Fusi et al, Diagnosis of acardiac twin 223

J. Perinat. Med.18 (1990) 223

When does death occur in an acardiac twin? Ultrasound diagnosticdifficulties

Luca Fusi, Nick Fisk, David Talbert, Gillian Gau, and Charles Rodeck

Institute of Obstetrics and Gynaecology, Royal Postgraduate Medical School,Hammersmith, Queen Charlotte's & Chelsea Hospitals, London, U. K.

1 IntroductionFetal acardia, a rare abnormality seen only inmultiple pregnancy, occurs once in every 35.000births [5]. The malformation affects one fetusonly and is thought to derive from an umbilicalartery to artery anastomosis within a fusedmonochorial and monoamniotic placenta. Con-sequent haemodynamic alterations have beensuggested to result in reverse arterial perfusionof the 'perfused' twin, by its sibling, the 'pump'twin [8].The twin reverse arterial perfusion sequence(TRAP) is associated with four major types ofabnormality: Acardius acephalus, with absenceof fetal head and thoracic organs, myelacephaluswith partially developed head and extremities,amorphus where there is no recognisable humanshape, and acornus where only the fetal headdevelops [2]. TRAP sequence is lethal for theaffected fetus, and causes death in up to 50% ofnormal co-twins, either from intrauterine cardiacfailure or the sequelae of prematurity [8]. Anten-atal recognition of the condition is imperative ifprospective management is to be instituted toimprove the outcome [6]. The purpose of thiscommunication is to report difficulties in ultra-sound diagnosis, and to stress the risk of suddenintra uterine death of the pump twin in absenceof compromise on ultrasound, Doppler studiesor fetal blood sampling.

2 Case reportA routine ultrasound scan at 17 weeks on a 22-year-old primigravid patient showed the presenceof monoamniotic twins with polyhydramnios.

I -Curriculum vitaeLUCA Fusi, MD;MRCOG, graduatedfrom the University ofRome, Italy, in 1976. Hespecialised in Obstetricsand Gynaecology in1980, and then trained asa fellow in PerinatalMedicine at St. Mary'sHospital, London. He iscurrently Senior Regis-trar at the Institute ofObstetrics & Gynaecology, London, and his main interestis Feto-Maternal Medicine.

Twin I was normal but twin II was consideredto have anencephaly and ascites. Fetal heartactivity was seen in each twin (figure 1). Becausetwin I appeared entirely normal, and twin II wasconsidered non viable, the parents were not of-fered selective fetocide and the pregnancy con-tinued. Repeat scan at 22 weeks showed that theheart of twin II had stopped beating and thisfetus had become grossly oedematous. Its um-bilical cord was tightly wrapped around the legof the other twin (figure 2), in which growth,anatomy, and Doppler blood flow velocity wave-forms in the umbilical artery remained normal.Fetal blood sampling, performed at 24 weeksfrom the cord of twin I to exclude genetic ab-normalities and DIC and confirm its well being,showed normal karyotype (46 xx), blood gases,haematological and clotting studies. The proce-dure was completely uncomplicated but threedays later the mother reported lack of fetal

1990 by Walter de Gruyter & Co. Berlin · New York

Brought to you by | University of Queensland - UQ LibraryAuthenticated

Download Date | 10/23/15 1:05 AM

224 Fusi et al., Diagnosis of acardiac twin

Figure 1. Ultrasound scan taken at 17 weeks. On the left a sagittal view of the chest of the acardiac monstershowing the structure which appeared to be pulsating. On the right a similar view of the normal twin.

movements and twin I was found on ultrasoundto be dead.Labour was induced with vaginal prostaglan-dins, resulting in an uncomplicated delivery oftwo female infants weighing 200 and 780 g. Postmortem revealed that twin II was anencephalicand acardiac (figure 3). There were early signsof maceration, and a double aortic arch arosefrom the lungs without any evidence of cardiactissue, while the oesophagus, stomach and liverwere absent. A cervical spina bifida was alsopresent. Twin I was normal, but on histologicalexamination fibrin clots were found in the lungs,kidneys and liver. Both artery to artery and veinto vein anastomoses were identified within themonochorionic placenta, which weighed 330 g.The cord of twin II, which was centrally insertedand contained three vessels, was tightly wrappedaround the other twin's leg, producing trophicchanges and constriction phenomena (figure 4).

3 Discussion

The diagnosis of acardiac monster must be madeantenatally if the prognosis for the normal co-twin is to be improved in TRAP. However it isonly recently that this abnormality has beenidentified antenatally on ultrasound [3]. The di-agnosis is straightforward in the presence of anamorphus mass of tissue or of an acephalusacardiac twin associated with an anatomicallynormal co-twin [7], which may show signs ofcardiac failure. The diagnosis can however bemore difficult with malformations such as anen-cephaly, especially if the normal co-twin has noevidence of chronic cardiac failure.

