Atrial Septal Defect

Relevant physical signs

• Inspection
  • Cyanosis
  • Respiratory distress
  • Dystonic posturing suggestive of previous CVA
  • Syndromic facies (Down’s syndrome)
  • Scars indicating previous mitral valvotomy
    • Iatrogenic ASD from balloon mitral valvotomy (usually trans-femoral)
  • Accessory phalanx or hypoplastic thumb (Holt-Oram syndrome)
    • Autosomal dominant, ostium secundum ASD with upper limb abnormalities
• Peripheries
  • Clubbed
  • Peripheral cyanosis
  • Stigmata of infective endocarditis
  • Pulse rate and rhythm (atrial fibrillation)
  • Central cyanosis
  • Jugular venous pulsation – raised / giant V waves
• Chest
  • Inspection – scars to suggest previous surgery
  • Palpation
    • Apex beat – usually not displaced, unless there is shunt reversal
    • Parasternal heave
    • Palpable thrill
  • Auscultation
    • Fixed splitting of S2
    • Loud P2 to indicate pulmonary hypertension
    • Associated murmurs
      • Ejection systolic murmur over pulmonary area (increased flow across the pulmonary valve from left-to-right shunt)
      • Mid-diastolic murmur (acquired MS, Lutembacher’s syndrome)
      • Pan-systolic murmur (ostium primum defect – MR, TR, VSD)
• Complications
  • Irregular, tachycardic pulse – atrial tachyarrhythmias
  • Pronator drift – paradoxical emboli
  • Cyanosis, pulmonary hypertension, cor pulmonale – Eisenmenger’s syndrome

Differential diagnosis

• Physiological splitting of S2
• Delayed closure of pulmonary valve
  • Reverse splitting of S2
    • Severe aortic stenosis
    • Left bundle branch block
    • HOCM
  • Decreased LV volume (aortic valve closes earlier)
    • Mitral regurgitation
    • Ventricular septal defect
  • Conduction delay
    • Right bundle branch block
  • Increased RV pressure / volume
    • Pulmonary stenosis
    • Pulmonary regurgitation

Types of ASD

• Ostium secundum defect – defects in the foramen ovale
  • 80% of ASDs
  • Results from poor growth of the septum secundum or excessive absorption of septum primum
  • In rare instances, may have partial anomalous pulmonary venous connection
  • Defects < 8mm usually close spontaneously within two years
  • May get smaller with age
• Ostium primum defect
  • 15 – 20% of ASDs
  • Occurs if septum primum does not fuse with endocardial cushions
  • Leaves a defect at the base of the inter-atrial septum, which tends to be large
  • Nearly always associated with atrioventricular valve defects as they are malformations of endocardial cushions
  • Often seen with trisomy 21
• Sinus venous ASD
  • 5% of ASDs
  • Located in the atrial septum immediately below the orifice of the superior vena cava
  • May not be haemodynamically significant

Clinical markers of haemodynamic significance

• Insignificant
  • Regular pulse
  • Fixed splitting of S2
• Significant, left to right shunt
  • Irregular pulse
  • Systolic thrill
  • Parasternal heave
  • Fixed splitting of S2
  • Ejection systolic murmur over pulmonary area
  • Loud P2
• Significant, right to left shunt
  • Clubbing
  • Cyanosis
  • Irregular pulse
  • Fixed splitting of S2
  • Parasternal heave
  • Loud P2

Complications

• Infective endocarditis
• Atrial arrhythmias
• Stroke from paradoxical emboli
• Pulmonary hypertension
• Eisenmenger’s syndrome

Investigations

• Electrocardiogram
  • Ostium secundum: right axis deviation, right bundle branch block
  • Ostium primum: bifascicular block, first-degree heart block
  • Pulmonary hypertension: dominant R wave in V1 (RVH)
• Chest radiograph
  • Cardiomegaly
  • Pulmonary oedema
  • Enlarged left atrium
  • Enlarged pulmonary arteries (pulmonary hypertension)
• Transthoracic echocardiogram
  • Confirm diagnosis
  • Assess severity
  • Look for pulmonary hypertension – estimated pulmonary artery systolic pressure
• Injection of agitated saline contrast – bubble study

Management

• Multidisciplinary team approach
• Patient education
• Medical management
  • No antibiotic prophylaxis required (unless cyanotic)
  • Rate control with anticoagulation for atrial fibrillation
  • Anticoagulation if paradoxical emboli occur
• Indications for closure
  • Right ventricular enlargement without pulmonary hypertension
  • Right ventricular enlargement with PH, if PH is reversible
    • Pulmonary vasodilator challenge – bosentan, sildenafil
  • Paradoxical embolism
  • Documented orthodeoxia-platypnoea

Presentation

Sir, this patient has an atrial septal defect which is haemodynamically significant. The direction of the shunt is clinically from left-to-right. On examination of the peripheries, there is an irregular pulse, which is currently rate controlled. There is no clubbing or cyanosis, and there are no stigmata of infective endocarditis. The jugular venous pulsation is raised. On examination of the precordium, the apex beat is not displaced. There is a right ventricular heave, together with a thrill over the pulmonary area. The second heart sound is widely-split with a loud pulmonary component, and there is an ejection systolic murmur heard loudest over the pulmonary area. There are no other murmurs to suggest mitral regurgitation, tricuspid regurgitation or a ventricular septal defect, which may co-exist with ostium primum defects.

In summary, this patient has a haemodynamically significant atrial septal defect, which is complicated by pulmonary hypertension.