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KembaraXtra-Medicine – Atrial Septal Defect
An atrial septal defect (ASD) is a congenital or iatrogenic defect in the atrial septum that creates an abnormal communication between the left and right atria, resulting in interatrial shunting of blood. This shunt is typically left to right due to higher left atrial pressures, leading to increased pulmonary blood flow and right-sided volume overload. ASDs are distinct from a patent foramen ovale (PFO), which represents postnatal failure of closure of a normal fetal structure rather than a true defect in septal formation. PFOs occur in approximately 20% to 25% of the adult population, whereas ASDs represent abnormal septal development established in utero.
ASDs are classified based on their anatomic location. Ostium primum defects occur in the inferior portion of the atrial septum due to failure of fusion of the septum primum with the endocardial cushions and are often associated with a cleft anterior mitral leaflet. Ostium secundum defects are the most common type and result from incomplete fusion of the septum primum and septum secundum, usually near the fossa ovalis. Sinus venosus defects occur near the junction of the right atrium with the superior or inferior vena cava and are frequently associated with anomalous pulmonary venous return. Coronary sinus septal defects, also known as unroofed coronary sinus, involve abnormal communication between the coronary sinus and the left atrium and are often associated with a persistent left superior vena cava. Iatrogenic ASDs may occur following procedures requiring transseptal puncture, such as electrophysiologic or structural heart interventions.
ASDs are among the most common acyanotic congenital heart diseases, occurring in approximately 0.1% of live births and accounting for 30% to 40% of clinically significant intracardiac shunts in adults. Ostium secundum defects account for about 75% of cases, followed by ostium primum defects (15%–20%), sinus venosus defects (5%–10%), and coronary sinus defects (<1%). secundum asds are more common in females, whereas gender distribution is similar other types. may occur isolation or association with genetic syndromes such as down syndrome, holt-oram noonan and digeorge well congenital cardiac abnormalities.< />pan>
Most ASDs are small and asymptomatic during infancy and childhood, but many patients develop symptoms later in life regardless of defect size. Exertional dyspnea and fatigue are the most common presenting symptoms. Small ASDs are often detected incidentally due to a cardiac murmur on routine examination. Large defects in infancy may lead to heart failure, recurrent respiratory infections, or failure to thrive. In adults, complications include atrial arrhythmias such as atrial fibrillation or flutter, paradoxical embolism causing ischemic stroke, and rarely platypnea-orthodeoxia syndrome. Physical examination findings may include right ventricular lift, wide fixed splitting of the second heart sound, systolic ejection murmurs due to increased pulmonary flow, and diastolic tricuspid flow murmurs in the presence of large shunts.
Diagnosis is based on clinical evaluation and imaging. Electrocardiography may show right axis deviation, right bundle branch block, atrial enlargement, or atrial arrhythmias depending on the ASD type. Chest radiography often demonstrates cardiomegaly, right-sided chamber enlargement, and increased pulmonary vascular markings. Transthoracic echocardiography is the primary diagnostic tool and is highly sensitive for secundum and primum defects, particularly when subcostal views and color Doppler imaging are used. Transesophageal echocardiography provides near-complete sensitivity and specificity and is essential when device closure is being considered, allowing accurate assessment of defect size and surrounding rims. Cardiac catheterization is used to quantify shunt magnitude (Qp:Qs), assess pulmonary vascular resistance, and evaluate pulmonary hypertension. Cardiac MRI and CT are valuable when echocardiography is inconclusive and for detailed assessment of right ventricular size, function, and anomalous pulmonary venous connections.
Management depends on patient age, symptoms, shunt magnitude, right-sided chamber enlargement, and pulmonary vascular status. In adults, ASD closure is recommended when there is significant left-to-right shunting (Qp:Qs >1.5:1), right atrial or ventricular enlargement, symptoms, or pulmonary hypertension that is not advanced or irreversible. Closure is also reasonable for paradoxical embolism or documented platypnea-orthodeoxia. Closure is contraindicated in patients with severe pulmonary hypertension, high pulmonary vascular resistance, or net right-to-left shunting. In children, closure is generally recommended before age 10 when significant shunting or right-sided dilation is present.
Percutaneous device closure is the preferred approach for suitable secundum ASDs and has a success rate exceeding 95% in appropriately selected patients. Surgical closure is indicated for primum, sinus venosus, and coronary sinus defects, or when anatomy is unsuitable for device closure. Iatrogenic ASDs often close spontaneously but may require intervention if associated with significant shunting or complications. Post-closure follow-up includes antiplatelet therapy for several months, serial echocardiography, and monitoring for arrhythmias or device-related complications.
Untreated large ASDs are associated with increased mortality and long-term complications, including right heart failure, pulmonary arterial hypertension, Eisenmenger syndrome, atrial arrhythmias, and embolic events. Patients with small shunts generally have a normal life expectancy but require periodic monitoring. ASD repair improves symptoms, exercise capacity, quality of life, and long-term survival, particularly when performed earlier in life. Long-term follow-up is recommended after repair, especially in adults, to monitor for arrhythmias, pulmonary hypertension, ventricular dysfunction, and residual shunts.
