Atrioventricular Septal Defect – Diagnosis And Treatment
Atrioventricular septal defect is a complex, congenital cardiac defect affecting interatrial septum, interventricular septum, mitral and tricuspid valvular apparatus. Spectrum of injuries is high, from simple forms of atrioventricular defects to sever forms of atrioventricular septal defcts with changes of valvular apparatus (cuspe and cordage of the mitral valve and tricuspid valve). The incidence of this malformation is 4% – 6% of all congenital cardiac malformations. Often id associated with other anomalies such as Down syndrome or Ellis van Credeld syndrome (ectodermal dysplasia, polydactyly).
Partial form of atrioventricular septal defect:
Associate large interatrial septal defect, situated immediately above the atrioventriculare valve, and mitral valve modifications because it is presenting three clefts (normally, mitral valve has two clefts). Tricuspid valve is rarely affected.
An important element to be known is that the subvalvular apparatus, in the case of partial form of atrioventricular septal defect presents anomalies in 20% of the cases, compared to full form of atrioventricular septal defect, where the subvalvular apparatus presents anomalies in only 3% of the cases. This element gives otherwise, the difficulty of mitral valve repair, a big number of reinterventions and the need to change the valve after a few years after the first surgery.
In pathophysiological terms, atrioventricular septal defect acts as a ostium secundum interatrial septal defect, which is associated with a mitral valve defect that is accentuating pulmonary stasis, increases the risk of pulmonary vascular disease and will lead to installation of Eisenmenger syndrome.
Symptoms and diagnosis of partial form of atrioventricular septal defect:
On clinical examination are seen precordial shock due to a hyperdynamic right ventricle, systolic murmur on the right ventricular outflow tract (due to increased blood flow), halved second cardiac sound and systolic murmur of mitral regurgitation which is significant.
- ECG – left axial deviation of the heart, right ventricular conduction disturbances and left anterior hemiblock;
- Chest radiography – X-ray shows cardiomegaly due to enlargement of the right atrium and right ventricle. Pulmonary hypervascularization with stasis.
- Echocardiography – that specifies the diagnosis in 2 D or in three-dimensional reconstruction of the heart, which will give anatomical and functional information about the heart and about the mechanism of mitral and tricuspid valve regurgitation.
- Cardiac catheterization – passage of the probe from the aorta, trough interatrial septal defect, into the right atrium, will certify the diagnosis. This exploration is bringing anatomical and functional information about the heart and valves, hemodynamic pressure, gas saturation of blood in the heart cavities and particularly can appreciate pulmonary hypertension and pulmonary vascular resistances.
Natural evolution of partial form of atrioventricular septal defect:
If atrioventricular septal defect is not diagnosed at birth, becomes symptomatic in the first years of life. Children have a short stature and weight deficit, signs of congestive heart failure, dyspnea, fatigue, recurrent lung infections. Once diagnosed, to avoid complications, is indicated that the surgery to be done around the age of 4 years. Diagnosis of atrioventricular septal defect in adulthood should be seen as an exception rather than a rule.
Surgical treatment of partial form of atrioventricular septal defect:
Surgical treatment aims to solve the two defects: closing interatrial septal defect and mitral valve plasty. Mitral valve repair is the key to long-term success. If repair is not possible, then mitral valve should be replaced by a mechanical or biological valve. Approximately 10% of the mitral plasty reach the second valve replacement surgery. The pericardial patch used for closing interatrial septal defect, can damage the atrioventricular node with the apparition of temporary or permanent heart block, which is requiring pacemaker implantation.
Complete form of atrioventricular septal defect:
This type of disease associates interatrial septal defect, ventricular septal defect and atrioventricular valvular defects (mitral and tricuspid). This type of atrioventricular septal defect can be associated with other anomalies such as tetralogy of Fallot, transposition of the great arteries and Down syndrome.
Symptoms and diagnosis of complete form of atrioventricular septal defect:
Infants with complete form of atrioventricular septal defect, presented frequent respiratory infections and a lack of appropriate physical development, signs of congestive heart failure, dyspnea, tachycardia, pulmonary stasis and hepatomegaly. Clinical examination can detect a sistolic murmur of the right ventricular outflow, sistolic murmur on the bottom left of the sternum, which is proving the presence of a ventricular septal defect and a mitral regurgitation murmur.
Diagnosis is indicated by paraclinical investigations and in particular by echocardiography.
- ECG – are described in the partial form of atrioventricular septal defect.
- Chest radiography – marked cardiomegaly and pulmonary stasis.
- Echocardiography – is the examination which is expected to confirm the diagnosis of atrioventricular septal defect. Study 2 D and 3 D reconstruction gives precise anatomical data on interatrial septal defect, ventricular septal defect, valvular apparatus, cardiac cavity size and functional data about the shunt direction, magnitude of the shunt and ventricular function.
- Cardiac catheterization – Is giving characteristic image of swan neck by higher and anterior position of the aortic valve in relation with mitral valve. This investigation is useful to assess the degree of pulmonary hypertension, because many children have severe obstructive vascular disease by the age of 2 years.
Complete form of atrioventricular septal defect can progress to congestive heart failure in the first months of life and require surgery. The major risk is the development of obstructive pulmonary vascular disease, severe pulmonary hypertension that would make surgery risky or contraindicated.
Treatment of complete form of atrioventricular septal defect:
Surgical treatment – It is indicated at any age. Total correction of atrioventricular septal defect can be done in the first months of life depending on the severity of symptoms and pulmonary hypertension. Creating a competent atrioventricular apparatus is the key of success for short and long term, of this intervention. Residual mitral valve regurgitation is usually the one that indicate the need for reinterventions.
Postoperative mortality of atrioventricular septal defect rate is below 5%. Survival at 20 years is 70%. Reinterventions for residual mitral regurgitation rate is around 10%. At reintervention it is tried a new valve repair or the replacement with mechanical valvular prosthesis.