Tetralogy of Fallot (TOF) is a cyanotic congenital heart disorder that encompasses four anatomic features: right ventricular hypertrophy, ventricular septal defect (VSD), overriding aorta, and right ventricular (RV) outflow obstruction. (See 'Anatomy' above.)
●In the United States, the prevalence of TOF is about 3.9 per 10,000 live births. TOF accounts for 7 to 10 percent of congenital heart disease. (See 'Epidemiology' above.)
●Although TOF typically occurs sporadically without other anomalies, it can be present as part of a known syndrome or genetic disorder, such as Down syndrome. In addition, other associated cardiac anomalies occur in about 40 percent of patients with TOF. (See 'Genetic factors' above and 'Associated cardiac features' above.)
●The pathophysiologic effects of TOF are largely dependent upon the degree of RV outflow obstruction. The direction of blood flow across the VSD is determined by the path of least resistance for blood flow and not by the size of the VSD. If the resistance to the RV outflow is lower than systemic resistance, then there is a predominant left-to-right flow, and the patient is not cyanotic. However, with significant RV obstruction, there will be a right-to-left shunt across the VSD, resulting in cyanosis (figure 1). (See 'Pathophysiology' above.)
●The clinical presentation is dependent on the degree of RV outflow obstruction and determines whether there is a left-to-right (acyanotic) or right-to-left shunt. In general, the earlier the onset of systemic hypoxemia, the more likely it is that severe pulmonary outflow tract stenosis or atresia is present. In addition to persistent cyanosis in severely affected patients, other findings include intermittent hypercyanotic (tet) spells, crescendo-decrescendo harsh systolic ejection murmur, and a single second heart sound. (See 'Clinical presentation' above.)
●The diagnosis of TOF is typically made by echocardiography, which can usually delineate the location and number of VSDs, the anatomy and severity of RV outflow tract obstruction, the coronary artery and aortic arch anatomy, the presence of any associated anomalies, and the hemodynamic abnormalities associated with the anatomical defects. (See 'Echocardiography' above.)
Anatomy of tetralogy of Fallot
Tetralogy of Fallot is characterized by a large ventricular septal defect (VSD), an aorta that overrides the left and right ventricles, obstruction of the right ventricular outflow tract, and right ventricular hypertrophy. As a result of the substantial obstruction of the right ventricular outflow tract, there is right-to-left shunting through the VSD resulting in cyanosis.
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Left ventricular angiogram in tetralogy of Fallot
The angiogram of the left ventricle (LV) in a patient with tetralogy of Fallot was obtained with the camera in a long axial oblique projection. There is a large malaligned ventricular septal defect (*) with the aorta (AO) overriding the intraventricular septum (IVS).
Photo courtesy of Thomas Doyle, MD.
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Right ventricular angiogram in tetralogy of fallot
The right ventricular (RV) angiogram in a patient with tetralogy of Fallot was obtained with the camera angled cranially and in a slight left anterior oblique projection. The subvalvar (*) obstruction is so severe that with systole there is absence of contrast in the RV outflow tract. The pulmonary valve annulus is small with a thickened valve. There is a small ridge of supravalvar narrowing (black arrow) and mild proximal left pulmonary artery (LPA) stenosis (red arrow).
MPA: main pulmonary artery; RPA: right pulmonary artery.
Photo courtesy of Thomas Doyle, MD.
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Main pulmonary artery angiogram in tetralogy of Fallot
An angled angiogram performed in the main pulmonary artery demonstrates severe proximal left pulmonary artery (LPA) stenosis (*). There is discrepancy in size between the proximal right pulmonary artery (RPA) and the proximal LPA.
Photo courtesy of Thomas Doyle, MD.
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Main pulmonary artery angiogram after stenting
Following placement of a balloon expandable stent in the proximal left pulmonary artery (*) of a patient with tetralogy of Fallot there is significant improvement in size of the proximal left pulmonary artery (LPA).
RPA: right pulmonary artery; RV: right ventricle; MPA: main pulmonary artery.
Photo courtesy of Thomas Doyle, MD.
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Subcostal coronal view of tetralogy of Fallot (TOF)
This still frame from an echocardiographic video clip of a subcostal coronal view highlights the infundibular hypertrophy in this patient with TOF. The arrows identify the muscle bundles in the right ventricle outflow tract (RVOT).
RV: right ventricle; RA: right atrium.
