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Prenatal diagnosis of fetal right ventricular diverticulum with massive pericardial effusion in one of monochorionic diamniotic twins: a case report with a favorable outcome following in utero pericardiocentesis

Background Congenital ventricular diverticulum is a rare abnormality that may occur as an isolated malformation. Most cases are accompanied by pericardial effusion. Prenatal counseling can be difficult because the prognosis is uncertain and there is no consensus approach to prenatal management. Case presentation: We describe a case of congenital cardiac diverticulum complicated by large pericardial effusion in one of monochorionic diamniotic twins. The case was diagnosed by ultrasonography at 21 weeks of gestation. Therapeutic pericardiocentesis at 22 weeks resulted in complete resolution of the effusion and led to a favorable fetal outcome. We summarize the interventions and pregnancy outcomes in cases of cardiac diverticula reported in the literature. Conclusions Better awareness of clinical features, in utero therapies, and pregnancy outcomes could help define and improve prenatal management of congenital ventricular diverticula.


Keywords
Ventricular diverticulum, pericardial effusion, pericardiocentesis, monochorionic diamniotic twins, fetal outcome, prenatal counseling Date received: 18 October 2020; accepted: 10 December 2020 Background Congenital ventricular diverticulum is a rare abnormality, in which there is saccular dilatation of the cardiac ventricular wall, showing bidirectional flow on Doppler studies. 1,2 The cardiac diverticulum of the heart protrudes through the stenosis connection, and prenatal diagnosis may fail to detect the diverticulum. Only a few cases diagnosed in utero have been reported. 3 Most cases are accompanied by pericardial effusion, which can compromise the fetal circulation and lung development. Prenatal counseling can be difficult because some cases resolve spontaneously in the second trimester, whereas others progress with worsening hydrops, sometimes resulting in intrauterine fetal death. [4][5][6] Most cases are found in singleton pregnancies; only one case in the literature reports ventricular diverticulum in one fetus of monochorionic diamniotic twins. Here, we describe another monochorionic diamniotic twin fetus in whom right ventricular diverticulum associated with a massive pericardial effusion was diagnosed at 22 weeks of gestation. Therapeutic pericardiocentesis resulted in complete resolution of the effusion and led to a favorable fetal outcome.

Case report
An 18-year-old healthy woman (gravida 2, para 1) had a spontaneous pregnancy of monochorionic diamniotic twins with unremarkable medical and family history. At the routine pregnancy check-up at 21 weeks' gestation, an abnormal fetal heart chamber was identified in one of the twins, and the patient was referred to our center with a diagnosis of bilateral hydrothorax in one fetus. Prenatal ultrasonography showed that the massive area of fluid was of pericardial, not pleural, origin. An abnormal heart chamber (4 Â 5 mm) was detected in the apex of the right ventricle in the four-chamber view (Figure 1a). The presumptive diagnosis was a ventricular diverticulum or ventricular aneurysm. The connection to the ventricle was narrow, color Doppler ultrasound detected blood flow in and out of the abnormal heart chamber, and M-mode assessment indicated normal synchronous contraction of its walls with those of the ventricle; these findings were consistent with a diagnosis of ventricular diverticulum. There was an anechoic space peripherally around the heart, and both lungs were severely compressed (>50% lung compression) into a posterior position in the fetal thorax. This finding distinguished our case from that of a pleural effusion manifesting as an anechoic space located peripherally around the compressed lungs. There was no evidence of other fetal structural abnormalities or hydrops, and no structural or functional heart defects were detected. The mitral valve apparatus appeared normal, and no arrhythmias or intracardiac thrombi were seen. We detected no sign of complications of monochorionic multiple birth, such as twin-to-twin transfusion syndrome or selective intrauterine growth restriction.
Ultrasound scans of the other twin appeared normal.
The couple was counseled regarding the increased incidence of fetal chromosomal abnormalities, the possibility of pulmonary hypoplasia and progressive hydrops, and the potential effect on the other fetus caused by vascular communications in the placenta. Pericardiocentesis and amniocentesis were performed at 22 þ2 weeks' gestation on the abnormal fetus only. Under ultrasound guidance, a 20-gauge needle was inserted percutaneously into the pericardial effusion, and 13 mL of strawcolored fluid was aspirated. Then, retracting the needle to the amniotic cavity, 35 mL of amniotic fluid was taken for chromosome analysis, including G-banding karyotype and chromosome microarray analysis. The fetal lungs expanded automatically immediately after the procedure. Pericardial fluid, amniotic fluid, and maternal serum were submitted for viral studies, and all were negative for toxoplasmosis, other (syphilis, varicella-zoster), rubella, cytomegalovirus, and herpes (TORCH) infections and for parvovirus B19. Cytology of the pericardial fluid identified lymphocytes and mesothelial cells. The protein content of the pericardial fluid was 23.9 g/L, consistent with transudate. The pericardial effusion did not reaccumulate after  . Chromosome analysis showed a normal female karyotype. Serial echocardiograms until birth showed no effusion and no cardiovascular compromise. The right ventricular diverticulum was no longer visible on ultrasound at 34 weeks' gestation. At 37 weeks' gestation, two healthy female infants were delivered, weighing 3040 and 2875 g, with Apgar scores of 9-10-10, which were appropriate for gestational age. The infants' prognoses were good and they were discharged without heart symptoms. An echocardiogram performed on the affected infant on day 10 after birth was normal ( Figure 1d). The infants had regular follow-ups at our hospital and remained asymptomatic without the need for medication at 12 months of age (at the time of this writing). Our study complied with the CARE case report guidelines. 7 We have de-identified the case details such that the identity of the patient cannot be ascertained in any way.

