Pericardial Effusion

Pericardial effusion (PE) is the accumulation of fluid in the pericardial space.

The finding of a thin rim of pericardial fluid (< 2 mm) during routine prenatal ultrasound is not uncommon, being observed in more than 40-50% of normal fetuses¹, particularly when the ultrasound beam is perpendicular to the ventricular wall and pericardial surface. However, this has no clinical significance^{1, 2} and is not considered as PE.

The incidence of true PE is unknown, since it should be considered as a marker of many other anomalies, eventually leading to fetal hydrops³.

PE may be the result of the mechanism that produces non-immune fetal hydrops in a significant proportion of cases, thus presenting with other fluid collections (ascites, pleural effusion, skin edema). Structural cardiac malformations and arrhythmias are the most common cause, while other conditions associated with fetal hydrops include genetic disorders, metabolic disorders, tumors, hematologic abnormalities and congenital infections.⁴

If the complete diagnostic work-up assessment is negative, the PE is classified as isolated. In such cases, the pathogenic mechanism is not well understood since most of the times the PE is transitory and regresses spontaneously.⁵

PE is associated with structural heart disease and arrhythmias.⁶  A quite commonly described association is the finding of a ventricular aneurysm or diverticulum, which may even tamponade in case of rupture.^7-10 In such cases, immediate emptying of the pericardial sac may be life-saving.^{9, 10} Other cardiac causes of fetal PE are constriction of the ductus arteriosus, idiopathic infantile arterial calcifications and cardiac tumors, mainly teratomas.^{6, 12-15}

PE is also associated with other congenital structural abnormalities such as diaphragmatic hernia/eventration¹⁶, abdominal wall defects¹⁷, and also with viral infections, including cytomegalovirus, Coxsackie A and B, parvovirus, human immunodeficiency virus and mycoplasma hominis^{18, 19}. PE has also been described to be associated with congenital hypothyroidism (20) and maternal systemic lupus erythematosus (21), very likely related to a heart failure due to primary myocarditis or anemia.

However, as aforementioned, the most common scenario is the finding of PE in the context of hydrops fetalis^{22, 23} or chromosomal anomalies²⁴, with the subsequent poor prognosis. If the PE is detected early in gestation and, particularly, is associated with nuchal and skin edema at 11-14 weeks, it is associated with chromosomal anomalies in up to 20-30% of the cases^24. Moreover, PE may be a transitional finding in trisomy 21 fetuses, in the same fashion as increased nuchal translucency, thus their disappearance should not reassure in this regard. The risk of abnormal chromosomes is not related to the thickness of the effusion neither. Because of these data, fetal karyotyping should be discussed with parents, even in isolated pericardial effusion²⁴.

Lastly, if there are no associated anomalies, the PE is classified as isolated, in which case the effusion is usually transient and have a significant better outcome^25-28.

The recurrence risk of PE depends on the underlying cause and the associated anomaly. Although the recurrence risk of isolated PE is not known, it should be very low^25-28.

Prenatal diagnosis of PE is based on the demonstration of more than 2 mm of fluid collection surrounding the heart and exceeding the level of the atria. Separation of the pericardial layers may be observed. PE can be observed close to the atrioventricular valves, at the length of the ventricles, or around the whole heart. Both lungs are attached to the posterior chest wall.

Pericardial fluid thickness is measured at the point of maximum thickness. The presence and origin of the normal hypoechoic rim around the fetal cardiac ventricles should be considered before diagnosing small pericardial effusions.

The diagnosis of PE is usually easy and straightforward, whenever the scan is performed by a medium experienced examiner. Possible false positive diagnosis would be:

1. hydrothorax, in which the fluid is surrounding the lungs
2. The normal rim of fluid collection between the myocardium and the pericardium, which is of less than 2 mm thickness.

Since the ethiology of PE may be related to a potentially serious disease, a complete echocardiographic evaluation to exclude cardiac structural or functional abnormalities is necessary. Karyotyping and viral screening are mandatory, especially if a heart defect or other serous effusions (pleural effusion, ascites) are detected, which would significantly increase the risk of chromosomal abnormalities^24,27,28.

If all these investigations are normal, the PE is isolated and will probably be transitory. In those cases, serial fetal scans must be performed in order to strictly follow-up until confirmation of the decrease and spontaneous resolution^{24, 27, 28}.

The outlook of a fetus with PE mainly depends on the underlying cause and the association with hydrops. Isolated PE does not appear to be associated with an adverse perinatal outcome and spontaneous resolution is a common finding. In the presence of hydrops, prenatal therapy with pericardiocentesis may be needed in order to avoid extreme prematurity and to improve survival. When the diagnosis of a pericardial effusion with hydrops is made before viability, the option of pregnancy termination should be offered.

