TOF Flashcards
(25 cards)
Among cyanotic CHO ——————relatively favorable natural history that allows survival beyond infancy in about 75% of cases
Tetralogy of Fallot
most common cyanotic CHO encountered beyond the age of 1-yr constituting almost 75% of all blue patients
Tetralogy of Fallot
classic tetrad
- severe right ventricle outflow obstruction,
- large VSD,
- aorta that overrides the VSD and
- right ventricular hypertrophy
Hemodynamics
pulmonic stenosis causes concentric right ventricular hypertrophy without cardiac enlargement and an increase in right ventricular pressure ➡️right to left shunt ➡️appears to decompress the right ventricle and the VSD is silent
The more severe the pulmonic stenosis, the less the flow into the pulmonary artery and the bigger the right to left shunt
Murmur heard in TOF
The flow from the right ventricle into the pulmonary artery occurs across the pulmonic stenosis producing an ejection systolic murmur
Thus the more severe the pulmonic stenosis, the shorter the ejection systolic murmur and the more the cyanosis
Thus the severity of cyanosis is directly proportional to
the severity of pulmonic stenosis
intensity of the systolic murmur is inversely related to
the severity of pulmonic stenosis
congestive failure never occurs in TOF why ?
Since the right ventricle is effectively decompressed by the VSD, congestive failure never occurs in TOF
Conditions where CHF occurs in TOF
(i) anemia; (ii) infective endocarditis; (iii) systemic hypertension; (iv) unrelated myocarditis complicating TOF; and (v) aortic or pulmonary valve regurgitation.
delay in the P2 is due to
The right ventricular outflow obstruction
P2 is also reduced in intensity why
pulmonary artery pressure is reduced
S2 feature
single and the audible sound is A2 is quite loud
ascending aorta in TOF
is large and may result in an aortic ejection click
On auscultation, the diastolic interval is completely clear in TOF as there is no third or fourth sound or a diastolic murmur.
Clinical Features
- anoxic spells (paroxysmal attacks of dyspnea)
- Cyanosis may be present from birth or make its appearance some years after birth.
- dyspnea on exertion and exercise intolerance
Anoxic spells
predominantly after waking up or following exertion. The child starts crying, becomes dyspneic, bluer than before and may lose consciousness. Convulsions may occur
The patients assume a sitting posture-squatting-as soon as they get dyspneic
Physical examination
cyanosis, clubbing, slightly prominent ‘a’ waves in the jugular venous pulse, normal sized heart with a mild parasternal impulse, a systolic thrill in less than 30% patients, normal first sound, single second sound and an ejection systolic murmur which ends before the audible single second sound
The electrocardiogram in TOF
- right axis deviation with right ventricular hypertrophy
- The ‘T’waves are usually inverted in right precordial leads
- V1 may show pure ‘R’ but transition to R/S complex occurs at V2
X Ray
- normal sized heart with upturned apex suggestive of right ventricular hypertrophy
- The absence of main pulmonary artery segment gives it the shape described as Coeur en Sabot
- The pulmonary fields are oligemic
Diagnosis
- confirmed by echocardiography
- cardiac catheterization is seldom necessary
- CT/MRI may be required in older children with limited echo windows.
Complications
- increasing exercise intolerance
- Each attack of paroxysmal dyspnea or anoxic spell is potentially fatal
- Anemia, by decreasing the oxygen carrying capacity of blood, reduces the exercise tolerance still further
- infective endocarditis
- Paradoxical embolism to central nervous system and venous thrombosis due to sluggish circulation from polycythemia can also result in hemiplegia.
- Brain abscess
Treatment
- Oral beta-blockers help prevent cyanotic spells
- Iron supplementation
- surgery
Oral beta blocker dose
Maximally tolerated doses of propranolol ranging from 0.5-1.5 mg/kg/dose
Definitive surgery for TOF involves
closure of the VSD and relief of the RVOT obstruction
relief of the RVOT obstruction involves
the placement of a trans annular patch across the pulmonary valve and valvectomy resulting in severe pulmonary regurgitation
There is growing emphasis on retaining the pulmonary valve during initial repair to prevent pulmonary regurgitation and its major late consequences (RV dilation, arrhythmia, heart failure and sudden death)
