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 IVC 3. Pulmonary vascular disease ; earlier onset than VSD 4. 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 regurgitation 3. Chest radiography 4. Electrocardiogram 5. Two-dimensional echocardiogram 6. Cardiac catheterization and cineangiogram 7. Special situation and associated defects

Natural History of ECD 1. Incidence 3) Complete form 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 survival 2. Mode of death 1) early : acute cardiac failure and pulmonary dysfunction 2) late : chronic or subacute cardiac failure 3. Incremental risk factors for premature 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 ventricle 4. Heart block & arrhythmia 5. Functional class 6. AV valve function 7. LVOT obstruction 8. Residual pulmonary hypertension

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