Abstract
This chapter reviews the incidence, presentation and types of atrial septal defects. The pathophysiology and hemodynamic effects of atrial septal defects are discussed. The surgical and catheter-based interventions are reviewed in relation to the anesthetic considerations.
A six-year-old female presents for annual physical examination.
Her current vital signs are: blood pressure 98/62 mmHg; heart rate 97/min; respiratory rate 15/min; SpO2 100% on room air. On auscultation, there is a systolic murmur with a split S2. Upon further questioning, the mother reports that she does have some shortness of breath with strenuous activity.
Chest X-ray reveals prominent pulmonary vascular markings and mild enlargement of the right-sided cardiac silhouette. An EKG is performed showing right axis deviation and right ventricular hypertrophy. The patient is sent for transthoracic echocardiography revealing a 7 mm secundum type atrial septal defect.
What Is the Incidence of Atrial Septal Defects (ASDs)?
The incidence of atrial septal defects (ASDs) is approximately 50–100 per 100,000 live births. ASDs are the third most common congenital heart defect and have a female predominance. While most cases are sporadic, a familial inheritance appears in affected families. While most ASDs occur in isolation, they may occur in association with many genetic syndromes, e.g., Down, Holt–Oram, Noonan among others, or as part of more complex congenital heart disease (CHD).
What Is the Most Likely Age for Presentation?
ASDs may occur as isolated defects or as part of a larger continuum of congenital structural defects. It may take decades before an unrepaired ASD causes symptoms that necessitate cardiac evaluation. ASDs can often be diagnosed early in life by an astute clinician auscultating a murmur prompting further evaluation. ASDs associated with larger congenital heart defects, e.g., complete AV canal defects, are often diagnosed in the early neonatal period or prenatally.
Identify the Four Main Types of Atrial Septal Defects
ASDs are classified based on the anatomic location of the defect (Figure 61.1). The main types of atrial septal defects are:
Primum
Secundum
Sinus Venosus (SV)
Coronary Sinus
Describe the Formation of the Atrial Septum
The atrial septum primum begins to develop at around day 28 of gestation. It grows from the superior portion of the common atrium toward the central endocardial cushions. Septum secundum develops as an atrial infolding to the right of the septum primum. The inferior segment of the atrial septum is an upward extension of the endocardial cushions. The foramen ovale, a normally occurring atrial septal defect in fetal development, is a small opening in the septum primum.
Describe the Defect Associated with a Secundum Type ASD
A secundum ASD is really a defect in the septum primum. There are often one or more small holes in the septum primum in the center of the fossa ovalis. Secundum ASDs are the most common atrial septal defect (Figure 61.2).
Figure 61.2 Left: Subcostal transthoracic echocardiography demonstrating a secundum type ASD. Right: Cardiac catheterization pictorial of a patient with a moderate ASD. There is a “step up” in saturation from the superior vena cava (76%) to the right atrium (88%).
Describe the Defect Associated with a Primum ASD
A primum ASD, because of its association with the endocardial cushions, may involve a cleft within the anterior leaflet of the mitral valve. If severe, this defect may be addressed during surgical intervention (Figure 61.3).