The main goal in the management of a fetus with PE is to delay the delivery until adequate lung maturity is achieved. Therefore, assessing the risk of hydrops with close monitoring of the fetal hemodynamics is mandatory.

If the PE is associated with other disorders, some situations will need a prenatal therapeutic approach, such as serial intrauterine transfusions in fetal anemia or antiarrhythmic drug administration, which may be life-saving. In cases of PE with hydrops and/or cardiac tamponade pericardiocentesis may be life-saving. To perform this procedure, a 20-gauge needle is inserted percutaneously into the pericardial effusion guided by ultrasound, and fluid is aspirated. Although pericardiocentesis is technically challenging in early gestation, it may be needed to recover from a cardiac tamponade and to allow normal pulmonary development by reexpansion of the compressed lungs. Also, pericardiocentesis may reduce systemic venous pressure, allowing for hydrops involution and avoiding fetal demise in most of the cases.

Postnatally, the majority of the disorders associated with PE have to be treated after an assisted delivery with the presence of the neonatologist, the pediatric cardiologist and even the pediatric cardiac surgeon. Intensive care of the neonate including the use of inotropics, diuretics, vasodilators, assisted ventilation, prostaglandins and other measures, as pericardiocentesis and surgery, may be necessary.

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11. Luchese S, Manica JL, Zielinsky P. Intrauterine ductus arteriosus constriction: analysis of a historical cohort of 20 cases. Arq Bras Cardiol 2003;81:405-410.

12. Levine JC, Campbell J, Nadel A. Prenatal idiopathic infantile arterial calcifications. Circulation2001;103(2):325-326.

13. Tollens M, Grab D, Lang D, Hess J, Oberhoffer R. Pericardial teratoma: prenatal diagnosis and course. Fetal Diagn Ther 2003;18(6):432-436.

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15. Laga S, Gewillig MH, Van Schoubroeck D, Daenen W. Imminent fetal cardiac tamponade by right atrial hemangioma. Pediatr Cardiol 2006;27:633-635.

16. Stevens RL, Mathers A, Hollman AS, MacKenzie JR, Galen P, MacDonald PD, Wilson N. An unusual hernia; congenital pericardial effusion associated with liver herniation into the pericardial sac. Pediatr Radiol 1996;26(11):791-793.

17. Daftary AS, Patole SK, Whitehall JS. Association of pericardial effusion with gastroschisis. Intensive Care Med 1999;25(4):422-423.

18. Talsma M, Vegting M, Hess J. Generalized Coxsackie A9 infection presenting in a neonate with pericarditis. Br Heart J 1984;52(6):683-685.

19. Parilla BV, Tamura RK, Ginsberg N A. Association of Parvovirus with isolated fetal effusions. Am J Perinatol 1997;14(6):357-358.

20. Rondanini GF, de Pannizza G, Bollati A, Manzoni P, Teenhghi A. Mutinelli MR, Corallo S, Chiumello G. Congenital hypothyroidism and pericardial effusion. Horm Res 1991;35(1):41-44.

21. Fox R, Hawkins DF. Fetal-pericardial effusion in association with congenital heart block and matemal systemic lupus erythematosus. Br J Obstet Gynaecol 1990;97(7):638-640.

22. Van Maldergem L, Jauniaux E, Fourneau C, Gillerot Y. Genetic causes of hydrops fetalis. Pediatrics 1992;89:81-86.

23. Norton ME. Nonimmune hydrops fetalis. Semin Perinatol 1994;18: 321–332.

24. Sharland G, Lockhart S. Isolated pericardial effusion: an indication for fetal karyotyping. Ultrasound Obstet Gynecol 1995;6(1):29-32.

25. Wyllie JP, Hunter S. Outcome of isolated fetal pericardial effusion. Cardiol Young 1993;3:44-46.

26. Di Salvo DN, Brown DL, Doubilet PM, Benson CB, Frates MC. Clinical significance of isolated fetal pericardial effusion. J Ultrasound Med 1994;13(4):291-293.

27. Azancot A, Diehl R, Dorgeret S, et al. Isolated pericardial effusion in the human fetus: a report of three cases. Prenat Diagn2003;23:193-197.

28. Mohan MS, Patole SK. Isolated fetal pericardial effusion: case report and review of the literature. Aust N Z J Obstet Gynaecol 2002;42:210.

Josep M Martinez, Narcís Masoller: Pericardial effusion, Visual Encyclopedia of Ultrasound in Obstetrics and Gynecology, www.isuog.com. June 2013.

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