Atrial Septal Defect Pathogenesis and Clinical Findings

Atrial Septal Defect (ASD):
Pathogenesis and clinical findings
Genetic syndromes (e.g., Holt- Oram, Noonan, and Down)
Gene mutations (e.g., TBX5, GATA4, and NKX2-5)
Authors: Ryan Wilkie George Tadros Reviewers: Julena Foglia Haotian Wang Shahab Marzoughi Tim Prieur* * MD at time of publication
Abnormal formation of the septum of the atria
Atrial Septal Defect (ASD)
An abnormal connection between the left and right atria of the heart
Following birth, lungs fill with air and resistance to blood flow in the lung vasculature ↓ Pressure within the right ventricle and right atrium ↓
Left atrial pressure exceeds right atrial pressure
Blood passes from left to right through the ASD (left-to-right shunt)
↑ Blood flow through the right heart
↑ Blood flow through
tricuspid valve
Mid-diastolic murmur
Right-sided heart dilation (enlargement of the right ventricle)
Enlarged ventricle cannot pump blood effectively
Congestive Heart Failure
↑ Blood flow through pulmonary valve and pulmonary vasculature
Right ventricular heave (visible or palpable chest wall impulse around sternum)
↑ Right atrial wall stress
Inspiration produces no net pressure change between communicating atria
Delayed closure of pulmonary valve (relative to aortic valve)
Morphologic changes in pulmonary vasculature from long standing exposure to high blood flow
Pulmonary vascular resistanceáover time, may surpass systemic vascular resistance
**Pulmonary Hypertension**
Mid-systolic ejection murmur
Heart is unable to pump enough blood to meet demand during activity (including feeding)
↑ Backup of blood in lungs
↑ Hydrostatic pressure in lung vasculature
Pulmonary edema
Damage to normal conduction of electrical signal from the atria to the ventricles
ECG Changes: Prolonged PR and QRS intervals, right bundle branch block, right axis deviation
Fixed split S2 (two distinct sounds are heard as part of S2)
Reduced exercise capacity
↓ Eating
Failure to thrive
Atrial arrhythmias (atrial fibrillation or flutter)
Irregular beats are felt in the chest wall
↓ Ability to clear foreign particles from interstitium due to presence of extra fluid
Respiratory tract infections
** See Relevant Calgary Guide Slide **
Pulmonary Hypertension: Pathogenesis and clinical findings
Sign/Symptom/Lab Finding
Published Nov 1, 2014; updated Mar 21, 2024 on