Congenital Heart Disease: Understanding and Evaluating Cardiac Shunts

Anatomy of Atria and Ventricles

• Objective: To discuss the anatomy of the atria and the ventricles.

Shunts: Location and Significance

• Objective: To discuss where shunts may occur and why the differences in anatomy are important.

Echocardiographic Approach to Characterizing Lesions

• Objective: To describe the echocardiographic approach to how to characterize these lesions as being hemodynamically significant or not and evaluate for associated lesions.

Transthoracic Echocardiography

• Very useful for evaluation of cardiac shunts.
• Identification typically begins using 2D imaging.
• Off-axis views are important because some structures are difficult to image in standard views.
• Color flow is helpful to demonstrate the size of the lesion and the direction of the shunt.
• Pulse wave and continuous wave Doppler are used to determine gradients across and the hemodynamic effect on the RVSP (Right Ventricular Systolic Pressure).
• Saline contrast is used to evaluate atrial level communications.
  • Very useful if there is a high suspicion for a shunt but it cannot be visualized.
• One of the most useful tools to evaluate hemodynamic burden.
  • Ventricular enlargement?
  • Atrial enlargement?
  • What's going on with the RVSP?

Transesophageal Echocardiography

• Helpful when you want to better define the anatomy.
  • Where is this lesion?
  • What part of the atrium or ventricle are we seeing this in?
• Invaluable for evaluating the rims of secundum atrial septal defects and looking for associated lesions like partial anomalous pulmonary venous connection.

Interatrial Communications

• Characterized from the right atrial perspective.
• Types:
  • Secundum ASD: most common
  • Sinus venosus ASD:
    • Where the superior vena cava inserts
    • Where the inferior vena cava inserts
  • Primum defects: endocardial cushion defect abnormality
  • Unroofed coronary sinus: least common

True Atrial Septal Defects

• PFO (Patent Foramen Ovale)
• Secundum Atrial Septal Defects
  • Defect in the oval fossa tissue.

Defects Outside the Atrial Septum

• Primum defects
• Sinus venosus defects
• Unroofed coronary sinus

Secundum Atrial Septal Defects

• Pathologic Picture:
  • Hole in the fossa ovalis, a true deficiency in tissue.
  • Multiple small fenestrations.
• Characterization on transesophageal echo.
  • Has implications for whether a patient can be closed percutaneously.

Imaging

• Transthoracic Imaging
  • Apical four-chamber view, especially if modified.
  • Subcostal view.
  • Color flow from left to right and some dilation of the right heart.
• Transesophageal echo
  • 120-degree view
  • Right atrium and left atrium
  • A defect in the atrial septum.
  • Color flow going from left to right between the atria.

Rims (Secundum Atrial Septal Defects)

• Favored way of closing secundum atrial septal defects is percutaneously if they're considered appropriate by anatomy criteria.
• Six rims to describe:
  • Superior vena cava rim
  • Inferior vena cava rim
  • Posterior rim
  • Aortic rim
  • Right upper pulmonary vein rim
  • AV valve rim, so the tricuspid valve rim
• Rims are considered adequate if they're more than 5 millimeters.
• Total diameter, the largest diameter of that ASD.
  • If it's greater than 38 millimeters, we may not be able to appropriately see to the closure device, and this patient may have to go on for a surgical intervention as opposed to percutaneous.

Measuring Rims

• PFO in the zero-degree view with the aortic valve.
  • Posterior and aortic rim.
• 120-degree view
  • Bicaval view with your IVC and SVC rim.
• Rotating slightly, you can bring out the right upper pulmonary vein rim.
• 14-degree view
  • Posterior and the AV valve rim.

Ostium Primum Defects (Partial AVSD)

• Key: common AV valve.
• Left AV valve and a right AV valve.
• A five-leaflet common valve with a common junction.
• Defect in tissue at the atrial level.
• Patients typically will have regurgitation of that left AV valve because the valve has three leaflets.

Sinus Venosus Defects

• Superior ones are by far the most common.
  • Connection between the right atrium and left atrium.
• Atrial septum begins, so this is outside of the atrial septal area.
• Inferior defects
  • More challenging to visualize, but we can visualize them both on transthoracic and transesophageal echo.

Superior Sinus Venosus

• Key view: subcostal view that's in short axis, angled upwards to view the superior portions of the atria.
  • Defect in the tissue at the superior portion with color flow.
• Transesophageal echo can be very, very helpful.
  • 120-degree view
    • Right atrium, left atrial appendage, tricuspid valve, and the SVC is coming in at this part of the screen.
    • Defect in the tissue between the left atrium and the right atrium.
    • The oval fossa. The superior sinus venosus defect is remote to the oval fossa.
    • Need to make an effort to look for a superior defect in the sinus venosus area and an inferior one because these defects do come in groups.

