Fisk, Nick

Fusi, Luca

Gau, Gillian

Rodeck, Charles

Talbert, David

University of Queensland eSpace

Fusi et al, Diagnosis of acardiac twin 223
J. Perinat. Med.
18 (1990) 223
When does death occur in an acardiac twin? Ultrasound diagnostic
difficulties
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 Introduction
Fetal acardia, a rare abnormality seen only in
multiple pregnancy, occurs once in every 35.000
births [5]. The malformation affects one fetus
only and is thought to derive from an umbilical
artery to artery anastomosis within a fused
monochorial and monoamniotic placenta. Con-
sequent haemodynamic alterations have been
suggested to result in reverse arterial perfusion
of the 'perfused' twin, by its sibling, the 'pump'
twin [8].
The twin reverse arterial perfusion sequence
(TRAP) is associated with four major types of
abnormality: Acardius acephalus, with absence
of fetal head and thoracic organs, myelacephalus
with partially developed head and extremities,
amorphus where there is no recognisable human
shape, and acornus where only the fetal head
develops [2]. TRAP sequence is lethal for the
affected fetus, and causes death in up to 50% of
normal co-twins, either from intrauterine cardiac
failure or the sequelae of prematurity [8]. Anten-
atal recognition of the condition is imperative if
prospective management is to be instituted to
improve the outcome [6]. The purpose of this
communication is to report difficulties in ultra-
sound diagnosis, and to stress the risk of sudden
intra uterine death of the pump twin in absence
of compromise on ultrasound, Doppler studies
or fetal blood sampling.
2 Case report
A routine ultrasound scan at 17 weeks on a 22-
year-old primigravid patient showed the presence
of monoamniotic twins with polyhydramnios.
I -
Curriculum vitae
LUCA Fusi, MD;
MRCOG, graduated
from the University of
Rome, Italy, in 1976. He
specialised in Obstetrics
and Gynaecology in
1980, and then trained as
a fellow in Perinatal
Medicine at St. Mary's
Hospital, London. He is
currently Senior Regis-
trar at the Institute of
Obstetrics & Gynaecology, London, and his main interest
is Feto-Maternal Medicine.
Twin I was normal but twin II was considered
to have anencephaly and ascites. Fetal heart
activity was seen in each twin (figure 1). Because
twin I appeared entirely normal, and twin II was
considered non viable, the parents were not of-
fered selective fetocide and the pregnancy con-
tinued. Repeat scan at 22 weeks showed that the
heart of twin II had stopped beating and this
fetus had become grossly oedematous. Its um-
bilical cord was tightly wrapped around the leg
of 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 weeks
from 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 three
days later the mother reported lack of fetal
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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 monster
showing the structure which appeared to be pulsating. On the right a similar view of the normal twin.
movements and twin I was found on ultrasound
to be dead.
Labour was induced with vaginal prostaglan-
dins, resulting in an uncomplicated delivery of
two female infants weighing 200 and 780 g. Post
mortem revealed that twin II was anencephalic
and acardiac (figure 3). There were early signs
of maceration, and a double aortic arch arose
from the lungs without any evidence of cardiac
tissue, while the oesophagus, stomach and liver
were absent. A cervical spina bifida was also
present. Twin I was normal, but on histological
examination fibrin clots were found in the lungs,
kidneys and liver. Both artery to artery and vein
to vein anastomoses were identified within the
monochorionic placenta, which weighed 330 g.
The cord of twin II, which was centrally inserted
and contained three vessels, was tightly wrapped
around the other twin's leg, producing trophic
changes and constriction phenomena (figure 4).
3 Discussion
The diagnosis of acardiac monster must be made
antenatally if the prognosis for the normal co-
twin is to be improved in TRAP. However it is
only recently that this abnormality has been
identified antenatally on ultrasound [3]. The di-
agnosis is straightforward in the presence of an
amorphus mass of tissue or of an acephalus
