Cardiovascular · UKMLA & AKT
Atrial septal defect (ASD)
A free high-yield preview for the UKMLA Applied Knowledge Test. Below are the key points to recognise atrial septal defect (asd) — the full SA Note notes add investigations, management, complications and 10 practice questions.
Key high-yield points
- Often asymptomatic in childhood - detected as incidental murmur
- Dyspnoea and fatigue - reduced systemic output, increased pulmonary flow
- Palpitations - AF/flutter from chronic atrial dilatation
- Stroke or TIA - paradoxical embolism: DVT crosses ASD into systemic circulation when right atrial pressure transiently exceeds left (Valsalva, coughing) or permanently in Eisenmenger syndrome
- Cyanosis and clubbing - late sign, indicates Eisenmenger syndrome (right-to-left shunt reversal)
- Ejection systolic murmur - upper left sternal border (pulmonary area); caused by increased flow across pulmonary valve, not flow through the ASD itself
- Fixed splitting of S2 - hallmark sign; right heart is volume-overloaded throughout the cycle, so pulmonary valve closure is delayed regardless of respiratory phase
In an uncomplicated ASD the shunt is left-to-right - patients are NOT cyanotic. Cyanosis and clubbing = Eisenmenger syndrome with shunt reversal. This distinction is a frequent exam trap.
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