Every day in the United States adult cardiac sonographers are put in the position of performing exams that are outside of their training and expertise. This occurs often when a facility that offers labor and delivery services has no pediatric trained sonographers. There are roughly 40,000 children born each year in the U.S. with some form of congenital heart disease (1). Many of these defects are easily seen and/or may not be serious. However there are some defects that may be missed by adult echo protocols and lead to serious complications. The purpose of this paper is not to be a substitute for a formal training in pediatric echo, but to help adult echocardiographers with a better understanding of how to perform a basic, thorough exam on a typical neonate.
The pediatric echocardiogram is a unique examination with features that distinguish it from adult echocardiograms. There is a wide spectrum of anomalies encountered in patients with congenital heart disease. Certain views are of added importance for pediatric examinations: the subxiphoid (or subcostal), suprasternal notch, and high parasternal views. The acquisition and proper display of images from these views are critical aspects of the pediatric transthoracic echocardiogram (TTE) and special techniques are often required. In fact, many centers that treat congenital heart disease (CHD) begin their protocol from the subcostal window to confirm the baby has normal abdominal situs (normal positioning of the abdominal viscera). This is achieved by starting with the probe just below the xyphoid process, scanning straight downward (no angulation) with the reference marker to 3 o’clock (2). You should identify the aorta and inferior vena cava in a transverse view. The aorta should be a thick walled, pulsatile vessel to the patient’s left. The IVC should be a thinner walled vessel to the patient’s right. You can use color Doppler to confirm the pulsatile flow in the aorta and phasic flow in the IVC. If both vessels appear phasic, we must carefully evaluate the aorta for coarctation. If the vessels are identified but are in an abnormal position, there is potential for significant misalignment of other organs as well.
(image 1 here)
Parasternal Windows
Once the patient’s situs is established, we return to the more familiar protocol, ie the parasternal windows. The parasternal views will not differ greatly from the adult exam. The aortic valve, annulus, sinuses of Valsalva, and the proximal portion of the ascending aorta can all be observed, as well as its relationship to the mitral valve (mitral-aortic continuity). The interventricular septum must be carefully visualized with color Doppler to evaluate for VSD’s. We must place a wide color window over the length of the IVS and sweep slowly from RV inflow, back across the parasternal long axis and then all the way to RV outflow. Capture the entire sweep on a single loop.
Since VSD’s only shunt during systole, they can be missed if this sweep is performed too quickly. At any time during the exam that a VSD is detected use spectral Doppler and get a max pressure gradient.
It is important to perform multiple sweeps in this type of exam. Sweeps using color flow Doppler are key to uncovering pathology that may be hidden from our adult transthoracic exam. VSD’s are easy to miss. Small VSD’s present with a systolic murmur that is most often easily recognized on auscultation but, they can also be easily missed with 2D echo only. Larger VSD’s are generally more obvious without the use of color. Small muscular VSD’s near the apex, and Perimembranous VSD’s near the aortic valve require great care during investigation.
After completion of all your typical parasternal long axis (PLAX) measurements of the left heart, we move on to the pulmonic and tricuspid valves. The right ventricular outflow tract, the pulmonary valve and branch pulmonary arteries must be heavily examined in neonates. Look for any flow disturbances or turbulence near and around the valve and pulmonary branches. Pulmonary branch stenosis is relatively common so color and pulsed wave spectral Doppler of both branches must be performed.
Tricuspid valve examination should be relatively routine as compared to the adult echo. As always be careful to assess the tricuspid insufficiency gradient from multiple windows and look for any structural anomalies.
The parasternal short axis (PSAX) exam will differ slightly in this protocol. In addition to the PW Doppler of the branch PA’s, we also pay careful attention to the aortic valve morphology and proximal coronary arteries. Assess the aortic valve leaflets carefully, especially if any turbulence or aortic insufficiency was observed in long axis. There are many different aortic valve leaflet malformations that can manifest. The most common is a bicuspid aortic valve (BAV) (3). Always evaluate for BAV during systole as it can appear misleadingly normal when closed. A normal tri-leaflet valve should have a pyramid shaped orifice, while a bicuspid valves resembles a football. Next we should evaluate the coronary arteries.
