Author: Rachelle Modeste, MD
Editors: Philippe Ayres, MD; Alec Feuerbach, MD
Faculty Editor: Anastasios Drenis, MD
A young woman comes crying through the Emergency Department doors with her 1-week-old baby boy saying, “Someone please help my baby. This is my first child. He turned blue and I don't know what to do. He’s hardly moving.” As the nurse takes the boy, you notice that he looks very tired and tachypneic with cyanosis around his lips. You recognize this bluish discoloration as a lack of circulating oxygen. Mom then states, “Since becoming pregnant, I tried to do everything naturally without medications or vitamins, but I don’t know what to do. Please help my baby.”
The baby’s vital signs are as follows:
HR 170/min; BP 67/50 mm Hg; RR 70/min; SpO2 75% on room air; Temperature 37 C
You begin providing supplemental oxygen through a nasal cannula.
To try and better understand what could be happening with this baby, we are going to discuss cyanotic congenital heart defects and their pathophysiology in part one of this post. This will lay the foundation for part two of this topic in which we will discuss the initial evaluation and management of these neonates.
Background
Congenital heart defects (CHD) are the most common birth defects in the world and affect almost 1% of births per year in the United States.[1] These defects affect the chambers and great vessels of the heart and can range from benign structural changes with no clinical manifestations to life-threatening defects. Thirty to 50 percent of infant mortality caused by birth defects is due to CHD.[2]
In the U.S. most of these neonates are diagnosed prenatally or during the newborn period via the critical congenital heart defect (critical CHD) screening that occurs prior to discharge from the hospital.[3,4]. Even so, many neonates with critical CHD go undiagnosed, especially if they do not have access to prenatal care or newborn screening tests. This missed critical CHD can present in the following weeks to months of life based on the type and severity of the defect.
There are different types of critical CHD such as shunting or mixing defects, cyanotic heart defects, and acyanotic heart defects. They can have a wide range of clinical presentations from nonspecific symptoms like cough or poor weight gain to extremis with respiratory insufficiency and shock.[3,5,6] In this post, we will be reviewing the normal fetal and neonatal physiology as well as the anatomy for the different cyanotic heart defects. This will serve as our basis for understanding the presentation and management of infants with suspected cyanotic, critical CHD which will be discussed in part two.
Fetal Circulation
Fetal gas exchange occurs in the placenta [7]. Once exchange has occurred, nutrient rich and oxygenated blood travels via the umbilical vein into the portal vein which becomes the hepatic vein before connecting to the inferior vena cava (IVC). Before the umbilical vein connects to the portal vein, 20% to 30% of the blood volume is shunted directly into the IVC via the ductus venosus.[8] This shunt allows for a higher oxygen content to be delivered to the systemic system. In the IVC, deoxygenated blood from the lower extremities mixes with the oxygenated placental blood from the ductus venosus before entering the right atrium. Meanwhile, deoxygenated blood from the upper extremities and head travels through the superior vena cava into the right atrium. From the right atrium, about two thirds of the blood travels through the foramen ovale, bypassing the lungs and directly entering the left side of the heart for systemic circulation.[9-11]
The blood that continues into the right ventricle enters the systemic circulation via the ductus arteriosus (DA). Since fetal lungs are filled with fluid causing high resistance, the DA serves as the path of least resistance for blood flow between the pulmonary trunk and the aorta. The DA shunts 90% of the blood flowing through the pulmonary trunk directly into the aorta while only 10% of the blood from the right ventricle continues past the DA directly into pulmonary circulation. No gas exchange occurs in the lungs.[12,13] After systemic perfusion, two umbilical arteries carry the deoxygenated and nutrient poor blood back to the placenta to start the cycle again (Figure 1).
The umbilical cord contains the umbilical vein and two umbilical arteries, therefore when the cord is clamped after birth, the placental circulation is cut off, initiating the transition of fetal circulation into neonatal circulation.[3, 7]
Figure 1: Fetal Circulation. A. Fetal circulation with blood flow through the foramen ovale. B. Blood flow through the ductus arteriosus. MPA, main pulmonary artery; LA, left atrium; LPA, left pulmonary artery; LV, left ventricle; RA, right atrium; RPA, right pulmonary artery; RV, right ventricle [12].
