TOF

Question 1

Among cyanotic CHO ——————relatively favorable natural history that allows survival beyond infancy in about 75% of cases

Answer 1

Tetralogy of Fallot

Question 2

most common cyanotic CHO encountered beyond the age of 1-yr constituting almost 75% of all blue patients

Answer 2

Tetralogy of Fallot

Question 3

classic tetrad

Answer 3

• severe right ventricle outflow obstruction,
• large VSD,
• aorta that overrides the VSD and
• right ventricular hypertrophy

Question 4

Hemodynamics

Answer 4

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

Question 5

Murmur heard in TOF

Answer 5

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

Question 6

Thus the severity of cyanosis is directly proportional to

Answer 6

the severity of pulmonic stenosis

Question 7

intensity of the systolic murmur is inversely related to

Answer 7

the severity of pulmonic stenosis

Question 8

congestive failure never occurs in TOF why ?

Answer 8

Since the right ventricle is effectively decompressed by the VSD, congestive failure never occurs in TOF

Question 9

Conditions where CHF occurs in TOF

Answer 9

(i) anemia; (ii) infective endocarditis; (iii) systemic hypertension; (iv) unrelated myocarditis complicating TOF; and (v) aortic or pulmonary valve regurgitation.

Question 10

delay in the P2 is due to

Answer 10

The right ventricular outflow obstruction

Question 11

P2 is also reduced in intensity why

Answer 11

pulmonary artery pressure is reduced

Question 12

S2 feature

Answer 12

single and the audible sound is A2 is quite loud

Question 13

ascending aorta in TOF

Answer 13

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.

Question 14

Clinical Features

Answer 14

• 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

Question 15

Anoxic spells

Answer 15

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

Question 16

Physical examination

Answer 16

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

Question 17

The electrocardiogram in TOF

Answer 17

• 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

Question 18

X Ray

Answer 18

• 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

Question 19

Diagnosis

Answer 19

• confirmed by echocardiography
• cardiac catheterization is seldom necessary
• CT/MRI may be required in older children with limited echo windows.

Question 20

Complications

Answer 20

• 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

Question 21

Treatment

Answer 21

• Oral beta-blockers help prevent cyanotic spells
• Iron supple­mentation
• surgery

Question 22

Oral beta blocker dose

Answer 22

Maximally tolerated doses of propranolol ranging from 0.5-1.5 mg/kg/dose

Question 23

Definitive surgery for TOF involves

Answer 23

closure of the VSD and relief of the RVOT obstruction

Question 24

relief of the RVOT obstruction involves

Answer 24

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)

Question 25

palliative options

Answer 25

Blalock-Taussig shunt, which consists of subclavian artery-pulmonary artery anastomosis using a Goretex graft