Atrial Septal Defect

Question 1

What are the clinical signs of an atrial septal defect?

Answer 1

Ejection systolic murmur in pulmonary area with widely splitted S2 (A2-P2)
Right ventricular heave
Functional TS with mid diastolic murmur
Ostium primum ASD has mitral regurgitation

1. Wide, fixed splitting of S2
2. Murmurs if shunt present - ESM over pulmonary area louder on inspiration
3. Signs of pulmonary hypertension
   - Functional TS (MDM at tricuspid area)
4. Eisenmenger shunt reversal (cyanosis and clubbing)
5. Signs of heart failure
   - Raised JVP
   - Pulmonary area thrill
6. Complications of IE
7. Syndromes: Down syndrome, thumb defect in Holt-Oram syndrome

Question 2

What are the types of atrial septal defect?

Answer 2

1. Ostium secundum (90%): foramen ovale defect with no valvular involvement
   - Mostly asymptomatic, if small < 2cm, normal life expentancy
   - Larger defects - 2nd or 3rd decade dyspnoea, fatigue
2. Ostium primum: anterior and inferior aspect with involvement of mitral and tricuspid valve
   - Failure of fusion of septum primum with endocardial cushions
   - A/w with atrioventricular septal defect and Down’s syndrome
3. Sinus venosus type: defect in septum just below entrance of SVC
   - Abnormal drainage of right pulmonary vein
   - Inverted P wave in inferior leads
4. Coronary sinus defect: unroofed coronary sinus allowing blood shunting from LA to coronary sinus into RA

Question 3

What are the complications of an atrial septal defect?

Answer 3

1. Paradoxical embolus through patent foramen ovale
2. Atrial arrhythmia
3. Right ventricular dilatation and eventual right heart failure
4. Eisenmenger’s syndrome (shunt reversal due to pulmonary hypertension)

Question 4

How would you investigate a patient with an atrial septal defect?

Answer 4

ECG
- Secundum: partial RBBB, RAD
- Primum: LBBB, LAD, low atrial rhythm
- Sinus venosus: inverted P in inferior leads
- Pulmonary hypertension: p pulmonale, RVH
- Atrial fibrillation

CXR
- Cardiomegaly
- Pulmonary plethora (well visualised pulmonary arteries)
- Pulmonary hypertension: double heart border, prominent pulmonary trunk
- Small aortic knob

TTE
- Site, size and shunt calculation, shunt direction
- PASP
- Amenability to closure

Cardiac catheterisation
- Determines severity and direction of shunt

Question 5

What are the indications and contraindications for closure of an atrial septal defect?

Answer 5

Indications:
- Symptomatic (embolus, breathless)
- Significant shunt
- Pregnancy
- Early childhood

Contraindications:
- Severe pulmonary hypertension
- Eisenmeinger’s syndrome

Question 6

How do patients with ASD present?

Answer 6

Secundum
- Asymptomatic
- Symptomatic in 2nd/3rd decade: fatigue, dyspnoea, right heart failure, AF (due to atrial dilatation), recurrent pulmonary infection, paradoxical emboli, IE

Primum
- Similar symptoms + syncope (heart block)

Question 7

What are the murmurs associated with ASD?

Answer 7

1. Pulmonary ESM, tricuspid MDM: increased blood flow trough PV and TV due to left to right shunting
2. Mitral MDM: Lutembacher’s syndrome (mitral valvulotomy causing iatrogenic ASD)
3. MR, TR or VSD murmur: ostium primum type
4. Fixed, wide splitting S2:
   - Wide: left to right shunt overloads RV, increased venous return prolongs right heart emptying and delay in P2 closure
   - Fixed: equalisation of RA and LA

Question 8

What are causes of wide splitting S2?

Answer 8

1. ASD
2. VSD
3. PR (increased RV volume)
4. PS (increased RV pressure)
5. RBBB (RV conduction delay)
6. MR (increased LV emptying)

Question 9

How do you differentiate flow murmur through PV vs PS murmur?

Answer 9

PS murmur has soft P2, delayed closure, varies with respiration

Large ASD will cause apex beat deviation

Question 10

What is Tetralogy of Fallot?

Answer 10

1. VSD
2. RVH
3. PS
4. Overriding of aorta

Question 11

What is Holt Oram syndrome?

Answer 11

1. Autosomal dominant
2. ASD secundum
3. Hypoplastic thumb with accessory phalanx

Question 12

How do you manage patient with ASD?

Answer 12

1. Education and counselling
   - Small and insignificant ASD: reassurance, asymptomatic, even pregnancy is well tolerated
   - Larger defects or complications: avoid pregnancy (increased mortality)
2. Medical treatment for HF, AF
3. Anticoagulation if bidirectional shunt to prevent strokes from paradoxical emboli
4. Surgical closure
   - Early childhood 5-10 years to prevent complications
   - Large ASD or pulmonary to systemic flow ratio > 2
   - Routine closure before pregnancy
5. Choice of surgery
   - Transcatheter button or clam-shell devices
   - Surgical closure