Prenatal diagnosis of isolated total anomalous pulmonary venous connection: a series of 10 cases

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1 Ultrasound Obstet Gynecol 2013; 41: Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: /uog Prenatal diagnosis of isolated total anomalous pulmonary venous connection: a series of 10 cases D. LAUX*, L. FERMONT, F. BAJOLLE*, Y. BOUDJEMLINE*, J. STIRNEMANN and D. BONNET* *Centre de Référence Malformations Cardiaques Congénitales Complexes M3C, Necker Hôpital Enfants Malades, Assistance Publique des Hôpitaux de Paris, Cardiologie pédiatrique, Faculté Paris Descartes, Paris, France; Institut de Puériculture, Unité de cardiologie pediatrique, Paris, France; Department of Gynecology and Obstetrics, Necker Hôpital Enfants Malades, Assistance Publique des Hôpitaux de Paris, Faculté Paris Descartes, Paris, France KEYWORDS: fetal echocardiography; prenatal diagnosis; total anomalous pulmonary venous connection ABSTRACT Objectives To report on a series of 10 fetuses with prenatally diagnosed isolated total anomalous pulmonary venous connection (TAPVC), focusing on echocardiographic features leading to diagnosis, assess accuracy of prenatal diagnosis and describe postnatal outcome. Methods In this review of our experience of prenatal diagnosis of isolated TAPVC, we analyzed retrospectively medical records and fetal echocardiography findings in all cases with prenatal diagnosis of isolated TAPVC delivered between 1 January 2001 and 1 October 2011 at a tertiary referral center, paying special attention to echocardiographic signs that led to referral. Results During the study period, 95 infants with isolated TAPVC were seen at the center. Initially, expert fetal echocardiography identified 14 fetuses with isolated TAPVC. Prenatal diagnosis was made at a mean gestational age of 31 (range, 25 37) weeks. Ten truepositive cases of TAPVC were confirmed after birth. The remaining four were considered false-positive cases: two had normal heart with left superior vena cava to coronary sinus, one had partial anomalous venous connection and one was lost to follow-up. Of the 85 diagnosed postnatally with TAPVC, only one had been seen prenatally by an expert cardiac sonographer. Echocardiographic signs leading to referral were related to pulmonary venous connection in half of the cases. Other suspected defects which led to referral were ostium prium atrial defect (n = 3), left right asymmetry (n = 1), abnormal mitral valve (n = 1) and hepatic vascular malformation (n = 1). All infants with TAPVC underwent surgery. There was one postoperative death and nine survivors, with a mean follow-up of 31 (range, 2 104) months. Conclusion Fetal diagnosis of isolated TAPVC is challenging even for experts. Echocardiographic anomalies may appear late in gestation. New tools should be proposed to identify abnormal venous drainage at the screening level. Copyright 2012 ISUOG. Published by John Wiley & Sons, Ltd. INTRODUCTION Total anomalous pulmonary venous connection (TAPVC) is a rare congenital heart disease (CHD), accounting for 1 3% of all cardiac malformations. It is characterized by an anomalous connection of the pulmonary s, draining via one or more systemic s to the right atrium instead of the left atrium (LA). There are several different possible sites of pulmonary venous (PV) connection to the systemic s, including supracardiac, cardiac and infracardiac sites, or a mixture of these. When the PV drainage is obstructed, TAPVC is lifethreatening. However, assessment of PV anatomy is not part of routine obstetric scanning for fetal cardiac defects. In contrast, careful attention is paid to the identification of any PV connection during expert echocardiography, especially when complex CHD, such as heterotaxy syndrome, is diagnosed prenatally. In other CHD, associated TAPVC is extremely rare, while partial anomalous pulmonary venous connection (PAPVC) is seen occasionally. Series focusing exclusively on the fetal diagnosis of isolated TAPVC are scarce 1, and it appears clear that diagnosing this cardiac defect prenatally is challenging. It is, however, worthwhile, as planned delivery in an institution where immediate postnatal surgical repair is feasible is mandatory. The aims of this study were to report on a series of 10 fetuses with isolated TAPVC, focusing on echocardiographic features leading to diagnosis, to determine the accuracy of prenatal diagnosis and to describe postnatal outcome. Correspondence to: Dr D. Bonnet, Necker-M3C, Pediatric Cardiology, Hôpital Necker Enfants Malades, 149, rue de Sèvres, Paris, France ( damien.bonnet@nck.aphp.fr) Accepted: 19 April 2012 Copyright 2012 ISUOG. Published by John Wiley & Sons, Ltd. ORIGINAL PAPER

