Fetal Heart Screening: Four-chamber View - USA

This course includes a discussion of fetal circulation, the four-chamber view of the heart, and an explanation of 2D-mode anatomy using diagrams, sonographic images, and videos. 
Successful completion of this training is eligible for American Society of Radiology Technician (ASRT) Category A continuing education units (CEU).

Prenatal care often includes routine sonographic examinations for dating, growth, and anatomic surveys. Multiple organ systems imaged during the sonographic examination provide determination of fetal normalcy. The embryonic fetal heart begins beating during the 22nd to 23rd days with four-chamber morphology complete by eight weeks.1   Sonographic detail allows imaging of the heart in the first trimester; however, the echocardiographic exam usually occurs between 18-22 weeks of age.1, 2 Images obtained as early as 13-weeks can show anatomy; however, the exam may be incomplete due to the small size of structures.   This United States penny measures 20 millimeters or ¾ of an inch. This is the approximately the same size as the 18-week fetal heart.3 Once the minimal view for the screening exam, the four-chamber view now accompanies pictures of the outflow tract and great vessels. This course focuses on the four-chamber view to help you understand imaged anatomy.  Congratulations! You have completed the Fetal Heart Screening: Four-chamber View course. Listed below are the key points presented in this course. Take time to review the material before you try the final assessment.   Download and print a copy of the detailed Course Review In this course you have learned to: Explain the unique prenatal circulation seen in the fetus. ​Determine situs of the fetal heart. ​Summarize internal and surrounding anatomy seen with the four-chamber view. View these instructions for information on navigating through the self-evaluation tools we call ‘Your Turns’. Click the icon below to start the self-evaluation exercise. Note: This is not part of the final Assessment. Learn How to Navigate the Your Turns Learn how to navigate the Your Turns. Instructions:Flash File:HTML5 File:/content/generator/Course_90022623/Navigation_Instructions_FE-01b/index.htmlPDF File: Upon completion of this course you will be able to:      Explain the unique prenatal circulation seen in the fetus      Determine situs of the fetal heart      Summarize internal and surrounding anatomy seen with the four-chamber view The heart completes formation in the eighth week of gestation pairing with the placenta to provide nutrients to the growing embryo.1 The foramen ovale and the ductus arteriosus allow blood flow to bypass the lungs. These close or atrophy in the neonatal period becoming anatomic landmarks in the adult.  Learn More about Fetal and Adult Circulation Learn more about fetal and adult circulation. Tab TitleTextAdult versus Fetal Structures1   Fetal Structure Purpose Adult Structure Foramen ovale (FO) Move blood from the right to left atrium. Fossa ovalis in the atrial septum. Ductus venosus Venous connection between the umbilical vein the inferior vena cava (IVC). Ligamentum venosum in the liver. Ductus arteriosus (DA) Provide a connection between the pulmonary artery and aorta bypassing the lungs. Ligamentum arteriosum.  Umbilical arteries (2) Move deoxygenated blood from the fetus to the placenta. Proximal sections become the internal iliac arteries and super vesical arteries. Distal becomes the medial umbilical ligaments. Umbilical vein Move oxygenated blood from the placenta to the fetus. Round ligament (ligamentum teres hepatis) in the liver. Adult versus Fetal Circulation1 The pediatric and adult circulation flows in a parallel manner (RA->RV->PA->PV->LA->LV->Ao->Body) without oxygenated and deoxygenated blood mixing. In contrast, the fetal circulation flows in a parallel fashion with a combination of oxygenated and deoxygenated blood. This is made possible via the DA, DV, and flow across the FO (green arrow). Your Turn Your Turn. Instructions:Flash File:HTML5 File:/content/generator/Course_90022623/FE-01-YourTurn-01c/index.htmlPDF File: Learn More about Fetal Circulation Learn more about fetal circulation. The anatomic survey of the fetal heart documents the position of not only heart structures, but also the cardiac axis, heart location within the thorax, and the fetal heart rate.   This image demonstrates an M-mode tracing taken across the interventricular septum (IVS). Positioning the M-line perpendicular to the IVS provides an optimal tracing of the IVS, both ventricles as well as the anterior and posterior heart walls.   