Avsd Q21.2

As early as 1846, Peacock described anatomical changes that indicate the presence of an AVSD defect. The first successful correction of an AVSD was performed in 1955 by C. Walton Lillehei (Ziemer 2010).

The atrioventricular septal defect (AVSD) comprises a group of heart defects in the area of the atrioventricular septum and the atrioventricular valves, the extent of which can vary greatly. In all forms of these defects, the atrioventricular septum is partially or completely missing. The term "atrioventricular septal defect" proposed by Becker and Anderson in 1982 thus describes the clinical picture anatomically correct. (Ziemer 2010).

In addition, the conduction system is dislocated and accompanying malformations such as persistent ductus arteriosus, tetralogy of Fallot and extracardiac malformations such as trisomy 21 are frequently found (Schmaltz 2017).

The AVSD is divided into 3 different groups:

• Partial AVSD (incomplete AVSD)
• This is a deep-seated atrial septal defect that extends into the AV valve level and corresponds to ASD I (ostium primum defect) as well as an additional cleft formation of the mitral valve. Although the two AV valves are separate from each other, they have an anterior and posterior sail (so-called bridging leaflet), which connects the two AV valves with each other with connective tissue (Herold 2019). Apposition lines (also called cleft) are present in both AV valves (Schmaltz 2008).
• Intermediary type (transitional form)
• The intermediary type also has an atrial septal defect of the type ASD I (ostium primum defect). There is also a ventricular septum defect in the inlet area. The AV valves lie on one level and each have separate valve rings (Herold 2019 and Schmaltz 2008).
• Complete AVSD
• In a complete AVSD there is a deep-seated ASD I, an inlet-ventricular septal defect and a cleft formation in the anterior mitral and septal tricuspid valve leaflet. This results in an open connection of all 4 heart cavities. The mitral and tricuspid valves are at the same level and form the AV valve opening from four to seven parts of their sails (Herold 2019).

This creates an anterior (anterior bridging leaflet) and a posterior (posterior bridging leaflet) sail of the AV valve components.

Depending on the position of the common valve, this is called:

• Left dominance, so-called unbalanced type (the valve can be assigned more to the left ventricle)
• Right dominance, also a so-called unbalanced type (the valve can be assigned more to the right ventricle)
• a balanced or equilibrated type.

Straddling or overriding of the AV valve can lead to hypoplasia of the affected ventricle. Abnormalities may also be present in the papillary muscles (e.g. closely spaced or singular papillary muscles) (Schmaltz 2008).

Based on the morphology of the anterior bridging sail, Rastelli created a more detailed classification, which was modified by Anderson:

• Rastelli A: Type A is with 70% (Kunert 2007) the most common constellation. It is often associated with trisomy 21. Here the bridging is minimal. The tendon threads of the anterior sail extend to the upper edge of the ventricular septum.
• Rastelli B: Here the bridging is more extensive. The abnormal apical papillary muscle attaches to the commissure.
• Rastelli C: The bridging is extreme in type C. The anterior papillary muscle connects the commissure with the right ventricle (Siewert 1998).

The frequency of an AVSD is approx. 0.19 / 1,000 live births (Borth- Bruhns 2004) and accounts for approx. 3 % of all congenital heart defects (Herold 2019). Both sexes are equally affected (Borth- Bruhns 2004).

Accompanying cardiac malformations such as the persistent ductus arteriosus are found in 10 % of cases, the tetralogy of Fallot in 6.5 % (Schmaltz 2017).

Extracardiac malformations such as trisomy 21 occur in 35% of cases and in 75% of children with trisomy 21 there is an AVSD (Erdmann 2006).

The ASVD is a congenital defect resulting from embryonic developmental retardation of the AV channel region, with the result that there is no final subdivision of the AV valve and final septation of both atria and ventricles (Borth-Bruhns 2004).

There is a familial accumulation of the defect. In about 14% of mothers with AVSD the defect is inherited by the child (Borth-Bruhns 2004).

An incomplete AVSD results in a right-left shunt at the atrial level. The increased blood volume leads to a volume strain of the right atrium, the right ventricle and the pulmonary vessels. The gap in the mitral valve leaflet leads to mitral valve insufficiency, which, however, is usually of no major hemodynamic significance.

In complete AVSD, the atrial septal defect plus ventricular septal defect leads to a considerable volume load on the right heart and pulmonary circulation. The atrial septal defect and mitral valve insufficiency also lead to a volume burden on the left heart (Herold 2019). Due to the pulmonary pressure increase, an obstructive pulmonary vascular disease develops relatively quickly. In 60 % of those affected, there is also insufficiency of the AV valve (Siewert 1998).

The size of the shunt depends on:

• the size of the defect
• the resistance ratios of both circuits

Both hemodynamics and clinical symptoms are determined by the size and relevance of the atrial septal defect, the ventricular septal defect and the degree of insufficiency of the left-sided AV valve (Herold 2019).