2 292 Laux et al. METHODS This study was conducted retrospectively at the National French Reference Centre of Complex Cardiac Congenital Malformations (M3C), a tertiary referral center. The institutional computer database was searched for all cases of pre- or postnatal diagnosis of isolated TAPVC delivered between 1 January 2001 and 1 October The total number of fetal expert echocardiographic examinations and the number of fetuses with postnatally confirmed CHD during the study period were also determined. In pregnancies with a prenatal diagnosis of isolated TAPVC, we reviewed all prenatal and postnatal records, including medical files, echocardiography loops and still frames, and written reports of obstetric fetal echocardiographic examinations leading to referral to the tertiary echocardiography center. All available imaging material was specifically reviewed by a single fetal cardiac expert (L.F.). The prenatally established diagnosis was confirmed, modified or changed according to postnatal echocardiography, surgery or autopsy findings. Attending cardiologists of children followed in other institutions were contacted for information on patient outcome. Twenty-five patients with pre- or postnatal diagnosis of complex CHD and TAPVC were excluded from the study, in order to concentrate on isolated TAPVC. RESULTS General characteristics of the study group During the study period, fetal echocardiographic scans were performed in our tertiary fetal diagnostic center and 5015 fetuses were diagnosed with CHD that was confirmed after birth. Overall, 95 liveborn infants with isolated TAPVC were identified from the database; 85 (89%) of these were diagnosed postnatally and 10 (11%) prenatally. Of the 85 patients diagnosed postnatally, one had had a prenatal diagnosis of ventricular asymmetry (right ventricular predominance and small left ventricle) with suspicion of coarctation. At postnatal assessment, this infant indeed had a coarctation but was also found to have an obstructed infracardiac TAPVC. This was the only false-negative case; the remaining 84 cases could not be considered false negatives as they were not seen prenatally by an expert cardiac sonographer. Prenatally, 14 fetuses had been diagnosed initially with isolated TAPVC (Table 1), in 10 of which the diagnosis was confirmed at postnatal assessment; the remaining four cases were considered false-positive cases. In two of these cases, the infant had a normal heart after birth. In another, the woman was seen at our institution only once for a second expert opinion very late in pregnancy and she was then lost to follow-up before delivery. Her fetus was diagnosed with a dysplastic aortic valve and TAPVC to the coronary sinus (CS), but we could find no information as to whether the prenatal diagnosis was confirmed after birth or the pregnancy was terminated (TOP). The only TOP concerned the fourth false-positive case, a fetus with a very late diagnosis of TAPVC and a concomitant late diagnosis of chromosomal abnormality [46,XX,add(6)(p25)]. Prenatal echocardiography led to suspicion of obstructed TAPVC without identification of a drainage site. Fetal autopsy revealed a partial anomalous venous connection with the two right pulmonary s draining directly into the right atrium and the two left pulmonary s connecting to the LA. Fetal echocardiographic features allowing diagnosis of isolated TAPVC This description of fetal echocardiographic features refers exclusively to the 12 liveborn infants diagnosed prenatally, including the 10 true-positive cases and the two false-positive cases with normal heart after birth, and excluding the TOP (Case 5) and the woman lost to follow-up (Case 14). In France, there are three levels for the screening of congenital cardiac anomalies. First-line sonographers screen all pregnancies and usually refer their patients to Level 2 but can also refer directly to Level 3 (expert cardiac sonography). Second-line sonographers (Level 2) are specialists in fetal ultrasound and have been trained to analyze the fetal heart and other organs but are not experts in fetal cardiology. At this level, when the suspicion of CHD is confirmed or cannot be excluded, the patient is referred to an expert fetal cardiac center for confirmation of diagnosis. At Level 3, information on prognosis is given, the outcome of pregnancy is discussed and planned delivery is organized when necessary. First-line sonography (Level 1) In the 12 fetuses, CHD was suspected by the obstetric sonographer at a mean gestational age of 25 (range, 18 32) weeks. Six women were referred for Level 2 or 3 specialist echocardiography because abnormality of PV connection was suspected by the first-line sonographer. This suspicion was based in four cases on difficulty in visualizing the pulmonary s connecting to the LA, associated in one of these cases with a small LA and in another with ventricular asymmetry and an ostium prium atrial defect. In the other two cases, suspicion of abnormal PV connection was raised by indirect signs: ventricular imbalance with a small LV and a small LA (n = 1) and dilated right superior vena cava (SVC) (n = 1). The six other women were referred for Level 2 or 3 specialist echocardiography because of suspicion of cardiovascular defects other than abnormal PV connection. These included ostium primum atrial defect (n = 3) with unbalanced ventricles in one, isolated ventricular imbalance with small left ventricle and small left LA (n = 1), abnormal mitral valve (n = 1) and hepatic vascular malformation (n = 1). The echo(cardio)graphic features leading to referral are summarized in Table 2.

