(14) Septal Defects

How does heart development begin embryologically?

As a primitive tube that bulges, loops, and twists to form chambers and valves

What structure forms the embryonic outflow tract between the primitive ventricle and the aorta?

Bulbus cordis

Which developmental structure contributes to the atrial septum and membranous ventricular septum?

Endocardial cushions

Which valves are partially formed by the endocardial cushions?

Mitral valve and tricuspid valve

What is the origin of the six paired aortic arches?

Distal truncus arteriosus

Which structures are formed by the right and left 3rd arches?

Right and left carotid arteries

What does the left 4th aortic arch contribute to?

The aorta

What does the right 4th aortic arch contribute to?

The innominate/right subclavian system

What is the developmental outcome of the right 6th aortic arch?

The right pulmonary artery

What two structures does the left 6th arch contribute to?

The left pulmonary artery and ductus arteriosus

What duration is recommended for sweeps through the anatomy when scanning adults for CHD?

$$10-20\,\text{seconds}$$

Why are dynamic sweeps preferred over short static clips in adult congenital echo?

To better capture complex anatomy through continuous motion

What does a median sternotomy scar usually indicate on a patient?

Prior open-heart surgery

What are three possible prior procedures indicated by a lateral thoracic scar?

Shunt placement, coarctation repair, or PDA ligation

What is the first step in establishing cardiac situs?

Obtaining a subcostal abdominal view

Define situs solitus based on the location of the aorta, stomach, and spleen.

Aorta, stomach, and spleen are left-sided

Define situs solitus based on the location of the liver and IVC.

Liver and IVC are right-sided

What is situs inversus?

The mirror image arrangement of situs solitus

What term describes variable organ arrangement that may include absent or multiple spleens?

Situs ambiguus

Define levocardia.

Cardiac apex is on the left

Define dextrocardia.

Cardiac apex is on the right

Define mesocardia.

Cardiac apex is in the midline

Which cardiac chamber is characterized by coarse trabeculations and a tricuspid valve?

$\mathbf{RV}$ (Right Ventricle)

Which cardiac chamber is characterized by smoother, thicker walls and the mitral valve?

$\mathbf{LV}$ (Left Ventricle)

How can the aortic arch be morphologically identified compared to the pulmonary artery?

The aortic arch normally has $3$ branches, while the pulmonary artery bifurcates into $2$ branches

What systematic steps should be taken once CHD anatomy is established?

Search for defects, calculate Qp/Qs if shunts are present, and document chamber or pressure consequences

What are the four categories of adult Congenital Heart Disease listed?

Abnormal intracardiac connections, abnormal chamber-to-vessel connections, congenital stenotic lesions, and congenital regurgitant lesions

What is the most common congenital cardiac anomaly in children?

Ventricular Septal Defect (VSD)

What type of murmur is typically associated with a VSD?

Holosystolic murmur

How is a small, restrictive VSD defined in terms of the aortic annulus?

Usually less than about $\frac{1}{3}$ the aortic annulus diameter

What is the clinical significance of a large, nonrestrictive VSD regarding chamber pressures?

RV and LV systolic pressures may be near-equal

What is the normal ratio for Qp/Qs?

$$1:1$$

What Qp/Qs ratio is considered significant?

$1.5:1$ or greater

What Qp/Qs ratio represents a large shunt in the source notes?

$2:1$ or greater

In a left-to-right shunt, which flow is higher: Qp or Qs?

$Qp$ (pulmonary flow) exceeds $Qs$ (systemic flow)

Where is the RVOT diameter measured for Qp/Qs calculations?

In PSAX near the pulmonary leaflet bases

What is the mathematical formula for Cross-Sectional Area (CSA)?

$$CSA = 0.785 \times D^2$$

Which Doppler measurement is used with CSA to calculate Stroke Volume (SV)?

$$\text{PW Doppler VTI}$$

What is the formula for Stroke Volume in the context of shunt calculations?

$$SV = CSA \times VTI$$

Where is the LVOT diameter measured for systemic stroke volume?

In PLAX at the aortic leaflet bases

How is the Qp/Qs ratio calculated using stroke volumes?

$$Qp/Qs = \frac{\text{pulmonary stroke volume}}{\text{systemic stroke volume}}$$

What is the most common type of VSD and its location?

Perimembranous VSD; located in the LVOT near the aortic valve

What clock-face position in PSAX is characteristic for a perimembranous VSD?

$$10-12\,\text{o'clock}$$

List three associations with perimembranous VSDs.

Aortic insufficiency, ventricular septal aneurysm, and aortic cusp prolapse

What are the common names for a VSD located in the muscular interventricular septum?

Muscular or trabecular VSD

What term describes multiple small muscular VSDs?

Swiss cheese

What are the best imaging windows for a muscular VSD?

Subcostal and apical $4$ or $5$ chamber views

What echo artifact may occur at the apex near a muscular VSD?

T-artifact

What is the second most common type of VSD?

Muscular VSD

Where is an outlet VSD (supracristal/subpulmonic) located?

RVOT near the pulmonic valve at PSAX $12-2\,\text{o'clock}$

Which aortic valve finding is common with an outlet VSD?

