Atrioventricular Septal Defect Seoul National University Hospital Department of Thoracic & Cardiovascular Surgery

Atrioventricular Septal 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 Septal Defect Historical note Rogers, Edwards : Recognized morphology of ostium primum ASD in 1948 Wakai, Edwards : Term of partial and complete AV canal defect in 1956 Bharati & Lev : Term of intermediate & transitional in 1980 Ugarte : Term of leaflet bridging ventricular septum in 1976 Rastelli : Described the morphology of common anterior leaflet in 1966 Lillehei : 1st repair of complete AV canal defect using cross circulation in 1954 Kirklin, Watkins, Gross ; Open repair using oxygenator

Atrioventricular Septum That portion of cardiac septum which lies between the right atrium and the left ventricle It consists of a superior membranous portion and an inferior muscular portion The atrioventricular septum is apparent because the septal attachment of tricuspid valve is more apical than the mitral valve The AV node lies in the atrial septum adjacent to the junction between the membranous and muscular portions of atrioventricular septum, and His bundle passes toward the right trigone between these two components

Atrioventricular Septal Defect  Pathophysiology Partial AV canal defects result from the failure of the endocardial cushions to meet the septum primum producing a low-lying (ostium primum) defect in the atrial septum ; a cleft mitral valve is also usually present. Complete AV canal defects result from maldevelopment of the endocardial cushions, producing a single, common AV valve & VSD in addition to an ostium primum ASD. Pathophysiology results from left-to-right shunting at the atrial and/or ventricular level as well as AV valve insufficiency, producing pulmonary overcirculation and congestive heart failure, particularly during early infancy.

Morphology of A-V Septal 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 AV valve tissue 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 obst. 7. Conduction system; LAD

Morphology of AV Septal 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

Atrioventricular Septal Defect  LV Outflow & Inflow Obstruction Incidence 1% in unoperated cases Higher incidence after operation Etiology 1. Elongation & narrowing due to more extensive area of direct fibrous continuity aortic valve & LSL 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

Schematic Drawings of AVSD

Partial AVSD

Complete AVSD

LVOT and AV Septal Defect Normal AVSD After Repair

Clinical Features and Diagnosis 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. Common atrium, Lt SVC, Isomerism, LVOTO

Natural History of AVSD 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. PV 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

AV Valve Repair in AVSD  Principles The most anterior point of LSL-LIL opposing edge should be found and sutured through it, and the anterior edges be sutured to the polyester patch The patch must be appropriate dimension & configuration and tailoring the waist of the patch is critical Remodeling leaflet closure by suturing portions of left superior leaflet and left inferior leaflet together in areas of regurgitation. Annuloplasty at commissure and making the edge of the pericardial patch along it shorter than the combined length of the base of leaflet

AV Septal Defect

Complete AVSD. Operative View

Partial AVSD

Complete AVSD

Septal Patch for AVSD Repair Too wide patch, theoretically left ventricular outflow obstruction & long patch with high AV valve level, possible AV valve regurgitation

Complete AVSD (1)

Complete AVSD (2)

AVSD. Repair of Mitral Cleft

Partial Annular Plication Two furling stitches with 3 pledgets or three furling stitches with 4 pledgets are placed along the annulus of either or both sides for mitral valve regurgitation

AV Valve Replacement After AVSD Repair Lengthening the mitral-aortic septum, thus the valve is well away from the LVOT

Features of Postoperative Care 1. Vigilance must be exercised to detect any important imperfections in the repair 2. LAP is higher 6 mmHg than CVP : suggest mitral valve stenosis or insufficiency 3. Prophylaxis against PA hypertensive crisis 4. Evaluation on left AV valve regurgitation : predispose patient to death within 1 year 5. Evaluation of left to right shunt 6. Reoperation is indicated in severe regurgitation and significant residual shunt

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) need for reoperation 10) single papillary m. 11) 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. 3. Coexisting cardiac anomalies Although certain major cardiac anomalies increase risk of AVSD, their presence rarely alters the indication for operation

Special Situation & Controversies 1. Pulmonary artery banding 2. Septal patches 1) Atrial 2) Ventricle 3. Avoiding heart block 4. Hypoplastic ventricle 5. Late reoperation 6. Extended atrial patch repair for c-AVSD

Isolated Cleft Mitral Valve Morphogenetically, there are two types: ICMV with normally related great arteries, and ICMV with abnormal conus associated with transposition in D- or L-ventricular loops or DORV. The group with normally related great arteries shares several characteristics with complete forms of AV canal and considered as a milder variation of the AV canal. In this group, the mitral valve cleft results in progressive mitral regurgitation. The group with abnormal conus is characterized by the presence of a conoventricular VSD & lack of similarities with AV canal malformations. Mitral valve cleft is seldom associated with significant mitral regurgitation but often produces obstruction of left ventricular outflow tract.