Atrioventricular Canal Defect

Seoul National University Hospital

Department of Thoracic & Cardiovascular Surgery

Atrioventricular Canal Defect

• Definition

A deficiency or absence of septal tissue immediately above & below

the normal level of the AV valves including the region normally occupied by the AV septum in heart with two ventricle and the AV valves are abnormal to a varying degree. Aortic valve is elevated, deviated anteriorly due to absence of usual wedged position of aortic valve above the AV valve.

AV septal defect AV defect ECD (Endocardial cushion defects) Ostium primum atrial septal defects Common AV orifice

Atrioventricular Canal Defect

• History Rogers, Edwards : Recognized in 1948

Wakai, Edwards : Term of partial and complete AV

canal defect in 1956

Rastelli : Described the morphology in 1966

Lillehei : 1st repair of complete AV canal defect in 1954

Morphology of A-V Canal Defect (I)

1. Interatrial communication 1) Ostium primum ASD 2) Common atrium entire limbus & fossa ovalis are absent

3) Absence of interatrial shunt rarely, due to complete attachment of Lt. AV valve to atrial septum

2. Interventricular communication 1) Partial form 2) Complete form 3. AV valves 1) Two AV valve orifice 2) Common AV valve orifice

3) Unusual AV valve

combination

4) Accessory orifice ; 5 %

5) Single papillary m.; 5 %

4. Ventricle

hypoplasia in 7%

5. Septal malalignment

6. LVOT or inflow obstruction

7. Conduction system

Lt axis deviation

Left Ventricular Outflow & Inflow Obstruction

• Incidence 1% in unoperated

Higher incidence after operation

• Etiology 1. Elongation & narrowing due to more extensive area

of direct fibrous continuity

2. Short, thick chordae that anchor to the crest of

ventricular septum

3. Bulging of anterolateral muscle bundle(m of Moulart)

4. Morphologically discrete subaortic membrane

or excrescences of aortic valve orifice

5. Abnormally positioned papillary muscle

Morphology of AV Canal Defect (II)1. Major associated cardiac anomalies 1) PDA(10%) 2) TOF(10%) 3) DORV(3%) 4) TGA(rarely) 5) Unroofed coronary sinus with Lt. SVC (6%, frequent in common atrium)2. Minor associated cardiac anomalies 1) ASD 2) Unroofed coronary sinus without Lt. SVC 3) Partially unroofed coronary sinus 4) Azygos extension of IVC3. Pulmonary vascular disease ; earlier onset than VSD4. Down syndrome 1) Rare in partial form & common in complete form (75%) 2) Lt-sided obstruction & associated anomalies less common 3) Frequent advanced pulmonary disease

Types of AVSD

AV Septal Defect

Partial AVSD

Complete AVSD

Clinical Features and Diagnostic Criteria

1. Pathophysiology 1) Shunt at atrial, ventricle level 2) AV valve incompetence . Prevalent in older patients with complete form . Partial : 10-15% . Complete : 20% (moderate), 15% (severe)2. Symptoms and Signs . Related to amount of shunt and AV valve regurgitation3. Chest radiography4. Electrocardiogram5. Two-dimensional echocardiogram6. Cardiac catheterization and cineangiogram7. Special situation and associated defects

Natural History of ECD

1. Incidence 1) 4% of CHD (30-40% in Down syndrome) 2) High incidence (14%) born to mother of ECD (other : 2-4%)2. Type of ECD 1) Partial form, mild AV valve incompetence . favorable, similar to large ASD 2) Partial form, significant AV valve incompetence . 20% symptomatic in infancy . Pulm. venous hypertension & shunt

3) Complete form . 80% unoperated on die by age 2 years . Pulmonary vascular disease under 1yr of age : 30% under 2yr of age : 80% under 3-5yr of age : 90%3. Mode of death 1) Refractory CHF, recurrent pulmonary infection 2) Valve incompetence and pulmonary vascular disease

Techniques of Operation

1. Direction

1) Closure of atrial communication

2) Closure of ventricular communication

3) Avoidance of damage to conduction

4) Creation of two competent valves

2. Technique

1) Repair of partial AV canal defect

2) Repair of complete AV canal defect

one - patch technique

two - patch technique

3) Repair of associated cardiac anomalies

c-AVSD ; Operative View

Partial AVSD

Complete AVSD (1)

Complete AVSD (2)

AVSD - Repair of Mitral Cleft

Results of Operation

1.Survival 1) early death 2) time related survival2. Mode of death 1) early : acute cardiac failure and pulmonary dysfunction 2) late : chronic or subacute cardiac failure3. Incremental risk factors for prematu

re death 1) earlier date of operation 2) functional class 3) prerepair AV valve incompetence 4) interventricular communication

5) accessory valve orifice 6) major associated cardiac anomalies 7) young age ; not now 8) Down syndrome 9) Single papillary m. 10) hypoplasia of ventricle4. Heart block & arrhythmia5. Functional class6. AV valve function7. LVOT obstruction8. Residual pulmonary hypertens

ion

Indications for Operation

1. Partial AV canal defect

Optimal age for operation is 1-2 years of age except

when CHF or growth failure is evident earlier in life.

2.Complete AV canal defect

Operation is indicated early in the 1st year of life

when the infants general condition is good,

repair can be delayed until 3-6 months of age.

Special Situation & Controversies

1. Pulmonary artery banding

2. Septal patches

1) Atrial

2) Ventricle

3. McGoon method of avoiding heart block

4. Fontan-type repair

Special Features of Postoperative Care

1. LAP is higher 6mmHg than CVP

suggest mitral valve stenosis or insufficiency

2. PA hypertensive crisis

3. Evaluation on Lt. AV valve regurgitation

: predispose the patient to death within 1 year