Right aortic cusp prolapse and aortic insufficiency

Where is an inlet VSD located?

Posterior septum near the posterior tricuspid leaflet

What larger defect spectrum is the inlet VSD associated with?

AV (atrioventricular) septal defect

Why are multiple windows needed to define VSD location?

To avoid dropout artifact and ensure accurate definition of the defect

In which direction is VSD shunting typically directed before pulmonary vascular disease develops?

Left-to-right

What information does CW Doppler provide regarding a VSD?

It measures the VSD jet gradient

What does a higher VSD jet gradient usually indicate?

A smaller, more restrictive defect

How do small-to-moderate shunts affect the left heart?

They cause LV and LA dilation from left-heart volume overload

What are the consequences of medium or large VSDs on the right heart?

RV pressure/volume overload and pulmonary hypertension

What is Eisenmenger physiology in the context of VSD?

The progression of large longstanding defects to right-to-left shunting

What is the formula to estimate RVSP using a VSD gradient?

$$RVSP \approx \text{systolic BP} - \text{VSD systolic pressure gradient}$$

What are the two common surgical or interventional methods for closing a VSD?

Transcatheter occluder devices and surgical patch or suture repair

What should be assessed during a post-repair echo of a VSD?

Residual shunt, LV size/function, LA size, and systolic pulmonary artery pressure

What is an Amplatzer-type device used for?

Transcatheter closure of septal defects like VSDs

What is the cause of a Patent Foramen Ovale (PFO)?

Failure of the foramen ovale flap to fuse permanently after birth

What normally keeps a PFO functionally closed in healthy adults?

Left atrial pressure

What is the estimated prevalence of PFO in adults according to the notes?

$$25\%$$

What diagnostic tool is used to assess right-to-left interatrial passage?

Agitated saline contrast

How can sensitivity for detecting a PFO be increased during a bubble study?

Using Valsalva maneuver or coughing to transiently raise right atrial pressure

When microbubbles appear in the LA within the first few cardiac cycles, what does it suggest?

An intracardiac shunt

What does the late appearance of microbubbles in the left atrium suggest?

An intrapulmonary shunt

What are Atrial Septal Defects (ASD) associated with in adults?

Interatrial septal aneurysm and systemic thromboembolism

What factors determine the hemodynamic impact of an ASD?

Defect size, location, ventricular compliance, and pulmonary vascular resistance

What is the cardiac consequence of a larger left-to-right ASD shunt?

Right-heart volume overload

Identify the most common type of ASD and its location.

Secundum ASD; located in the mid atrial septum/fossa ovalis region

What valve pathology is sometimes associated with secundum ASD?

Mitral valve prolapse

Describe the location of a primum ASD.

Inferior septum near the AV valves

What two conditions are associated with primum ASDs?

Cleft mitral valve and AV septal defect spectrum

Where occurs a sinus venosus ASD?

Near the SVC or IVC entrance

What is a common association for a sinus venosus ASD?

Partial anomalous pulmonary venous return

Where is a coronary sinus defect located and what is it associated with?

Located in the inferior/posterior septal region; associated with persistent left SVC

What is common atrium, and what syndrome is it associated with?

Near-complete absence of the atrial septum; associated with Ellis-van Creveld syndrome

Describe the classic murmur and heart sound finding for an ASD.

Systolic murmur with a fixed split $S2$

Name four symptoms of an ASD that may manifest in adulthood.

Exertional dyspnea, orthopnea, jugular venous distention, and peripheral edema

Which echo view is optimal for 2D, Color, and Doppler evaluation of the atrial septum?

Subcostal views

Why is the apical view less ideal for the atrial septum?

Edge dropout (T artifact) may occur

Describe the normal flow pattern of an ASD.

Predominantly left-to-right, with a potential transient reversal in early systole

What does bidirectional or low-velocity flow in a large ASD indicate?

Right atrial pressure is approaching left atrial pressure

What effect does increased right-sided pressure have on the IVS in an ASD patient?

Flattening of the IVS in diastole, creating a D-shaped LV

What Qp/Qs threshold represents a significant ASD shunt?

$$1.5:1$$

Within how many beats should bubbles appear in the LA to support an intracardiac shunt?

$$1-3\,\text{beats}$$

What constitutes a negative bubble study?

No bubbles crossing the septum into the left atrium

What is the common treatment for a suitable secundum ASD?

Percutaneous transcatheter closure

What two factors must be evaluated before ASD device placement?

Defect rim and diameter

Which imaging modalities might guide transcatheter ASD device closure?

$$\text{TEE or intracardiac echo}$$

Why do primum and sinus venosus defects usually require surgery?

Because of their adjacent anatomy

What should follow-up echo confirm after ASD treatment?

Device/patch position, absence of residual shunt, and pulmonary pressure response

What is the primary developmental cause of an atrioventricular septal defect (AVSD)?

Incomplete development of the endocardial cushions

Which genetic condition is strongly associated with AVSD?

Trisomy $21$

List four clinical findings of AVSD.

Holosystolic murmur, dyspnea, cyanosis, and fatigue