Ostium Secundum Atrial Septal Defects Clinical Presentation

Updated: Sep 12, 2019
  • Author: Ira H Gessner, MD; Chief Editor: Syamasundar Rao Patnana, MD  more...
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Presentation

History

Patients with ostium secundum atrial septal defects rarely have symptoms resulting directly from the defect. Decreased exercise tolerance in relation to peers may occur in older children and young adults. Some reports suggest that children with secundum atrial septal defects are smaller than other children; if so, this is an association. A cause-and-effect relationship has not been established.

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Physical

Patients are acyanotic and may have a slender build. Respirations are normal except in the young infant, in whom mild tachypnea may occur.

The jugular venous pulse demonstrates equal a and v waves when the defect is large enough to allow equilibration of right and left atrial pressure. A right ventricular lift occurs along the lower left sternal edge, and a mild precordial bulge may be present in the same location, both caused by right ventricular dilation. A pulmonary artery systolic impulse may be felt at the upper left sternal edge. The normal left ventricular apical impulse may be absent because the left ventricle is displaced posteriorly because of the dilated anterior right ventricle. The first heart sound may be split. This is not a particularly helpful observation except that it should not be confused with the presence of a pulmonary ejection sound.

A systolic ejection murmur is found over the pulmonary trunk in the second left intercostal space. This murmur peaks in mid systole and is never more than grade 2-3/6. If a thrill is palpated in this location, the patient likely has pulmonic valve stenosis. The murmur radiates well over both lung fields. This murmur, by itself, is indistinguishable from an innocent pulmonic flow murmur. Significance of the systolic murmur depends upon identification of an abnormal second heart sound (S2) and a diastolic murmur. The S2 is widely split, and respiratory variation in the splitting interval cannot be identified.

Indeed, with a large shunt caused by a secundum atrial septal defect, the splitting interval does not vary at all with respiration; it is fixed. Wide fixed splitting of S2 typically occurs with a large atrial shunt caused by an atrial septal defect. Identifying by auscultation alone that S2 splitting is fixed, as opposed to very wide but with some respiratory variation (eg, with right bundle branch block), may be difficult. Diagnosis of an atrial septal defect by auscultation requires identification of the characteristic diastolic murmur.

A medium frequency mid diastolic murmur at the lower left sternal edge occurs with rapid ventricular filling of the right ventricle after the tricuspid valve opens. The murmur is never more than grade 1-2/6, and identifying it usually takes effort. If the shunt is large enough to cause wide, seemingly fixed, splitting of S2, this murmur should be audible.

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Causes

Isolated secundum atrial septal defect occasionally demonstrates familial inheritance in an autosomal dominant pattern, particularly when associated with prolonged atrioventricular conduction (ie, prolonged PR interval on ECG). Familial secundum atrial septal defect also occurs in Holt-Oram Syndrome.

Even when not associated with an identifiable inheritance pattern, the incidence of secundum atrial septal defect is 2-3 times higher in first-degree relatives than in the general population. [11] A PTPN11 gene mutation has been identified in patients with Noonan syndrome in whom heart defects occur in 85%. [12] The most prevalent defects are secundum atrial septal defect and pulmonary valve stenosis; these defects were significantly associated with this gene mutation. Evidence suggests that increased folic acid intake in the general population by fortification of grain products can produce a 20% reduction in occurrence of atrial septal defects. [13]

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