Inferior Sinus Venosus Defect

• Short axis view subcostal
  • Visualize the inferior portion of the atria with a connection.
• Transesophageal echo in the low gastric load GE junction view
  • 60 degrees the inferior vena cava coming in and a defect between the inferior portions of the left atrium and the right atrium with left/right shunting.

Unroofed Coronary Sinus

• Very rare.
• Defects in the posterior portion of the left atrial wall which can connect into the coronary sinus.
• Echo:
  • May see a true defect there or color flow between both chambers.

Report Inclusions

• Anatomy: Where is the defect?
• Measurements of the defect?
• Describe the right heart size and function and the effect on the RVSP.
• Associated lesions
  • Partial anomalous pulmonary venous connection.
  • In the setting of a partial AVSD, the function of the left AV valve.
• Secundum ASDs
  • Describe the rims because it has implications for countless patients being closed percutaneously.

Post-Repair

• Comment on the RV size and function.
• Patch leaks.
  • Necessitate antibiotic prophylaxis.
• Patients even after repair will go on to have pulmonary hypertension.
• Comment on RVSP if possible.

Ventricular Communications

• Classified from the RV side.
• Types:
  • Perimembranous: most common, fibrous floor.
  • Juxta-arterial: fibrous roof, just under the semilunar valves.
  • Muscular ventricular septal defects: muscles surrounding them the entire way.

Anatomy

• Diagrams show the muscular, the membranous septum, and the inlet septum.
• Perimembranous VSDs:
  • Parasternal long axis view.
  • Short axis:
    • Nine o'clock to quote 12 o'clock: membranous defects.
    • Twelve o'clock to three o'clock: juxta-arterial defects.

Perimembranous VSDs

• LV, aorta
• Tissue separating it from these semilunar valves.
• Restrictive ventricular septal defect in the membranous region.
  • Parasternal long axis view showing left-to-right flow.
  • Short axis view, that same area where the membranous septum is between that nine o'clock and twelve o'clock.
• Location of this VSD jet, it can cause prolapse of the right coronary cusp and can cause progressive aortic insufficiency.
  • In some cases, the patient may have a small defect that's restrictive; it doesn't meet criteria for closure from a VSD point of view, but if it causes progressive aortic regurgitation, there may be an indication for VSD closure.

Juxta-arterial or Outlet VSDs

• Modified parasternal long axis view.
• Directly under the semilunar valves, you have the defect.
• Short axis view, in the noon to three o'clock position.
  • Defect between the aortic valve and the pulmonic valve.

Muscular VSDs

• Can be quite complicated.
• Describe the number of channels where it is.
• Modified V chamber with a four-chamber view.
  • Color flow in the distal portion of the interventricular septum.
  • At least two channels.

Restrictive vs. Non-Restrictive VSDs

• Continuous wave Doppler through the defect with an appropriate tracing.
• Is the pressure gradient high between the ventricles?
• No specific number we're looking for; it does have to be greater than 70 or 100, but if you find a very high pressure difference between the ventricles, that's likely a restrictive defect.
  • May not be hemodynamically significant or require closure unless there's some other problem that's going on also at times.
• The VSD jet may contaminate the tricuspid regurgitation jet, so evaluation of RVSP can be a little bit more challenging.
• Measuring RVSP:
  • Measure the systolic blood pressure and subtract the pressure over the VSD. (RVSP = SystolicBP -
    abla VSD)

Report Inclusions (Ventricular Septal Defect)

• Location of the defect
• Measurement of the defect
• Direction of the shunt
  • Left-to-right
  • Right-to-left
  • Bi-directional
• Systolic pressure gradient over the defect.
• Because the ventricular septal defect is after the tricuspid valve, it will volume load to the left heart, so it's important to describe the LV size and function as well as the left atrial size.
• VSP assessment is important.

Associated Lesions

• Aortic regurgitation
• Ventricular outflow tract obstruction.

Post-Repair

• Comment on LV size and function to see if there's been remodeling.
• Look for residual leaks by color flow.
• Look for aortic arch obstruction or a pulmonary artery branch stenosis depending on how the lesion was repaired.

Summary

• Anatomic evaluation and characterization is very important for cardiac shunts.
• Classify the presence, the location, and the size.
• Use tools including 2D, color Doppler, and in some cases, 3D.
• Understand the hemodynamics.
• Pre-tricuspid shunt, the volume loads the right heart.
• Post-tricuspid shunt, it will typically volume load the left heart.
• Pulmonary hypertension is an important consequence to evaluate for in every echo.
• Evaluate for associated lesions depending on the type of shunt that you have.