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Emergency Medicine > CARDIOVASCULAR
Tetralogy of Fallot
Article Last Updated: Mar 22, 2006
AUTHOR AND EDITOR INFORMATION
Section 1 of 11  
Author: Mark Spektor, DO, Medical Director, Department of Emergency Medicine, Maimonides Medical Center
Mark Spektor is a member of the following medical societies: American College of Emergency Physicians, American College of Physician Executives, and Society for Academic Emergency Medicine
Coauthor(s):
Kurt Pflieger, MD, Active Staff, Department of Pediatrics, Lake Pointe Medical Center
Editors: Theodore J Gaeta, DO, MPH, FACEP, Clinical Associate Professor, Department of Emergency Medicine, Joan and Sanford Weill Medical College at Cornell University; Vice Chairman and Program Director of Emergency Medicine Residency Program, Department of Emergency Medicine, New York Methodist Hospital; Academic Chair, Adjunct Professor, Department of Emergency Medicine, St George's University School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Gary Setnik, MD, Chair, Department of Emergency Medicine, Mount Auburn Hospital; Assistant Professor, Division of Emergency Medicine, Harvard Medical School; John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center; Charles V Pollack, Jr, MD, MA, FACEP, Professor, Department of Emergency Medicine, University of Pennsylvania College of Medicine; Chairman, Department of Emergency Medicine, Pennsylvania Hospital
Author and Editor Disclosure
Synonyms and related keywords:
TOF, Fallot tetrad, Fallot's tetrad, congenital heart disease, tetralogy of Fallot, maldevelopment of right ventricular infundibulum, subaortic ventricular septal defect, right ventricular infundibular stenosis, aortic valve positioned to override the right ventricle, right ventricular hypertrophy, right-to-left shunting, right ventricular outflowtractobstruction, cyanosis, hypertrophy of the infundibular septum, dyspnea, retarded growth, aortic ejection click, systolic thrill, systolic ejection murmur, clubbing, scoliosis, squatting position, retinal engorgement, hemoptysis, conotruncal abnormalities, DiGeorge syndrome, branchial arch abnormalities, fetal hydantoin syndrome, fetal carbamazepine syndrome, fetal alcohol syndrome, maternalphenylketonuria birth defects
Background
Tetralogy of Fallot (TOF) is a complex of anatomic abnormalities arising from the maldevelopment of the right ventricular infundibulum. In 1888, Fallot described the anatomy as consisting of a subaortic ventricular septal defect (VSD), right ventricular infundibular stenosis, aortic valve positioned to override the right ventricle, and right ventricular hypertrophy (RVH). See Image 1 for a schematic illustration of these abnormalities.
Pathophysiology
Wide variation exists in the basic anatomic morphology, pathophysiology, clinical signs and symptoms, and surgical methods of therapy. Pathophysiology is dependent primarily upon severity of the right ventricular outflow tract (RVOT) obstruction. Right-to-left shunting is typical.
Frequency
United States
TOF represents approximately 10% of cases of congenital heart disease.
Mortality/Morbidity
Natural history is variable.
- Natural history is determined mainly by the degree of RVOT obstruction.
- Approximately 25% of untreated patients with TOF and RVOT obstruction die within the first year of life, 40% by 4 years, 70% by 10 years, and 95% by 40 years.
Sex
Incidence is slightly higher in males than females.
Age
Newborns
History
- Cyanosis develops within the first few years of life.
- First presentation may include poor feeding, fussiness, tachypnea, and agitation.
- Symptoms generally progress secondary to hypertrophy of the infundibular septum.
- Cyanosis occurs and demands surgical repair.
- Dyspnea on exertion is common.
- Squatting is uniquely characteristic of a right-to-left shunt that presents in the exercising child.
- Hypoxic "tet" spells are potentially lethal, unpredictable episodes that occur even in noncyanotic patients with TOF. These spells can be aborted with relatively simple procedures.
- The rare patient may remain marginally and imperceptibly cyanotic, or acyanotic and asymptomatic, into adult life.
- Severe cyanosis may present at birth in a patient with TOF and associated pulmonary atresia.
- Birth weight is low.
- Growth is retarded.
- Development and puberty may be delayed.
Physical
- Right ventricular predominance on palpation
- May have a bulging left hemithorax
- Systolic thrill at the lower left sternal border
- Aortic ejection click
- Single S2 - Pulmonic valve closure not heard
- Systolic ejection murmur - Varies in intensity inversely with the degree of RVOT obstruction
- More cyanotic patients have greater obstruction and a softer murmur.
- An acyanotic patient with TOF (pink tet) has a long, loud, systolic murmur with a thrill along the RVOT.
