Makindo Medical Notes.com

Related Subjects: |Congenital Acyanotic Heart Disease |Congenital Cyanotic Heart Disease |Cardiac Embryology |Cyanosis - Central and Peripheral |Down's syndrome (Trisomy 21) |Tetralogy of Fallot |Patent Foramen Ovale (PFO) |Ventricular Septal defect (VSD)

Tetralogy of Fallot (TOF) is a congenital heart defect that is classically characterized by four anatomical abnormalities of the heart. It is one of the most common cyanotic heart defects, accounting for approximately 10% of all congenital heart defects. Many babies with Fallot are pink at birth but gradually become cyanosed over the first few months of life as RVOT obstruction worsens.

About

• Commonest cause of Congenital cyanotic heart disease
• It may not be apparent at birth and diagnosis may be delayed
• In some patients the RV outflow gradually gets worse up to 6-9 months of age.
• Spells may be caused by RVOT obstruction due to adrenergic stimulation
• Cyanosis at birth is more likely to be transposition

Structure: 4 defects

• Overriding Aorta: aorta is over the VSD, allows oxygen-poor blood from the RV to enter the aorta and systemic circulation.
• Right ventricular hypertrophy: secondary to the RV outflow obstruction
• Sub-Pulmonary stenosis: (RV outflow obstruction at/below the valve) reduces blood to the lungs.
• VSD: usually large allows oxygen-poor blood to mix with oxygen-rich blood

Diagram

Aetiology

• Right-sided outflow obstruction leads to poor pulmonary blood flow and impaired blood oxygenation.
• Large VSD just shunts even more blood into the right ventricle until eventually as RV pressures rise
• RV pressure exceeds LV and deoxygenated blood passes into the systemic system and patient is cyanosed
• This is Eisenmenger syndrome and is centrally cyanosed.

Clinical

• Fatigue. Cyanosis - may not be apparent at birth
• Murmur: harsh ejection systolic murmur left sternal edge pulmonary flow. Absent P2
• Tet spells due to increased RVOT gradient and increased R/L shunting with cyanosis
• Finger and toe clubbing

Investigations

• CXR: shows a "boot-shaped" heart due to RVH. Pulmonary Oligaemia due to reduced blood flow
• ECG: RVH
• Echocardiography: shows the four anatomical defects and assessing the severity of the disease.
• Cardiac MRI or CT Scan: for detailed anatomical assessment, especially when planning surgery.

Management

• Acute: Prostaglandin E1: Administered to newborns with severe pulmonary stenosis or atresia to maintain a patent ductus arteriosus, ensuring some blood flow to the lungs.
• Tet Spells: place child in a knee-chest position, give Oxygen, and morphine and beta-blockers.
• Surgical Management: Complete Repair ideally within the first year of life. Closes VSD with a patch and relieving the pulmonary stenosis, typically by widening the pulmonary valve and artery. Surgery before 5 years old at latest.
• Palliative Surgery: Blalock-Taussig shunt might be performed to increase pulmonary blood flow until the child is ready for full repair.
• Post-Surgical Outcomes: most children have good long-term outcomes but with lifelong follow-up is necessary to monitor for arrhythmias, residual defects, and right ventricular dysfunction.
• Long-Term Monitoring: regular echocardiograms, ECGs, and possibly MRI scans to assess heart function and detect any late complications.