Young age
EXTENDED OUTLINE
1. Embryology
a) Endocardial cushions
i) Anterior and posterior margins of A-V canal
ii) Fusion results in septation of primitive heart (10mm embryo)
iii) Left and right endocardial cushions close secondary interventricular foramen, forming inlet septum
b) A-V septal (canal) defects
i) Failure of fusion of major endocardial cushions
ii) Free borders of septum primum have nothing with which to fuse à interatrial communication
iii) Abnormalities of 3 aspects of A-V canal:
a) Atrial portion of A-V canal septum
b) Ventricular portion of A-V canal septum
c) A-V valves
2. Anatomy
a) Wedge position of aorta (between TV and MV) absent
i) Aortic valve is elevated and deviated anteriorly
ii) LVOT narrowed, but rarely hemodynamically significant
iii) LV-gram - gooseneck LVOT
b) Ventricular dominance
i) Balanced = A-V junction evenly shared between RV and LV
ii) Dominant = valve orifice committed to that side- opposite side is hypoplastic
c) 40-45% of Downs pts have A-V septal defects
d) Associated anomalies are common
3. Partial A-V septal defect
a) Ostium primum ASD
b) Left A-V valve abnormalities
i) Cleft in midportion of anterior leaflet (septal cleft or commisure)
ii) Others define L A-V valve as tricuspid
iii) Left lateral, superior and inferior leaflets
c) R A-V valve: superior, lateral, inferior
d) Conduction system
i) CS ostium often displaced inferiorly
ii) A-V node displaced inferiorly between CS and ventricular crest-nodal triangle
e) Associated anomalies: PDA, unroofed CS, persistent LSVC
4. Complete A-V septal defect
a) Primum ASD, common A-V valve orifice, VSD
b) 6-leaflet A-V valve - see 3 b,c above
c) Rastelli classification (based upon anatomy of anterior bridging leaflet)
i) A: Common leaflet but cordae attached to crest of interventricular septum ii) B: Papillary muscle attached to left part of leaflet from right of septum - rare
iii) C: Free floating common anterior leaflet without cordal attachment to ventricular crest
d) Dominance - LV usually smaller in unbalanced
e) Conduction
i) A-V node displaced inferiorly (as in partial defect)
ii) His bundle
a) Travels anteriorly and superiorly from A-V node, reaching ventricular crest where it fuses posteriorly with common A-V valve annulus
b) Passes along crest of septum, giving off left bundle branches, then becomes RBB, runs toward muscle of Lancisi
f) Associated anomalies
i) DORV - unique to complete
ii) TOF - see below
iii) TGA - rare
5. Complete A-V septal defect without atrial communication (rare)
6. Diagnosis
a) Presentation a fxn of: degree of Left to Right shunting and A-V valve incompetence
b) A-V valve incompetence (common)=> pulmonary vascular dz early
c) RV=LV pressure => high PA pressure
d) Partial defect
i) Symptoms of increased pulmonary flow- dyspnea, failure to thrive, repeated respiratory infections
ii) PE: active precordium, prominent pulmonic flow murmur, widely split S2
iii) ECG: often diagnostic
a) Left axis deviation
b) Prominent P waves
c) Prolonged PR interval
iv) CXR
a) Cardiac enlargement
b) Increased pulmonary flow
v) 2-D echo
vi) Cardiac catheterization - may be unnecessary
a) Confirm diagnosis
b) Assess degree of pulmonary vascular disease
c) LV-gram - MV regurgitation, gooseneck LVOT
vii) Natural history
a) Survival (w/o tx) unusual beyond 40 yo
b) Dysrhythmias common
e) Complete defect
i) Present earlier, usually w/severe CHF
ii) PE
a) Thin, breathless
b) Marked precordial activity, prominent thrill
c) Cyanosis in 15%