- Cyanosis and clubbing - Variable
- Squatting position
- Scoliosis - Common
- Retinal engorgement
- Hemoptysis
Causes
- As one of the conotruncal malformations, TOF can be associated with a spectrum of lesions known as CATCH 22 (cardiac defects, abnormal facies, thymic hypoplasia, cleft palate, hypocalcemia). Cytogenetic analysis may demonstrate deletions of a segment of chromosome band 22q11 (DiGeorge critical region).
- Ablation of cells of the neural crest has been shown to reproduce conotruncal malformations.
- These abnormalities are associated with the DiGeorge syndrome and branchial arch abnormalities.
- TOF frequently is associated with the following:
- Fetal hydantoin syndrome
- Fetal carbamazepine syndrome
- Fetal alcohol syndrome
- Maternal phenylketonuria (PKU) birth defects
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Anemia, Sickle Cell
Aortic Stenosis
Asthma
Patent Ductus Arteriosus
Pediatrics, Apnea
Pediatrics, Bacteremia and Sepsis
Pediatrics, Bronchiolitis
Pediatrics, Crying Child
Pediatrics, Foreign Body Ingestion
Pediatrics, Pneumonia
Pediatrics, Reactive Airway Disease
Pediatrics, Respiratory Distress Syndrome
Pneumothorax, Iatrogenic, Spontaneous and Pneumomediastinum
Pulmonic Valvular Stenosis
Shock, Cardiogenic
Shock, Septic
Other Problems to be Considered
Ebstein malformation of the tricuspid valve
Pulmonary atresia
Ventricular septal defect
Pseudotruncus arteriosus
Lab Studies
- Oximetry and arterial blood gases
- Oxygen saturation is variable, but pH and pCO2 are normal unless the patient is in extremis, such as during a tet spell.
- Oximetry is particularly useful in the dark-skinned patient or the anemic patient whose level of cyanosis is not apparent.
- Cyanosis is not evident until 3-5 g/dL of reduced hemoglobin is present.
- A decrease in systemic vascular resistance (SVR) during exercise, bathing, or fever potentiates a right-to-left shunt and causes hypoxemia.
- Hematology
- Prolonged cyanosis causes reactive polycythemia that increases the oxygen-carrying capacity.
- Hyperviscosity and coagulopathy often ensue and are particularly deleterious in patients with a right-to-left intracardiac shunt.
- Stroke and brain abscess are natural corollaries.
Imaging Studies
- Chest roentgenography
- Coeur en sabot (boot-shaped heart) secondary to uplifting of the cardiac apex from RVH and the absence of a normal main pulmonary artery segment (see Image 2)
- Normal heart size due to the lack of pulmonary blood flow and congestive heart failure
- Decreased pulmonary vascularity
- Right atrial enlargement
- Right-sided aortic arch (20-25% of patients) with indentation of leftward-positioned tracheobronchial shadow
- May be normal in acyanotic TOF or may resemble findings of small- to moderate-sized VSD with mild RVH, right atrial enlargement, and increased pulmonary vascular markings
- Echocardiography reveals a large VSD with an overriding aorta and variable degrees of RVOT obstruction.
Other Tests
- Electrocardiogram (see Image 3)
- Right axis deviation (+120° to +150°)
- Right or combined ventricular hypertrophy
- Right atrial hypertrophy
Procedures
- Cardiac catheterization
- Assesses pulmonary annulus size and pulmonary arteries
- Assesses the severity of RVOT obstruction
- Locates the position and size of the VSD
- Rules out possible coronary artery anomalies
Prehospital Care
- Any infant with cyanosis and/or respiratory distress requires oxygen.
- Blow-by O2 (BBO2) is the least objectionable. Use the open-end of a cannula or tube.
- Permit the baby to remain with the mother or father.
- Do not provoke the infant by attempting to start an intravenous (IV) line, especially if not skilled in pediatric IV starts.
- An intraosseous insertion could be an immediate lifesaving tool.
Emergency Department Care
The ED physician should be able to recognize and treat a hypercyanotic episode as one of the very few pediatric cardiology emergencies that may present to the ED.
- Hypoxic tet spell: Hypercyanotic episodes are characterized by paroxysms of hyperpnea, prolonged crying, intense cyanosis, and decreased intensity of the murmur of pulmonic stenosis.
- Mechanism - Secondary to infundibular spasm and/or decreased SVR with increased right-to-left shunting at the VSD, resulting in diminished pulmonary blood flow
- If left untreated, may result in syncope, seizure, stroke, or death
- Treatment for the acute setting of hypercyanosis includes the following:
- Knee-chest position: Place the baby on the mother's shoulder with the knees tucked up underneath. This provides a calming effect, reduces systemic venous return, and increases SVR.
- Oxygen is of limited value since the primary abnormality is reduced pulmonary blood flow.
- Morphine sulfate, 0.1-0.2 mg/kg IM/SC, may reduce the ventilatory drive and decrease systemic venous return.
- Phenylephrine, 0.02 mg/kg IV, is used to increase SVR.