In our case the assessment was made even moredifficult by normal heart activity seen in theacardiac fetus on the initial scan. Retrospectiveanalysis of the original ultrasound scan togetherwith the autopsy findings led us to speculate that

J. Perinat. Med. 18 (1990)

Brought to you by | University of Queensland - UQ LibraryAuthenticated

Download Date | 10/23/15 1:05 AM

Fusi et al., Diagnosis of acardiac twin 225

Absence of fetal heart activity on ultrasound isthe gold standard for diagnosis of intrauterinefetal death, yet in acardia this assessment is notpossible. The demonstration of reflex movements

Figure 3. The acardiac twin.

Figure 2. Ultrasound scan of the umbilical cord of theacardiac monster tightly wrapped around the leg ofthe pump twin.

the heart motion seen was a mass of lung tissuewith dilated vessels which pulsed, as a conse-quence of the reverse perfusion, at the samecardiac rhythm as the other twin. The eventualdisappearance of this pulsation may have oc-curred as a consequence of the interruption ofthe reverse perfusion when the cord becametightly wrapped around the leg.

Figure 4. Twin I, the "pump" twin. Note the signs ofearly maceration and the oedema of the right foot,caused by the entangled cord of twin II.

J. Perinat. Med. 18 (1990)

Brought to you by | University of Queensland - UQ LibraryAuthenticated

Download Date | 10/23/15 1:05 AM

226 Fusi et al, Diagnosis of acardiac twin

in acardiac fetuses suggests that they are still'alive', but no information exists on the accuracyof absent movements in diagnosing fetal death.Diagnostic difficulty may also arise in the inter-pretation of reflex movements in monoamniotictwins when, like in our case, the dead twin is'towed' around the amniotic cavity by its co-twin. In view of the original ultrasound, we as-sume that both fetuses were alive at 17 weeks,and subsequent fetal death was diagnosed whenno heart activity was seen in the abnormal fetus.However this sign in the acardiac fetus is depen-dant upon the heart activity of the other twinand unimpeded perfusion through placental an-astomoses. We suggest that in the presence ofcord entanglement, perfusion varied with the de-gree of tautness. At autopsy, only mild macera-tion was found in the acardiac fetus, suggestingthat tissue death had occurred much more re-cently than suggested by the three weeks of ab-sent cardiac activity seen on scan. Presumablyintermittent loosening and tightening of the loopof cord with consequent resumption and inter-ruption of reverse perfusion could have occurreduntil shortly before delivery, leading to a stateof progressive avascular necrosis or 'partial'death. Under these circumstances the ultrasounddetection of intermittent pulsatile activity in the'dead' fetus may pose ethical and diagnostic dif-ficulties.Several possibilities exist for the cause of deathin the pump twin. The normal co-twin oftendevelops chronic cardiac failure because of thereverse perfusion, producing a mortality of 50%[8]. In our case there was no evidence of com-promise in the pump twin, on the basis of boththe normal haematological and gas values ob-tained at fetal blood sampling, and of the normalultrasound and doppler studies. Specifically,there was no evidence of cardiac failure withonly mild ventriculomegaly in the absence of

oedema or hepato-splenomegaly being found atautopsy. Fetal death as a complication of bloodsampling appears unlikely since the procedurewas uncomplicated, and the death occurred atleast 48 hours after normal fetal heart rate andmovements were recorded following the proce-dure.Loosening and tightening of the cord of theperfused twin would on the other hand haveproduced intermittent circulatory shunts in thepump twin, with the release of de-oxygenatedblood into the circulation when the cord relaxed.The resulting series of hypo- and hypertensiveepisodes in the normal twin, could then lead todeath from vagal cardiac inhibition, acute cir-culatory collapse or haemorrhage. Intrauterinedeath can occur in 73% of monochorionic twins[1] and is often attributed to cord entanglement,absent however, in our normal twin.

The finding of intravascular fibrin deposis in theliver, lungs and kidneys of the normal twin ispuzzling since the fetal clotting screen was nor-mal 48 hours before death. Fetal disseminatedintravascular coagulation has been suggested tooccur after intrauterine death of one twin [4],but has not previously been reported in the pumptwin in TRAP. Recurrent hypotensive and hy-pertensive episodes could, on the other hand,have caused multiple haemorrhages with fibrindeposition via a hydromechanical mechanism.

In conclusion, care should be taken in the ultra-sound diagnosis of single intrauterine death inmultiple pregnancy to exclude the presence of anacardiac fetus. The co-twin in TRAP is alwaysat increased risk of sudden death, even withoutultrasound or biochemical evidence of compro-mise. This case illustrates a diagnostic pitfall andrises the question of when death occurs if noheart or brain are present.