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Electrocardiagram from an infant with tetralogy of Fallot
The ECG in tetralogy of Fallot shows prominent P waves in V1 (*) suggesting right atrial enlargement. There are also prominent right ventricular forces (tall R waves in V1), an upright T wave in V1, and a marked rightward axis suggesting right ventricular hypertrophy.
Courtesy of Thomas Doyle, MD.
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Tetralogy of Fallot
This chest radiograph demonstrates some of the classic findings of tetralogy of Fallot. The lungs are hyperinflated, and there is overall decreased pulmonary vascularity. There is a right aortic arch. The cardiac apex is upturned due to right ventricular enlargement.
Courtesy of Jeanne Chow, MD, and Children's Hospital Boston.
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Right ventricular angiogram in tetralogy of Fallot
The lateral projection of a right ventricular (RV) angiogram in tetralogy of Fallot shows an hypertrophied infundibulum (INF) with anterior and cephalad deviation of the septum, resulting in significant subpulmonary obstruction; the pulmonary valve annulus (*) is much larger than the subvalvar area.
Photo courtesy of Thomas Doyle, MD.
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Left ventricular angiogram in tetralogy of Fallot
A left venticular (LV) angiogram with the camera in a right anterior oblique projection in tetralogy of Fallot does not permit good visualization of the ventricular septal defect (VSD); however, the left to right flow across the VSD does allow excellent visualization of the hypertrophied infundibulum (INF) and the severe subpulmonary obstruction (*).
MPA: main pulmonary artery.
Management and outcome of tetralogy of Fallot
— The management of tetralogy of Fallot (TOF) encompasses initial medical care, surgical palliative procedures and intracardiac repair, and long-term care including detecting and caring for postoperative complications.
●The need for medical intervention is dependent on the degree of right ventricular outflow tract (RVOT) obstruction.
•Neonates with severe RVOT obstruction may require intravenous prostaglandin therapy (also known as alprostadil) to maintain ductal patency and pulmonary flow pending surgical repair. (See 'Neonates with severe RVOT obstruction' above.)
•The step-wise management approach of patients who experience hypercyanotic ("tet") spells includes knee-chest positioning of the patient to increase systemic vascular resistance, inhaled oxygen therapy, the use of intravenous morphine and fluid bolus, and, if the above measures fail, the use of intravenous beta blockers. A palliative surgical procedure may be needed if medical therapy fails. (See 'Tet spells' above.)
•Patients with minimal obstruction and increased pulmonary blood flow may develop symptoms of heart failure, and require pharmacologic treatment (loop diuretic therapy and digoxin). (See 'Heart failure' above.)
●We recommend that patients with TOF undergo primary intracardiac repair (Grade 1B). Intracardiac repair can be performed by three to six months of age and consists of patch closure of the ventricular septal defect, and enlargement of the RVOT with relief of all sources of obstruction (figure 2). Palliative procedures may be performed urgently for patients during a medically refractory hypercyanotic spell or for those with severe RVOT obstruction who may not be initially acceptable candidates for intracardiac repair (eg, premature infants and those with unfavorable coronary anatomy). (See 'Surgical procedures' above.)
●Patients after intracardiac repair are at risk for chronic postoperative complications, which may require reintervention. These include pulmonary regurgitation with associated right ventricular enlargement, residual RVOT obstruction, right ventricular dysfunction, aortic root dilation and aortic valve insufficiency, and arrhythmias including atrial tachycardia and ventricular tachycardia. (See 'Chronic postoperative complications' above and'Surgical survival and morbidity' above.)
●Longitudinal follow-up care is required in all patients with TOF in conjunction with a cardiologist with expertise in congenital heart disease. Clinicians need to know the associated complications following surgical repair, and also for the rare unoperated patients. Follow-up care is focused on identifying and managing long-term complications. It encompasses annual or more frequent routine health care visits with a focused cardiac history and physical examination. Routine cardiac testing is dependent on the patient's age, type of repair, symptoms, and on-going clinical concerns. Tests include electrocardiogram, echocardiogram, Holter monitoring, exercise testing, and occasionally cardiac magnetic resonance imaging or computerized tomography. (See 'Long-term health care maintenance' above.)
●Survival is poor for individuals with uncorrected TOF. Surgical correction has resulted in excellent long-term survival. In particular, patients who are operated on at a young age have a reported survival rate greater than 90 percent 25 years after surgical repair. Arrhythmia and heart failure that lead to sudden cardiac death are the most common causes of late death following surgical repair. However, the rate of reported postoperative interventions ranges from 20 to 30 percent of patients. In addition, patients with TOF are at risk for long-term neurodevelopmental impairment. (See 'Long-term outcomes' above and 'Sudden cardiac death' above.)