- Treat acidosis with sodium bicarbonate, which may reduce the respiratory center stimulating effect of acidosis.
- General anesthesia is a last resort.
Consultations
Pediatric cardiology/surgery
The goals of therapy are to reduce the ventilatory drive, decrease systemic venous return, and increase peripheral venous return.
Drug Category: Analgesics
These agents reduce ventilatory drive. Pain control ensures patient comfort and promotes pulmonary toilet. Most analgesics have sedating properties, which are beneficial for patients who are having hypercyanotic episodes.
| Drug Name | Morphine sulfate (Duramorph, Astramorph, MS Contin) |
|---|
| Description | DOC for narcotic analgesia because of its reliable and predictable effects, safety profile, and ease of reversibility with naloxone.
Administered IV, may be dosed in number of ways and commonly titrated until desired effect obtained. |
|---|
| Pediatric Dose | 0.05-0.2 mg/kg dose IV prn; not to exceed 15 mg/dose |
|---|
| Contraindications | Documented hypersensitivity; hypotension; potentially compromised airway with uncertain rapid airway control; respiratory depression; nausea; emesis; constipation; urinary retention |
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| Interactions | Phenothiazines may antagonize analgesic effects; TCAs, MAOIs, and other CNS depressants may potentiate adverse effects |
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| Pregnancy | B - Usually safe but benefits must outweigh the risks.
|
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| Precautions | Avoid in hypotension, respiratory depression, nausea, emesis, constipation, and urinary retention; caution in atrial flutter and other supraventricular tachycardias; has vagolytic action and may increase ventricular response rate |
|---|
Drug Category: Alpha-adrenergic agonist
These agents improve hemodynamic status by improving myocardial contractility and increasing heart rate, resulting in increased cardiac output. Peripheral resistance is increased by vasoconstriction. Increased cardiac output and increased peripheral resistance increase blood pressure.
| Drug Name | Phenylephrine (Neo-Synephrine) |
|---|
| Description | Strong postsynaptic alpha-receptor stimulant with little beta-adrenergic activity; produces vasoconstriction of arterioles, increasing peripheral venous return. |
|---|
| Pediatric Dose | 5-20 mcg/kg/dose IV bolus q10-15min prn
0.1 mg/dose IV/SC q1-2h prn
0.1-0.5 mcg/kg/min IV infusion |
|---|
| Contraindications | Documented hypersensitivity; severe hypertension; ventricular tachycardia |
|---|
| Interactions | Bretylium may potentiate action on adrenergic receptors, possibly resulting in arrhythmias; MAOIs may significantly enhance adrenergic effects, and pressor response may be increased 2- to 3-fold; guanethidine may increase pressor response of direct-acting vasopressors, possibly resulting in severe hypertension |
|---|
| Pregnancy | C - Safety for use during pregnancy has not been established.
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| Precautions | Caution in elderly patients, hyperthyroidism, myocardial disease, bradycardia, partial heart block or severe arteriosclerosis; in hypovolemia, not substitute for replacement of blood, fluids and electrolytes, and plasma (these should be restored promptly when loss has occurred) |
|---|
Further Inpatient Care
- Palliative surgery
- Blalock-Taussig shunt
- Pott procedure
- Waterston shunt
- Total surgical correction with patch closure of the VSD and relief of the ventricular outflow obstruction is preferred (see Image 4).
Further Outpatient Care
- Good dental hygiene
- Endocarditis prophylaxis
- Arrhythmia prophylaxis may be warranted.
Complications
- Erythrocytosis
- Brain abscess
- Acute gouty arthritis
- Infective endocarditis
- Cerebrovascular thrombosis
- Delayed puberty
- Postoperative complications
- Congestive heart failure (right or left, residual outflow obstruction, VSD, and/or pulmonic regurgitation
- Atrial flutter, ventricular arrhythmias, right bundle-branch block, or left anterior hemiblock
- Infective bacterial endocarditis
Prognosis
- If right ventricular outflow tract obstruction is severe, the mortality rate is high without palliative or corrective surgery.
Patient Education
Special Concerns
- Hypoxic tet spells
- Physical and cognitive growth impairment
- Brain abscess and stroke, secondary to the right-to-left shunt
- Infective endocarditis
- Polycythemia
| Media file 2:
Uplifted apex and absence of pulmonary artery segment typifies the "coeur en sabot" (ie, boot-shaped heart) of tetralogy of Fallot. |
 |  View Full Size Image | |
Media type: X-RAY
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| Media file 3:
Typical preoperative ECG for tetralogy of Fallot. |
 | View Full Size Image | |
Media type: ECG
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| Media file 4:
Typical findings on postoperative ECG for tetralogy of Fallot. |
 | View Full Size Image | |
Media type: ECG
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Tetralogy of Fallot excerpt Article Last Updated: Mar 22, 2006
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