Abstract

Fetal acardia is a rare abnormality of multiple preg-nancies, which is lethal for the affected fetus and cancause death in 50% of normal co-twins. Antenatalrecognition with early ultrasound is essential to insti-tute a prospective management to improve the out-come. Our communication outline the difficultieswhich may be encountered in ultrasound diagnosis. Inparticular the problem of distinguishing a fetal heartfrom large pulsating mediastinal vessels, which can beKeywords: Acardia, twins, ultrasound.

present in these fetuses, and the difficulty of diagnosingdeath in an acardiac fetus. Our report confirms thatthe co-twin remains at increased risk of sudden death,even without ultrasound evidence of cardiac failure orbiochemical compromise. The finding in this fetus ofintravascular fibrin deposits suggests the possibility ofacute disseminated intravascular coagulation, not pre-viously reported in association with an acardiac twin.

J. Perinat. Med. 18 (1990)

Brought to you by | University of Queensland - UQ LibraryAuthenticated

Download Date | 10/23/15 1:05 AM

Fusi et al., Diagnosis of acardiac twin 227

Zusammenfassung

Wann tritt beim Zwillings-Akardiakus der Tod ein? Dia-gnostische Probleme beim UltraschallWir berichten über einen fetalen Akardiakus, bei demim zweiten Trimenon sonographisch Herzaktionen ge-sehen wurden, die jedoch bei nachfolgenden Ultra-schalluntersuchungen nicht mehr nachweisbar waren.Die Nabelschnur des Zwillings-Akardiakus war straffum das Bein gewickelt. Unsere Hypothese lautet, daßdiese „Herzaktionen" durch Pulsationen erweiterterThoraxgefaße hervorgerufen wurden. Der Nachweis

Schlüsselwörter: Akardiakus, Ultraschall, Zwillinge.

dieser Pulsationen war abhängig von der Straffheit derverwickelten Nabelschnur — ein partielles Absterben(progressive Nekrose) war die Folge.Großflächige Fibrinablagerungen, die sich bei der Au-topsie des gesunden Zwillingspartners nachweisen lie-ßen, lassen an eine disseminierte intravaskuläre Koa-gulation denken. Darüber wurde bisher im Zusam-menhang mit einem fetalen Akardiakus noch nichtberichtet.

Resume

Quand la mort survient-elle chez im jumeau acardiaque?Difficultes diagnostiques a FechographieNous presentons un cas de foetus acardiaque chezlequel une echographie du second trimestre suggeraitune activite cardiaque bien que celle ci n'ait pas eteobservee sur les coupes ulterieures. Le cordon du ju-meau acardiaque se trouvait etre etroitement enrouleautour de la jambe de l'autre jumeau. Nous emettonsl'hypothese que cette activite «cardiaque» etant se-

Mots-cles: Acardiaque, echographie, jumeaux.

condaire aux pulsations des vaisseaux dilates dans lethorax. La presence ou l'absence de cette pulsationdependaient du caractere plus ou moins serre de Fen-roulement du cordon conduisant ä un etat de mortpartielle (necrose progressive). La presence de depotsde fibrine etendus trouvee a Pautopsie du jumeau nor-mal suggere la possibilite d'une coagulation intravas-culaire disseminee, ce qui na pas ete anterieurementrapporte en association avec un foetus acardiaque.

References

[1] D'ALTON ME, ER NEWTON, CL CETRULO: Intrau-terine fetal demise in multiple gestation. Acta GenMed Gemollol 33 (1984) 43

[2] LACHMAN R: The acardiac monster. Eur J Paediat134 (1980) 195

[3] MARCK LA, MG GRAVETT, CM ROMACK, GR LEO-POLD, RA SCHOR, WP SHURAN, JV ROGERS: An-tenatal ultrasonic evaluation of acardiac monsters.J Ultrasound Med 1 (1982) 13

[4] MOORE CM, AJ Me ADAMS, J SUTHERLAND: In-trauterine disseminated intravacular coagulation: asyndrome of multiple pregnancy with a dead fetus.J Paediat 74 (1969) 523

[5] NAPOLITANI FQ, I SCHREIBER: The acardiac mons-ter. Am J Obstet Gynecol 80 (1960) 584

[6] PLATT LD, GR DE VORE, A BIERNIARZ, P BENNER,R RAO: Antenatal diagnosis of acephalus acardia:a proposed management scheme. Am J Obstet Gy-necol 146 (1983) 857

[7] ROBIE GF, GG PAYNE, MA MORGAN: Selectivedelivery of an acardiac acephalic twin. N Eng JMed 320 (1989) 512

[8] VAN ALLEN MI, DW SMITH, TH SHEPARD: Twinreverse arterial perfusion sequence. A study of 14twin pregnancies with acardius. Sem Perinat 7(1983) 285

Received February 2, 1990. Accepted February 12,1990.

Luca Fusi, MD, MRCOGInstitute of Obstetrics & GynaecologyHammersmith HospitalDu Cane RoadLondon W12 OHJU.K.

J. Perinat. Med. 18 (1990)

Brought to you by | University of Queensland - UQ LibraryAuthenticated

Download Date | 10/23/15 1:05 AM