Cardiovascular System I PART II

Kishore S Rajan

Coarctation of Aorta•The word coarctation has been derived from

Latin word ‘COACTERE’, meaning to contract.•Definition: A congenital narrowing of upper

descending thoracic aorta adjacent to the site of attachment of ductus arteriosus.

•Occurrence rate: 0.2-0.6/1000 live births.•Represents 5-8% of all congenital heart disease.•8th most common congenital heart defect.

Pathophysiology

•This is due to arterial duct tissue encircling the aorta just at the point of insertion of the duct.

•When the duct closes, aorta also constricts, causing severe obstruction to the left ventricular outflow. This is the commonest cause of collapse due the left outflow obstruction.

• It is postulated that the coarctation maybe initiated in the fetal life by the presence of a cardiac abnormality that results in decreased blood flow anterograde through the aortic valve.

• Preductal- proximal – infantile type▫very high load on left ventricle

elevation of both systolic & diastolic pressures absence of collaterals immediately symptomatic with CCF from birth.

• Postductal type: distal to ductus/ ligamentum arteriosum or subclavian artery - adult type.▫development of collaterals connecting

branches of subclavian artery to arteries arising from aorta from in-utero life distal level of coarctation spares infant from LVF.

Clinical features

•Coarctation of aorta recognized after infancy is rarely associated with significant symptoms.

•Examination on the first day of life is usually normal.

•Neonates present with acute circulatory collapse at 2 days of age when the duct closes.

•The classical sign is a disparity in pulsation and blood pressure in the arms and legs.

•The femoral, popliteal, posterior tibial and dorsalis pedis pulses are weak or absent in contrast to the bounding pulses of the arms and carotids.

•Metabolic acidosis due to kidney failure.

Investigations

•Chest X-ray▫Normal heart size with prominent ascending

aorta and aortic knuckle•ECG▫Right or biventricular hypertrophy in neonates▫Normal in young children▫LVH in older children

•Echocardiography▫Cardiomegaly▫Visualization of coarctation.

Management

•Surgery is performed soon after diagnosis.

•Balloon angioplasty•Resection of coarctation and end-to-end

anastomosis at any age but lowest risk at 1-10yrs.

•Medical includes management of complications like CCF in infancy and hypertension.

Tetralogy of Fallot• It is the most common cyanotic heart defect

and the most common cause of blue baby syndrome.

• It accounts for 6-10 percent of all CHDs•This condition is characterized by the

combination of four defects: ▫1. Subpulmonary stenosis causing RV outflow obstruction

thus,▫2. Right ventricular hypertrophy▫3. Overriding or dextroposed aorta, and ▫4. Ventricular septal defect (VSD)

Causes

•Unclear•Children born to mothers with PKU are

highly susceptible as are mothers who drink during birth.

•Genetic

Pathophysiology •Physiologically the pulmonary stenosis

causes concentric right ventricular hypertrophy without cardiac

enlargement and an increase in right ventricular pressure.

•When the right ventricular pressure is as high as the left ventricular or the aortic pressure, a right to left shunt appears to

decompress the right ventricle.

• Once the right and left ventricular become identical, increasing severity of pulmonary stenosis

reduces the flow of blood into the pulmonary artery and increases the right to left shunt.

• As the systolic pressures between two ventricle are identical there is little or no left to right shunt and

the VSD is silent.

• The flow from the right ventricle into the pulmonary artery occurs across the pulmonary

stenosis producing an ejection systolic murmur

• More severe the pulmonary stenosis, the less the flow into the pulmonary artery and the bigger the

right to left shunt, more the cyanosis

• Thus the severity of cyanosis is directly proportional to the severity of pulmonary

stenosis

• The VSD of TOF is always large enough to allow free exit to the right to left shunt

• Thus Congestive failure never occurs in TOF.

Clinical features•Clinical manifestations depend on the size of the

VSD and the degree of LV outflow obstruction.• SYMPTOMS:▫Severe cyanosis▫Hypercyanotic spells

Associated with irritability or inconsolable crying because of the hypoxia and

Breathlessness and pallor due to acidosis▫Squatting on exercise.

• SIGNS:▫Clubbing in older groups▫Loud harsh ejection systolic murmur which will

shorten as RV outflow increases.

•Squatting (a compensatory mechanism) is uniquely characteristic of a right- to-left shunt that presents in the exercising child.