Establishing the situs of the heart begins with first determining if the fetal position is breech, cephalic or transverse. The upper abdomen is an important beginning point since the left sided anechoic stomach bubble corresponds to the apex of the correctly positioned heart. A series of transverse images, a dual image, a sagittal image, or a cine loop showing the stomach and the heart confirms orientation.    Correct direction and angle of the heart results in the right ventricle positioned adjacent to the anterior chest wall and the spine posterior to the left atrium. Learn More about Determining Heart Situs Learn more about determining heart situs. Tab TitleTextSagittal View – 2D-mode One method to ensure the fetal heart and stomach are on the same side is to obtain a sagittal view.     This fetus is in a vertex position with the apex towards the maternal anterior abdominal wall. The stomach (orange) lies inferior to the diaphragm (yellow). The hypoechoic diaphragm images between the ventricles and stomach helping to rule out a diaphragmatic hernia. The heart (red) lies posterior to the ribs (arrows).Sagittal View - Video Transverse View – 2D-mode Sequential transverse views through the fetal upper abdomen and chest help establish that the stomach and heart are on the left side. The apex of the heart (red) points to the left sided stomach (orange).    Transverse View – Video   The four-chamber view has been the minimum cardiac picture required during the obstetric examination.2, 4-6 This somewhat oblique image allows for assessment of the rhythm, position, size, and anatomy of the heart ruling out the majority of congenital anomalies. The four-chamber view, also known as the apical four-chamber view, allows for imaging of the atrioventricular valves, ventricles, atria, and the septum between the chambers. Also imaged in some patients are the pulmonary arteries and fossa ovalis. Due to a heart rate over 100 beats per minute7 (bpm) it may be difficult to differentiate the small heart structures.    Use of the Cine function allows for frame-by-frame analysis of the heart.8   Learn More about Four-chamber Anatomy Learn more about four-chamber anatomy. Tab TitleTextFour-chamber Diagram Anatomy seen in the four-chamber view include the tricuspid valve located between the right atrium (RA) and right ventricle (RV), and the mitral valve located between the left atrium (LA) and left ventricle (LV). The fossa ovale (FO) provides a communication between the RA and LA. Four-chamber – Video Four-chamber Imaging Checklist - Internal Anatomy Four-chamber imaging checklist-internal anatomy. Checklist TitleChecklist TypeChecklist ContentDoes the FO bow into the LA?HTML The FO provides a bypass of the lungs in the fetus. The FO closes a few days after birth.7, 9 Is there a moderator band in the RV?HTML The LV has a smooth inner wall (orange arrow), forms the heart apex, and is longer than the RV.9 The moderator band (yellow arrow) lies towards the apex of the RV.9, 10 Aorta – red circle. Where do the chordae tendineae attach?HTML The chordae tendineae image as linear structures, connecting the atrioventricular valve (mitral and tricuspid) leaflets to the papillary muscles (arrows) in the ventricles.9  Are the atria and ventricles the correct size?HTML The left and right atria appear equal in size. The ventricles also mirror each other in both size and contractability.9Is the septum continuous?HTML The IVS (orange arrow) images as continuous structure from the apex to the crux of the heart. The atrial primum (open arrow) appears intact.7    Use a 90-degree angle of incidence to obtain optimal septal images. Where are the TV and MV?HTML The mitral valve is slightly superior to the tricuspid valve in the normal heart. A large displacement of the tricuspid valve towards the apex raises suspicion for Ebstein's anomaly (aka Ebstein’s malformation).  