acardiac twin associated with an anatomically
normal co-twin [7], which may show signs of
cardiac failure. The diagnosis can however be
more difficult with malformations such as anen-
cephaly, especially if the normal co-twin has no
evidence of chronic cardiac failure.
In our case the assessment was made even more
difficult by normal heart activity seen in the
acardiac fetus on the initial scan. Retrospective
analysis of the original ultrasound scan together
with the autopsy findings led us to speculate that
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Fusi et al., Diagnosis of acardiac twin 225
Absence of fetal heart activity on ultrasound is
the gold standard for diagnosis of intrauterine
fetal death, yet in acardia this assessment is not
possible. The demonstration of reflex movements
Figure 3. The acardiac twin.
Figure 2. Ultrasound scan of the umbilical cord of the
acardiac monster tightly wrapped around the leg of
the pump twin.
the heart motion seen was a mass of lung tissue
with dilated vessels which pulsed, as a conse-
quence of the reverse perfusion, at the same
cardiac rhythm as the other twin. The eventual
disappearance of this pulsation may have oc-
curred as a consequence of the interruption of
the reverse perfusion when the cord became
tightly wrapped around the leg.
Figure 4. Twin I, the "pump" twin. Note the signs of
early maceration and the oedema of the right foot,
caused by the entangled cord of twin II.
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226 Fusi et al, Diagnosis of acardiac twin
in acardiac fetuses suggests that they are still
'alive', but no information exists on the accuracy
of absent movements in diagnosing fetal death.
Diagnostic difficulty may also arise in the inter-
pretation of reflex movements in monoamniotic
twins 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 when
no 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 twin
and unimpeded perfusion through placental an-
astomoses. We suggest that in the presence of
cord entanglement, perfusion varied with the de-
gree of tautness. At autopsy, only mild macera-
tion was found in the acardiac fetus, suggesting
that tissue death had occurred much more re-
cently than suggested by the three weeks of ab-
sent cardiac activity seen on scan. Presumably
intermittent loosening and tightening of the loop
of cord with consequent resumption and inter-
ruption of reverse perfusion could have occurred
until shortly before delivery, leading to a state
of progressive avascular necrosis or 'partial'
death. Under these circumstances the ultrasound
detection of intermittent pulsatile activity in the
'dead' fetus may pose ethical and diagnostic dif-
ficulties.
Several possibilities exist for the cause of death
in the pump twin. The normal co-twin often
develops chronic cardiac failure because of the
reverse 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 both
the normal haematological and gas values ob-
tained at fetal blood sampling, and of the normal
ultrasound and doppler studies. Specifically,
there was no evidence of cardiac failure with
only mild ventriculomegaly in the absence of
oedema or hepato-splenomegaly being found at
autopsy. Fetal death as a complication of blood
sampling appears unlikely since the procedure
was uncomplicated, and the death occurred at
least 48 hours after normal fetal heart rate and
movements were recorded following the proce-
dure.
Loosening and tightening of the cord of the
perfused twin would on the other hand have
produced intermittent circulatory shunts in the
pump twin, with the release of de-oxygenated
blood into the circulation when the cord relaxed.
The resulting series of hypo- and hypertensive
episodes in the normal twin, could then lead to
death from vagal cardiac inhibition, acute cir-
culatory collapse or haemorrhage. Intrauterine
death 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 the
liver, lungs and kidneys of the normal twin is
puzzling since the fetal clotting screen was nor-
mal 48 hours before death. Fetal disseminated
intravascular coagulation has been suggested to
occur after intrauterine death of one twin [4],
but has not previously been reported in the pump
twin in TRAP. Recurrent hypotensive and hy-
