Atrial septal defect

Published on 05/05/2015 by admin

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Last modified 22/04/2025

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22 Atrial septal defect

Instruction

Examine this patient’s heart.

Listen to her heart.

Salient features

History

Diagnosis

This patient has an atrial septal defect (ASD) (lesion) that is congenital in origin (aetiology); she is not in cardiac failure and there is no reversal of shunt (functional status).

Advanced-level questions

What are the types of atrial septal defect

• Ostium secundum defect accounts for 70% of the cases. The defect is in the middle portion of the atrial septum and is usually 2–4 cm in diameter (incomplete right bundle branch block pattern, QRS axis rightward) (Fig. 22.2A,B).

• Sinus venosus type is a defect in the septum just below the entrance of the superior vena cava into the right atrium (leftward P wave axis so that P waves are inverted in at least one inferior lead) (Fig. 22.2C).

• Ostium primum type is a defect in the lower part of the septum and clefts may occur in the mitral and tricuspid valves (QRS axis leftward). A junctional or low atrial rhythm (inverted P waves in the inferior leads) occurs with sinus venosus defects.

Fig. 22.2 Electrocardiography in atrial septal defect. (A,B) Ostium secundum defect right precordial leads V₁ and V₂ illustrate two variants of an incomplete right bundle branch block pattern, the rSrT pattern (A) and the rsR’ pattern (B). (C) Ostium primum type: endocardial cushion defect with the QRS axis is leftward counterclockwise and superior.

What do you understand by the term patent foramen ovale?

In the fetus, the right and left atria communicate with each other through an oblique valvular opening, which is called the foramen ovale. The foramen ovale persists throughout fetal life. After birth, the left atrium receives blood from the lungs and the pressure in this chamber becomes greater than that in the right atrium; this causes the closure of the foramen ovale.

What is the importance of patent foramen ovale?

The prevalence of patent foramen ovale is significantly higher in patients with stroke (N Engl J Med 1988;318:1148–52).

What is Holt–Oram syndrome?

This is an ostium secundum ASD with a hypoplastic thumb and an accessory phalanx. In addition, the thumb lies in the same plane as the other digits (Br Heart J 1960; 22:236). The inheritance is autosomal dominant and is associated with mutations in chromosome 12q2 (N Engl J Med 1994;330:885–91).

At what age does the reversal of shunt occur?

Usually after the end of the second decade.

What is the mechanism of fixed split second sound?

In normal individuals, on inspiration there is a widening of the split between the two components of the second sound caused by a delay in closure of the pulmonary valve. In ASD, the effect of respiration is eliminated because of communication between the left and right sides of the heart.

In which conditions is an abnormally widely split second sound present?

• ASD, ventricular septal defect (VSD), pulmonary regurgitation (caused by increased right ventricular volume)

• Pulmonary stenosis (caused by increased right ventricular pressure)

• Right bundle branch block (caused by right ventricular conduction delay)

• Mitral regurgitation, VSD (caused by premature left ventricular emptying).

What is Lutembacher syndrome?

ASD with an acquired rheumatic mitral stenosis (Arch Mal Coeur 1916;9:237).

What is Fallot’s triology?

ASD, pulmonary stenosis and right ventricular enlargement.

How would you investigate a patient with atrial septal defect?

• Often has right axis deviation and incomplete right bundle branch block (Fig. 22.2A,B)

• In ostium primum defects left axis deviation also occurs (Fig. 22.2C)

• In sinus venosus defects, a junctional or low atrial rhythm (inverted P waves in inferior leads) occurs.

• Chest radiography:

• Prominent pulmonary arteries (large pulmonary conus)

• A peripheral pulmonary vascular pattern of ‘shunt vascularity’ (in which the small pulmonary arteries are especially well visualized in the periphery of both lungs)

• Small aortic knob

• Enlarged RV and right atrium

• ‘Uilar dance’ on fluoroscopy.

• Echocardiography:

• Transthoracic echocardiography visualizes ostium secundum and primum defects but usually does not identify sinus venosus defects

• Sensitivity can be enhanced by injecting microbubbles in the peripheral vein after which the movement across the defect can be seen

• Transoesophageal and Doppler colour-flow echocardiography is useful in detecting and determining the location of atrial septal defects and also in identifying anomalous venous drainage and sinus venosus defects.

• Cardiac catheterization is often unnecessary in diagnosis but is useful in determining the magnitude and direction of shunting and to determine the severity and reversibility of pulmonary hypertension

What are the complications of atrial septal defect?

