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SECTION I - ATRIAL SEPTAL DEFECT

Part I - Background Information

Atrial septal defect (ASD) includes the following types: ostium secundum, sinus venosus and coronary sinus. Ostium primum [partial atrioventricular septal defect (AVSD)] is discussed in Section III.

A "clinically significant" ASD:
  • Causes right heart volume and sometimes pressure overload.
  • May cause exercise limitation.
  • May be associated with atrial arrhythmias (atrial fibrillation, atrial flutter, usually over age 30).
  • May cause late right heart failure (usually over age 40).
  • May permit paradoxical embolism resulting in TIA/stroke.
  • May lead to pulmonary hypertension, although pulmonary hypertension may also develop from other causes.


Part II - Prevalence and Genetics

Although usually sporadic, some ASDs are inherited as an autosomal dominant and/or are associated with other congenital lesions e.g. Holt-Oram syndrome.

Part III - History and Management of Unoperated Patients

Most patients with "significant" ASDs (see above) will eventually develop symptoms, although the timing of symptom development is unpredictable and may be after the 5th decade.

The most common symptoms are exercise intolerance (dyspnea and fatigue) and symptomatic supraventricular arrhythmias (atrial fibrillation, atrial flutter, or sick sinus syndrome).

Any condition causing reduced left ventricular compliance (e.g. left ventricular hypertrophy due to hypertension, cardiomyopathy or myocardial infarction) will tend to increase the left-to-right shunt through an ASD and worsen symptoms. Their prevention and/or early treatment should be addressed.

In Lutembacher syndrome (congenital ASD with acquired mitral stenosis), the mitral valve obstruction increases the left-to-right shunt. The combination of lesions is usually poorly tolerated.

Part IV - Diagnostic Recommendations

An adequate diagnostic workup:
  • Documents the presence and type of ASD(s).
  • Determines the size (diameter) of the defect(s).
  • Determines the functional importance of the defect either by:
    1. shunt size (Qp/Qs).
    2. right ventricular size, function and volume overload and right atrial size
    3. pulmonary artery pressures and if elevated, pulmonary vascular resistance.
  • Identifies other associated conditions that may influence management (e.g. anomalous pulmonary venous connection, significant valve disease; or coronary artery disease).
The initial workup should include at a minimum:
  • A thorough clinical assessment.
  • ECG.
  • Chest x-ray.
  • Transthoracic echo-Doppler evaluation by an appropriately trained individual.
  • Transesophageal (TEE) echo/Doppler examination to prove the existence of an ASD, better define its/their location(s) and size(s) and shape(s), assess pulmonary venous connections, and to evaluate the cardiac valves, if this information is not provided by transthoracic echocardiography (TTE). A transesophageal examination is essential to determine if the ASD is suitable for device closure and must be performed prior to the procedure.
  • Resting oxygen saturation.
The diagnostic workup may require:
  • Heart catheterization (if determination of pulmonary artery pressures and resistances is of concern; to assess pulmonary vascular reactivity; or delineate anomalous pulmonary venous connections).
  • Coronary angiography in patients at high risk of coronary artery disease or in patients over the age of 40 years if surgical repair is planned.
  • Magnetic resonance imaging (MRI) to prove the existence of an ASD or to assess pulmonary venous connections if doubts remain after other imaging modalities. MRI can also be used to estimate Qp/Qs.
  • Oxygen saturation with exercise if there is any suggestion of pulmonary hypertension. If there is severe pulmonary hypertension or resting desaturation of < 85%, the patient should not be exercised.
  • Open lung biopsy should only be considered when the reversibility of the pulmonary hypertension is uncertain from the hemodynamic data. It is potentially hazardous and should be done only at centres with substantial relevant experience in CHD.
Part V - Indications for Intervention

Indications for closure are debated. There is little proof of firm guidelines. We offer a consensus view.

The mere presence of a "significant" ASD may warrant intervention especially if there is a significant shunt (> 2:1).

If pulmonary hypertension is present [pulmonary artery pressure (PAP) > 2/3 systemic arterial blood pressure (SABP), or pulmonary arteriolar resistance > 2/3 systemic arteriolar resistance], there must be a net left-to-right shunt of at least 1.5:1; or evidence of pulmonary artery reactivity when challenged with a pulmonary vasodilator (e.g. oxygen, nitric oxide and/or prostaglandins); or lung biopsy evidence that pulmonary arterial changes are potentially reversible (Heath Edwards grade II-III or less).

A cryptogenic cerebrovascular event in the presence of a small ASD or PFO and right-to-left shunting demonstrated on contrast echo. This indication is "softer" than the others.

