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Clinical manifestations, pathophysiology, and diagnosis of atrioventricular (AV) canal defects

Craig E Fleishman, MD
Aykut Tugertimur, MD, FACC
Section Editors
John K Triedman, MD
Heidi M Connolly, MD, FASE
Deputy Editor
Carrie Armsby, MD, MPH


Atrioventricular (AV) canal defects are a group of congenital cardiac defects involving the AV septum and AV valves (ie, mitral and tricuspid valves). They are also referred to as AV septal defects, endocardial cushion defects, or persistent AV ostium. Combinations of these anatomic abnormalities result in complete (both atrial and ventricular septal defects [ASD/VSD]) and partial (only ASD) forms that are manifested in varying clinical presentations.

The anatomy, pathophysiology, clinical features, and diagnosis of AV canal defects will be reviewed here. The management and outcome of patients with AV canal defects are discussed separately. (See "Management and outcome of atrioventricular (AV) canal defects".)


AV canal defects account for about 4 to 5 percent of congenital heart defects with a reported prevalence of 0.3 to 0.4 per 1000 live births [1,2]. AV canal defects in fetuses accounted for a larger proportion of detected congenital heart disease (CHD), approaching 18 percent of CHD cases based on data from large fetal echocardiographic series [3,4]. The male-to-female distribution of AV canal defect is approximately equal [5], and complete AV canal defects with both atrial and ventricular septal defects occur in half of the cases [1,2].

There is a strong association between AV canal defects and trisomy 21 (also referred to as Down syndrome), with a 40 to 50 percent risk of Down syndrome in fetuses in whom an AV canal defect is detected [6]. Nonsyndromic AV canal defects appear to be associated with maternal diabetes and obesity [7]. (See 'Trisomy 21' below.)


Overview — AV canal defects encompass a broad range of AV septal defects and abnormalities of the AV valves. An initial classification separates the different types of AV canal defects based on anatomical features (eg, complete versus partial form) and their impact on physiology. In addition, variations of complete AV canal defects are categorized by AV valve morphology (Rastelli classification) and relative ventricular size. These classifications are used to guide surgical management.

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Literature review current through: Nov 2017. | This topic last updated: Jan 14, 2016.
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