Repair of tetralogy of Fallot
These figures depict two options for the surgical correction of right ventricular outflow tract (RVOT) obstruction in patients with tetralogy of Fallot. In figure A, the RVOT is enlarged by opening the RVOT and pulmonary valve, resecting the subinfundibular muscle bundles, and patching the area open. In figure B, a conduit containing a prosthetic valve is inserted to connect the right ventricle and the main pulmonary artery, bypassing the RVOT.
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NYHA and other classifications of cardiovascular disability
| Class | New York Heart Association functional classification[1] | Canadian Cardiovascular Society functional classification[2] | Specific activity scale[3] |
| I | Patients with cardiac disease but without resulting limitations of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea, or anginal pain. | Ordinary physical activity, such as walking and climbing stairs, does not cause angina. Angina with strenuous or rapid prolonged exertion at work or recreation. | Patients can perform to completion any activity requiring ≥7 metabolic equivalents, eg, can carry 24 lb up eight steps; do outdoor work (shovel snow, spade soil); do recreational activities (skiing, basketball, squash, handball, jog/walk 5 mph). |
| II | Patients with cardiac disease resulting in slight limitation of physical activity. They are comfortable at rest. Ordinary physical activity results in fatigue, palpitation, dyspnea, or anginal pain. | Slight limitation of ordinary activity. Walking or climbing stairs rapidly, walking uphill, walking or stair climbing after meals, in cold, in wind, or when under emotional stress, or only during the few hours after awakening. Walking more than two blocks on the level and climbing more than one flight of ordinary stairs at a normal pace and in normal conditions. | Patients can perform to completion any activity requiring ≥5 metabolic equivalents, eg, have sexual intercourse without stopping, garden, rake, weed, roller skate, dance fox trot, walk at 4 mph on level ground, but cannot and do not perform to completion activities requiring ≥7 metabolic equivalents. |
| III | Patients with cardiac disease resulting in marked limitation of physical activity. They are comfortable at rest. Less than ordinary physical activity causes fatigue, palpitation, dyspnea, or anginal pain. | Marked limitation of ordinary physical activity. Walking one to two blocks on the level and climbing one flight in normal conditions. | Patients can perform to completion any activity requiring ≥2 metabolic equivalents, eg, shower without stopping, strip and make bed, clean windows, walk 2.5 mph, bowl, play golf, dress without stopping, but cannot and do not perform to completion any activities requiring >5 metabolic equivalents. |
| IV | Patients with cardiac disease resulting in inability to carry on any physical activity without discomfort. Symptoms of cardiac insufficiency or of the anginal syndrome may be present even at rest. If any physical activity is undertaken, discomfort is increased. | Inability to carry on any physical activity without discomfort. Anginal syndrome may be present at rest. | Patients cannot or do not perform to completion activities requiring >2 metabolic equivalents. Cannot carry out activities listed above (specific activity scale III). |
NYHA: New York Heart Association
References:
- The Criteria Committee of the New York Heart Association. Nomenclature and Criteria for Diagnosis of Diseases of the Heart and Great Vessels, 9th ed, Little, Brown & Co, Boston, 1994. p.253.
- Campeau L. Grading of angina pectoris. Circulation 1976; 54:522.
- Goldman L, Hashimoto B, et al. Comparative reproducibility and validity of systems for assessing cardiovascular functional class: Advantages of a new specific activity scale. Circulation 1981; 64:1227.
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Classification of sports based on peak static and dynamic components during competition
This classification is based on peak static and dynamic components achieved during competition; however, higher values may be reached during training. The increasing dynamic component is defined in terms of the estimated percentage of maximal oxygen uptake (VO2max) achieved and results in an increasing cardiac output. The increasing static component is related to the estimated percentage of maximal voluntary contraction reached and results in an increasing blood pressure load. The lowest total cardiovascular demands (cardiac output and blood pressure) are shown in the palest color, with increasing dynamic load depicted by increasing blue intensity and increasing static load by increasing red intensity. Note the graded transition between categories, which should be individualized on the basis of player position and style of play.
* Danger of bodily collision (see related table on sports according to risk of impact and educational background)
¶ Increased risk if syncope occurs.[1]
¶ Increased risk if syncope occurs.[1]
Reference:
- Mitchell JH, Haskell W, Snell P, Van Camp SP. Task Force 8: classification of sports. J Am Coll Cardiol 2005; 45:1364.
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