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Atrial Septal Defect

Atrial Septal Defects and Partial Anomalous Pulmonary Venous Connection

1. Definitions

A. ASD: Hole in atrial septum
B. Left to right shunt
C. PAPVR: Some of pulmonary veins return to RA or its tributaries

2. ASD Morphology

A. Fossa ovalis (ostium secundum) - Most common
B. Posterior
C. Ostium primum
D. Coronary sinus
E. Subcaval
F. Confluent

3. PAPVR Morphology

A. Sinus venosus syndrome
B. RSPV to SVC
C. RPV to RA
D. RPV to IVC - Scimitar syndrome
E. Rare connections of RPV
F. Anomalous LPV connections
G. Bilateral PAPVC

4. Scimitar Syndrome

A. RPV to IVC
B. Anomalous vein parallel to pericardium
C. Enters at or below IVC - RA junction
D. Associated with anomalies of right lung
E. Associated with cardiac and diaphragmatic anomalies in about 20%

5. Cardiac Chambers in ASD

A. Increased RA/LA normal
B. Increased RV/LV normal or decreased
C. Mitral Valve and ASD
D. Mitral prolapse 20%
E. Mitral regurgitation 2-10%
F. Cleft mitral valve

6. Clinical Features

A. Symptoms - Respiratory, Cardiac, Emboli
B. Signs
1) Chest X-ray - PA, Arch, Sinus venosus, Scimitar
2) ECG
3) Echocardiogram
4) Catheterization
5) Others

7. Miscellaneous Features

A. Survival
B. Pulmonary hypertension
C. Spontaneous closure
D. Ventricular function
E. AV valves
F. Supraventricular arrhythmias
G. Systemic hypertension

8. Indications for Repair (ASD or PAPVC)

A. Qp/Qs > or = 2
B. Scimitar
C. PAPVR
D. Part of one lung; < or = 1.8 - No
E. Whole lung - Yes
F. Age
G. Pulmonary vascular disease
H. TVD, MVD

9. Special Considerations

A. Percutaneous closure
B. Cardioplegia
C. Direct vs patch closure
D. Late sinus venosus syndrome

10. Post-Operative Care and Results

A. Older patients - Increased LA
B. 35 years - Coumadin
C. Survival/Morbidity
D. Complications
E. Recurrence

EXTENDED OUTLINE

1. Introduction

A. Present in 10-15% of pts w/CHD
B. Most common congenital lesion in adults
C. First cardiac lesion successfully repaired w/extracorporeal circulation (Gibbon, 1953)

2. Anatomy

A. Defects near IVC/SVC result from regression of the interatrial fold
B. Patent foramen ovale
1) Present in 20% of normal people
2) High RA pressures result in R to L shunting
3) Distended atria leads to communication
4) Should be routinely closed during other procedures (except when R ht failure expected)
C. Secundum ASD
1) Foramen ovale type (2/3)
a) Underdevelopment of the septum primum
b) 0.5-2cm wide x 1-6cm long, fenestrated atrial tissue
2) Sinus venosus or superior vena cava type - junction of RA + SVC (10%)
a) Inferior portion is superior limbic septum - SVC orifice displaced to left
b) Almost always assoc. w/ partial anomalous connection (RUL & RML)
3) Low or IVC type - between inferior limbic septum and IVC ( 20%)
a) Occasional RLL venous connection to RA
b) No inferior rim - avoid compromising IVC orifice
c) May be associated w/CS to LA
d) Unroofed CS (usually associated w/ LSVC) may allow RA-LA communication
4) Common atrium (single atrium) - endocardial cushion defect if primum ASD present

3. Associated lesions (ASD may be associated w/ any congenital anomaly)

A. Pulmonary stenosis - 10%
B. Partial anomalous venous return - 7%
C. VSD - 5%
D. ASD + rheumatic mitral stenosis = Lutembacher syndrome

4. Pathophysiology (flow depends upon size and ventricular compliance)

A. Normally, RV compliance is greater than LV compliance, therefore shunting is L to R (limited for small defects)
B. Defects 1-2cm 2, atrial pressures are equal, shunting depends upon ventricular compliance
1) Newborn: compliance is roughly equal, so there is mixed shunting
2) First weeks of life, RV compliance decreases, leading to L to R shunting
3) Unrestricted ASD, Qp = 2-4xQs
C. Increased Pulmonary flow
1) Children: 5-8% have PA pressure 50mm Hg
2) Age 40: 35-50%
3) May have difficulty maintaining high systemic output during exercise
4) Eventually shunt reverses (2 to increased PVR) causing increased cyanosis (no longer surgical candidates)
5) Incidence of arrhythmias and MV disease increase w/age
D. Life expectancy = 50 yrs untreated (progressive CHF)

5. Clinical features

A. Typically asymptomatic w/ murmur
1) 50-60% have easy fatigability
2) “gracile” (thin) habitus
3) M:F = 1:2
B. PE
1) Prominent RV impulse along lower left sternal border
2) Systolic ejection murmur along L sternal border from increased pulmonary flow
3) Mid-diastolic murmur near apex from increased TV flow
4) Fixed splitting of 2nd heart sound
C. ECG
1) RVH, QRS axis +95 - +150
2) Incomplete RBBB
D. CXR = cardiomegaly, increased pulmonary vascularity (CXR may be normal)
E. ECHO
F. Cath - usually not needed

6. Differential diagnosis

A. AV canal defect, VSD
B. Other causes of oxygen step-up in RA
1) Anomalous PV connection
2) Sinus of valsalva aneurysm w/ rupture into RA
3) Coronary artery fistula into RA
4) Left sided obstructive lesions causing L to R shunt

7. Treatment

A. Indications for surgery
1) Significant ASD (by PE, EKG, echo)
2) 3-5 yo
3) Spontaneous closure extremely rare after 2 yo
4) Infant in CHF w/failure of medical therapy
5) Adults L? R shunt 1.5-2:1
B. Contraindication to surgery: severe pulmonary vascular disease (PVR 1/2-2/3 systemic)
C. Operative management
1) Incision - median sternotomy, submammary, R thoracotomy
2) Cardioplegia & aortic cross-clamping
3) Primary or patch (pericardial or prosthetic) closure
4) Attention to SA node and to tension on septal tissue
5) Sinus venosus type- pericardial baffle (leave a small, high PV draining into SVC)
6) Air
7) Catheter-based devices

8. Results

A. <1% mortality
B. Complications
1) Air embolus (CVA, RCA MI)
2) SVT
3) Injury to SA or AV nodes
C. Cardiomegaly usually resolves if ASD corrected before third decade