Straddling & Overriding Tricuspid or Mitral Valve

1. Straddling & Overriding Tricuspid or Mitral Valve Seoul National University Hospital Department of Thoracic & Cardiovascular Surgery

2. Straddling & Overriding AV Valve • 1. Definition • 1) Straddling : when a part of tension apparatus of the valve • crosses the VSD and the crest of the IVS • to attach to the septum, or a papillary muscle • in the opposite (inappropriate) ventricle • 2) Overriding : when the atrioventricular junction to which the AV • valve leaflets attach is connected to both ventricle • 2. History • Lambert : Recognized in 1951 • Van Praagh : Recognized in 1964 • Mehrizi : Recognized in 1966 • Pacifico : Surgical management in 1979

3. Straddling & Overriding AV Valve • Morphologic syndromes 1. This anomaly is associated with a posteriorly placed (juxtacrucial) VSD in the inlet portion of ventricular septum when viewed from the RV aspect • 2. Always occurs in relation to VSD, that is simple • part of CHD such as transposition of great arteries, • double outlet right ventricle, corrected TGA, • double inlet ventricle • 3. Straddling & overriding valves are often accompanied • by ventricular hypoplasia of variable severity. • 4. Overriding or straddling AV valve may occasionally • produce subpulmonary or subaortic obstruction.

4. Straddling & Overriding AV Valve • Conduction System • 1. When AV valve is overriding or straddling a VSD • that does not reach the crux cordis, the conduction • is usually unaffected. • 2. When AV valve overrides a VSD that is juxtacrucial, • the AV node is situated anomalously in heart with • AV concordant connection. • 3. When the VSD is juxtacrucial and AV discordant • connection, it is the left AV valve that overrides • and the AV node occupies an anterolateral position • near right AV valve annulus as is usual in hearts • with AV discordant connections.

5. Clinical Features & Diagnosis • 1. Incidence • 3% of CHD • More common in discordant connection • 2. More prevalent among hearts with AV discordant • connection, but in concordant heart it commonly • occur in DORV, TGA • 3. Coexisting cardiac anomalies generally determine the • clinical syndrome, natural history & diagnostic feature • 4. Straddling & overriding AV valves are usually • competent and have no features • 5. Echocardiography is the technique generally accepted

6. Types of Straddling (Tabry) • 1. Type A : Mild, with the chordae that cross VSD • attaching to a limited area within 1cm of VSD • 2. Type B : Moderate, with the chordae attaching • to the septum farther away from VSD • 3. Type C : Severe, with the chordae and papillary muscles • attached to the inner surface of the free wall of • the inappropriate ventricle

7. Techniques of Operation • 1. Section of straddling cords • 2. Slotting of repair patch • 3. Reattachment of sectioned tensor apparatus • 4. Minor septation • 5. Replacement of straddling AV valve • 6. One and a half ventricle repair • 7. Fontan operation • 8. Cardiac transplantation

8. Minor Septation Procedure

9. Intraventricular Repair • Incorporating a minor septation for straddling & overriding • left atrioventricular tricuspid valve in patients with congenitally • corrected transposition of great arteries

10. Results of Operation • 1. Early & intermediate survival • Not satisfactory • 2. Heart block • 3. Fontan operation or cardiac transplantation • Survival after operation is unrelated to cardiac • anomaly and not lessened by the presence of • a straddling or overriding AV valve.

11. Indications for Operation • 1. Indications for operation lies with the • coexisting anomalies rather than with • the AV valve anomaly. • 2. Strategy of operation is greatly influenced • by the AV valve anomalies, and whenever • possible that strategy should be decided in • very early life. • 3. When straddling is severe, septation or even • lesser procedure seem likely high early risk