Children with a complete AVSD predominantly become symptomatic already in the first weeks of life.

The following symptoms may occur:

• Recurrent broncho-pulmonary infections
• limited physical capacity
• Growth disorders
• Developmental delay
• Signs of severe heart failure

(Herald 2019)

• Tachypnea
• as a signum male occurrence of cyanosis

(Borth- Bruns 2004)

With incomplete AVSD, on the other hand, it is quite possible that patients remain asymptomatic into adulthood (Borth- Bruns 2004).

Chest X-ray

In complete AVSD, there is:

• severe cardiomegaly with dilatation of all four cardiac cavities and increased transverse diameter
• strongly increased pulmonary vascularity (Borth- Bruhns 2004)
• prominent pulmonary truncus (Herold 2019)

Echocardiography

Echocardiographically, the following conclusions can be made:

• Localization and size of the ASD and VSD.
• Determination of the size and function of the atria, ventricles, aorta and truncus pulmonalis
• Examination of the anatomy and function of the AV valve (straddling, overriding, etc.) and the mitral valve
• Detection of an atypical shape (narrowed and elongated) of the left ventricular outflow tract, the so-called goose neck deformity (also called goose neck deformity) (Herold 2019).

The Doppler procedure should determine:

• the shunt direction

and estimated:

• the right ventricular pressure
• pulmonary arterial pressure
• the interventricular pressure gradient
• Qp / Qs to determine shunt flow (Qp = sum of mean flows in left and right pulmonary artery; Qs = mean flow in descending aorta) (Herold 2019).

MRI

If the patient is difficult to scan or if diagnostic questions remain after performing (transesophageal) echocardiography, a cardio- MRI should be performed. This will provide specific information:

• quantification of the shunt
• the anatomical conditions of the heart
• the function of the heart, especially the ventricles (Herold 2019).

Cardiac catheterization and angiography

During right heart catheterization, more detailed information can be obtained on:

• pulmonary vascular resistance (Pinger 2019).

Cardiac catheterization diagnostics or angiography can provide more detailed information on:

• exact determination of intraventricular pressures
• size of the shunt
• Pulmonary vascular morphology
• pulmonary vascular resistance
• detection or exclusion of associated cardiac anomalies
• Detection or exclusion of CHD
• the left ventricular outflow tract is clearly elongated in complete AVSD (so-called goose neck deformity) (Pinger 2019).

Inspection

• Cyanosis (since the patient is primarily acyanotic, cyanosis already indicates an increasing resistance of the pulmonary vessels)
• Voussure (also called hump of the heart; the thoracic wall protrudes to the left of the sternum [Holldack 2005])

If the development of Eisenmenger's syndrome occurs in the course of the disease, there are also:

• drum flail fingers and toes
• Watch glass nails

Palpation

• arterial hypotension
• small blood pressure amplitude
• on the left lower sternal margin there is a systolic buzzing
• above the right ventricle and the right ventricular outflow tract there are lifting pulsations
• the pulmonary valve closure is palpable
• the apex of the heart is:
  • hyperactive
  • broadened
  • shifted downwards and outwards

Auscultation

• the 2nd heart sound is fixed split with accentuated pulmonary valve part in pulmonary hypertension
• in the 2nd / 3rd ICR left parasternal in ASD with relative pulmonary stenosis, an immediate systolic murmur can be auscultated
• in the 4th / 5th ICR left parasternal finds a systolic noise due to a VSD or tricuspid valve insufficiency
• an immediate systolic murmur can be auscultated above the apex of the heart in mitral valve insufficiency
• a short, early diastolic sound can be auscultated at the lower left sternal margin or above the apex of the heart (corresponds to the flow sound of the mitral or tricuspid valve)

ECG

The following changes may be present in the ECG:

• the main vector shifts to the left; change of the position type up to the overturned left type
• Right thigh block
• signs of right, left or biventricular hypertrophy
• extended PQ time (sometimes called AV Block I. The cause, however, is an atypical stimulus conduction system and no disturbance in the AV node) (Borth-Bruhns 2004)
• P-dextrocardials (P in II and III is acute positive with > 0.2 mV and in V1, V2 the positive part of the P-wave is acute positive and higher than 0.15 mV) or - sinistrocardials (P > 0.11 sec., double peaked P-wave with emphasis on the 2nd peak) (Larsen 2009).

With AVSD there are the possibilities of conservative, purely symptomatic treatment and surgical therapy.

Conservative therapy

In AVSD, conservative therapy can be exclusively symptomatic, but not causal. Nevertheless, it can be an important preoperative bridging measure. For example, in the case of existing heart failure, appropriate drug treatment with diuretics, digitalis, ACE inhibitors, etc. can be used. (Borth-Bruhns 2004) in order to bring the patient into a more stable overall condition preoperatively (Apitz 2002).

