PATIENT STORY

A 35-year-old woman presented to the Adult Congenital Heart Disease Clinic 1 month after successful caesarean section (C-section) of her second child. A C-section was performed only as a result of fetal distress. She reported that compared to her prior pregnancy, symptoms of increasing shortness of breath in the third trimester that persisted postpartum. At the time of her initial outpatient clinic visit she experienced dyspnea with routine activities.

Her physical examination revealed the following vital signs: blood pressure (BP) 111/72 mm Hg, heart rate (HR) 74 bpm with 98% oxygen saturations in room air. Chest examination demonstrated no evidence of a right ventricular (RV) lift or heave. Cardiac examination demonstrated a regular rate and rhythm with a normal S1 and a fixed, split S2. The P2 component of the second heart sound was not accentuated. There was a soft II/VI systolic ejection murmur best appreciated at the left, upper sternal border. No diastolic murmurs, rubs, or gallops were heard. Extremities were warm and well perfused without clubbing, cyanosis, or edema.

A 12-lead electrocardiography (ECG) demonstrated a normal sinus rhythm, normal axis, and incomplete right bundle branch pattern (Figure 2-1). A transthoracic echocardiogram (TTE) demonstrated right atrial and ventricular enlargement (Figures 2-2 and 2-3) as a consequence of a large atrial septal defect, secundum type.

CASE EXPLANATION

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  Patients with an atrial septal defect (ASD) often have fixed splitting of the second heart sound. However, its absence does not exclude an ASD. The absence of a loud P2 component of the second heart sound minimizes the possibility of pulmonary hypertension. The systolic ejection murmur is consistent with increased pulmonary blood flow.

  
  
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  The incomplete right bundle branch block pattern on 12-lead ECG suggests right ventricular volume overload.

  
  
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  Findings of right atrial and ventricular enlargement on echocardiogram should prompt an evaluation for possible ASD.

EPIDEMIOLOGY

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  ASDs are common and can present at any age. Interatrial communications are the third most common type of congenital heart defect and the type most likely to be diagnosed in adulthood.

  
  
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  Female gender constitutes 65% to 75% of patients with secundum ASDs.¹

ANATOMY

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  There are 3 major types of interatrial communications: ostium secundum, ostium primum, and sinus venosus defects.¹ The secundum defect is a true defect of the atrial septum and it involves the region of the fossa ovalis. The ostium primum defect is within a spectrum of defects known as atrioventricular (AV) septal defects. Finally, the sinus venosus defect is located at the junction of the right atrium and superior vena cava and often associated with partial anomalous pulmonary venous return, most often of the right sided pulmonary veins.

  
  
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  Uncommon types of ASD include the coronary sinus defect and the inferior vena cava form of ASD.

  
  
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  Down syndrome is associated primarily with AV septal defects, but secundum defects occur with increased frequency.¹ Ostium primum defects have been associated with both DiGeorge and Ellis-van Creveld syndromes.

  
  
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  ASDs are the most common cardiac manifestation of Holt-Oram syndrome, which has been caused by mutation of TBX5.²

ETIOLOGY AND PATHOPHYSIOLOGY

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  Failure of normal development of the septum secundum between the left and right atrial chambers will result in a secundum-type ASD that permits blood to flow in either direction (left to right or right to left).³

  
  
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  Flow across an interatrial communication is determined in part by the size of the defect and in part by the relative ventricular compliances. Small defects (usually less than 8-10 mm) can be restrictive and limit both blood flow and pressure transmission.

  
  
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  Flow across a large, unrestrictive defect is dependent on the difference in compliance between the right and left ventricle, rather than the pressure difference between the atria. Since the RV compliance is usually higher than LV, shunt flow is from left to right across the defect. The shunt causes volume loading of the right heart, resulting in both right atrial and right ventricular enlargement.

  
  
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  Increased pulmonary blood flow over time can damage the pulmonary vascular endothelium leading to an increase in pulmonary vascular resistance called pulmonary vascular obstructive disease.

DIAGNOSTIC TESTING

Clinical Presentation/History

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  The history and clinical examination are pivotal to determine the presence of key clinical features associated in the adolescent or young adult with unoperated ASD.

  
  
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  Clinical features to identify include shortness of breath or palpitations due to atrial arrhythmias as the presenting symptoms, cardiac enlargement on chest x-ray (CXR), or a heart murmur is detected.

  
  
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  The clinical examination should document evaluation of the right ventricular impulse if present, the presence of a wide and fixed split second heart sound, commonly associated in ASD physiology, a pulmonary systolic ejection murmur at the left upper sternal border, and the presence of an accentuated pulmonary component of the second heart sound. This last physical examination finding is of great importance as this may represent increased pulmonary arterial pressure in the unoperated adult with ASD physiology.

ECG

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  A 12-lead ECG when obtained may show right-axis deviation and incomplete right bundle branch block pattern (rSr′ or rsR′).⁴ A complete bundle branch block is not uncommon with increasing age.

  
  
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  The presence of an abnormal P-wave axis may suggest the finding of a sinus venosus ASD. Left-axis deviation (moderate to extreme) may suggest a primum ASD.

Echocardiography

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  A transthoracic echocardiogram often confirms the diagnosis of ASD through a combination of both color Doppler interrogation and a wide variety of views that include subcostal, parasternal, and apical 4-chamber views.

  
  
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  Ostium secundum defects are best visualized in the midportion of the atrial septum from the subcostal 4-chamber view. Typically, these defects are bordered on all sides by atrial septal tissue. They are differentiated from the sinus venosus defect as this defect is located in the most posterior and superior location of the atrial septum and no tissue is visualized between the defect and the posterior right atrial wall. Often with sinus venosus–type defect, one or more pulmonary veins often drain anomalously to the right atrium.

