Atrioventricular Canal Defect

• • A congenital heart lesion that increases pulmonary artery (PA) blood flow

  • Causes left to right shunt, results in lung infection, pulmonary vascular congestion, PA hypertension, right heart failure, pulmonary vasoconstriction, pulmonary vascular obstructive disease

  • Eisenmenger syndrome: Increased pulmonary hypertension to such extent that left to right shunt ceases and shunt becomes right to left, requiring heart-lung transplant

  • Inhaled nitric oxide, oxygen, or IV tolazoline reverses PA vasoconstriction

  • PA band is palliative and can reduce PA flow to alleviate RV failure and progression of pulmonary hypertension

  • Deficiency of tissue in central region of heart (lower atrial septum-septum primum, mitral valve, tricuspid valve)

  • Defect in endocardial and conal tissue development

  • Range of defects possible

  • Partial AV canal defect: Septum primum atrial septal defect (ASD), deficient lower atrial septum only

  • Transitional AV canal defect: Intermediate form with ASD and minor deficiency in upper ventricular system

  • Complete AV canal defect: ASD and severe valve anomalies

  • Associated with left superior vena cava (SVC), additional ventricular septal defect (VSD), anomalous pulmonary venous connection, patent ductus arteriosus (PDA), tetralogy of Fallot

Epidemiology

• • Can occur in patients with trisomy 21 (Down syndrome) who are more prone to pulmonary vascular obstructive disease

Symptoms and Signs

• • Heart failure common in infancy

  • Cardiomegaly present

  • Blowing pansystolic murmur (varies)

  • Loud S2, fixed split

  • Left to right shunt modified by mitral regurgitation

  • Severity depends on structural defects

  • Partial defect may be asymptomatic

  • Pulmonary hypertension and mitral regurgitation natural history

Laboratory Findings

• • ECG: Left axis deviation and counterclockwise frontal QRS vector loop

Imaging Findings

• • Echocardiography best for diagnosis

  • Catheterization for patients older than 6 mos if pulmonary hypertension is a concern

• • Must define extent of canal defect to plan correction

• • Echocardiography

  • Cardiac catheterization if patient is older than 6 months

• • Timing of correction indicated by degree of anomaly and symptoms

  • Partial defect: Patch closure

  • Complete defect: Patch closure of septal defects and reconstruction of valves (suture closure of valve with or without annuloplasty)

Surgery

Indications

• • Defect warrants repair

  • Complete defect: Repair by 6 months of age

  • -Repair by 1 year of age in other less severe types

  • Mitral regurgitation: Repair regardless of age

Complications

• • Postoperative mitral regurgitation: 10-40%, 10% require reoperation

  • Many patients will require additional mitral valve work in adulthood

Prognosis

• • Mortality varies with defect and age

  • Partial defect: 10-year survival is 98%

  • Complete defect:

  • -Operative mortality is 3-5%

    -10-year survival is 90%

    -< 1 year life expectancy from congestive heart ...