Note: After the onset of Eisenmenger's syndrome, surgical closure of the defect alone is contraindicated. In this case a symptomatic treatment should also be performed - if necessary up to transplantation (Herold 2019).

The indication for the surgical measure and especially the timing are determined by:

• the extent of the heart failure
• according to pulmonary vascular resistance (Schmaltz 2017)

Indication for a complete AVSD:

With a complete AVSD, surgery is usually performed within the first 6 months of life, mainly between the 3rd and 6th month of life (Fabry 2016).

Using one or two patches, the septal defects in the atrium and ventricles are closed, the AV valves are reconstructed and the apposition zone is closed with a cleft suture (Schmaltz 2017).

Indication for a partial AVSD:

In the case of an incomplete AVSD, the indication for the surgical measure is set in relation to the volume load of the right ventricle and/or mitral insufficiency (Schmaltz 2017).

Surgical intervention should be performed in any case:

• for all symptomatic infants
• as soon as echocardiography shows evidence of right heart enlargement
• when the blood flow in the pulmonary circulation is in relation to the blood flow in the systemic circulation (Qp / Qs) ≥ 1.5 to 2.0: 1
• after paradoxical embolism and exclusion of other causes (Herold 2019)

As a rule, children are operated on between the ages of 2 and 4 (Schmaltz 2017).

AV valve insufficiency:

• In symptomatic patients:

Immediate surgery - if possible valve preserving - is indicated in symptomatic patients with moderate to severe left aortic valve insufficiency.

• In asymptomatic patients:

In asymptomatic patients: Surgical correction is indicated when there is moderate to severe left-sided AV valve insufficiency that is likely to be valve-preserving and there is volume stress on the left ventricle.

In addition, asymptomatic patients with a left ventricular endstolic diameter (LVESD) of > 45 mm and/or a limited left ventricular function with a left ventricular ejection fraction (LVEF) of < 60 % should be operated on (Herold 2019)

Subaortic stenosis:

In approx. 3 % - 7 % of children with AVSD a fixed subaortic stenosis can be expected (Apitz 2013).

However, subaortic stenosis can also develop postoperatively (Borth-Bruhns 2004). In this case the mean echogradient rises to > 50 mmHg and left ventricular hypertrophy occurs (Herold 2019). Here a re-operation is necessary (Apitz 2002).

Palliative surgical intervention:

Pulmonary banding with subsequent corrective surgery in the second year of life, which was practiced during the 1980s, is nowadays only performed in exceptional cases, e.g. in the case of pronounced ventricular dominance or accompanying anomalies which do not permit primary correction (Schmaltz 2017).

In a study by Hanley it could be shown that the operative mortality of infants who are operated on before the age of 6 months is lower than that of older children (Apitz 2002).

Surgical correction in balanced AVSD:

Correction is performed either with the single patch technique or the double patch technique. First, the ventricular septal defect is closed, then the AV valve is reconstructed or replaced and finally the atrial septal defect is closed with a patch (Herold 2019).

Surgical correction for unbalanced AVSD:

In unbalanced AVSD a circulatory separation in the sense of a partial cavopulmonary anastomosis (PCPC) with subsequent total cavopulmonary anastomosis (TCPC) is performed (Herold 2019).

Heart and lung transplantation:

In patients with Eisenmenger's syndrome, heart-lung transplantation is the only surgical option (Herold 2019). Closure of the defect is contraindicated. (Pinger 2019).

Natural course: Mostly signs of pulmonary hypertension with frequent pulmonary infections and failure to thrive develop already in the first year of life. The increase in pulmonary vascular resistance leads to Eisenmenger's syndrome (Pinger 2019).

Without surgical measures, 50% of the children die within the first 6 months of life and only 15% experience the 2nd year of life (Höfler 2019).

In partial AVSD, the prognosis corresponds to that of ASD I (Herold 2019), for which the prognosis is also very poor in infancy if left untreated. The lethality rate in the 1st year of life is about 50% (Stierle 2014).

Since the risk of endocarditis is still increased postoperatively due to residual functional findings, patients should receive endocarditis prophylaxis for life (Schmaltz 2017).

Therapy suggestion:

• Amoxicillin or ampicillin 2 g p. o.
• if oral administration is not possible, ampicillin or cefalexin 2 g i.v. is recommended
• in case of ampicillin or penicillin allergy, clindamycin 600 mg should be given orally or i.v. - Clindamycin 600 mg i.v.

(Herald 2018)

It is necessary to carry out lifelong follow-up examinations. If the overall result of the operation is good, these examinations should be carried out every 2 - 3 years, or more frequently if necessary.

With regard to physical fitness, there are no restrictions for patients with a good postoperative result. In all other cases, a decision should be made on a case-by-case basis.

In case of desire for children, genetic counselling is recommended for women with AVSD.

(Pinger 2019)

Pregnancy is not recommended in cases of severe pulmonary hypertension or Eisenmenger syndrome.

(pingers 2019)

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