The three most important and common types of acyanotic congenital heart disease are:

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  Atrial septal defect.

  
  
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  Ventricular septal defect.

  
  
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  Patent ductus arteriosus.

All three conditions are covered sequentially in this chapter.

Patient Story

A 4-year-old recent immigrant from Nicaragua presents to her pediatrician for a well-child examination. She does not have any significant past medical history. On examination, she was found to have a normodynamic precordium, widely split and fixed S₂ and a grade 2/6 systolic ejection murmur in the pulmonary auscultation area. She is diagnosed with an atrial septal defect (ASD) (Figure 42-1).

Introduction

Any opening in the atrial septum is described as an ASD. Although many of these defects close spontaneously, early diagnosis and follow-up is essential in preventing sequelae from undiagnosed ASD’s.

Epidemiology

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  Atrial septal defects (ASD) account for 10 percent of all congenital heart disease and as much as 20 to 40 percent of congenital heart disease presenting in adulthood.^1,2

Etiology and Pathophysiology

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  There are three major types of atrial septal defects.

  
  
  
  
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    Ostium secundum defect is the most common type of ASD. It results from incomplete adhesion between the flap valve associated with the foramen ovale and the septum secundum after birth. It also includes patent foramen ovale, which results from abnormal resorption of the septum primum during the formation of the foramen secundum.

    
    
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    Ostium primum defects are the second most common type of ASD. This is a form of atrioventricular septal defect and is commonly associated with mitral valve abnormalities. These defects are caused by incomplete fusion of septum primum with the endocardial cushion.

    
    
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    Sinus venosus defect is the least common of the three. The defect is located along the superior (SVC type) or inferior (IVC type) aspect of the atrial septum. Anomalous connection of the right-sided pulmonary veins is common and should be expected in the SVC type. Abnormal fusion between the embryologic sinus venosus and the atrium causes these defects.

    
    
    
    
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      A clinically significant moderate to large defect, if undiagnosed and untreated, can cause enlargement of right atrium and right ventricle.

      
      
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      Dilation of the right atrium can also lead to the development of atrial arrhythmias.

      
      
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      Older patients may develop pulmonary vascular disease leading to Eisenmenger syndrome, which is the most significant long-term complication of an ASD.

Risk Factors

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  ASDs may occur on a familial basis.

  
  
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  Holt-Oram syndrome and Ellis van Creveld syndrome are associated with ASDs.

Diagnosis

Clinical Presentation

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  ASD can go undiagnosed for decades due to subtle physical examination findings and lack of symptoms.

  
  
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  Defects which are even moderate-to-large typically do not cause symptoms in childhood as in the previous vignette described.

  
  
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  Some patients however may manifest symptoms of easy fatigability, recurrent respiratory infections, or exertional dyspnea.

Physical Examination

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  Patients can have a hyperdynamic right ventricular impulse due to increased diastolic filling and large stroke volume.

  
  
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  A dilated pulmonary artery can cause a palpable pulsation and an ejection click.

  
  
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  S² is often widely split and fixed because of persistence of left to right shunting during inspiration as well as expiration causing delayed closure of the pulmonary valve.

  
  
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  A systolic ejection murmur heard in the pulmonary area is a result of increased right ventricular stroke volume across the pulmonary outflow tract.

  
  
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  The blood flow across the ASD does not cause a murmur at the site of the shunt because no substantial pressure gradient exists between the atria.

Ecg Findings

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  Patients with untreated clinically significant ASDs can have right axis deviation, RSR’ pattern suggestive of right bundle branch block of various degrees and right atrial enlargement (tall ‘p’ waves in the limb leads >2.5 mm).

  
  
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  The “crochetage” pattern is described as the presence of a notch in the apex of R waves in the inferior leads which is characteristic of an ASD (Figure 42-2).

Imaging

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  Definitive diagnosis is made with a transthoracic echocardiogram.

  
  
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  Doppler and contrast echocardiography can provide additional confirmation by visualizing atrial shunting.

Differential Diagnosis

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  Physical exam findings of systolic murmur over the pulmonary area with a widely split (but not fixed) S₂ can be found in patients with pulmonary stenosis.

Management

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  For practical purposes, any defect 8 mm or larger with evidence of left to right shunt should be closed when identified, even at a very young age, because such defects will likely never close spontaneously.^3–5 SOR A

  
  
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  Smaller defects (<3 mm) in asymptomatic patients can be followed clinically as a majority of them spontaneously close.⁶ SOR A

  
  
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  Closure can be achieved surgically or with device closure via catheterization.

  
  
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  The size of the lesion is the major determining factor regarding the type of closure, which can be used.

Referral

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  Children diagnosed with an ASD require referral to a pediatric cardiologist.

Prognosis

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  The prognosis for patients who are diagnosed with ASD and do not develop pulmonary vascular disease is generally good.

Follow-Up

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  Close follow-up of patients diagnosed with an ASD is essential in determining the need for an intervention or continued observation.