Atrioventricular Canal Defects

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Infant with congestive heart failure

• Physical findings include primum atrial septal defect (ASD) plus mitral (left-sided atrioventricular [AV] valve) regurgitation

• Cardiac imaging shows a common AV valve annulus, 1 or more abnormal AV valves, and defects at the atrial or the ventricular level that can be detected in utero

GENERAL CONSIDERATIONS

• Also called endocardial cushion defect

• AV canal defect is a spectrum of lesions associated with maldevelopment of the AV septum and adjoining AV valves

• A partial AV canal defect has a cleft mitral valve along with a defect in the inferior portion of the AV septum

• Complete AV canal defect is a complex combination of:

  • – An ASD

  • – A nonrestrictive ventricular septal defect

  • – Complex morphology of a common AV valve

• The condition is associated with other congenital anomalies such as:

  • – Patent ductus arteriosus

  • – Tetralogy of Fallot

  • – Double-outlet right ventricle

  • – Transposition of the great arteries

  • – Unroofed coronary sinus with left superior vena cava

  • – Asplenia or polysplenia syndromes

• Very common in Down’s syndrome (approximately 20%)

• Large defects are usually repaired in the first 3–6 months of life

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Complete AV canal defects:

  • – Presentation under age 1 year with a history of frequent respiratory infections and poor weight gain

  • – Heart failure in infancy common

• Partial AV canal defects:

  • – Presentation may be later, with dyspnea and signs and symptoms of right ventricular (RV) failure due to right-sided volume overload

• Patients with persistent complete AV canal defects > age 2 years invariably develop pulmonary vascular disease and possibly Eisenmenger’s syndrome

• Arrhythmias

PHYSICAL EXAM FINDINGS

• Findings similar to patients with ASDs but may include the following:

  • – Holosystolic apical murmur of mitral regurgitation

  • – Holosystolic lower left sternal border murmur of interventricular communication

DIFFERENTIAL DIAGNOSIS

• Secundum ASD with mitral regurgitation due to rheumatic disease or prolapse

• Ventricular septal defect

• Other causes of heart failure

DIAGNOSTIC EVALUATION

ELECTROCARDIOGRAPH

• First-degree AV block

• Complete right bundle branch block

• Left anterior fascicular block

• RV hypertrophy

IMAGING STUDIES

• Chest x-ray:

  • – Right atrial and ventricular cardiomegaly

  • – Prominent RV outflow tract

  • – Increased pulmonary vascular markings

• Echocardiographic features of a partial AV canal defect:

  • – Right atrial and ventricular enlargement

  • – Increased pulmonary artery flow velocity

  • – A defect in the inferior portion of the interatrial septum immediately adjacent to the AV valves, either of which may be deformed and incompetent

  • – The mitral valve is often cleft and sometimes has a double orifice

  • – Doppler findings of pulmonary hypertension may be present with or without RV dysfunction

• Echocardiographic features ...