Following birth, immediately after the baby’s first breath is taken the pulmonary vascular resistance decreases as oxygen starts filling the lungs. The pulmonary vessels around the alveoli dilate due to the increased partial pressure of oxygen, allowing for fluid to move out of the lungs and for gas exchange to occur.[7] With increased pulmonary circulation and blood flow into the left atrium, as well as decreased right atrial blood flow due to the separation of the umbilical-placental circulation, the left atrial pressure becomes higher than the right atrial pressure. This causes functional closure of the foramen ovale. Its anatomical closure occurs at around one year of life.[7,12] (In about 25% of neonates, a patent but smaller foramen ovale opening may still persist after this developmental period and into adulthood. [9])
Closure of the DA is initiated due to decreased blood flow through the structure. At the same time, prostaglandin, which was produced by the placenta to keep the DA open in-utero, is broken down by neonatal lung enzymes.[13] In a healthy newborn, the DA is functionally closed in 12 to 24 hrs of life and permanently closed by 2 to 3 weeks.[13] This completes the separation of the pulmonary and systemic circulation in the normal neonatal heart, and the right ventricle dominant fetal heart begins transitioning to left ventricular dominance (Fig. 2).[12] The ductus venosus and umbilical veins also close and remain as ligaments.
Figure 2: Comparison of Fetal and Newborn Cardiac Anatomy [14]
Differential Diagnosis of Cyanosis in the Neonatal Period
Before we jump into our descriptions of cyanotic heart defects below, remember to keep your differential broad as all of the following pathologies can lead to cyanosis in a neonate: CHD, persistent pulmonary hypertension, sepsis, pneumonia, Respiratory Syncytial Virus, bronchiolitis, reactive airway disease, acute respiratory distress syndrome, foreign body aspiration, in-born errors of metabolism, and hemoglobinopathies (e.g., methemoglobinemia).[5]
Right-Sided Ductal Dependent Defects
Left-Sided Ductal Dependent Defects
Mixing Defects
Take Home Points 
-Congenital heart defects may go undiagnosed prenatally or prior to the neonates discharge from the hospital
-Neonates undergo a transition from gas exchange in the placenta to gas exchange in the alveoli with their first breath
-The ductus arteriosus, which is needed for circulation in-utero, begins to close due to decreased blood flow through the structure and decreased circulation of prostaglandin.
-Certain congenital cardiac defects cause hypoxemia and cyanosis when the ductus arteriosus closes
-Cyanotic congenital cardiac defects typically present around one to four weeks of life with cyanosis, poor weight gain, and non-specific symptoms
-Congenital heart defects should be suspected in cyanotic neonates
Resources:
1. “Data and Statistics on Congenital Heart Defects.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 24 Jan. 2022, www.cdc.gov/ncbddd/heartdefects/data.html.
2. Cucerea M, Simon M, Moldovan E, Ungureanu M, Marian R, Suciu L. Congenital Heart Disease Requiring Maintenance of Ductus Arteriosus in Critically Ill Newborns Admitted at a Tertiary Neonatal Intensive Care Unit. J Crit Care Med (Targu Mures). 2016 Nov 8;2(4):185-191.
3. Judge P, Meckler Mshs G. Congenital Heart Disease In Pediatric Patients: Recognizing The Undiagnosed And Managing Complications In The Emergency Department. Pediatr Emerg Med Pract. 2016 May;13(5):1-28; quiz 27-8. Epub 2016 May 1. PMID: 27096879
4. “Critical Congenital Heart Defects Screening Methods.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 3 Feb. 2023, www.cdc.gov/ncbddd/heartdefects/hcp.html.
5. Strobel AM, Lu le N. The Critically Ill Infant with Congenital Heart Disease. Emerg Med Clin North Am. 2015 Aug;33(3):501-18. doi: 10.1016/j.emc.2015.04.002. PMID: 26226862.
6. Ossa Galvis MM, Bhakta RT, Tarmahomed A, et al. Cyanotic Heart Disease. [Updated 2022 Jun 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK500001/
7. Vo, Andrea T, and Christine S Cho. “Neonatal Resuscitation in the Emergency Department: EB Medicine.” Emergency Medicine & Urgent Care CME, 1 Dec. 2020, www.ebmedicine.net/topics/critical-care/neonatal-resuscitation.
8. Sidhu PS, Lui F. Embryology, Ductus Venosus. [Updated 2022 Jul 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK547759/
9. Marty M, Kerndt CC, Lui F. Embryology, Fetal Circulation. [Updated 2022 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
10. Lee JY. Clinical presentations of critical cardiac defects in the newborn: Decision making and initial management. Korean J Pediatr. 2010 Jun;53(6):669-79. doi: 10.3345/kjp.2010.53.6.669. Epub 2010 Jun 23. PMID: 21189937
11. “Blood Circulation in the Fetus and Newborn.” Children's Hospital of Philadelphia, The Children's Hospital of Philadelphia, 24 Aug. 2014, www.chop.edu/conditions-diseases/blood-circulation-fetus-and-newborn#:~:text=About%20two%20thirds%20of%20the,continues%20on%20to%20the%20lungs.