• Atrial arrhythmias: atrial fibrillation is most common. Atrial fibrillation is often accompanied by the appearance of tricuspid regurgitation. Patients are usually in normal sinus rhythm in the first three decades of life, after which atrial arrhythmias including atrial fibrillation and supraventricular tachycardia may appear

• Pulmonary hypertension with the development of right ventricular disease

• Eisenmenger syndrome with reversal of shunt

• Paradoxical embolus

• Infective endocarditis in patients with ostium primum defects only

• Recurrent pulmonary infections.

How is pregnancy tolerated in a women with an atrial septal defect?

Pregnancy is usually well tolerated in uncomplicated atrial septal defects. However, when complicated by significant pulmonary hypertension, there is increased maternal and fetal morbidity and mortality and hence pregnancy should be avoided in Eisenmenger syndrome. Rapidly progressive pulmonary vascular disease may develop during pregnancy and, therefore, routine closure of atrial septal defect is recommended before pregnancy.

How would you manage an uncomplicated atrial septal defect?

• When detected in early childhood, surgical closure is recommended between the age of 5 and 10 years to prevent the late onset of either right ventricular failure, atrial arrhythmias or right heart failure.

• In adults, small ASDs can be left alone, although many believe all ASDs must be closed. Those operated on before the age of 25 years have an excellent prognosis and one may anticipate normal long-term survival, but older patients require regular supervision. In a recent study, surgical repair of atrial septal defects in middle-aged and elderly patients was found to improve longevity and reduce functional limitation caused by heart failure and was, therefore, superior to medical treatment. However, the risk of atrial arrhythmias, especially fibrillation and flutter, and the attendant risk of thromboembolic events were not reduced by closure of the defect.

• Left-to-right shunt saturations of 1.5:1 or more require surgical closure to prevent right ventricular dysfunction.

• Other indications for surgery include evidence of pulmonary vascular reactivity when challenged with pulmonary vasodilators or a lung biopsy with pulmonary arterial changes being potentially reversible.

• A history of a cryptogenic cerebrovascular event in the presence of a small ASD with right-to-left shunting is also recommended for closure.

• Closure in adults results in a reduction in right ventricular size and improves symptoms.

More recently, ASDs are being occluded by transcatheter button or ‘clam-shell devices’, particularly when the ASD is under 35 mm in diameter and in patients who have a sufficient (>5 mm) rim of surrounding atrial tissue present. Percutaneous closure of secundum ASD is safe (periprocedural morbidity <10%, periprocedural mortality 0%), highly effective (procedural success >95%) and durable. Periprocedural and long-term morbidity and mortality are particularly low in patients whose defect is closed when patients are under <25 years of age. Even in older individuals, however, closure is recommended to reduce morbidity and mortality. During long-term follow-up after successful closure, atrial tachyarrhythmias may become manifest. The next generation of percutaneous devices would be biodegradable devices

Is prophylaxis against infective endocarditis recommended in atrial septal defect?

Prophylaxis against infective endocarditis is not recommended for patients with atrial septal defects (repaired or unrepaired) unless a concomitant valvular abnormality (e.g. mitral valve cleft or prolapse) is present.

What do you know about the embryology of atrial septal defect?

There are seven septa involved in the partitioning of the heart: three form passively (i.e. when an area of tissue forms a septum because of the rapid growth of contiguous tissue) and these include septum secundum at the atrial septum, the muscular portion of the ventricular septum and the aorticopulmonary septum. The actively formed portions of the septums of the heart include the septum of the atrioventricular canal, the conal septum and the truncal septum. The atrial septum begins as a passively formed septum; however, active growth from the endocardial cushions completes the septum.

What do you know about ostium primum defects?

They are associated with endocardial cushion defects often resulting in cleft mitral valve (usually anterior leaflet) causing mitral regurgitation. The ECG shows right bundle branch block and left axis deviation (Fig. 22.2C). Treatment is surgical closure with repair of cleft mitral valve, which generally involves simple interrupted suture repair of the cleft or the addition of a mitral annuloplasty for annular reduction and stabilization.

Leonardo da Vinci’s description in 1513 of a ‘perforating channel’ in the atrial septum is believed to be the first recorded account of a congenital malformation of the human heart.

Rene Lutembacher, a French physician, described the Lutembacher syndrome in 1916.

Mary Holt, cardiologist, King’s College Hospital, London.

Samuel Oram, cardiologist, King’s College Hospital, London.

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