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 2. Heart block
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