3 Isolated fetal TAPVC 293 Table 1 Prenatal diagnosis, postnatal characteristics and outcome in 14 cases with prenatally diagnosed total anomalous pulmonary venous connection (TAPVC) Case GA (weeks) Prenatal diagnosis Prenatal obstruction Associated CHD Postnatal diagnosis Diagnosis at postnatal echocardiography/ operation/autopsy Outcome 1 37 Infracardiac TAPVC No No Confirmed Infracardiac TAPVC A&W 2 26 Infracardiac TAPVC No No Modified Mixed TAPVC: 3 PV with A&W infracardiac drainage, SLPV drainage to innominate 3 25 Supracardiac TAPVC Suggested Pm VSD Confirmed Supracardiac TAPVC to A&W LSVC 4 25 Supracardiac TAPVC Suggested No Confirmed Supracardiac obstructed A&W TAPVC to innominate 5 37 TAPVC* Suggested No Modified PAPVC with 2 PV draining TOP to RA, 2 PV to LA 6 25 Supracardiac TAPVC No No Confirmed Supracardiac TAPVC to A&W innominate 7 28 Supracardiac TAPVC Suggested No Confirmed Supracardiac obstructed A&W TAPVC to innominate 8 32 Intracardiac TAPVC to CS No No Confirmed Intracardiac TAPVC A&W drainage to CS 9 31 Infracardiac TAPVC No No Confirmed Infracardiac TAPVC A&W Supracardiac TAPVC Suggested No Confirmed Supracardiac obstructed TAPVC to innominate Died at 6 weeks Infracardiac TAPVC No No Confirmed Infracardiac obstructed A&W TAPVC Intracardiac TAPVC to CS* No No No Normal PVC, LSVC to CS A&W Intracardiac TAPVC to CS* No No No Normal PVC, LSVC to CS A&W Intracardiac TAPVC* No Dysplastic AV Lost to follow-up Lost to follow-up Lost to follow-up *False-positive cases: two infants had a normal heart, one was lost to follow-up and one was terminated, with a final diagnosis of partial anomalous pulmonary venous connection at autopsy. All other infants had diagnosis of TAPVC confirmed after delivery. Confirmation or modification of prenatal diagnosis by postnatal findings. A&W, alive and well at time of writing; AV, aortic valve; CHD, congenital heart disease; CS, coronary sinus; GA, gestational age at prenatal diagnosis; LA, left atrium; LSVC, left superior vena cava; PAPVC, partial anomalous pulmonary venous connection; Pm VSD, perimembranous ventricular septal defect; PV, pulmonary (s); PVC, pulmonary venous connection; RA, right atrium; SLPV, superior left pulmonary ; TOP, termination of pregnancy. Second-line echocardiography (Level 2) Three women from different parts of France were initially referred to a regional referral center. Cardiac malformation, PV drainage site and absence of PV obstruction were correctly diagnosed by the regional expert in two fetuses: one with cardiac TAPVC to the CS (Case 8) and the other with an infracardiac TAPVC (Case 9). One woman referred for suspicion of ostium primum type atrioventricular septal defect had a diagnosis of normal heart at the regional center and came for a third opinion to our institution (Case 13). Third-line echocardiography (Level 3) Nine women were referred to our institution for expert echocardiography directly after first-line echocardiography. Three women were seen in a regional referral center first and came to our institution for a third opinion. TAPVC was diagnosed at a mean gestational age of 31 (range, 24 37) weeks (Table 2). Three had intracardiac, four had infracardiac and five had supracardiac connections (Table 1). One of the twelve fetuses had a concomitant small perimembranous ventricular septal defect (VSD). This patient was considered to have isolated TAPVC as the VSD had no hemodynamic consequence. Positive prenatal diagnosis was based on indirect and direct echocardiographic signs of TAPVC (Table 2). Ventricular asymmetry with dominant right ventricle was observed in seven cases as an indirect sign. There was an oval-shaped LA that appeared small in the four-chamber view in five fetuses (Figure 1). In the same view, the descending aorta sometimes appeared more distant than usual from the posterior wall of the LA (n = 5) (Figures 1 and 2) allowing the PV confluence to be detected more easily. Other indirect signs included dilatation of the right SVC as a consequence of supracardiac drainage (n = 5). The CS appeared dilated in three cases as an indirect sign of TAPVC to the CS, including the fetus that had been diagnosed with a normal heart by a Level 2 specialist sonographer.