pertensive episodes could, on the other hand,
have caused multiple haemorrhages with fibrin
deposition via a hydromechanical mechanism.
In conclusion, care should be taken in the ultra-
sound diagnosis of single intrauterine death in
multiple pregnancy to exclude the presence of an
acardiac fetus. The co-twin in TRAP is always
at increased risk of sudden death, even without
ultrasound or biochemical evidence of compro-
mise. This case illustrates a diagnostic pitfall and
rises the question of when death occurs if no
heart or brain are present.
Abstract
Fetal acardia is a rare abnormality of multiple preg-
nancies, which is lethal for the affected fetus and can
cause death in 50% of normal co-twins. Antenatal
recognition with early ultrasound is essential to insti-
tute a prospective management to improve the out-
come. Our communication outline the difficulties
which may be encountered in ultrasound diagnosis. In
particular the problem of distinguishing a fetal heart
from large pulsating mediastinal vessels, which can be
Keywords: Acardia, twins, ultrasound.
present in these fetuses, and the difficulty of diagnosing
death in an acardiac fetus. Our report confirms that
the co-twin remains at increased risk of sudden death,
even without ultrasound evidence of cardiac failure or
biochemical compromise. The finding in this fetus of
intravascular fibrin deposits suggests the possibility of
acute disseminated intravascular coagulation, not pre-
viously reported in association with an acardiac twin.
J. Perinat. Med. 18 (1990)
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Fusi et al., Diagnosis of acardiac twin 227
Zusammenfassung
Wann tritt beim Zwillings-Akardiakus der Tod ein? Dia-
gnostische Probleme beim Ultraschall
Wir berichten über einen fetalen Akardiakus, bei dem
im zweiten Trimenon sonographisch Herzaktionen ge-
sehen wurden, die jedoch bei nachfolgenden Ultra-
schalluntersuchungen nicht mehr nachweisbar waren.
Die Nabelschnur des Zwillings-Akardiakus war straff
um das Bein gewickelt. Unsere Hypothese lautet, daß
diese „Herzaktionen" durch Pulsationen erweiterter
Thoraxgefaße hervorgerufen wurden. Der Nachweis
Schlüsselwörter: Akardiakus, Ultraschall, Zwillinge.
dieser Pulsationen war abhängig von der Straffheit der
verwickelten 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 nicht
berichtet.
Resume
Quand la mort survient-elle chez im jumeau acardiaque?
Difficultes diagnostiques a Fechographie
Nous presentons un cas de foetus acardiaque chez
lequel une echographie du second trimestre suggerait
une activite cardiaque bien que celle ci n'ait pas ete
observee sur les coupes ulterieures. Le cordon du ju-
meau acardiaque se trouvait etre etroitement enroule
autour de la jambe de l'autre jumeau. Nous emettons
l'hypothese que cette activite «cardiaque» etant se-
Mots-cles: Acardiaque, echographie, jumeaux.
condaire aux pulsations des vaisseaux dilates dans le
thorax. La presence ou l'absence de cette pulsation
dependaient du caractere plus ou moins serre de Fen-
roulement du cordon conduisant ä un etat de mort
partielle (necrose progressive). La presence de depots
de fibrine etendus trouvee a Pautopsie du jumeau nor-
mal suggere la possibilite d'une coagulation intravas-
culaire disseminee, ce qui na pas ete anterieurement
rapporte en association avec un foetus acardiaque.
References
[1] D'ALTON ME, ER NEWTON, CL CETRULO: Intrau-
terine fetal demise in multiple gestation. Acta Gen
Med Gemollol 33 (1984) 43
[2] LACHMAN R: The acardiac monster. Eur J Paediat
134 (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: a
syndrome 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: Selective
delivery of an acardiac acephalic twin. N Eng J
Med 320 (1989) 512
[8] VAN ALLEN MI, DW SMITH, TH SHEPARD: Twin
reverse arterial perfusion sequence. A study of 14
twin pregnancies with acardius. Sem Perinat 7
(1983) 285
Received February 2, 1990. Accepted February 12,
1990.
Luca Fusi, MD, MRCOG
Institute of Obstetrics & Gynaecology
Hammersmith Hospital
Du Cane Road
London W12 OHJ
U.K.
J. Perinat. Med. 18 (1990)
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When Does Death Occur in An Acardiac Twin - Ultrasound Diagnostic Difficulties

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