Topic: congenital cyanotic heart disease, respiratory distress syndrome
Question: Describe the clinical findings and investigations in TOF
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Tetralogy of Fallot (TOF) is a congenital heart defect that affects the normal flow of blood through the heart. It is characterized by four different abnormalities in the heart’s structure, including a ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta.
1. Pulmonary stenosis: Narrowing of the pulmonary valve and artery reduce blood flow to the lungs.
2. Ventricular septal defect: A hole between the left and right ventricles allowing mixing of oxygenated and deoxygenated blood.
3. Right ventricular hypertrophy: The right ventricle becomes enlarged due to having to pump against the obstruction.
4. Overriding aorta: The aorta is displaced posteriorly and to the right, receiving blood from both the left and right ventricles.
Clinical findings:
– Cyanosis: Present from birth due to mixing of deoxygenated right ventricular blood with arterial blood. Often exacerbated by crying or feeding.
– Finger clubbing: Due to longstanding hypoxemia and pulmonary stenosis since birth.
– Loud heart murmur: Due to turbulent blood flow across the VSD and pulmonary valve. Often a mid-systolic ejection murmur at the left upper sternal border.
– Dyspnea with feeding (Tet spell): When pulmonary stenosis is severe, increased blood flow to the lungs during feeding can lead to hypoxia and irritability. Requires emergency care.
– Hypoxic spells: These are episodes of sudden and severe cyanosis, which can occur during feeding, crying, or defecation.
– Poor growth: Infants with TOF may have poor growth due to the increased energy expenditure required to breathe.
– Squatting: Older children may adopt a squatting position during exercise or exertion, which can improve systemic oxygenation.
– Murmurs: On auscultation, a systolic ejection murmur may be heard over the pulmonary area.
Investigations:
– Pulse oximetry: Resting oxygen saturations usually 75-85%. Drops with activity or feeding in severe cases.
– ECG: RECG may show right ventricular hypertrophy, right axis deviation, and a right bundle branch block.
– Chest X-ray: Enlarged right ventricle with concave pulmonary artery border. Plethoric lungs. May also show the characteristic “boot-shaped” appearance of the heart, which results from the right ventricular hypertrophy.
– Echocardiogram: It is the primary investigation for the diagnosis of TOF. Shows size of VSD, severity of pulmonary stenosis, RV hypertrophy and override of aorta. Helps in surgical planning.
– Cardiac catheterization: Only required if echocardiogram cannot fully define the anatomy or obtain accurate haemodynamic measurements. Mainly done during surgical correction.It helps in the assessment of the degree of pulmonary stenosis and the presence of any other associated cardiac anomalies.
– Blood tests: CBC may show polycythemia from chronic hypoxemia. Prior to surgery, coagulation studies, LFTs and blood gases are also checked.
– Pulse oximetry: It measures the oxygen saturation level in the blood, and low oxygen saturation is a characteristic finding in TOF.
The only curative treatment for TOF is open heart surgery to close the VSD and relieve the pulmonary stenosis. A Blalock-Taussig shunt may be required as temporary measure in neonates prior to full repair. The prognosis following surgery is generally good with survival into adulthood and normal life expectancy.
