Examine this patient's heart.
Listen to her heart.
Ostium secundum defect (anatomically in the region of the fossa ovalis)
• Asymptomatic, particularly small detects with minimal left-to-right shunting. Moderate or large defects
often have no symptoms until the third or lourth decades despite substantial left-to-right shunting
(characterized by a ratio of pulmonary to systemic flow of 1.5 or more).
• Fatigue.
• Dyspnoea.
• Palpitations indicating atrial arrhythmias.
• Productive cough indicating recurrent pulmonary infections.
• Symptoms of paradoxical emboli.
• Right heart failure.
Ostium primum defect (in the lower part of the atrial septum)
Patients may develop symptoms and heart failure in childhood:
• Failure to thrive.
• Chest infections.
• Poor development.
In adults, in addition to the same symptoms as for secundum defect, the following
• Syncope: indicating heart block.
• Symptoms suggesting endocarditis.
• Diffuse or normal apical impulse.
• Left parasternal heave.
• Ejection systolic flow murmur in the left second and third intercostal space.
• Wide, fixed, split second heart sound (occasionally a slight movement of P2 occurs).
• Infrequently, a mid-diastolic murmur may be heard in the tricuspid area (indicating a large left-to-right
Look for signs of.'
• Pulmonary hypertension (Eisenmenger syndrome).
• Congenital defects of the thumb (Holt-Oram syndrome).
Note. Atrial secundum defect is often confused with pulmonary stenosis (P2 is soft, delayed and moves
with respiration).
This patient has an atrial septal defect (lesion) which is congenital in origin (aetiology); she is not in
cardiac failure and there is no reversal of shunt (functional status).
What are the types of atrial septal defect (ASD)?
• Ostium secundum detect accounts for 70% of the cases. The defect is in the middle portion of the atrial
septum and is usually 24 cm in diameter (incomplete right bundle branch block pattern, QRS axis
• 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).
• 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.
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?
There 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 to chromosome 12q2 (N Engl J Med 1994; 330:885-91 ).
At what age does reversal of the shunt occur?
Usually after the end of the second decade.
What is the mechanism of the fixed split second sound?
In normal individuals on inspiration there is a widening of the split between the two components of the
second sound due to a delay in closure of the pulmonary valve. In ASD the effect of respiration is
eliminated due to the communication between the left and right sides of the heart.
In which conditions is an abnormally widely split second sound present?
• ASD, VSD, pulmonary regurgitation (clue to increased right ventricular volume). • Pulmonary stenosis
(due to increased right ventricular pressure).
• Right bundle branch block (due to right ventricular conduction delay).
• Mitral regurgitation, VSD (due to premature left ventricular emptying).
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 con-tiguous tissue); these include the septum
secundum at the atrial septum, the mus-cular portion of the ventricular septum and the aorticopulmonary
septum. The actively formed portions of the septa of the heart include the septum of the atrio-ventricular
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 is Lutembacher syndrome?
ASD with an acquired rheumatic mitral stenosis (Arch Mai Coeur 1916; 9: 237).
What is Fallot's trilogy?
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.
• In ostium primum defects left axis deviation also occurs, whereas a junctional or low atrial rhythm
(inverted P waves in inferior leads) occurs in sinus venosus defects.
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 right ventricle and right atrium.
• 'Hilar dance' on fluoroscopy.
• Transthoracic echocardiography visualizes ostium secundum and primum defects but usually does
not identify sinus venosus defects.
• Sensitivity can be enhanced by injecting microbubbles into a peripheral vein. after which the
movement across the defect can be seen.
• Trans-oesophageal 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
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 ASD?
• 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, alter 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 woman with ASD?
Pregnancy is usually well tolerated in uncomplicated atrial septal defects; however, when the defect is
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, therefore routine closure of atrial septal
defect is recommended before pregnancy.
How would you manage an uncomplicated atrial septal defect?
Early childhood
If the defect is detected in early childhood, surgical closure is recommended between the ages of 5 and
10 years to prevent the late onset of either right ven-tricular failure, atrial arrhythmias or right heart
In adults
• Small ASDs can be left alone, although many believe that all ASDs must be closed. Those operated
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 due to heart failure, and is therefore superior to medical treatment. However, the risk of atrial
arrhythmias, especially fibrillation and flutter, and the attendant risk of thromboembolic events was 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
• 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'.
Is prophylaxis against infective endocarditis recommended in ASD?
Prophylaxis against infective endocarditis is not recommended for patients with atrial septal defects
(repaired or unrepaired) unless a concomitant valvular abnor-mality (e.g. mitral valve cleft or prolapse)
is present.
keonardo 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% Culluge Hu~pltdI, London.
Samuel Oram, cardiologist, King's College Hospital, London.