect this condition. Contact your healthcare provider for more information as every case is different.⁷

Summary 

This article discusses the condition of overriding aorta, a component of Tetralogy of Fallot, emphasizing its rarity as an isolated occurrence. The normal position of the aorta and its deviation in this congenital heart defect are outlined, affecting blood flow in the body. The causes and risk factors include: gender, family history, Down syndrome, and various pregnancy-related factors. Symptoms vary in severity, and the diagnostic process involves various tests, such as physical examinations, blood tests, and imaging techniques. While there is no cure for Tetralogy of Fallot, medications can manage symptoms, and surgical interventions are necessary. The prognosis, dependent on early detection, is generally positive, with advancements in cardiac surgeries contributing to extended life expectancy. Prevention strategies during pregnancy are important. One must contact their healthcare provider for more information on their personal case.