TETRALOGY OF FALLOT
DEFINITION
- Tetralogy of fallot (TOF) is a defect that consists of 4 pathologies which lead to obstruction of bloodflow to the lungs, causing cyanosis. The degree of cyanosis depends on the degree of pulmonary stenosis or atresia. The four pathologies include:
o Pulmonary stenosis / pulmonary atresia
o Right ventricular hypertrophy
o Overriding aorta
o Ventricular septal defect
- Tetralogy of fallot is classified into cyanotic and acyanotic.
o
Cyanotic: classic tetralogy of fallot is
a cyanotic defect, and this is due to the degree of pulmonary stenosis. The
greater the obstruction of the right ventricular outflow tract, the greater the
degree of cyanosis, and the greater severity of symptoms.
o
Acyanotic: acyanotic tetralogy of fallot,
also known as the “pink tet” is less common than the cyanotic type. The degree
of pulmonary stenosis is not enough to cause persistent right to left shunting.
Symptoms may include only mild cyanosis with agitation or exercise. However,
signs of right heart damage can be seen without symptoms, and these include
right ventricular hypertrophy, right ventricular and right atrial enlargement.
This defect is usually closed before six months of age.
EPIDEMIOLOGY
- Most common form of cyanotic heart disease.
- 1 in 4 will die before 12months of age if unrepaired
- >50% chance of death by age 4 years if unrepaired
PATHOPHYSIOLOGY
- An obstruction of blood flow to the lungs which causes hypoxia, cyanosis and enlargement if the right heart.
- Events that cause an increase in pulmonary pressure, ie agitation, crying and bowel movements, contribute to an increase in pulmonary stenosis. The stenosis leads to further obstruction of blood flow to the lungs causing the classic hypoxic spell. The blood then shunts to the left side of the heart and returns to the body as deoxygenated blood.
- The obstruction of blood flow to the lungs cause cyanosis, which can cause the classic hypoxic spell. Characteristics of hypoxic spell include the following:
o
Rapid and deep respiration
o
Irritability and prolonged crying
o
Increasing cyanosis
o
Decreased intensity of heart murmur
o
Loss of consciousness, seizure, stroke and death
can occur if the spell is not relieved.
CLINICAL
SIGNS AND SYMPTOMS
- Acyanotic:
o
Mild pulmonary stenosis, Mild Left to right,
asymptomatic “pink tet”
- Cyanotic:
o
Moderate to severe pulmonary stenosis, right to
lest shunting, symptomatic, “blue tet”
- The severity of the following symptoms is directly dependent upon the severity of pulmonary stenosis (PS)
o
Clubbing
o
Cyanosis
o
Dyspnea on exertion
o
Shortness of breath
o
Exercise intolerance/easy fatigability.
o
Squatting
o
Systolic thrill, systolic ejection murmur at
middle LSB
o
EKG: RAD, RVH
o
Chest X ray : “boot – shaped “heart, normal
heart size
o
ECHO: anatomy, coronary arteries
o
CXR- TOF
 |
| “boot – shaped “heart |
 |
| Clubbing |
MEDICAL
MANAGEMENT
- Medical management include management of the acute and chronic phases of the disease.
- Chronic medical management:
o
Digoxin
o
Beta blockade (propranolol)
- Acute medical management of cyanotic/ hypoxic spells
o
Calm the baby (place the baby in mother’s arms,
feed, pacifier)
o
Knee/chest position: increases blood return to
the heart and systemic vascular resistance (SVR) and forces blood flow into the
lungs.
o
Oxygen: the most potent pulmonary vasodilator.
Even though blood is shunting right to left, oxygen will decrease the pulmonary
vascular resistance (PVR) and may shift the flow of blood to the lungs as the
pulmonary resistance falls.
o
Morphine sulfate: reduces pulmonary vascular
resistance (PVR)
o
Hyperpnea: reduces PVR
o
Phenylephrine
o
NaHCO3 for acidosis
 |
| Knee/chest position |
SURGICAL
MANAGEMENT
- BT Shunt
o
Is a palliative procedure that is performed to
buy time until a complete repair can performed.
o
Provides secure unobstructed blood flow to the
lungs.
o
Usually a 3mm, 3.5mm or 4.0mm gortex tube graft
connecting the innominate artery to the pulmonary artery.
o
Is a non-cardiopulmonary bypass procedure.
o
Is sometimes used if the baby is very
symptomatic, ie having cyanotic spells, and also weighs less than 3kg.
 |
| BT Shunt |
- Complete repair
o
Usually around 6 months of age, or sooner if
symptomatic
o
The pulmonary stenosis is surgically relived.
o
The VSD is closed.
o
The overriding aorta is realigned during the
closure of the VSD.
o
The right ventricular hypertrophy resolves over
time.
POSTOPERATIVE
MANAGEMENT AND NURSING IMPLICATIONS
- Maximize CO – Inotropes, lusotropes, vasodilators, diuretics
o
Common inotropic continuous infusions may be epinephrine,
dopamine, and milrinone.
- Assess for residual VSD/RVOT obstruction
o
Evidenced by continued desaturation.
- Arrhythmia:
o
Heart block: temporary external pacing
o
Jet: cooling , amiodarone, pacing
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