What is an atrial septal defect (ASD) and what causes it?
ASD is a defect in the atrial septum caused by impaired growth or excessive resorption of the atrial septum during fetal development → This allows oxygenated blood to shunt from the left atrium to the right atrium.
What are the main types and pathophysiology of atrial septal defects?
1- Hemodynamic characteristics
• Typically a low-pressure, low-volume, minor left-to-right shunt (therefore, patients are usually asymptomatic)
2-Hemodynamic sequence in Atrial Septal Defect (ASD)
1. ASD → oxygenated blood shunting from LA to RA
2. ↑ O₂ saturation in the RA
3. ↑ O₂ saturation in the RV and pulmonary artery
4. ↑ Pulmonary blood flow (pulmonary overcirculation)
5. Volume overload of the right ventricle
6. Right ventricular dilation and hypertrophy
7. Increased flow returning from lungs → left atrial enlargement
8. Chronic pulmonary vascular changes → pulmonary hypertension (late)
9. If pulmonary pressure exceeds systemic pressure → shunt reversal (right-to-left)
10. Development of Eisenmenger syndrome → systemic desaturation and cyanosis
What conditions are associated with atrial septal defect?
Down syndrome, fetal alcohol syndrome, intrauterine infections (e.g., TORCH), and Holt-Oram syndrome (autosomal dominant disorder characterized by ASD, first-degree heart block, and upper limb abnormalities such as absent radial bones).
What are the typical clinical features of atrial septal defect?
Clinical Feature
1. Small defects
• Usually asymptomatic
- Medium to large defects
• Clinical presentation varies from asymptomatic to overt heart failure.
• Symptoms typically manifest with advancing age (∼ 30–40 years of age). - Clinical features include
1) Nonspecific Findings
1. Failure to thrive
2. Recurrent bronchopulmonary infections
3. Normal skin tone
4. Exercise intolerance
• Fatigue, pallor, and diaphoresis (sweating)
• Tachycardia
• Dyspnea
• Grunting, nasal flaring, retractions, and/or head bobbing may be seen
2) Palpitations (e.g., due to supraventricular arrhythmias)
3) Symptoms of heart failure (e.g., peripheral edema)
4) Stroke or TIA (e.g., from paradoxical embolism)
What are the classic auscultation findings in atrial septal defect?
1- Mid-systolic ejection murmur at the second left intercostal space [Relative pulmonary stenosis due to an increase in stroke volume]
2- Widely split and fixed S2 (does not change with respiration)
3- Soft mid-diastolic murmur at the lower left sternal border [Due to increased flow across the tricuspid valve]
What investigations confirm atrial septal defect?
1- Echocardiography is the confirmatory test (best seen in apical four-chamber and subcostal views)
2- ECG may show
1) right ventricular hypertrophy:
right axis deviation, P pulmonale, or right bundle
branch block
2) Atrial tachyarrhythmias, e.g., atrial fibrillation, atrial flutter
3- Chest X-ray may show
1) Rounding of the left heart contour due to an enlarged right atrium, right ventricle, and pulmonary artery
2) and increased pulmonary vascular markings.
What is the management of atrial septal defect?
1) Small or asymptomatic ASDs: observation with periodic examination and echocardiography
2) Larger or symptomatic ASDs: closure using transcatheter device, patch repair, or open surgery.
What are the major complications of atrial septal defect?
1) Paradoxical embolism leading to ischemic stroke a
2) heart failure;
long-standing cases may also lead to pulmonary hypertension and arrhythmias.
• supraventriclar arrhythmias
• Pulmonary hypertension
• Eisenmenger syndrome
What are the main types of atrial septal defects (ASD) and their typical locations?
- Ostium secundum ASD (~80%): located centrally in the fossa ovalis →
- Ostium primum ASD (~10%): located just above the atrioventricular valve level →
- Sinus venosus defects (~10%): occur at the junction of the vena cava with the right atrium (upper type near the superior vena cava and lower type near the inferior vena cava).upper more common than the lower
Indications of surgical management
1) Large left-to-right shunts
2) Right atrial or ventricular hypertrophy
3) Symptoms of heart failure
4) History of paradoxical embolism
5) Platypnea-orthodeoxia syndrome
A rare syndrome characterized by dyspnea and cyanosis in the upright position due to a right-to-left shunt, e.g., in patent foramen ovale and atrial septal defect.
