What is Type A Rastelli Atrioventricular Canal Defect (AVCD)?

Type A Rastelli Atrioventricular Canal Defect (AVCD)

Type A Rastelli AVCD is a specific anatomic classification of complete atrioventricular septal defect characterized by the superior (anterior) bridging leaflet of the common atrioventricular valve being divided and attached to the crest of the interventricular septum by chordae tendineae, with the left ventricular portion of this leaflet having attachments to the left side of the septum. 1

Anatomic Classification System

The Rastelli classification describes anatomic variations of the superior bridging leaflet of the common atrioventricular valve in complete AVSD 1:

• Type A (most common): The superior bridging leaflet is divided and has chordal attachments to the crest of the interventricular septum on the left ventricular side 1, 2
• Type B: The superior bridging leaflet is attached to an anomalous right ventricular papillary muscle 2
• Type C: The superior bridging leaflet is free-floating without septal attachments, extending across the ventricular septal defect 2, 3

Core Structural Features

Complete AVCD with Type A anatomy includes 1, 4:

• A common atrioventricular junction with single valve orifice
• Primum atrial septal defect (interatrial communication above the valve)
• Inlet ventricular septal defect (interventricular communication below the valve)
• Five leaflets of the common AV valve: anterior bridging, posterior bridging, left mural, right anterosuperior, and right inferior leaflets 1, 2
• Characteristic "goose neck" deformity of the left ventricular outflow tract due to anterior displacement 1

Clinical Significance

Type A represents the most favorable anatomy for surgical repair because the bridging leaflet attachments to the septum provide better structural support for valve reconstruction. 2

Key Management Points

• Requires surgical repair typically before 6 months of age to prevent irreversible pulmonary vascular disease and Eisenmenger physiology 1, 4
• The specific Rastelli type guides surgical technique for valve division and patch placement 1
• Type A anatomy allows for more straightforward two-patch repair technique compared to Types B and C 2

Long-term Complications Requiring Surveillance

Lifelong monitoring is essential for 1, 4:

• Left atrioventricular valve regurgitation (most common late complication requiring reoperation) 1
• Left ventricular outflow tract obstruction due to abnormal LVOT geometry 1
• Conduction abnormalities including late-onset complete heart block 1
• Residual shunts at atrial or ventricular level 4, 5

Diagnostic Imaging

Three-dimensional echocardiography allows clear visualization of all five leaflets, confirms the common annulus and absence of AV septum, and definitively classifies the defect as Type A by demonstrating the bridging leaflet attachments to the interventricular septum. 1

Associated Conditions

Type A Rastelli AVCD has strong associations with 1, 4:

• Trisomy 21 (Down syndrome) - most common syndromic association
• Other congenital cardiac lesions including tetralogy of Fallot, coarctation of aorta, and heterotaxy 1, 3