Straddling & Overriding Tricuspid or Mitral Valve

Seoul National University Hospital

Department of Thoracic & Cardiovascular Surgery

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

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.

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.

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

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

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

Minor Septation Procedure

Intraventricular Repair

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

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.

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