Grade: C
Level: III
Refs: 3-8

If closure of atrial septal defects is being planned, it is recommended that closure be performed without undue delay (< 25 years for mortality benefit, and probably before 40 years for arrhythmia benefit). As a rule, younger patients have a better outlook after repair (3,9,10).

Transvenous pacing should be avoided in patients with unrepaired ASDs, since paradoxical emboli may occur. For the same reason venous thromboemboli from any source are a potential hazard.

Grade: C
Level: V
Refs: 11,12


Part VI - Surgical/Interventional Technical Options

Device closure may now be offered as an alternative to surgical closure to patients with secundum ASD of up to 36-38 mm in diameter. The intervention should be performed under general anesthesia with transesophageal guidance in centres and by individuals with a commitment to the technique and to its clinical evaluation.

Grade: C
Level: V
Refs: 13-17

Surgical closure may also be offered, and may be especially attractive should the patient prefer the time-honoured surgical approach, or especially if atrial arrhythmia surgery (atrial maze procedure for atrial fibrillation and radiofrequency or cryoablation for atrial flutter) may be offered concurrently.

The availability of an inframammary or right mini thoracotomy or mini sternotomy approach to a typical secundum ASD should be made known to potentially interested patients considering surgery.

Patients with a sinus venosus ASD or ostium primum ASD cannot be closed by percutaneous devices and should be surgically repaired by congenital heart surgeons.

Grade: C
Level: V
Refs: 18,19


Part VII - Surgical/Interventional Outcomes

Device closure.

Early and intermediate follow-up is excellent after device closure. The intermediate results are comparable to surgery with a high rate of shunt closure and few major complications. Long-term outcome is unknown. Longer follow-up is needed to determine the incidence of arrhythmias and thromboembolic complications late after device closure.

Functional capacity improves and supraventricular arrhythmias are better tolerated and more responsive to pharmacologic management.

Surgical closure.

For secundum ASD without pulmonary hypertension surgical closure should result in a very low (< 1%) operative mortality. Early and long-term follow-up is excellent.

Following surgical repair, pre-operative symptoms, if any, should decrease or abate. Pre-existing atrial flutter and fibrillation may persist unless cryo- or radiofrequency ablation (for the former) or a right atrial maze including pulmonary vein encirclement (for the latter) has been performed. Likewise, atrial flutter and/or fibrillation may arise de novo after repair, but are better tolerated and often more responsive to antiarrhythmic therapy.

Left ventricular failure may occur in patients with associated cardiovascular disease (e.g. coronary artery disease, hypertension, mitral valve incompetence).

Post-operative ASD patients are especially prone to cardiac tamponade for the first several weeks after surgery.

Grade: Consensus


Part VIII - Arrhythmias

Late atrial fibrillation may occur in up to 1/3 of patients, especially in adults older than 40 years and/or if atrial arrhythmias were present pre-operatively. Physicians may elect to anticoagulate these high risk patients with warfarin for the first 6 post-operative months, as they are at risk of atrial fibrillation and stroke. Anticoagulation can probably be discontinued thereafter, if they remain arrhythmia-free and there are no other risk factors.

The presence of preoperative atrial flutter/fibrillation may warrant surgical closure of the defect with concomitant cryosurgical/ablative therapy or an atrial maze procedure.

Grade: C
Level: V
Ref: 20


If atrial fibrillation occurs, both anticoagulants and antiarrhythmic therapy are usually indicated.

Grade: A
Level: I
Ref: 21


Part IX - Pregnancy

Pregnancy is well tolerated in patients after ASD closure. Pregnancy is also well tolerated in women with unrepaired ASDs, but the risk of paradoxical embolism is increased during pregnancy as well as the post partum period.

Pregnancy is contraindicated in Eisenmenger syndrome because of the high maternal (up to 50%) and fetal (up to 60%) mortality.

Grade: C
Level: V
Ref: 22


Part X - Follow Up

The following ASD patients require periodic follow up by an ACHD cardiologist.
  • Those repaired as adults.
  • Elevated pulmonary artery pressures at the time of repair.
  • Atrial arrhythmias pre- or post-operatively.
  • Ventricular dysfunction pre-operatively.
  • Co-existing heart disease (e.g. coronary artery disease, valvular heart disease, hypertension).
  • Those with device closure need follow-up in specialized centres with serial ECGs and echocardiograms to determine the late outcomes of these new techniques.
Endocarditis prophylaxis and aspirin are recommended for 6 months following device closure.

Grade: Consensus