Atrioventricular canal defect

How av canal was formed
pathophysiology after birth
symptoms,diagnosis and surgical treatment

1. ATRIOVENTRICULAR CANAL DEFECT By Dr VASANTHI DNB- CARDIAC SURGERY MADRAS MEDICAL MISSION

2. Formation of interatrial and interventricular septum

3. AV canal formation

4. AV CANAL DEFECT Characterized by complete absence of AV septum Mechanism of development : Abnormal differentiation and remodeling of endocardial cushion mesenchyme into valvoseptal tissue

5. Also called as Endocardial cushion defect, Canalis atrioventricularis communis , persistent atrioventricular ostium

6. Features: A common atrioventricular ring A five leaflet valve that guards the common AV orifice An unwedged left ventricular outflow tract

7. Mitral & tricuspid valves achieve the same septal insertion level because the mitral annulus is displaced toward the apex The distance from mitral annulus to the left ventricular apex is less than the distance from the aortic annulus to the apex

8. In the normal heart, the aortic valve is wedged between the mitral and tricuspid annuli. In AVSD the aortic valve is displaced anteriorly and creates an elongated, so-called gooseneck deformity of the LVOT

9. Incidence AVSDs account for 4% to 5% of congenital heart disease Gender distribution is approximately equal or may show a slight female preponderance

10. History Rogers, Edwards : Recognized morphology of primum ASD in 1948 Wakai , Edwards : Term of partial and complete AV canal defect in 1956 Bharati & Lev : Term of Intermediate & Transitional in 1980 Rastelli : Described the of common anterior leaflet in 1966 Lillehei : 1strepair of AVSD in 1954 Kirklin , Watkin , Gross: Open repair using oxygenator

11. Morphology –classification 1

12. In partial AVSDs , incomplete fusion of the superior and inferior endocardial cushions results in a cleft in the midportion of the AML ,often associated with MR Complete AVSD associated with lack of fusion between the superior and inferior cushions

13. Anatomical classificationII ( Rastelli ) Based on the relationships of the anterior bridging leaflets to the crest of the ventricular septum or RV papillary muscles Rastelli type A : the anterior bridging leaflet is tightly tethered to the crest of the IVS, occurring in 50% to 70%

14. Rastelli type B : (3%), the anterior bridging leaflet is not attached to the IVS; rather, it is attached to an anomalous RV papillary muscle and is almost always associated with unbalanced AV canal with right dominance Rastelli type C : (30%) a free-floating anterior leaflet is attached to the anterior papillary muscle.

15. Classificiation III Based on level of shunting Interatrial and interventricular sunt Interatrial shunt only ( primum ASD ) Interventricluar shunt only( av canal VSD) AVCD with intact IAS and IVS

16. Classification IV Depending upon the size of ventricular chambers( univentricular or biventricular) Balanced type Unbalanced type

17. Unbalanced AVCD: 1.ventircular hypoplasia,2.malalignment of the AV valve junction. later may affect size of ventricle development Unbalanced Right dominant type : associated with arch hypoplasia,coarctation of aorta Unbalanced with left dominant : associated with pulmonary stenosis / atresia

18. Lev description of conduction Inferior displacement of AV node and coronary sinus. Bundle of His is also displaced inferiorly and coursing at the inferior rim of scooped out basal portion of IVS

19. Associated anomalies Partial AVSD: Most common ostium secondum ASD & LSVC to CS Complete AVSD Type A usually is an isolated defect and is frequent in patients with Down syndrome . Type C –TOF, DORV, TGA and heterotaxy syndromes

20. Fetal physiology Oxygenated blood may cross the IAS to the RA Increase the PO2 of blood in RA, RV, PA Slightly higher PO2of blood perfusing the lungs would decrease pulmonary vasoconstriction and increase pulmonary blood flow It may retard the development of a thick medial muscle layer , so that a more rapid decrease in PVR may occur after birth

21. An interesting association may develop in some infants of an obligatory left-to-right shunt through the AV canal defect simultaneous right-to-left shunting through the ductus arteriosus The increased pulmonary blood flow and PA pressure interfere with the normal postnatal maturation of the pulmonary arterioles leads to early development of Pulmonary vascular obstructive disease

22. Clinical manifestation Partial AVSD Patients with primum ASD - usually asymptomatic during childhood. Dyspnea , easy fatigability, recurrent RTI and growth retardation may be present early in life if associated with major MR or common atrium Complete AVSD Tachypnea and failure to thrive invariably occur early in infancy & virtually all patients have symptoms by 1 year of age because of pulmonary vascular obstructive disease

23. Echocardiography Primary imaging technique for diagnosing AVSD The internal cardiac crux is the most consistent imaging landmark Apical four-chamber imaging plane clearly visualizes the internal crux The primum ASD is seen as an absence of the lower IAS

24. Cardiac cath Rarely required for diagnosis In older patient it may have a role in assessing the degree of pulmonary vascular obstructive disease or CAD A large Lt to Rt shunt at the atrial level demonstrated by a significantly higher oxygen saturation sampled from the RA compared with the blood in the IVC & SVC In complete AVSD the PASP is invariably at or near systemic level , while in partial AVSDs, the PASP is usually <60% of systemic pressure LV angiography -gooseneck deformation of the LVOT

25. Goose neck deformity The left ventricular outflow tract is elongated and narrowed. The arrows point to the mitral cleft.

26. Management Elective surgical repair -2 to 4 months of age. Early in case of down syndrome because of their known tendency to develop early pulmonary vascular obstructive disease Palliative: Unbalanced AV canal (PA banding )

27. Corrective surgeries Single patch technique Double patch technique Modified single patch technique

28. Double patch technique Separate patch for both ASD and VSD closure VSD – dacron and ASD – pericardial patch to avoid hemolysis in case of AVVR Mitral valve cleft is closed by coaptation of SBL and IBL using horizontal mattress Kirklin tech : attaching ASD patch to the right of AV node invloves suturing the right inferior leaflet .leaving CS ->LA Advantage : far from conductive tissue Diaadvantgae : some desaturation becoz of CS->LA

29. Mcgoon tec h:ASD patch is attached to the left inferior leaflet draining CS-> Ra.

30. Single patch tehcnique

31. Modified Single patch tehcnique c/a australian technique

32. Disadvantage : development of lvoto because of VSD is closed primarily witout patch material

33. Corrective