An atrial septal defect (ASD) is a congenital or iatrogenic defect in the atrial septum that creates an abnormal communication between the left and right atria, resulting in interatrial shunting of blood. This shunt is typically left to right due to higher left atrial pressures, leading to increased pulmonary blood flow and right-sided volume overload. ASDs are distinct from a patent foramen ovale (PFO), which represents postnatal failure of closure of a normal fetal structure rather than a true defect in septal formation. PFOs occur in approximately 20% to 25% of the adult population, whereas ASDs represent abnormal septal development established in utero.
ASDs are classified based on their anatomic location. Ostium primum defects occur in the inferior portion of the atrial septum due to failure of fusion of the septum primum with the endocardial cushions and are often associated with a cleft anterior mitral leaflet. Ostium secundum defects are the most common type and result from incomplete fusion of the septum primum and septum secundum, usually near the fossa ovalis. Sinus venosus defects occur near the junction of the right atrium with the superior or inferior vena cava and are frequently associated with anomalous pulmonary venous return. Coronary sinus septal defects, also known as unroofed coronary sinus, involve abnormal communication between the coronary sinus and the left atrium and are often associated with a persistent left superior vena cava. Iatrogenic ASDs may occur following procedures requiring transseptal puncture, such as electrophysiologic or structural heart interventions.
ASDs are among the most common acyanotic congenital heart diseases, occurring in approximately 0.1% of live births and accounting for 30% to 40% of clinically significant intracardiac shunts in adults. Ostium secundum defects account for about 75% of cases, followed by ostium primum defects (15%–20%), sinus venosus defects (5%–10%), and coronary sinus defects (<1%). secundum asds are more common in females, whereas gender distribution is similar other types. may occur isolation or association with genetic syndromes such as down syndrome, holt-oram noonan and digeorge well congenital cardiac abnormalities.< />pan>
Most ASDs are small and asymptomatic during infancy and childhood, but many patients develop symptoms later in life regardless of defect size. Exertional dyspnea and fatigue are the most common presenting symptoms. Small ASDs are often detected incidentally due to a cardiac murmur on routine examination. Large defects in infancy may lead to heart failure, recurrent respiratory infections, or failure to thrive. In adults, complications include atrial arrhythmias such as atrial fibrillation or flutter, paradoxical embolism causing ischemic stroke, and rarely platypnea-orthodeoxia syndrome. Physical examination findings may include right ventricular lift, wide fixed splitting of the second heart sound, systolic ejection murmurs due to increased pulmonary flow, and diastolic tricuspid flow murmurs in the presence of large shunts.
Diagnosis is based on clinical evaluation and imaging. Electrocardiography may show right axis deviation, right bundle branch block, atrial enlargement, or atrial arrhythmias depending on the ASD type. Chest radiography often demonstrates cardiomegaly, right-sided chamber enlargement, and increased pulmonary vascular markings. Transthoracic echocardiography is the primary diagnostic tool and is highly sensitive for secundum and primum defects, particularly when subcostal views and color Doppler imaging are used. Transesophageal echocardiography provides near-complete sensitivity and specificity and is essential when device closure is being considered, allowing accurate assessment of defect size and surrounding rims. Cardiac catheterization is used to quantify shunt magnitude (Qp:Qs), assess pulmonary vascular resistance, and evaluate pulmonary hypertension. Cardiac MRI and CT are valuable when echocardiography is inconclusive and for detailed assessment of right ventricular size, function, and anomalous pulmonary venous connections.
Management depends on patient age, symptoms, shunt magnitude, right-sided chamber enlargement, and pulmonary vascular status. In adults, ASD closure is recommended when there is significant left-to-right shunting (Qp:Qs >1.5:1), right atrial or ventricular enlargement, symptoms, or pulmonary hypertension that is not advanced or irreversible. Closure is also reasonable for paradoxical embolism or documented platypnea-orthodeoxia. Closure is contraindicated in patients with severe pulmonary hypertension, high pulmonary vascular resistance, or net right-to-left shunting. In children, closure is generally recommended before age 10 when significant shunting or right-sided dilation is present.
Percutaneous device closure is the preferred approach for suitable secundum ASDs and has a success rate exceeding 95% in appropriately selected patients. Surgical closure is indicated for primum, sinus venosus, and coronary sinus defects, or when anatomy is unsuitable for device closure. Iatrogenic ASDs often close spontaneously but may require intervention if associated with significant shunting or complications. Post-closure follow-up includes antiplatelet therapy for several months, serial echocardiography, and monitoring for arrhythmias or device-related complications.
Untreated large ASDs are associated with increased mortality and long-term complications, including right heart failure, pulmonary arterial hypertension, Eisenmenger syndrome, atrial arrhythmias, and embolic events. Patients with small shunts generally have a normal life expectancy but require periodic monitoring. ASD repair improves symptoms, exercise capacity, quality of life, and long-term survival, particularly when performed earlier in life. Long-term follow-up is recommended after repair, especially in adults, to monitor for arrhythmias, pulmonary hypertension, ventricular dysfunction, and residual shunts.
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