4 294 Laux et al. Table 2 Echocardiographic features leading to referral by Level-1 obstetric sonographer for expert (Level-3) echocardiography and direct and indirect signs at expert echocardiography that led to prenatal diagnosis of isolated total anomalous pulmonary venous connection (TAPVC) (n = 12) Level 1 Level 3 Case GA* (weeks) Echo(cardio) graphic sign(s) leading to referral Suspected APV drainage GA (weeks) SVC dilation CS dilation Indirect signs Small LA Ventric. asym. Direct signs Vertical PV confl. Postnatal diagnosis 1 26 Ventric. asym., Infracardiac TAPVC small LA PV to LA only, Mixed TAPVC PV confl.? 3 24 Abnormal mitral Supracardiac TAPVC valve 4 23 Small round LA, Supracardiac TAPVC PV confl.? 6 18 Ventric. asym., Supracardiac TAPVC ASD I 7 22 PV confl.? Supracardiac TAPVC 8 23 ASD I,1PVto Intracardiac TAPVC LA only, ventric. asym Ventric. asym., Infracardiac TAPVC small LA Dilatation of right Supracardiac TAPVC SVC Intrahepatic Infracardiac TAPVC vascular malformation Overriding aorta, LSVC to CS ASD I ASD I 34 + LSVC to CS Cases are numbered as in Table 1. Case 5 (terminated) and Case 14 (lost to follow-up) have been excluded from this table. Cases 12 and 13 had prenatal diagnosis of intracardiac TAPVC to the coronary sinus (CS), but were diagnosed after birth with a normal heart and LSVC to the CS. *Gestational age (GA) at referral. GA at prenatal diagnosis. Cases 8, 9 and 13 were seen by a Level-2 specialist sonographer (regional referral center) before referral to Level 3. APV, anomalous pulmonary venous; ASD I, ostium prium atrial defect; confl., confluence; LA, left atrium; LSVC, left superior vena cava; PV, pulmonary ; SVC, superior vena cava; Ventric./ventric. asym., ventricular asymmetry (dominant right and small left ventricle). In 10 fetuses the pulmonary s could not be shown draining to the LA, as a direct sign of TAPVC. In all of these cases a retroatrial PV confluence could be visualized in the four-chamber view, and the confluence was seen joining a descending or ascending vertical in all nine fetuses with an infracardiac or supracardiac connection (Figures 3 and 4). To attempt to describe the anatomy of the pulmonary s and their connection to the systemic s, we used low-flow color Doppler mapping and when possible tried to identify the drainage site and determine whether it was obstructed. PV obstruction was suspected in four cases of supracardiac connection prenatally (Table 1). In these cases color Doppler showed aliased flow at the site of connection of the ascending vertical to the innominate or the left SVC. Pulsed Doppler identified high-velocity continuous flow > 0.5 m/s (Figure 5). In the other cases, we could not identify Doppler tracing anomalies suggestive of obstruction. In addition, as the study was retrospective, there was no available pulsed Doppler flow profile of the vertical or of the PV confluence in some patients. Therefore, we found only two fetuses with a demodulated PV flow without a notched tracing, as described previously 2,3. Postnatal outcome of prenatally diagnosed isolated TAPVC All women with a prenatal diagnosis of TAPVC were referred to the obstetrics department of our institution for follow-up of pregnancy. Whenever possible, labor was induced during weekdays rather than over weekends. All infants were delivered at term (range, weeks). The mean weight at birth was 2.9 (range, ) kg. Ten of the 12 infants were delivered vaginally; there were two Cesarean sections for fetal reasons. Ten of the deliveries took place as scheduled at our institution; for logistic reasons one infant was delivered and underwent surgery at another institution, and the woman who had had a discordant prenatal diagnosis varying from normal heart to TAPVC to CS (Case 13) chose to deliver in another hospital. The pediatric cardiology department, the surgeon and the cardiac intensive care unit were informed when delivery of a child with a prenatal diagnosis of TAPVC was scheduled. Echocardiographic assessment in the delivery room allowed a decision as to whether immediate transfer to the intensive care unit and surgery was necessary. Prenatal diagnosis of TAPVC was confirmed in 10 of the 12

