Tetralogy of Fallot

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Associate Editors-In-Chief: Keri Shafer, M.D. [2]; Atif Mohammad, M.D., Priyamvada Singh, MBBS

Tetralogy of fallot treatment

ACC/AHA guidelines tetralogy of fallot

Tetralogy of fallot surgical techniques

Tetralogy of fallot post-surgical prognosis

Tetralogy of fallot prevention

External Links for VSD

• Pediatric Heart Surgery
• The Congenital Heart Surgery Video Project
• VSD Repair, Perimembranous Ventricular Septal Defect
• VSD Repair Powerpoint™ Presentation

Acknowledgements and Initial Contributors to Page

Leida Perez, M.D. Redmond Burke M.D.

References

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Symptoms

The primary symptom is low blood oxygen saturation with or without cyanosis from birth or developing in the first year of life. Without cyanosis, the baby is referred to as a "pink tet". Other symptoms include a heart murmur which may range from almost imperceptible to very loud, difficulty in feeding, failure to gain weight, retarded growth and physical development, dyspnea on exertion, clubbing of the fingers and toes, and polycythemia.

Tet spells are characterized by a sudden, marked increase in cyanosis, syncope, and may result in hypoxic brain injury and death.

Diagnosis

1. ECG: usually the ecg shows a right axis deviation and right ventricular hypertrophy.
2. Often a simple chest x-ray is enough to determine the presence of this condition. The heart may present with a "boot-like" appearance (an upturned right ventricular apex and a concave main pulmonary arterial segment), rather than the symmetric appearance of a normal heart. A right sided aortic arch may be present.
3. Echocardiogram is helpful in characterizing the defects as well as better understanding the hemodynamics in the heart. Right to left shunting through the VSD can be visualized by color Doppler imaging, and the severity of right ventricular outflow tract obstruction can be determined by spectral Doppler measurementsFor more info and images, see Echo in Tetralogy of Fallot
4. Arterial oxygen desaturation is evident, as is compensatory erythrocytosis, the magnitude of which is proportional to the severity of the desaturation.
5. Cardiac catheterization and coronary angiography; Although this is an invasive method, it is possible to confirm the diagnosis and obtain additional anatomical and hemodynamic data, including the location and magnitude of right to left shunting, the level and severity of right ventricular outflow obstruction, the anatomical features of the right ventricular outflow tract and the main pulmonary artery and its branches, and the origin and course of the coronary arteries.
6. Cardiac MRI

Treatment

Tetralogy of Fallot is treated on two levels: with immediate emergency care for hypoxic or "tet" spells and with corrective surgery.

Emergency management of tet spells

Consequential acute hypoxia may be treated with beta-blockers such as propranolol, but acute episodes may require rapid intervention with morphine to reduce ventilatory drive and phenylephrine to increase blood pressure. Oxygen is ineffective in treating hypoxic spells because the underlying problem is lack of blood flow through the pulmonary circuit and not alveolar oxygenation. There are also simple procedures such as the knee-chest position which increases aortic wave reflection, increasing pressure on the left side of the heart, decreasing the right to left shunt thus decreasing the amount of deoxygenated blood entering the systemic circulation.

Palliative surgery

The condition was initially thought untreatable until surgeon Alfred Blalock, cardiologist Helen B. Taussig, and lab assistant Vivien Thomas at Johns Hopkins University developed a surgical procedure, which involved forming an anastomosis between the subclavian artery and the pulmonary artery. It was actually Helen Taussig who convinced Alfred Blalock that the shunt was going to work. 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 greatly relieving symptoms in patients. The first Blalock-Thomas-Taussig shunt surgery was performed on 15-month old Eileen Saxon on November 29, 1944 with dramatic results.

The Pott shunt and the Waterson procedure are other shunt procedures which were developed for the same purpose.

Currently, Blalock-Thomas-Taussig shunts are not normally performed on infants with TOF except for severe variants such as TOF with pulmonary atresia.

Total surgical repair

The Blalock-Taussig procedure was the only surgical treatment until the first total repair was performed in 1954. Between 1944 and when total repair became available at major surgical centers in the early 1960s, many infants and children were treated with Blalock-Taussig procedures.

The total repair was performed by C. Walton Lillehei at the University of Minnesota in 1954 on a 10-month boy. Total repair initially carried a high mortality risk which has consistently improved over the years. Surgery is now often carried out in infants 1 year of age or younger with a <5% perioperative mortality. The surgery generally involves making incisions into the heart muscle, relieving the right ventricular outflow tract stenosis by careful resection of muscle, and repairing the VSD using a Gore-Tex or Dacron patch or a homograft. Additional reparative or reconstructive work may be done on patients as required by their particular anatomy.

Patients who have undergone "total" repair of tetralogy of Fallot often have good to excellent cardiac function after the operation with some to no exercise intolerance and have the potential to lead normal lives. Surgical success and long-term outcome greatly depends on the particular anatomy of the patient and the surgeon's skill and experience with this type of repair.

Prognosis

Untreated, tetralogy of Fallot results in progressive right ventricular hypertrophy and dilatation due to the increased resistance on the right ventricle. The dilated cardiomyopathy progresses to right heart failure, usually with accompanying left heart failure. Actuarial survival for untreated tetralogy of Fallot is approximately 75% after the first year of life, 60% by four years, 30% by ten years, and 5% by forty years.

Patients with repaired tetralogy of Fallot have the potential to lead normal lives with continued excellent cardiac function, with some considerations:

Current techniques for total surgical repair greatly improve the hemodynamic function of the heart with tetralogy of Fallot but do not provide a lifetime correction of the defect. Ninety percent of patients with total repair as infants develop a progressively leaky pulmonary valve as the heart grows to its adult size. Patients also may have some degree of residual right outflow stenosis and damage to the electrical system of the heart from surgical incisions, causing abnormalities as detected by EKG and/or arrhythmias.

Long-term follow up studies show that this patient population is at risk for sudden cardiac death and for heart failure. Therefore, lifetime follow-up care by an adult congenital cardiologist is recommended to monitor these risks and to recommend treatment, such as interventional procedures or re-operation, if it becomes necessary. Risk factors for sudden death include older age at repair, male sex, advanced NY heart association class, repair via atriotomy. Two major electrocardiographic risk factors include complete heart block beyond the third post operative day and QRS duration > 18 milliseconds, and rapid development of QRS prolongation in the first 6 months after repair. There is limited data regarding defibrillator implantation.

Antibiotic prophylaxis is indicated during dental treatment in order to prevent infective endocarditis.

See also

• Trilogy of Fallot
• Pentalogy of Fallot

External links

• Tetralogy of Fallot information from Seattle Children's Hospital Heart Center
• Information by University of Michigan Health System
• Diagram of the condition
• Information for adults with ToF from the Adult Congenital Heart Association
• Michael Warman's Website on ToF

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