12. Siassi B, Ebrahimi M, Acherman RJ. Suspecting Congenital Heart Disease*. In: Siassi B, Noori S, Acherman RJ, Wong PC. eds. Practical Neonatal Echocardiography. McGraw Hill; 2018.emergencies-2/
13. Gillam-Krakauer M, Mahajan K. Patent Ductus Arteriosus. [Updated 2021 Aug 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430758/
14. BruceBlaus. “Neonatal Heart Circulation.” Wikimedia Commons, 12 Nov. 2015, commons.wikimedia.org/wiki/File:Neonatal_Heart_Circulation.png.
15. Helman, A, Joubert, G, Strobel, A. Congenital Heart Disease Emergencies. Emergency Medicine Cases. https://emergencymedicinecases.com/congenital-heart-disease-emergencies-2/. https://emergencymedicinecases.com/congenital-heart-disease-emergencies-2/
16. Diaz-Frias J, Guillaume M. Tetralogy of Fallot. [Updated 2022 Jan 18]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.
17. King L, Young KD. Congenital Heart Disease. In: Tenenbein M, Macias CG, Sharieff GQ, Yamamoto LG, Schafermeyer R. eds. Strange and Schafermeyer's Pediatric Emergency Medicine, 5e. McGraw Hill; 2019.
18. Minocha PK, Phoon C. Tricuspid Atresia. [Updated 2022 Sep 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.
19. Singh DP, Hussain K, Mahajan K. Ebstein Anomaly And Malformation. [Updated 2022 Jun 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.
20. Fuchs, S.R., and J.H. Soslow. “Diagnosis and Imaging of Congenital Heart Disease.” Encyclopedia of Cardiovascular Research and Medicine, 2018, pp. 17–46., doi:10.1016/b978-0-12-809657-4.99714-x. (https://www.sciencedirect.com/science/article/pii/B978012809657499714X)
21. Heaton J, Kyriakopoulos C. Pulmonic Stenosis. [Updated 2022 Sep 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK560750/.)
22. Arya B, Maskatia SA. Coarctation of the aorta: Prenatal assessment, postnatal management and neonatal outcomes. Semin Perinatol. 2022 Jun;46(4):151584. doi: 10.1016/j.semperi.2022.151584. Epub 2022 Mar 12.
23. Ramirez Alcantara J, Mendez MD. Interrupted Aortic Arch. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.
24. Cara T. Mai, Jennifer L. Isenburg, Mark A. Canfield, Robert E. Meyer, Adolfo Correa, Clinton J. Alverson, Philip J. Lupo, Tiffany Riehle‐Colarusso, Sook Ja Cho, Deepa Aggarwal, Russell S. Kirby. National population‐based estimates for major birth defects, 2010–2014. BDR Oct 2019.
25. Kritzmire SM, Cossu AE. Hypoplastic Left Heart Syndrome. [Updated 2022 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.
26. Centers for Disease Control and Prevention (CDC). Improved national prevalence estimates for 18 selected major birth defects--United States, 1999-2001. MMWR Morb Mortal Wkly Rep. 2006 Jan 6;54(51):1301-5.
27. Al-Mutairi M, Aselan A, Al-Muhaya M, Abo-Haded H. Obstructed infracardiac total anomalous pulmonary venous connection: The challenge of palliative stenting for the stenotic vertical vein. Pediatr Investig. 2020 Jun 24;4(2):141-144. doi: 10.1002/ped4.12204. PMID: 32851359; PMCID: PMC7331390.
28. Kao CC, Hsieh CC, Cheng PJ, Chiang CH, Huang SY. Total Anomalous Pulmonary Venous Connection: From Embryology to a Prenatal Ultrasound Diagnostic Update. J Med Ultrasound. 2017 Jul-Sep;25(3):130-137. doi: 10.1016/j.jmu.2017.08.002. Epub 2017 Sep 12. PMID: 30065477
rmodeste7
Latest posts by rmodeste7 (see all)
- Why so Blue, Baby? Part II - July 7, 2023
- Why so Blue, Baby? Part I - May 13, 2023
0 Comments