5 Isolated fetal TAPVC 295 Figure 1 Case 10. Fetal four-chamber view at 33 weeks, showing three indirect signs of total anomalous pulmonary venous connection: ventricular asymmetry, with a small left ventricle (LV), a small left atrium (LA) and increased distance between it and the descending aorta (ao). As a direct sign, one can detect the presence of a small pulmonary venous confluence (pv con) immediately posterior to the LA. RA, right atrium; RV, right ventricle. Figure 3 Case 11. (a) Two-dimensional echocardiographic image derived from the parasagittal inferior vena cava view in a fetus with a total infracardiac anomalous pulmonary venous connection. This view shows the vertical (vv) descending towards the liver between aorta and inferior vena cava, neither of which is visible in this image. LA, left atrium; RA, right atrium. (b) Corresponding color Doppler image in the same fetus. Color Doppler is set on low velocity mapping to enhance visualization of slow venous flow in the descending vertical (vv). Figure 2 Case 11. Fetal four-chamber view at 34 weeks, showing a clearly visible pulmonary venous confluence (pv con) between the left atrium (LA) and the descending aorta (ao), which are more distant from each other than normal. LV, left ventricle; RA, right atrium; RV, right ventricle. (83%) patients by postnatal echocardiography (Tables 1 and 2). Five had supracardiac TAPVC, three had infracardiac connection, one had intracardiac TAPVC and one had mixed TAPVC. The latter (Case 2) was the only patient in whom the classification of drainage site was modified at postnatal assessment, from infracardiac to mixed TAPVC. The prenatally suggested PV obstruction was confirmed in four infants with supracardiac TAPVC after birth. Two of the 12 (17%) infants (Cases 12 and 13) actually had a normal PV connection observed after delivery. The only cardiac abnormality found, in both of these cases, was a left SVC connecting to the dilated CS. Surgical repair was performed within the first 24 h in seven of the 10 infants with confirmed TAPVC. It was postponed in two infants with supracardiac TAPVC and in the only infant with intracardiac connection because there was neither relevant obstruction nor pulmonary hypertension. There was one postoperative in-hospital death in the series (Case 10). This infant, with a supracardiac TAPVC and PV obstruction at birth, had persistent pulmonary hypertension after surgery. Stenosis of the PV anastomosis was excluded by cardiac catheterization. He never left hospital after surgical repair and eventually died at the age of 6 weeks in the intensive care unit because of severe pulmonary infection. At the time of data collection, the remaining nine children were alive and in good health, at a mean follow-up of 31 (range, 2 104) months. At the last follow-up visit, to either our outpatient department or the relevant institution, all had unobstructed PV anastomosis and normal pulmonary pressure. DISCUSSION We have reported on a series of 10 cases of postnatally confirmed isolated TAPVC seen at a single institution

6 296 Laux et al. Figure 4 Case 10. Fetal sagittal superior vena caval (SVC) view at 27 weeks, showing a supracardiac total anomalous pulmonary venous connection to the SVC. The vertical with two visible pulmonary s (PV) is seen ascending towards the innominate (in ). Figure 5 Case 7. Fetal pulsed Doppler flow profile at 35 weeks, showing high-velocity flow of > 1 m/s at the obstructed drainage site of a supracardiac total anomalous pulmonary venous connection to the innominate. Normal venous flow has a velocity < 0.5 m/s. during a study period of more than 10 years. This is, to our knowledge, the largest series of prenatally diagnosed isolated TAPVC. The only other series focusing on prenatally diagnosed isolated TAPVC was published recently and included eight patients over a 7-year period across 19 centers and three different countries 1. Indirect and direct echocardiographic signs suggesting the prenatal diagnosis of TAPVC have been well described in the literature Right ventricular predominance, one