The evaluation of the coronaries will be the biggest departure from the adult exam to this point. Understanding the anatomy is key here. The right & left coronary arteries normally attach to their respective sinus of Valsalva just cephalad to the aortic valve. If we compare the aortic valve in short axis to a clock face, the left coronary is typically seen at the 4 o’clock position. The right CA has slightly more variability (4). It is most often seen between 10-12 o’clock, although usually difficult to image. If there is systolic dysfunction extra effort must be made to prove location and blood flow in the CA’s. Using color Doppler and dropping the color scale to accentuate flow is recommended. If there is systolic dysfunction, and the coronaries cannot be clearly defined this could be a serious complication.
(images 2 & 3 here)
Before moving on to the apical portion of the exam, we must perform another sweep of the IVS with color. This sweep will require a wide color box and should cover the septum from right to left. Sweep slowly from the apex all the way to aortic valve, as perimembranous VSD’s and outlet (subpulmonic) VSD’s can be found at the base view of PSAX. Once you have swept through from apex to outlet valves you will have covered the septum from top to bottom and hopefully uncovered any remaining shunts missed in parasternal long. image 4 – PSAX IVS sweep
Apical Windows
The apical windows come next and, depending on the reading physician’s preferences, you may need to invert the up/down orientation of the image. This is typically standard in the apical as well as portions of the subcostal pediatric protocol and takes some practice. Remember- we only invert the 2D image, never color or spectral Doppler!
Providing a 2 dimensional apical 4 chamber image allows for proper examination of the chambers & inlet valves, helping clarify morphology and segmental analysis. This helps to rule out pathology such as AV canal defect and Ebstein Anomaly. Next we do another color sweep of the IVS. Place the color box tall and narrow, to include the entire IVS from apex to the cardiac crux.
This sweep is begun with a posterior tilt (tail slightly up), the opposite of where we find apical 5. This will allows us to image the posterior atrioventricular groove and the coronary sinus. Begin the sweep from there and slowly sweep anteriorly from coronary sinus, past apical 4 and apical 5. If you continue to sweep anteriorly past the aortic valve you will eventually reach the pulmonic valve, the most anterior valve. Once you have swept through from coronary sinus to pulmonic valve you will have covered the septum from front to back and hopefully uncovered any remaining shunts missed from the parasternal views.
image 5 – Apical IVS sweep
After completing this sweep evaluation of the valves is fairly routine with few exceptions. The mitral inflow pattern may show E/A reversal but this is not uncommon in newborns. The addition of pulmonic valve evaluation to the 2D/color Doppler/spectral Doppler exam is important here.
Subcostal WindowsAt the point, if you did not begin the exam with the subcostal view to establish abdominal situs, it is done here. The subcostal view provides the most comprehensive information on cardiac structure. After establishing situs and evaluation of the IVC & aorta longitudinally, we will again invert to the up/down perspective. Evaluate the atrial septum from the 4 chamber view with 2D & color flow Doppler. Take another look at the IVS with color as well, and obtain VSD max pressure gradient. By tilting the probe anteriorly (tail down) the LVOT, aortic valve and aortic arch can be visualized.
After the 4 chamber scan, rotate the probe clockwise until the reference marker is at 6 o’clock (pointing at the feet). From here perform a short axis sweep from apex to vena cava entrance. Start the sweep from the patient’s far left (LV apex) continuing until the probe is angled towards the patient’s right shoulder. The end of the sweep provides a view of both vena cava feeding into the right atrium and another angle of the IAS. This bi-caval view is very important for showing sinus venosus ASD’s. Another way of achieving the bi-caval view is start from the 4 chamber image & rotate the probe clockwise to 6 o’clock until the ventricles are gone & the vena cava appear!
