What is the treatment approach for Atrioventricular Septal Defect (AVSD)?

Atrioventricular Septal Defect (AVSD): Classification, Examination, and Treatment

Classification

AVSDs represent 4-5% of congenital heart defects and are classified by anatomic variations involving a primum ASD, inlet VSD, and common atrioventricular valve. 1

Anatomic Types

• Partial AVSD: Primum ASD component only with typically a cleft left atrioventricular valve, with separate left and right-sided orifices created by central fusion of bridging leaflets 1
• Complete AVSD: Both ASD and VSD components with a common atrioventricular valve and single orifice, with septal defect extending into both interatrial and interventricular septum 1
• Transitional/Intermediate AVSD: Incomplete atrial and ventricular septal defects with incomplete abnormalities of the common atrioventricular valve 1

Rastelli Classification

• Describes anatomic variations of the superior bridging leaflet of the atrioventricular valve, which guides surgical approach 1
• Ventricular balance (balanced vs. unbalanced) determines whether biventricular or single ventricle repair is appropriate 1

Associated Conditions

• 35% of AVSD patients have Down syndrome (trisomy 21), with most complete AVSDs occurring in Down patients and most partial AVSDs in non-Down patients 1
• Associated lesions include tetralogy of Fallot, coarctation of aorta, and heterotaxy syndromes 1

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Clinical Examination Findings

Physical Examination

Unoperated patients may present with findings of ASD, VSD, AV valve regurgitation, LVOT obstruction, or pulmonary arterial hypertension with cyanosis. 1

• Apical systolic murmur indicates residual mitral regurgitation or subaortic obstruction in repaired patients 1
• Single loud second heart sound with no murmur suggests severe pulmonary arterial hypertension 1
• Cyanosis and clubbing indicate Eisenmenger syndrome or RV outflow obstruction 1

Electrocardiogram

• Superior left-axis deviation with counterclockwise loop in the frontal plane is typical 1
• First-degree AV block may be present due to displaced AV node positioned posterior and inferior to coronary sinus 1
• Atrial flutter or fibrillation may develop in older patients 1
• Left atrial enlargement and LV hypertrophy indicate significant left AV valve regurgitation 1
• RV hypertrophy predominates with pulmonary arterial hypertension or RVOT obstruction 1

Chest X-Ray

• Cardiomegaly from dilation of right or left AV heart chambers depending on valve regurgitation degree and shunt direction 1
• Increased pulmonary vascular markings with significant left-to-right shunt 1
• Pulmonary venous congestion with long-standing mitral regurgitation 1
• Prominent main pulmonary artery with distal vessel pruning indicates pulmonary arterial hypertension 1

Echocardiography

Transthoracic echocardiography is the primary imaging modality for AVSD assessment. 1

• Evaluate primum ASD borders, VSD presence, AV valve morphology and function, ventricular size, shunting, and subaortic stenosis 1
• Measure pulmonary artery pressures via tricuspid regurgitation and pulmonary regurgitation jet velocity with simultaneous systemic blood pressure 1
• Distinguish residual LV to right atrial shunt from tricuspid regurgitation to avoid erroneous pulmonary arterial hypertension diagnosis 1

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Treatment Approach

Surgical Indications for Primary Repair or Residual Shunt Closure

Surgery for primary repair or closure of residual shunts is recommended when there is net left-to-right shunt (Qp:Qs ≥1.5:1), PA systolic pressure <50% systemic, and pulmonary vascular resistance <1/3 systemic. 1

Class I Recommendations (Must Perform)

• Surgery for severe left atrioventricular valve regurgitation per guideline-directed medical therapy indications for mitral regurgitation 1
• Symptomatic patients with moderate to severe AV valve regurgitation should undergo valve surgery, preferably AV valve repair 1
• Asymptomatic patients with moderate or severe left-sided valve regurgitation and LVESD >45 mm and/or LVEF <60% should undergo valve surgery when other causes of LV dysfunction are excluded 1

Class IIa Recommendations (Reasonable to Perform)

