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Atrioventricular septal defects

  2. INTRODUCTION • Group of anomalies that share a defect in atrioventricular septum and abnormal AV valves. • Also known as Endocardial cushion defect, AV canal defect, canalis atrioventricularis communis, persistent atrioventricular ostium • Broadly divided into partial and complete forms.
  3. DEMOGRAPICS • 4 TO 5 % Of congenital heart defects. • Estimated occurrence of 0.19 in 1,000 live births • Male = female or slight female preponderance. • Downs syndrome: 40 to 45% have heart disease. • Of which 45% have avsd. • > 75 % of these are the complete form. • Conversely approximately 50% of avsd patients have downs syndrome.
  4. HISTORY  Rogers, Edwards : Recognised morphological similarity of ostium primum ASD and complete defect in 1948  Wakai, Edwards : Term of partial and complete AV canal defect in 1956  Bharati & Lev : Term of Intermediate & Transitional in 1980  Rastelli: Described the of common anterior leaflet in 1966  Lillehei : 1st repair of AVSD in 1954  Kirklin, Watkin, Gross: Open repair using oxygenator
  6. • Defect in endocardial cushion development and fusion. • Additional pathways have now been illustrated, which shows that “dorsal mesenchymal protrusion”(vestibular spine) is responsible for formation of avsd. • In partial AVSDs, incomplete fusion of the superior and inferior endocardial cushions results in a cleft in the mid- portion of the left AV valve anterior leaflet often associated with regurgitation. • In contrast, complete AVSD is associated with lack of fusion between the superior and inferior cushions and, consequently, with the formation of separate anterior and posterior bridging leaflets along the subjacent ventricular septum
  7. • Since the dextrodorsal conus cushion contributes to the development of the right AV valve and the outflow tracts lie adjacent to their respective inflow tracts, AVSDs may be associated with conotruncal anomalies, such as tetralogy of Fallot and double-outlet right ventricle (RV). In addition, shift of the AV valve orifice may result in connection of the valve primarily to only one ventricle, creating disproportionate or unbalanced ventricles.
  9. Pathology  In the normal heart, the aortic valve is wedged.  In AVSD the aortic valve is displaced anteriorly and creates an elongated, k/a gooseneck deformity of the LVOT 14
  11. • Normal MV – Posterior leaflet : 2/3 circumference • AVSD MV – Left lateral leaflet : 1/5 circumference
  13. ANATOMICAL CLASSIFICATION (RASTELLI) • Prior to 1964, hospital mortality for patients with AVSD was 60 %. • Rastelli et al. from the Mayo Clinic published their work in 1968 and operative mortality between 1964 and 1967 decreased to 20 % .
  14. Anatomical Classification of AVSD (Rastelli’s, 1966) Based bridging of LSL across IVS Rastelli type A : (55%) Anterior bridging leaflet divided and attached to crest of ventricular septum. • Interventricular communication beneath the anterior bridging leaflet may be minimal or absent in some cases owing to extensive interchordal fusion. 20
  15. Anatomical Classification of AVSD (Rastelli’s, 1966) Rastelli type B : (3%) anterior bridging leaflet larger , straddles the septum and papillary muscle attachment to the septum/moderator band of RV. Chordal anchors are absent ,hence interventricular communication is present. 21
  16. Anatomical Classification of AVSD (Rastelli’s, 1966)  Rastelli type C : (30%) anterior bridging leaflet is larger than in type B. • its medial papillary muscle attachments fuse to the right-sided anterior papillary muscle. • Free interventricular communication is present. • Also called free floating chordae. 22
  17. • The subtype of complete AVSD has some bearing on the likelihood of associated lesions. • Type A usually is an isolated defect and is frequent in patients with Down syndrome • Type C is encountered with other complex anomalies, such as tetralogy of Fallot, double- outlet RV, complete transposition of the great arteries, and heterotaxy syndromes
  20. • Two separate annuli • Ostium primum asd and cleft left anterior av valve. • The cleft in the left AV valve anterior leaflet is directed toward the midportion of the ventricular septum, along the anteroinferior rim of the septal defect. • The left AV valve orifice is triangular rather than elliptical ( as in a normal heart) and resembles a mirror-image tricuspid valve orifice. • The cleft left AV valve usually is regurgitant and, with time, becomes thickened and exhibits histologic alterations that resemble myxomatous mitral valve prolapse.