of the indirect echocardiographic signs, is the consequence of volume overload due to TAPVC, even though pulmonary flow is low in fetal life. However, discrepancy in ventricular size can also be due to left heart obstruction or hypoplasia, as suggested prenatally in the false-negative case in our series which had coarctation and TAPVC. Similar cases have been reported previously 5. As right ventricular asymmetry can represent a normal physiological variant in the third trimester, this echocardiographic sign can also lead to false-positive diagnosis of TAPVC, as reported by Papa et al. 11. A smooth appearance of the posterior wall of the LA and its small size in the four-chamber view is another indirect sign recently reported 7, seen in five cases in our series. While this may be due to the reduced left atrial flow during fetal life, small LA size in TAPVC is probably also due to the fact that the embryological common pulmonary does not fuse with the LA during development. The dilated CS can be an indirect sign of cardiac TAPVC to the CS or may be related to a persisting left SVC to the CS. This can lead to a false-positive diagnosis of intracardiac TAPVC, as seen in two cases in our series. Dilated CS is a common cause for referral for an expert cardiac scan in the fetus. It may mimic ostium prium atrial defect 10 and has also been associated with an increased risk of coarctation. Dilation of the SVC can be the consequence of an anomalous supracardiac connection in the absence of upper body arteriovenous fistula. Visualization of an additional intrahepatic vessel between the aorta and the heart can be an indirect sign of infracardiac TAPVC or may be mistaken for a hepatic vascular malformation, as reported here. In our series, referral was as a result of one or more of the abovementioned indirect echocardiographic features associated with difficulty in visualizing PV connection in half of the cases, while other defects were suspected in the remaining patients. At expert fetal echocardiography, imaging of the PV confluence or the vertical allowed for an accurate prenatal diagnosis in 10 of 12 fetuses (excluding the one lost to follow-up and the TOP), with only two (16%) found to have a normal heart after birth. Retrospectively, in those two cases with false-positive diagnosis, PV confluence was not identified clearly and it was only dilatation of the CS that raised the suspicion of TAPVC to the CS. This underlines the necessity of visualizing directly the PV confluence and/or the vertical to suspect TAPVC prenatally. Additionally, there were no available low-flow color images in these two fetuses. Low-flow color Doppler mapping can be a valuable tool in making the difficult diagnosis of TAPVC 2,3,5. In the two false-positive cases of TAPVC to the CS, use of this technique could have shown the s draining directly to the atrium and not to the CS. We currently use it to facilitate the identification of s in the fetus but we were not able to analyze the efficiency of this tool in the present series due to the retrospective design and incomplete data. Another known screening tool to suggest that the pulmonary is not connected to the atrium could be the absence of notched tracing of the PV flow on pulsed Doppler, as previously described 2. However, this presupposes that an abnormal vertical or PV confluence has been detected. It is of note that the diagnosis of TAPVC was made late in gestation in our series, despite the fact that diagnosis of the majority of CHD is made in France between 16 and 20 weeks. We think that this delay in diagnosing isolated TAPVC is not specifically related to the national organization of fetal screening and diagnosis of CHD but