•Squatting increases the peripheral vascular resistance, which diminishes the right-to-left shunt and increases pulmonary blood flow.

Investigations •Chest X-ray ▫Small heart.▫Boot shaped heart

(due to ventricular hypertrophy). It means apex is lifted up.

▫Concavity in the region of pulmonary artery

▫Right sided aortic arch.▫ Oligaemic lung fields.▫ Hilar vessels are few,

lung vessels also few.

•ECG- normal at birth. Right ventricular Hypertrophy when older.

•Echocardiography- demonstrate the four cardinal features

Management

• Initial management is medical with definitive surgery at around 6 months of age.

•Surgical involves closing the VSD and relieving the right ventricular outflow tract obstruction, sometimes with a artificial patch.

• Infant, very cyanosed in the neonatal period, require a shunt to increase Pulmonary blood flow.

•This is usually done by surgical placement of an artificial tube between the subclavian artery and the pulmonary artery (Blalock-Taussig shunt) or sometimes by balloon dilatation of right ventricular outflow tract.

•Hypercyanotic spells are usually self-limiting followed by a period of sleep.

• If prolonged (>15min) – t/t▫Sedation and pain relief (morphine but

watch out for SE)▫IV propranolol (or α adrenoceptor agonist) –

peripheral vasoconstrictor and relieve subpulmonary muscular obstruction.

▫IV fluids.▫Bicarbonates to correct acidosis.▫Muscle paralysis and artificial ventilation to

reduce O2 demand.

Transposition of Great Arteries• Transposition of the great arteries (TGA) is a

serious heart defect which the two main arteries leaving the heart are reversed (transposed)

• 1 of 4000-5000 births, annual incidence 20-30 per 100.000 live birth.

• Second most common cause of cyanosis in infancy (5-7% of congenital heart disease)

•No race predilection.•History of diabetic mother.• 60-70% male predominance.•Cause is unknown.

• The transposition of the great arteries, ventriculo-arterial discordance or discordant VA connection, in which the aorta arises from the morphologic right ventricle and the pulmonary artery arises from the morphologic left ventricle.

Pathophysiology • The pulmonary and systemic circulations function in parallel

rather than in series

• Transposition of great arteries

• Oxygenated pulmonary venous blood returns to the left atrium and left ventricle

• Re-circulated to the pulmonary vascular bed via the abnormal pulmonary arterial connection to the left ventricle.

• Deoxygenated systemic venous blood returns to the right atrium and right ventricle

• Pumped to the systemic circulation, effectively bypassing the lungs

• Deficient oxygen supply to the tissues and an excessive right and left ventricular workload.

• It is incompatible with prolonged survival unless mixing of oxygenated and deoxygenated blood

occurs at some anatomic level like

• ASD or VSD or PDA or therapeutic interventions.

Clinical features

•Symptoms: Cyanosis – profound and life threatening.

•Presentation is usually on 2nd day when ductal closure occurs

•Cyanosis will be less if other anomalies present, like ASD, VSD etc.

•Physical signs: Cyanosis, Loud S2, may present with a systolic murmur from increased flow or stenosis within the left ventricle.

Investigations •Chest X-ray Classical finding

of a narrow upper mediastinum with an ‘egg on side’ appearance of the cardiac shadow. This is due to anterior posterior relationship of the great vessels, narrow vascular pedicle and hypertrophied right ventricle.

•ECG This is usually normal.

•Echocardiography This is essential to demonstrate the

abnormal arterial connections and associated abnormalities.

Management

• In the sick cyanotic neonate – key is to improve Mixing.

•Maintaining the patency of the Ductus arteriosus is important – Prostaglandin infusion.

•Balloon Atrial Septostomy

•Arterial switch in the neonatal period.

•Balloon Atrial Septostomy – life saving procedure.

•A catheter with an inflatable tip is passed through the umbilical or femoral vein and then on through the right atrium and foramen ovale.

•The balloon is inflated within the right atrium and pulled back through the atrial septum.

•This tears the atrial septum, allowing mixing of systemic and pulmonary venous blood within the atrium.

•Arterial Switch Procedure.•Performed in the neonatal period •The pulmonary artery and the aorta are

transected above the arterial valves and switched over

•The coronary arteries have to be transferred across the new aorta.

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