image 6 – bicaval view
Suprasternal Window
Start this scan much like you would the in adult arch exam with 2D, color Doppler & CW velocities from the ascending and descending aorta. Look carefully at the isthmus to rule out coarctation. After that evaluate arch sidedness & normal branching. Begin by tilting the probe towards the patient’s right shoulder. Color Doppler will reveal a large vessel with blue flow, the superior vena cava (SVC). From here begin a sweep from SVC, past the aortic arch, and to the left of the arch. This can help rule out double or persistent right aortic arch anomalies. Then, return to the standard arch view for one last sweep. Rotate the reference marker to 3 o’clock for a short axis view of the transverse arch, with elongation of the right pulmonary artery just below. As you sweep up towards the neck, follow the first take-off, the brachiocephalic artery. The brachiocephalic should continue up & to the right, then split into 2 vessels.
image 7 – brachiocephalic bifurcation
Please document any deviation that can be appreciated, then return to the short axis view of the arch. From here, the notch should be at roughly 3 o’clock. Jump below the clavicle and tilt slightly posterior. You should see the 2 great arteries in the transverse view. Directly below those lies the left atrium. By using color with this view of the LA we can see all 4 pulmonary veins emptying in, one from each corner (top 2 blue, bottom 2 red). Finally, by angling the beam anteriorly towards the pulmonary artery, we open up the branch PA’s. This widened view of the branches allows for better evaluation of a patent ductus arteriosus (PDA). If a PDA is present, always use CW Doppler to show a max gradient.
image 8 – pulm branches)
image 9 – crab view (Left atrium)
Conclusion
Having completed the basics of the neonatal echo here a few footnotes.
1.Less is More: Don’t go overboard with pictures as this protocol is long enough without adding multiple views of the same thing. Keep the scan and reading time “as low as reasonably achievable”.
2- If there is suspicion of Down Syndrome be on extra alert. With many genetic syndromes comes the increase risk of structural heart disease. Trisomy 21 the prevalence is 40-60% (5).
3. Use this checklist when performing any pediatric exam to help make sure no stone was left unturned:
1. Is the heart normally positioned in the chest?
2. Are the ventricular relationships normal?
3. Are all 4 chambers normal?
4. Are all 4 valves normal?
5. Are the ventricular inflows obstructed?
6. Are the ventricular outflow tracts normal?
7. Are the chordae and papillary muscles normal?
8. Are the atrial and ventricular septa normal?
9. Are the pulmonary venous connections normal?
10. Are the systemic venous connections normal?
11. Is the coronary sinus normal?
12. Are the main pulmonary artery and branches normal?
13. Are all the segments of the aorta and its branches normal?
14. Is there evidence of persistent fetal circulation?
15. Is there suspicion of genetic disorders?
4. the pediatric cardiologist should be immediately consulted if any abnormality is detected or suspected.
With practice and patience you can master all the skills covered in this article. I hope this encourages you to continue learning about the world of pediatric echo & congenital heart disease. Good Luck!
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References
1.Alexander Egbe , Santosh Uppu, Annemarie Stroustrup, Simon Lee, Deborah Ho, Shubhika Srivastava.
Incidences and Sociodemographics of Specific Congenital Heart Diseases in the United States of America: An Evaluation of Hospital Discharge Diagnoses
Pediatr Cardiol2014 Aug;35(6):975-82.
doi: 10.1007/s00246-014-0884-8. Epub 2014 Feb 22.
https://pubmed.ncbi.nlm.nih.gov/24563074/
2.Josh Kailin, MD
Pediatric Echocardiography: Subcostal Liver/Spine – How to Obtain
https://pedecho.org/library/normal/echocardiogram/subcostal-liver-spine-p4a
3. Samuel C. Siu, MD, SM and Candice K. Silversides, MD, SM
Bicuspid Aortic Valve Disease Journal of American College of Cardiology vol. 55 no. 25 2789-2800
http://www.onlinejacc.org/content/55/25/2789
4.Subhash D. Joshi, Sharda S. Joshi, and Sunita Arvind Athavale
Origins of the Coronary Arteries and Their Significance Clinics vol.65 no.1 São Paulo 2010
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2815286/
5. Min-A Kim, You Sun Lee, Nan Hee Yee, Jeong Soo Choi, Jung Yun Choi, and Kyung Seo
Prevalence of Congenital Heart Defects Associated with Down Syndrome in Korea J Korean Med Sci. 2014 Nov; 29(11): 1544–1549. Published online 2014 Nov 4.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4234923/
