Definition: atrioventricular septal defect is also known as an endocardial cushion defect (embryological defect of the endocardial cushion). Complete AVSDs are characterised by a primum ASD and an inlet VSD with a common AV valve (prevalence 3% of CHD, most common congenital lesion associated with Trisomy 21).
Partial AVSDs consist of a primum ASD and TV/MV clefts.
Complete lesions will be classified according to Rastelli’s classification – Type A, B and C. These are classified according to the common AV valves dominance to either side.
Physiology:
The shunt in AVSD is in keeping with their respective ASD and VSD – left to right usually. The degree of shunt can be influenced by whether the common AV valve is left or right sided dominant, the degree of MR/TR or MS/TS and the type of AV connection.
Can be complicated by LVOTO due to accessory valve tissue, AV conduction abnormalities and left AV valve regurgitation.
In Trisomy 21, the onset of pulmonary vascular disease occurs earlier which often means earlier surgical repair.
Clinical findings:
Partial lesions mimic ASD signs. Complete lesions usually present with FTT, repeated respiratory tract infections +/- CHF.
3-4/6 pansystolic murmur at the lower LSE. Mid diastolic rumble due to relative TS/MS. Systolic thrill and hyperactive precordium may be found.
CXR shows cardiomegaly and in complete AVSD, increased pulmonary vascular markings. May show PA prominence.
ECG: RVH and RBBB. May have 1st degree heart block and LVH. Superior QRS axis.
Diagnosis:
ECHO and cardiac catheter
Preoperative management:
Diuretic therapy may be instituted to treat CHF
May benefit from an ACE inhibitor
Thorough and detailed transthoracic echo to assess the morphology of the common AV valve as well as bridging leaflets (Rastelli’s)
Preoperative preparation:
ECG, CXR, CUS, FBE, clotting, UECs, PRBC (4), FFP (2), platelets (2), cryoprecipitate (2)
Methylprednisolone in neonates
Surgery:
Either a one or two patch technique.
One patch involves direct closure of the VSD and repair of the common AV valve leaflets by suturing the leaflets to the crest of the ventricular septum. A Dacron patch is then applied to the ASD.
The two patch technique involves two Dacron patches to both septal defects and then a separate repair of the valve leaflets.
The other point of controversy is whether the valve cleft should be closed to form a 2-leaflet valve as opposed to a 3-leaflet valve. The literature leans towards closure of the cleft if possible without causing stenosis.
Timing is generally before 6-12 months. Most operations occur between 3 and 6 months. This is to reduce the incidence of PHT.
Postoperative management:
- Keep intubated, ventilated, sedated and paralysed for 24 hrs
- Inotropes: milrinone plus dopamine or adrenaline (plus noradrenaline)
- Haemodynamics: age adjusted in neonates: SBP >60 mmHg, MAP >40 mmHg (increasing over time), LAP 8-12 mmHg, CVP 8-12 mmHg
- Respiratory: normoxaemia, normocapnea
- Fluid restriction: 1ml/kg/hr, trophic feeds
- Haemostasis
Specific problems:
- Most common is pulmonary hypertension (especially in children with prior pulmonary vascular disease)
- Postoperative pulmonary venous obstruction (in the immediate postoperative period): check for left AVVR; decrease afterload if blood pressure allows
- Arrhythmia: SVT, JET, bradycardia (pacing), AV Block (pacing)Â Â
- Low urine output: start PD
- Left AV valve regurgitation is the most common reason to re-operate on these children
Outcome:
Long term survival very good between 80-95%
Some papers suggest mortality for Trisomy 21 is now 0%
The natural history of this lesion without an operation has a survival rate of only 4%
References:
[1] Nelson’s Textbook of Pediatrics 18th Edition
[2] Pediatric Cardiology for Practitioners 5th Edition. Park, M
[3] Heart 2006; 92:1879-1885: Craig et al: Atrioventricular Septal Defect: From Fetus to Adult
[4] Orphanet Journal of Rare Diseases 2006; 1:8: Calabro et al: Complete Atrioventricular Canal
[5] Ann Thoracic Surg. 2010 February; 89(2): 530-536: Minich et al: Partial and Transitional Atrioventricular Septal Defect Outcomes
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