  
  
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  Atrial septal defects are often difficult to diagnose using the apical 4-chamber view alone. This is because the atrial septum is parallel to the ultrasound beam, and as a result, artifactual dropout is frequently noted in the region of the atrial septum. Therefore, in patients with poor acoustic windows (eg, obese, pregnant patient) where subcostal windows cannot be obtained, the atrial septum can be visualized from the parasternal window by sliding the transducer to a “low parasternal 4-chamber view” to image the atrial septum nearly perpendicular to the sound beam (Figure 2-4A).

  
  
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  Echocardiography is often the noninvasive imaging modality of choice to assess the atrial septum in the assessment of the adult patient with suspected ASD. However, complementary imaging with cardiac magnetic resonance has become increasingly utilized in the adult congenital patient population to provide information to clarify the nature of the defect, nature of the shunt (Qp:Qs), biventricular size and function, and associated defects, particularly anomalous pulmonary venous abnormalities⁵ (Figure 2-4B).

Cardiac Catheterization

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  Cardiac catheterization is no longer utilized to make a diagnosis or evaluate the anatomy of the ASD.

  
  
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  Cardiac catheterizations may be performed to determine patient suitability for transcatheter closure of the ASD (see later).

MANAGEMENT

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  Patients with a significant ASD, such as the case outlined above with signs of right heart dilation, should be offered elective closure soon after the diagnosis of ASD is established, irrespective of age.

  
  
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  Potential benefits of ASD closure include improved exercise capacity and functional class. Closure of ASD prevents both the development of right heart failure and pulmonary arterial hypertension. Although the risk of these complications is relatively small, it is inversely related to the age of patient at time of ASD closure.

  
  
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  Indications for ASD closure include the following¹:

  
  
  
  
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    Right atrial and ventricular enlargement identified by noninvasive imaging studies (transthoracic echocardiography, cardiac magnetic resonance, computed tomography angiography)

    
    
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    ASD greater than 10 mm

    
    
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    No evidence of advanced pulmonary hypertension

    
    
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    Qp:Qs greater than 1.5:1 measured by transthoracic echocardiography, cardiac magnetic resonance or cardiac catheterization

  
  
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  However, several important caveats should be kept in mind as to why an ASD should not be closed include the following:

  
  
  
  
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    Conservative management of the small ASD (<10 mm) without evidence of right heart enlargement on noninvasive imaging studies.

    
    
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    Advanced pulmonary arterial hypertension that requires the ASD as a physiologic “pop-off.” Such patients often demonstrate cyanosis at rest and increasing cyanosis during peak exercise.

    
    
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    Similarly, the ASD that serves as a pop-off in the presence of severe left ventricular (LV) systolic dysfunction.

    
    
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    ASD that is identified during pregnancy should be followed and when appropriate, therapy may be deferred approximately 6 months postpartum.

  
  
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  All secundum ASDs should be considered for transcatheter closure with currently available devices.

  
  
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  Defects up to 40 mm in diameter can be considered for device closure with multiple different closure devices including the Amplatzer Septal Occluder (ASO; AGA Medical Corp., Golden Valley, Minnesota, USA) device guided by transesophageal or intracardiac echocardiography⁶ (Figures 2-5 and 2-6).

  
  
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  These imaging techniques are often performed simultaneously to evaluate those patients with inadequate septal rims that may not permit stable device deployment, defects in close proximity to the atrioventricular valves, the coronary sinus, or those with defects in close proximity to the vena cava. Patients with anatomy unsuitable for transcatheter intervention should be considered for surgical repair.

  
  
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  Otherwise, device closure is considered a safe and effective procedure with reported complications such as cardiac perforation or device embolization occurring in fewer than 1% of patients.⁷

FOLLOW-UP

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  Currently, there is no consensus available for appropriate follow-up of the adult late after ASD device closure. Although device-related complications are rare (device migration, erosion, or other complications), this patient population should be evaluated periodically.

  
  
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  The American College of Cardiology/American Heart Association 2008 Guidelines for the Management of Adults with Congenital Heart Disease recommends evaluation 3 months to 1 year after device closure and periodically thereafter.⁸

LONG-TERM COMPLICATIONS

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  Atrial arrhythmias (atrial flutter or fibrillation) are very common in older adults with large ASDs. In a surgical series reported by Roos-Hesselink et al., demonstrated that pre- and postoperative risk of atrial flutter and fibrillation correlated closely with patient’s age above 40 years.⁹ Patients who undergo repair of an atrial communication prior to 25 years of age appear to have a normal lifespan and low risk for pulmonary hypertension and arrhythmias.

  
  
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  One may speculate that increased utilization of device closure at a younger age may reduce the atrial arrhythmia burden in this patient population.

PATIENT STORY

A 24-year-old man with a history of a small, perimembranous ventricular septal defect (VSD) presents to the Adult Congenital Heart Disease Clinic for initial evaluation and consultation. He reports normal exercise tolerance and no evidence of functional decline since his last outpatient visit with his pediatric cardiologist several years ago. He denies symptoms of palpitations or syncope.

Physical examination revealed the following vital signs: BP 118/70 mm Hg, HR 62 bpm with oxygen saturations of 100% on room air. He is a well-appearing, well-built young adult man. Chest examination shows a normal active precordium. On auscultation there is a normal S1 and physiologic split S2 with a harsh, grade III/VI S1 coincident or holosystolic murmur best heard at the left sternal border in the fourth intercostal space. No diastolic murmurs, rubs, or gallops are appreciated. Normal pulses are noted throughout all extremities. No clubbing, cyanosis, or edema was appreciated and his extremities were warm and well perfused.