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Fallot’s Tetralogy

Title

Ñ    Fallot’s Tetralogy

Definition

Ñ    Ventricular septal defect

Ñ    Overriding of the aorta

Ñ    Right ventricular outflow obstruction

Ñ    Right ventricular hypertrophy

Pathogenesis

Risk Factors

Ñ    Unknown

Ñ    Possible multifactorial genetic link

Ñ    Higher incidence in maternal rubella infection

Ñ    Higher incidence in diabetic mothers

Ñ    Higher incidence in children with Down’s syndrome

Pathophysiology

Ñ    Clinical features dependent on the degree of right ventricular outflow obstruction

Ñ    Pulmonary blood flow diminished due to right ventricular outflow obstruction

Ñ    Pulmonary blood flow dependent on patent ductus arteriosus or bronchial collaterals

Ñ    High right ventricular pressure causes right to left shunting

Ñ    Central cyanosis

Clinical Features

History

Age

Ñ    Congenital

Ñ    Infants smaller than expected for age

Ñ    Clubbing and cyanosis obvious at 12 months

Sex

Ñ    Males > Females

E&M

Ñ    Failure to thrive

CVS

Ñ    Fatigue

Ñ    Fallot’s spells:

Hypoxic episodes on exertion

Ñ    Squatting

IS

Ñ    Central cyanosis

RS

Ñ    Dyspnoea

Ñ    Haemoptysis

CVS

Ñ    Seizures

Ñ    Strokes

Past Illnesses

Ñ    Maternal rubella

Ñ    Maternal diabetes

Family History

Ñ    Usually sporadic

Personal History

Ñ    Maternal alcohol abuse

Examination

E&M

Ñ    Failure to thrive

CVS

Ñ    Left parasternal heave

Ñ    Systolic thrill, lower left sternal edge:

VSD

Ñ    Ejection systolic murmur over pulmonary area:

Right ventricular outflow obstruction

Ñ    Systolic murmur left sternal edge:

VSD

IS

Ñ    Central cyanosis

Ñ    Clubbing of fingers and toes

HS

Ñ    Polycythaemia

Complications:

Ñ    Bacterial endocarditis

Ñ    Paradoxical embolism causing strokes

Ñ    Pulmonary embolism

Investigations

Fluids

Blood 

Haematology

Ñ    Elevated haemoglobin and haematocrit:

Polycythaemia

Imaging

Chest X-ray

Ñ    Chest X-ray shows boot shaped heart:

Large right ventricle and small pulmonary artery

Contrast Studies

Ñ    Cardiac catheterisation:

Right ventricular outflow obstruction and degree

Size of ventricles and pulmonary artery

ECHO

Ñ    Visualise cardiac anatomy

Ñ    Colour flow Doppler to assess VSD and right ventricular outflow obstruction

MRI

Ñ    Good views of the aorta, right ventricular outflow tract, VSD, right ventricular hypertrophy, pulmonary artery and its branches

Physiological studies

Ñ    Pressure and oxygen saturations in each chamber to calculate degree of shunt

Electrophysiology

ECG

Ñ    Right ventricular hypertrophy

Ñ    Right axis deviation

Management

Cure

Surgery

Ñ    Complete surgical correction

Ñ    Now possible in infancy

Control

Drugs

Ñ    Beta blockers

Fallot’s spells

Ñ    Diamorphine:

Relax right ventricular outflow obstruction

Surgery

Ñ    Palliative procedure (Blalock shunt):

Anastomosis between the subclavian artery and the pulmonary artery

Performed in infants to increase the blood supply to the lungs

Prevention

Ñ    Antibiotic prophylaxis:

Prevent infective endocarditis

Prognosis

Ñ    Without surgical intervention 1 year survival 66%

Ñ    With complete surgical correction the survival rate at 20 years is approximately 90-95%

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