7 Isolated fetal TAPVC 297 rather is due to the fetal physiology of TAPVC. We could hypothesize that an increase in pulmonary blood flow late in gestation is responsible for the late appearance of certain echocardiographic features, such as left right asymmetry or visibility of the retroatrial PV confluence, that led to diagnosis of TAPVC in our series. Our study is limited because of the low number of cases and its retrospective nature. We can only postulate that optimal postnatal planning positively influences survival and long-term outcome in cases of prenatally diagnosed TAPVC. Survival and mid-term outcome was favorable in our series. This is consistent with the recent multicenter series 1 and large surgical series describing outcome of postnatally diagnosed TAPVC 12,13. In contrast, it is not surprising that former series that included a mix of isolated and complex TAPVC reported a poor outcome, which was clearly driven by the association with complex CHD 6. In summary, fetal diagnosis of isolated TAPVC is extremely challenging to both the first-line sonographer and the expert. Indirect echocardiographic signs can be difficult to interpret and visualization of the PV confluence can be complicated, with this vascular structure becoming more easily visualized late in gestation. The rarity of series of isolated TAPVC clearly highlights the difficulty in detecting this cardiac defect in fetal life. Low-flow color mapping to identify pulmonary s during routine scanning could be a valuable tool to improve diagnosis. Abnormal pulsed Doppler flow can give additional information for the expert 2,3. Keeping in mind that isolated TAPVC is a rare CHD, priority in obstetric scanning should go to evaluation of the standard fetal cardiac views in order to detect major cardiac abnormalities, with referral of women to a tertiary fetal ultrasound center for an expert opinion in case of doubt. ACKNOWLEDGMENTS We thank Jérôme Le Bidois, a close collaborator of Laurent Fermont at Institut de Puériculture, for reading the manuscript critically and giving advice on fetal imaging. REFERENCES 1. Seale AN, Carvalho JS, Gardiner HM, Mellander M, Roughton M, Simpson J, Tometzki A, Uzun O, Webber SA, Daubeney PEF, on behalf of the British Congenital Cardiac Association. Total anomalous pulmonary venous connection: impact of prenatal diagnosis. Ultrasound Obstet Gynecol 2012; 40: Feller Printz B, Allan LD. Abnormal pulmonary venous return diagnosed prenatally by pulsed Doppler flow imaging. Ultrasound Obstet Gynecol 1997; 9: Valsangiacomo ER, Hornberger LK, Barrea C, Smallhorn JF, Yoo SJ. Partial and total anomalous pulmonary venous connection in the fetus: two-dimensional and Doppler echocardiographic findings. Ultrasound Obstet Gynecol 2003; 22: Yeager SB, Parness IA, Spevak PJ, Hornberger LK, Sanders SP. Prenatal echocardiographic diagnosis of pulmonary and systemic venous anomalies. Am Heart J 1994; 128: Allan LD, Sharland GK. The echocardiographic diagnosis of totally anomalous pulmonary venous connection in the fetus. Heart 2001; 85: Patel CR, Lane JR, Spector ML, Smith PC, Crane SS. Totally anomalous pulmonary venous connection and complex congenital heart disease: prenatal echocardiographic diagnosis and prognosis. J Ultrasound Med 2005; 24: Law KM, Leung KY, Tang MH, Chau AK. Prenatal two- and three-dimensional sonographic diagnosis of total anomalous pulmonary venous connection. Ultrasound Obstet Gynecol 2007; 30: Inamura N, Kado Y, Kita T, Kayatani F. Fetal echocardiographic imaging of total anomalous pulmonary venous connection. Pediatr Cardiol 2006; 27: Cormier CM, Kramer LA, Gupta-Malhotra M. Prenatal diagnosis of a mixed type of total anomalous pulmonary venous return. Fetal Diagn Ther 2010; 27: Barrea C, Biard JM, Hutchings G, Bernard P. Prenatal diagnosis of isolated total anomalous systemic venous return to the coronary sinus. Ultrasound Obstet Gynecol 2010; 35: Papa M, Camesasca C, Santoro F, Zoia E, Fragasso G, Giannico S, Chierchia SL. Fetal echocardiography in detecting anomalous pulmonary venous connection: four false positive cases. Br Heart J 1995; 73: Hancock Friesen CL, Zurakowski D, Thiagarajan RR, Forbess JM, del Nido PJ, Mayer JE, Jonas RA. Total anomalous pulmonary venous connection: an analysis of current management strategies in a single institution. Ann Thorac Surg 2005; 79: ; discussion Kelle AM, Backer CL, Gossett JG, Kaushal S, Mavroudis C. Total anomalous pulmonary venous connection: results of surgical repair of 100 patients at a single institution. J Thorac Cardiovasc Surg 2010; 139: e3.