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Atrial Septal Defect

Title               

Ñ    Atrial Septal Defect

Definition

Ñ    Defect in the atrial septum

Ñ    Allowing communication

Ñ    Between the left and right atria

Pathogenesis;

Ostium secundum defects

These do not border the atrioventricular valves.

Ñ    Oval fossa defect:

Most common

Ñ    Inferior vena cava defects

Ñ    Superior vena cava defects

Ñ    Coronary sinus defect

Ostium primum defects

This may affect:

Ñ    Anterior cusp of the mitral valve

Ñ    Septal cusp of the tricuspid valve

Ñ    Ventricular septum may be deficient

Pathophysiology

Ñ    Left atrial pressure > right atrial pressure

Ñ    Left to right shunt

Ñ    Increased right heart output

Ñ    Increased pulmonary blood flow

Later (after age 30 years usually):

Ñ    Pulmonary vascular resistance increases

Ñ    Pulmonary hypertension develops

Ñ    Right ventricular hypertrophy occurs

Ñ    Right atrial pressure increases

This causes:

Ñ    Atrial fibrillation

Ñ    Right to left shunt:

Eisenmenger syndrome

Clinical Features

History

Ñ    Ostium secundum is usually asymptomatic until adult life

Ñ    Ostium primum natural history is worse than ostium secundum because of associated mitral regurgitation and disturbance of conducting tissue

CVS

Ñ    Palpitations

Ñ    Dyspnoea

RS

Ñ    Bronchitis

Ñ    Haemoptysis

Examination

E&M

Ñ    Females with ASD are slender:

Gracile habitus

CVS

Ñ    Pulse normal or small volume

Ñ    JVP elevated

Ñ    Left parasternal heave

Ñ    Loud P₂

Ñ    Fixed splitting of the second heart sound

Ñ    Ejection systolic pulmonary flow murmur

Ñ    Mid diastolic murmur due to increased flow through the tricuspid valve

Ñ    Signs of mitral regurgitation in ostium primum defects

Associations

Ñ    Holt-Oram syndrome:

Hypoplastic thumbs, accessory phalanges, abnormalities of the forearm

Autosomal dominant inheritance

Ñ    Lutembacher’s syndrome:

Associated mitral stenosis

Complications

IS

Ñ    Cyanosis:

·          Reversal of shunt:

Eisenmenger syndrome

Ñ    Clubbing:

Reversal of shunt

CVS

Ñ    Atrial fibrillation

Ñ    Pulmonary systolic click:

If pulmonary hypertension develops

Ñ    Eisenmenger syndrome:

Reversal of shunt

Ñ    Endocarditis

RS

Ñ    Pulmonary hypertension

Ñ    Bronchitis

CNS

Ñ    Paradoxical embolism

Investigations

Fluids

Blood

Haematology

Ñ    Polycythaemia:

Reversal of shunt

Imaging

Chest X-ray 

Ñ    Prominent pulmonary arteries and pulmonary plethora

Ñ    Pruning of pulmonary vessels:

If pulmonary hypertension develops

ECHO

Ñ    Transthoracic ECHO may show the defect

Ñ    Transoesophageal ECHO:

More sensitive

Electrophysiology

ECG

Ñ    Prominent right atrial P waves

Ñ    Prolongation of the PR interval

Ñ    Right bundle branch block

Ñ    Right axis deviation

Physiological studies

Cardiac catheterisation

Ñ    For diagnosis and to assess the degree of pulmonary vascular disease

Ñ    Step up of oxygen saturation in the right atrium

Management

Cure

Surgery

Ñ    Repair of the defect (open surgery or percutaneous, transcatheter device closure):

·          Significant defect;

Pulmonary blood flow > 50% more than systemic blood flow

·          Paradoxical embolism

·          Should be repaired before age 10 or as soon as possible if diagnosed in adult life

Ñ    Smaller defects:

Doubts about efficacy of surgery when the diagnosis is made later in life

Prognosis

Ñ    Excellent results in patients operated in childhood and adolescence

 

Inject agitated saline into antecubital vein; microbubbles appearing in left atrium is a positive study

Valsalva manoeuvre facilitates shunting

Ñ    Transoesophageal echo:

More sensitive

Management

Cure

Surgery

Ñ    Surgical closure

Ñ    Catheter based closure

Prevention

Drugs

Ñ    Aspirin:

Prevent stroke

Ñ    Warfarin:

Prevent stroke

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