d) Split S1 due to pulm HTN
e) Holosystolic murmur along LSB from VSD
f) High-pitched apical murmur from MV regurgitation
g) Mid-diastolic flow murmur across common A-V valve
iii) Echo: attachment of pap. muscles and cordae
iv) Cath
a) Assess degree of pulmonary vascular disease
b) Angio shows long, narrow LVOT
v) Natural history
a) 96% 5-yr mortality w/o treatment
b) Surgery recommended at 3-4 months
c) Associated abnormalities may preclude biventricular repair - need PA band early in infancy
vi) Complete A-V septal defect without atrial communication
7. Surgical technique
a) General
i) SVC and IVC cannulation
ii) +/- hypothermic circulatory arrest - 18-20°C (up to 45 min is safe)
iii) LSVC
a) If pressure remains < 25mm Hg (IJ), clamp
b) If pressure > 25mm Hg
(1) Cannulate
(2) Low flow + sump sucker in CS
(3) Circ arrest
iv) Open RA close to AV groove
v) Test A-V valve w/cold saline - float leaflets
b) Partial A-V septal defect
i) Valve repair
a) Approximate tips (kissing edge) of left superior and inferior leaflets with a suture - do not tie
b) This defines septal commisure (cleft)
c) Close cleft with interrupted 5-0 or 6-0 sutures
d) Some (Carpentier) recommend leaving three-leaflet valve - can become severe regurgitation
e) Size valve according to BSA
ii) Closure of ASD
a) Pericardial patch
b) Close CS into LA or RA
c) Complete A-V septal defect
i) L A-V valve repair as above
ii) Two-patch technique (Carpentier)
a) Superior bridging leaflet is not divided
b) VSD patch (dacron)
(1) Interrupted or running suture along right side of ventricular septum
(2) Suture top edge of patch to middle of bridging leaflets
(3) Now close septal cleft
(4) Measure valve orifice
c) ASD patch (pericardium)
(1) Close CS into LA or RA
iii) One-patch technique
a) Superior common (bridging) leaflet is divided to annulus (veering a bit to the right to increase Left A-V valve orifice
b) Divide inferior bridging leaflet
c) Suture patch (Dacron or PTFE)to right side of septum, staying 3-5mm from crest
d) Valve leaflets attached to patch w/ interrupted sutures +/- pledgets
e) Closure of ASD as above (CS to LA or RA)
d) Complete A-V septal defect and tetralogy of Fallot
i) Present in nearly 10% of AVSD - especially w/Downs
ii) Small PAs - BT shunt to allow PAs to grow - complete repair at 3-5 yrs - pulmonary bed is protected
iii) VSD extends to subaortic area
iv) Valved conduit if PV excised (and TV incompetent)
e) Complete A-V septal defect without atrial communication
i) Repair L A-V valve via secundum ASD (existing or surgical)
ii) Top edge of patch sutured to bridging leaflet
8. Post-op care
a) Pulmonary HTN
b) Reactive pulmonary vasculature
i) Fentanyl prophylaxis
ii) Phenoxybenzamine
iii) Prostacyclin
iv) Nitric oxide
v) pO2 > 150mmHg
vi) pCO2 < 35mmHg
9. Results
a) Risks for premature sudden death:
i) Severe pre-op Leeft A-V valve incompetence
ii) Poor status
iii) Accessory A-V valve orifice
iv) Downs syndrome
b) 98% 1-yr, 96% 20-yr survival (Mayo)
i) Reoperation in 18 (9%)
c) Downs syndrome
i) Survival not influenced
ii) Fewer associated cardiac anomalies
d) Age - controversial
e) Date of operation - earlier = worse
f) Hanley - 7% re-operation for Left A-V valve problems
g) Higher mortality for complete w/o VSD
10. Timing of operation
a) Complete
i) Complete repair by 3-6 months
ii) By 1yr for asymptomatic (Boston = 6 months)
b) Partial (pulmonary HTN rare)
i) Elective repair at 3-5 yrs (Boston = by 1yr)
ii) Significant Left A-V valve regurgitation occurs earlier