Discussion
Cardiac ventricular diverticulum is defined as a protrusion of the free ventricular wall. The main differential diagnosis is ventricular aneurysm. 4 The terminology is confusing and it is not always possible to distinguish by prenatal ultrasound. Sonographically, diverticula are saccular with a narrow neck communicating with the ventricle and contracting synchronously with the rest of the ventricular cavity. Aneurysms, by contrast, have a wider base and appear to be hypokinetic. Histologically, diverticula are composed of three layers: pericardium, myocardium, and endocardium, in accordance with cardiac tissue, whereas aneurysms are composed of thinned myocardium mixed with fibrous tissue. 8,9 Diverticula are more likely to be associated with midline defects or intracardiac abnormalities, 10 whereas aneurysms are mostly isolated and have a poorer prognosis. The etiology of cardiac diverticula and aneurysms in fetal life is poorly understood. They may occur as a result of focal weakening of the ventricular wall due to an interruption during embryogenesis, such as the occurrence of congenital infection, trauma, coronary anomalies, or ischemia of the myocardium. 3 Pericardial effusions associated with fetal ventricular diverticula have been reported in several cases. 8,[11][12][13] The presence of pericardial effusion not only enhances the visibility of the diverticulum on ultrasound, but the effusion also acts as a cushion protecting the aneurysmal sac from rupture. The main differential diagnosis of massive fetal pericardial effusion is bilateral hydrothorax. Several cases of fetal pericardial effusion in previous reports were initially misdiagnosed as bilateral fetal hydrothorax, 14 as in our case. Sonographically, in our case, the lungs of the fetus diagnosed with pericardial effusion were compressed into a posterior position in the fetal thorax, a presentation distinct from a diagnosis of pleural effusion, which would present as an anechoic space located peripherally around the compressed lungs. In addition, the heart may be shifted into the contralateral hemithorax and appear smaller than normal in patients with bilateral hydrothorax.
We summarized interventions and pregnancy outcomes in cases of cardiac diverticula reported in the literature (Table 1). A total of 40 cases of prenatally diagnosed ventricular diverticula have been reported. The most frequent location is on the right ventricle (26/40, 65%), and the most frequently involved area is the heart apex (20/40, 50%). Ultrasonographic findings associated with diverticula include pericardial effusion, cardiomegaly, septal defects, arrhythmia with fetal death before delivery, and hydrops. Pericardial effusion is the most frequently associated finding (24/40,   In reported cases of ventricular diverticula associated with massive pericardial effusion, the most common outcome was termination of pregnancy before a prenatal intervention was implemented. Intrauterine pericardiocentesis allows compressed lungs to re-expand, reduces systemic venous pressure, and prevents potential fetal edema and intrauterine death. Of the 40 cases of fetal ventricular diverticula reported in the literature plus our case, 24 were associated with pericardial effusion. Of these 24, 3 patients opted for pregnancy termination because of the perceived risk of pulmonary hypoplasia, and 9 patients opted for expectant management. Of these 9 patients, fetal death occurred in 2, spontaneous resolution occurred in 5, and, of the remaining 2, 1 was asymptomatic at 18 months of life and 1 underwent surgery postnatally. Of the 24 cases in the literature associated with pericardial effusion, 12 underwent intrauterine pericardiocentesis (1 fetal death occurred, likely because of rupture of the diverticulum, and 11 cases had a favorable prognosis). In our case, the effusion completely absorbed and the lungs re-expanded rapidly after intrauterine pericardiocentesis. Although the natural evolution of this condition remains unknown, some researchers speculate that without proper intervention, persistent lung compression may result in fatal pulmonary hypoplasia. Nevertheless, spontaneous resolution has been reported several times with good prognosis. Concerns about lung development and heart failure have led some researchers to recommend intrauterine pericardiocentesis when a large pericardial effusion is diagnosed. Further studies are needed to determine whether intrauterine pericardiocentesis throughout pregnancy could be of benefit to the fetus.

Conclusion
We report a case of right ventricular diverticulum associated with a massive pericardial effusion in one (monochorionic diamniotic) twin diagnosed at 22 weeks that resulted in a favorable fetal outcome following intrauterine pericardiocentesis. In addition, we summarized interventions and pregnancy outcomes of 40 cases of cardiac diverticula reported in the literature. Better awareness of the clinical features, intrauterine therapies, and pregnancy outcomes will help in defining appropriate prenatal management of congenital ventricular diverticula.

Ethics statement
The study was approved by the Institutional Review Board/Medical Ethics Committee of Guangdong Women and Children Hospital (IRB reference number: 201612089). Written informed consent was obtained from the participating family for publication of the case report.

Declaration of conflicting interest
The authors declare that there is no conflict of interest.

Funding
The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by the Medical Science and Technology Research Project of Guangdong Province (grant nos. A2019358, B2019010, and A2018260). The funding body did not play a role in the design of the study; the collection, analysis, or interpretation of data; or in writing the manuscript.