  21. • Although patients with partial AVSD may be asymptomatic until adulthood, symptoms of excess pulmonary blood flow typically occur in childhood • Tachypnea and poor weight gain occur most commonly when the defect is associated with moderate or severe left AV valve regurgitation or with other hemodynamically significant cardiac anomalies. • Patients with primum ASDs usually have earlier and more severe symptoms, including growth failure, than patients with secundum ASDs.
  22. COMPLETE AVSD • Tachypnea and failure to thrive invariably occur early in infancy as a result of excessive pulmonary blood flow • All patients with complete AVSD have symptoms by 1year of age • AV valve regurgitation compounds these problems.
  24.  The outcome of live-born patients with AVSD depends on the  specific morphology of the defect  The size of the ventricular septal defect  Degree of ventricular hypoplasia  Degree of AV valve regurgitation  Presence or absence of LVOT obstruction  Presence or absence of coarctation of aorta  Associated syndromes (cardiac and noncardiac) Natural History 35
  25.  Patients with the complete form of AVSD and large VSD not undergoing repair die in infancy with CHF & PAH  Those who survive without surgery into childhood usually develop pulmonary vascular obstruction and eventually die with Eisenmenger’s syndrome  Berger and his colleagues found that only 54% of patients born with a complete form of AVSD were alive at 6 months of age, 35% at 12 months, 15% at 24 months, and 4% at 5 years of age  This data would support surgical intervention in the first 3–6 months of age 36 Natural History Berger TJ,et al Ann Thorac Surg 1979; 27: 104–11.
  26.  Infants with 10 ASD presenting in infancy have a poor outcome, mainly because of the associated risk factors that bring these infants to early attention  Those with the partial form of AVSD and minimal left AV valve regurgitation seem to fare the best without surgery, although there is still likely considerable morbidity and mortality  According to Somerville, 50% die before 20 years of age and only 25% survive beyond 40 years of age  Atrial fibrillation in these patients was an important cause of late morbidity and mortality 37 Natural History
  27.  ECG  Superior” QRS axis with the QRS axis between -40 and -1500  Most of the patients have a prolonged PR interval  More than 50% have atrial enlargement  RVH or RBBB is present in all cases (2/3rd have rsR, RSR or Rr in lead V1, and the rest have a qR or R pattern) & many have LVH  In 10 ASD findings are same as 20 ASD except for enlargement of the LA & LV when MR is significant  In complete AVSD cardiomegaly is always present and involves all four cardiac chambers. Pulmonary vascular markings are increased, and the main PA segment is prominent ECG 38
  28.  Primary imaging technique for diagnosing AVSD  The internal cardiac crux is the most consistent imaging landmark  Apical four-chamber imaging plane clearly visualizes the internal crux Echocardiography 39
  29.  Several echocardiac features are shared by all forms of AVSD:  Deficiency of a portion of the inlet ventricular septum  Inferior displacement of the AV valves 40 Echocardiography
  30.  The most common left AV valve abnormality, a cleft, is best visualized from the parasternal and subcostal short-axis imaging planes. Echocardiography 42
  31.  In the transitional form of partial AVSD, there is aneurysmal replacement of a portion of the inlet ventricular septum Echocardiography 43
  32.  Rarely required for diagnosis  In older patient it may have a role in assessing the degree of pulmonary vascular obstructive disease or CAD  A large Lt to Rt shunt at the atrial level demonstrated by a significantly higher oxygen saturation sampled from the RA compared with the blood in the IVC & SVC  In complete AVSD the PASP is invariably at or near systemic level, while in partial AVSDs, the PASP is usually <60% of systemic pressure  LV angiography - gooseneck deformation of the LVOT Cardiac Catheterization & Angiography 44
  33.  Left to-right shunting increases the oxygen saturation in RA  Sample from high in the SVC usually represents the best mixed venous oxygen saturation (normal or 40 to 50%)  Usually a further increase in oxygen saturation in the RV  Pulmonary venous oxygen saturation is frequently reduced to 93–95% in older individuals with very large L to R shunts  LA & LV O2 saturation is often decreased to as low as 86–88% 45
  34. INDICATIONS • Complete AVSD a. Uncontrolled heart failure: Complete surgical repair as soon as possible (Class I) b. Controlled heart failure: Complete surgical repair by 3 months of age (Class I) c. Pulmonary artery banding: May be considered in select patients under 3 months of age (Class IIb). ii. Partial or intermediate AVSD, stable, and with normal pulmonary artery pressures: Surgical repair at 2–3 years of age (Class I) iii. Associated moderate or severe AV valve regurgitation may necessitate early surgery in partial or intermediate forms. iv. Pulmonary artery banding is reserved for complex cases and in patients with contraindications for cardiopulmonary bypass (Class IIb).