What is the heart rate?HTML Obtain an M-mode or spectral tracing of the fetal heart rate.7 A rate below 100 bpm in an active fetus raises concern for bradycardia. Sinus tachycardia shows a rate of 180-200 bpm while supraventricular tachycardia ranges from 220-240 bpm. Higher rates may result in atrial flutter or fibrillation.11 Learn More about Fetal Chest Anatomy Learn more about fetal chest anatomy. Instructions:Flash File:HTML5 File:/content/generator/Course_90022623/FE-anatomy/index.htmlPDF File: Four-chamber Imaging Checklist - Global Anatomy Four-chamber imaging checklist - global anatomy. Checklist TitleChecklist TypeChecklist ContentIs the LA closest to the spine?HTML On the sonographic image the LA lies closest to the triangular spine.7, 9 Where is the descending aorta?HTML The descending aorta lies between the spine and the left atrium.7, 9, 10 Do the heart and chest wall form a 45° angle?HTML Visually 2/3 of the heart is on the left and 1/3 on the right.7, 9, 10 Are the stomach and heart apex on the left side?HTMLHow to determine situs of the heart.7, 9, 10 Locate the heart apex on the left side using the transverse plane. Localize the stomach (inferior) and heart (superior) in relation to the diaphragm. ​Image both heart and stomach on a longitudinal plane. ​ Labeling the heart right, left and apex helps the clinician orient to the heart anatomy.  The size of the heart is another consideration in determining normalcy. Not only does the heart enlarge with some congenital problems, physiologic processes also contribute to an abnormal size.12 Usually evaluated via visual estimate, the ratio of the heart circumference or area has become the standard to assess the size of the fetal heart.   When determining normalcy of the heart size, keep in mind the size of the thorax directly influences measurement results (i.e., Small thorax with a normal heart).9 Learn More about Determining Normal Heart Size Learn more about determining normal heart size. Tab TitleTextC/T Circumference Ratio The cardiothoracic ratio (CTR) found its beginnings in the methods used during the evaluation of the chest radiograph.13 Calculation of the CTR uses the transverse diameter of the heart divided by the thoracic circumference. The method used (i.e., ellipse, diameter, area) influence the accuracy of the CTR.  Use multiple biometric measurements to ensure detection of the abnormally sized heart.3, 7, 9 To ensure the correct level of measurement scan at the level of the diaphragm dome.     For example: Heart circumference = 90 mm; Thoracic circumference = 162 mm  CTR = H/T         = 90/162         = 0.55 The CTR ranges vary from 0.45 at 17-weeks’ gestation to 0.50 at term.9CTR Image The CTR uses the circumference of the heart (yellow) divided by the thoracic circumference (orange) to provide a unitless value to help determine cardiac size.  Placenta – Yellow arrows.  Your Turn Your Turn. Instructions:Flash File:HTML5 File:/content/generator/Course_90022623/FE-01-YourTurn-02-V3/index.htmlPDF File: Explore the links below for the Glossary, References, and Further Reading opportunities. Glossary Glossary. Anterior – towards the front; in front of   Atrial fibrillation – Irregular rapid heart rate where the atria and ventricles contract independently.   Atrial flutter – Condition where the atria contract faster than the ventricles.   Axis – Line which the body rotates.   Bradykinin – Hormone released upon birth that closes the ductus arteriosus.   Bradycardia – Fetal heart rate below 100 bpm sustained for 10-minutes or longer.   Breech – Presenting with the fetal bottom closest to the cervix.   Cephalic – Presentation with the fetal cranium closest to the cervix.   Chordae tendineae – Linear structures connecting the atrioventricular valves to the heart.   Crux (Heart) – Portion of the heart formed by the membranous interventricular septum, septum primium of the atrial septum, and the septal leaflets of the atrioventricular valves.   Diaphragmatic hernia – Abnormal opening in the diaphragm which allows abdominal organs into the chest.    Ebstein’s anomaly (Ebstein’s malformation) – A group of congenital malformations which include an atrial septal defect, and a tricuspid valve displaced towards the heart apex.   Hypoechoic – Sonographic appearance of an organ or tissue that has a darker (fewer echoes) appearance than the surrounding anatomy.    Moderator band – Muscular band of tissue usually found in the right ventricle allowing for quick identification of the RV.   Morphology – Size shape and structure of an organ.   Parturition - Birth   Perpendicular – At ninety-degrees.   Posterior – Towards the back; behind   Pulmonary – Pertaining to the lungs.   Sagittal – Plane dividing the body into right and left sides.   Situs – Normal location within the body.   Tachycardia – Abnormally rapid heart rate.   Thorax – Pertaining to the chest.   Transverse (Axial) – Plane that divides the body into top and bottom sections.  References and Further Reading References and Further Reading. 