• Cardiac catheterization when pulmonary hypertension is suspected 1
• Operation for discrete LVOT obstruction with maximum gradient ≥50 mm Hg, lesser gradient if heart failure symptoms present, or if concomitant moderate-to-severe mitral or aortic regurgitation present 1
• Surgical repair in asymptomatic patients with moderate or severe left-sided AV valve regurgitation who have LV volume overload signs and substrate very likely amenable to surgical repair 1

Class IIb Recommendations (May Be Considered)

• Surgery may be considered with net left-to-right shunt (Qp:Qs ≥1.5:1) if PA systolic pressure ≥50% systemic and/or pulmonary vascular resistance >1/3 systemic 1

Class III: Harm (Must NOT Perform)

Surgery should not be performed with PA systolic pressure >2/3 systemic, pulmonary vascular resistance >2/3 systemic, or net right-to-left shunt (Eisenmenger physiology). 1

• Cardiac surgery must be avoided in patients with Eisenmenger physiology, with pulmonary vascular resistance testing recommended if doubt exists 1

Optimal Timing of Surgical Repair

Complete AVSD should be repaired early in life (typically <6 months of age) to prevent irreversible pulmonary vascular disease and Eisenmenger physiology. 1

• Primary complete repair in children <3 months of age achieves 94.2% survival at 20 years versus 58.4% with pulmonary artery banding staged approach 2
• Neonatal repair can be achieved with 100% survival at 10 years 2
• Partial AVSD repair should be deferred until ages 5-8 years when performed electively, as later age at operation (median 7.9 years) achieves only 8% cumulative incidence of more than moderate LAVVR by 2 years versus 31% with earlier repair 3
• Repair during infancy for partial AVSD results in 87.9% survival at 30 years versus 98.1% when repair performed in older children, even after propensity matching 4

Surgical Technique

• Two-patch technique with complete cleft closure is safe and reproducible, achieving very low mortality and stable long-term outcomes even in neonates 5
• Definitive early repair for complete AVSD achieves 98% survival at 1 year, 95% at 5 years, with 89% freedom from reoperation for left AV valve dysfunction at 5 years 6

Medical Management

Most patients need no regular medication in the absence of specific problems. 1

• ACE inhibitors and/or diuretics are indicated for patients with AV valve regurgitation and chronic heart failure symptoms 1
• Pulmonary vasodilation therapy may be indicated in patients with pulmonary arterial hypertension and no significant left-to-right shunt who are high-risk for surgical repair, but this approach carries high mortality risk and should be approached with extreme caution 1

Follow-Up Protocol

Lifelong regular follow-up of all patients (operated and unoperated) is recommended at specialized adult congenital heart disease centers. 1

Surveillance Intervals by Physiological Stage

• Stage A (no hemodynamic abnormalities): Every 24-36 months with ECG and TTE 1
• Stage B (mild hemodynamic abnormalities): Every 24 months with ECG and TTE 1
• Stage C (moderate hemodynamic abnormalities): Every 6-12 months with ECG and TTE every 12 months 1
• Stage D (severe hemodynamic abnormalities): Every 3-6 months with ECG and TTE every 12 months 1

Key Surveillance Parameters

• Monitor for left atrioventricular valve regurgitation and stenosis, which is the most common reason for later surgical intervention 1
• Assess for LVOT obstruction attributable to abnormal LVOT shape 1
• Screen for tachyarrhythmias and bradyarrhythmias, including late-onset complete heart block (as late as 15 years post-surgery) 1
• Evaluate residual shunt, RV and LV enlargement and dysfunction, pulmonary artery pressure elevation, subaortic stenosis 1

Critical Pitfalls to Avoid

• Do not perform surgery in patients with established Eisenmenger syndrome, as left-to-right shunting decline with pulmonary arterial hypertension therapies carries high mortality risk 1
• Monitor for late-onset complete heart block even in patients discharged with normal conduction, particularly those with transient postoperative heart block 1
• Distinguish residual LV to right atrial shunt from tricuspid regurgitation with RV hypertension to avoid misdiagnosing pulmonary arterial hypertension 1
• Recognize that surgical treatment was historically withheld in Down syndrome patients, so these patients may present unoperated with complete AVSD and Eisenmenger syndrome 1