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

  • Atrial septal defect.

  • Ventricular septal defect.

  • Patent ductus arteriosus.

All three conditions are covered sequentially in this chapter.

Atrial Septal Defect

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).


Atrial septal defect with flow from the left atrium to the right atrium as depicted by the red arrow. (Reprinted with permission, Cleveland Clinic Center for Medical Art & Photography © 2012. All Rights Reserved.)


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.


  • 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

  • There are three major types of atrial septal defects.

    • 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.

    • 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.

    • 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.

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

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

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

Risk Factors

  • ASDs may occur on a familial basis.

  • Holt-Oram syndrome and Ellis ...

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