  35. Surgery for moderate-to-severe left AV valve regurgitation is recommended as per the guidelines for mitral regurgitation.(Class I). vi. Surgery for left ventricular outflow tract obstruction is reasonable with a peak systolic gradient of ≥50 mmHg, or at a lesser gradient if heart failure symptoms are present, or if concomitant moderate-to-severe atrioventricular or aortic regurgitation is present (Class IIa). vii. Those presenting beyond 6 months of life with significant pulmonary hypertension and suspected elevated PVR should be referred to a higher center for further evaluation to assess operability.
  37. SIZING THE PATCH • Too wide: LVOTO • Too long : AV Valve regurgitation.
  39. Australian technique (Modified single patch technique) • For complete AV canal defect with minimal AV valve distortion
  42. Results (single v/s double patch)
  43. Results (single v/s double patch)
  44. Results (single v/s double patch)
  45. What to perform ??
  46. FOLLOW UP Recommendations for follow-up i. Lifelong follow-up is required. ii. In patients with no significant residual abnormality,annual follow-up is required till 10 years of age followed by 2– 3-yearly follow-up. The patient should undergo physical examination, ECG, and echocardiography at each visit, and a Holter monitor test may be required in select cases. iii. IE prophylaxis is recommended for 6 months after surgical closure. However, all patients are advised to maintain good oro-dental hygiene after this period also.

Notas do Editor

  1. The development of the heart starts with the generation of the precardiac mesoderm forming two bilateral primary heart fields. These heart fields eventually fuse thereby creating the linear primary heart tube [27,28]. This heart tube consists of a myocardial outer mantle, an acellular matrix, often referred to as the cardiac jelly, and an inner endocardial tube [29]. The heart tube is initially suspended from the rest of the embryo over its entire length by the dorsal mesocardium. During cardiac looping this dorsal mesocardium largely disintegrates with the exception of the persisting dorsal mesocardium at the venous pole of the heart [30]. As the heart tube remodels, the atrial and ventricular chambers expand by a process sometimes referred to as ballooning [31]. During this process the chambers gradually lose most of the cardiac jelly between the myocardium and endocardium with the exception of the cardiac jelly at the atrioventricular junction (AVJ) and the outflow tract (OFT). In these parts of the heart, the cardiac jelly is accumulating in the subendocardial space resulting in the formation of prominent cushions. While in the early stage of their development these extracellular matrix-rich cushions do not contain any cells, a subsequent endocardial epithelial-to-mesenchymal transformation (endoEMT) generates a cohort of endocardially-derived mesenchymal cells that gradually migrates into and populates the cushions a process that is initiated around ED 9.5 in the mouse [32]. Within the AV junction, the two major (or midline) AV cushions form first. Around ED12.5, the major cushions fuse, thereby dividing the common AV canal into the left and right AV junction. In the left AV junction, forming the communication between the left atrium and left ventricle, the left AV valve (or mitral valve in the human) will develop, and in the right AV junction, connecting right atrium and right ventricle, the right AV valve (or tricuspid valve in the human) will form. The fused major AV cushions play a significant role in AV valve development as the aortic (or anterior) leaflet of the left AV valve, as well as the septal leaflet of the right AV valve derive from the fused major cushions [33,34]. Importantly, the fused major cushions also form the mesenchymal base on which the atrial septal complex develops [35]. After the formation of the major AV cushions a second set of cushions forms at the lateral AV junctions (Figure 2). These lateral AV cushions, which also become populated with mesenchymal cells as a result of endoEMT, are significantly smaller than the major cushions. The right lateral cushion eventually forms the parietal leaflet of the right AV valve, while the left lateral cushion forms the parietal (or mural/posterior) leaflet of the mitral valve.
  2. Transitional AVSD is a subtype of partial AVSD. This term is used when a partial AVSD also has a small inlet VSD that is partially occluded by dense chordal attachments to the ventricular septum. Intermediate AVSD is a subtype of complete AVSD that has distinct right and left AV valve orifices despite having only one common annulus. These separate orifices are referred to as right and left AV valve orifices rather than tricuspid and mitral. This also is true when describing the valves after repair of complete AVSD. The VSD in intermediate AVSD is large similar to other forms of complete AVSD