Atrial Septal Defect

Most common CHD in adults

Associated with some genetic syndromes, e.g. Noonan, trisomy 21

More likely in females than males.

1. Ostium secundum
   1. 70% of all ASD
   2. Often show right bundle branch block with right axis deviation on ECG
2. Ostium primum
   1. 15% of all ASD, associated with atrioventricular node abnormalities
   2. Often have right bundle branch block with left axis deviation on ECG
3. Sinus venous defect
   1. 5% of all ASD
   2. Associated with an anomaly in the insertion of the inferior or superior vena cava
4. Coronary sinus defect
   1. Less than 1% of all ASD
   2. Associated with a missing or partial wall between the left atrium and coronary sinus

Often symptomatic after 4th decade: palpitations, dizziness (an atrial arrhythmia), shortness of breath, dyspnoea, fatigue, reduced exercise tolerance

Most common:

1. Systolic Ejection Murmur – loudest at the left upper sternal border, radiates to the back. This is due to excess blood flow across the pulmonary valve.
2. Fixed second heart sound splitting – split second heart sound, even in expiration.

Uncommon:

1. Risk factors: maternal alcohol consumption, female
2. Mid-diastolic murmur: if moderate to large left-to-right shunt
3. Finger clubbing

ECG: typically normal in small ASD but tall P waves and large R waves in V1 (moderate to severe)

Chest X-ray: normal if small ASD, possible cardiomegaly (moderate to severe)

Qp:Qs <1.5 – observation, may resolve spontaneously

Qp:Qs ≥ 1.5 or enlargement of the right atrium – corrective surgical or transcatheter closure

Pulmonary Vascular Resistance >5

1. Pulmonary vasodilator
2. If PVR drops < 5 – corrective closure and prophylactic antibiotics
3. If PVR remains >5 – consider cardiopulmonary transplantation

If there is no evidence of pulmonary vascular obstructive disease, there is an excellent prognosis.

The older the age of the patient at the point of repair, the increased risk of adverse events.