1. Moore, K.L., Persaud, T.V.N., and Torchia, M.G. (2013). Cardiovascular system. (Eds.), The developing human: clinically oriented embryology (pp. 283-336). Philadelphia: Elsevier.   2. Carvalho, J.S., Allan, L.D., Chaoui, R., Copel, J.A., DeVore, G.R., Hecher, K., . . . Yagel, S. (2013). ISUOG Practice Guidelines (updated): sonographic screening examination of the fetal heart. Ultrasound in Obstetrics & Gynecology. 41(3): 348-359.   3. DeVore, G.R., Tabsh, K., Polanco, B., Satou, G., and Sklansky, M. (2016). Fetal Heart Size. Journal of Ultrasound in Medicine. 35(12): 2543-2562.   4. AIUM. (2013). AIUM practice guideline for the performance of fetal echocardiography. Journal of Ultrasound in Medicine. 32(6): 1067-1082.   5. AIUM–ACR–ACOG–SMFM–SRU Practice Parameter for the Performance of Standard Diagnostic Obstetric Ultrasound Examinations. (2018). Journal of Ultrasound in Medicine. 37(11): E13-E24.   6. Rychik, J., Ayres, N., Cuneo, B., Gotteiner, N., Hornberger, L., Spevak, P.J., and Van Der Veld, M. (2004). American society of echocardiography guidelines and standards for performance of the fetal echocardiogram. Journal of the American Society of Echocardiography. 17(7): 803-810.   7. Morris, S.A., Ayres, N.A., Espinoza, J., Maskatia, S.A., and Lee, W. (2017). Sonographic evaluation of the fetal heart. In Norton, M.E., L.M, S., and Feldstein, V.A., (Eds.), Callen's ultrasonography in obstetrics and gynecology (pp. 346-370).   8. Abuhamad, A. and Chaoui, R. (2016). Optimization of the two-dimensional grayscale image in fetal cardiac examination. (Eds.), A practical guide to fetal echocardiography: normal and abnormal hearts (pp. 136-143). Philadelphia: Wolters Kluwer.   9. Abuhamad, A. and Chaoui, R. (2016). Cardiac chambers: the four-chamber and short-axis views. (Eds.), A practical guide to fetal echocardiography: normal and abnormal hearts (pp. 78-96). Philadelphia: Wolters Kluwer. 10. Saou, G., Devore, G., and Ambrowitz, K. (2018). Fetal echocardiography. In Stephenson, S.R. and Dmitrieva, J., (Eds.), Diagnostic medical sonography: obstetrics and gynecology (pp. 509-540). Philadelphia: Wolters Kluwer.   11. Abuhamad, A. and Chaoui, R. (2016). Fetal arrhythmias. (Eds.), A practical guide to fetal echocardiography: normal and abnormal hearts (pp. 547-564). Philadelphia: Wolters Kluwer.   12. Abuhamad, A. and Chaoui, R. (2016). Fetal cardiac measurements and reference ranges. (Eds.), A practical guide to fetal echocardiography: normal and abnormal hearts (pp. 247-252). Philadelphia: Wolters Kluwer.   13. Paladini, D., Chita, S.K., and Allan, L.D. (1990). Prenatal measurement of cardiothoracic ratio in evaluation of heart disease. Archives of disease in childhood. 65(1 Spec No): 20-23. The reproduction, transmission or distribution of this training or its contents is not permitted without express written authority. Offenders will be liable for damages.   All names and data of patients, parameters and configuration dependent designations are fictional and examples only.   All rights, including rights created by patent grant or registration of a utility model or design, are reserved.   Please note that the learning material is for training purposes only!   For the proper use of the software or hardware, please always use the Operator Manual or Instructions for Use (hereinafter collectively “Operator Manual”) issued by Siemens Healthineers. This material is to be used as training material only and shall by no means substitute the Operator Manual. Any material used in this training will not be updated on a regular basis and does not necessarily reflect the latest version of the software and hardware available at the time of the training.   The Operator Manual shall be used as your main reference, in particular for relevant safety information like warnings and cautions. Note: Some functions shown in this material are optional and might not be part of your system. The information in this material contains general technical descriptions of specifications and options as well as standard and optional features that do not always have to be present in individual cases.   Certain products, product related claims or functionalities described in the material (hereinafter collectively “Functionality”) may not (yet) be commercially available in your country. Due to regulatory requirements, the future availability of said Functionalities in any specific country is not guaranteed. Please contact your local Siemens Healthineers sales representative for the most current information.   Copyright © Siemens Healthcare GmbH, 2019

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