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Introduction
Acardia (complete absence of the heart), also referred as the twin reversed arterial perfusion sequence (TRAP) is a rare and one of the most bizarre congenital malformations occurring in multiple pregnancies. The incidence is 1 in 35,000 pregnancies in general and 1 in 100 monozygotic twin pregnancies.[1] Usually one twin has acardia and the other is structurally normal. The acardiac twin (the recipient) is transfued by the normal co-twin (the donor or pump twin) through arterial to arterial and venous to venous anastomosis between the twins.[4] This blood flow is characterized by reversed arterial perfusion. Hence the name TRAP. The acardiac twin presents with many bizarre anomalies such as lack of head, thorax and upper extremities.
Case Report
A 23 years old female, 2nd gravida with 29 weeks gestation (has one live issue) was referred to the department of Obstetrics- Gynecology. The ultrasonography (USG) report documented intrauterine twin pregnancy with one fetus of 24 weeks gestation and the other showing absent head and a large multiloculated cyst engulfing the thoraco-abdominal cavity of the fetus.
Repeat USG revealed both the fetuses to be dead and confirmed rest of the findings. There was no history of consanguineous marriage and no bad obstetrics history. Pregnancy was terminated by instillation of Ethacridine (Emcredil) and of the expelled twins, one of was anomalous and the other was without any anomaly.
Autopsy study of the anomalous fetus revealed a grossly abnormal baby (Fig 1)with easily identifiable lower limb. A large fluid filled cystic sac measuring 8 x 7 cm was seen in place of head and thorax, which were absent. Baby weighed 150 gms & measured 35 cm in lengh. Upper limbs were represented by arms and hands with no forearms. Both sided upper and lower limbs revealed club- hands and club- feet. Some of the digits were missing. External genitalia were poorly developed.
The big sac was filled with clear fluid along with some of the abdominal organs viz. intestines, both the kidneys and both the testes. Rest of the abdominal organs viz. liver, spleen, pancreas, adrenals, stomach and all the thoracic organs including heart and major blood vessels were absent. Brain tissue was not identified both grossly and microscopically.
X ray of whole body of the fetus revealed absent skull, cervical spines and both sided radii & ulnae.(Fig 2)
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Fig 1: Acephalic Acardiac Fetus. |
Fig 2: X – ray of whole body of the fetus with absent skull, cervical spines and both sided radii & ulnae |
The fetus was diagnosed as Acephalic Acardiac Fetus.
Discussion
Acardiac monster was first described by Beneditti in 1533. Twin reversed arterial perfusion ( TRAP) was defined by Greenwald in 1942.[6] Fnutiger (1969) reported that acardias were predominantly female. Spence (2001) found only 29% cases to be female.
The acardiac twin (recipient twin) is haemodynamically disadvantaged anddevelops severe anamolies that are incompatible with life. Four categories of this condition have been described depending upon the degree of cephalic and truncal mal development.[7]
1. Acardiac Anceps: This lesion has relatively well developed fetus. Parts of the brain, skeleton of face, meninges and scalp hairs are present. Entire vertebral column is intact with all four extremities. Oesophagus, stomach, Intestines, lungs, adrenals, Kidneys, bladder, testes and ovaries are represented. Diaphragm is absent. Remnants of heart is present. Large fliud filled spaces (cervical hygromas) on either side of cervical vertebrae are seen.
2. Acephalic Acardiac Fetus: This lesion has absence of head and thoracic organs. Ribs are usually present and thoracic vertebra are either missing or decreased in number. Remnants of liver, spleen, kidney and intestines are present. Pelvis and lower extremities are usually well developed but arms may be absent.
3. Acardiac Acormus: Rarest lesion. Also called as Bodyless Head.
4. Acardiac Amorphus: This lesion has lump of tissue coverd by skin. It contains bone, cartilage, fat, muscles. In this lesion well developed forefoot with 5 toes, hyperplastic tibia, normal size femur and part of bony pelvis and vertebral column are present. Generalised odema with several prevertebral lymphatic cysts are also present.
The present case had the features of Acephalic Acardiac Fetus.
Pathophysiology: TRAP sequence is believed to result from abnormal placental vascular anastomoses between the twins leading to imbalance of interfetal circulation. Of the several theories put forth to explain the abnormal circulation in this syndrome, the most widely accepted explanation is that there occurs sudden reversal in the direction of blood flow within vessels of the affected embryo or fetus and the blood passes through arterio-arterial anastomosis in the placenta, retrograde through the umbilical artery to arterial system of the damaged embryo. Then it goes via venous pathways through the venous system, the umbilical vein and placental veno-venous anastomoses back to the normal twin. The pump twin supplies deoxygenated blood via vascular anastomoses to acardiac twin. Inadequate perfusion is thought to be responsible for development of anomalies.
Chromosomal abnormalities associated with such lesion of Acardia includes trisomies and mosaicism of the affected twin; donor twin has normal karyotype.[7]
With the use of ultrasonography, transvaginal doppler ultrasonography and doppler velocimetry, diagnosis of acardia is possible even in the first trimester of pregnancy by detecting inversion of blood flow in the recipient acardiac fetus (Bonilla Musoles et al ).[1]
Most common differential diagnosis for acardiac twin is hydropic, recently demised twin. This condition is excluded by documentation of blood flow to the twin and the growth of lower extremities. Another differential diagnosis is teratoma; identification of umbilical cord and well developed organs in acardiac twin will exclude teratoma.
Mortality of acardiac twin is universally fatal either in utero or at the time of delivery. Normal pump twin is at increased risk because of high cardiac output, congestive cardiac failure, hydrops and polyhydraminios.[2] Normal fetuses may die of prematurity and respiratory distress syndrome (RDS). The overall mortality of pump twin is approximately 50-75%.[5]
Both fetuses in the present case however died in utero.
Management for the pump twin includes tocolytic agents and volume reduction amniocentesis to treat preterm labour and frequent interval monitoring studies for detection of signs of congestive cardiac failure. If the fetal distress occurs, invasive procedures like hysterotomy, ligation of the cord of the acardiac twin or radiofrequency ablation are done.
Early diagnosis of TRAP and appropriate treatment will definitely improve the outcome.[3]
Acknowledgements:
We thank Dr. Sahoo, Head of Radiology, KIMSDU, Karad, for the radiological images.
References:
- Dhall U, Kayalvizhi I, Magu S. Acardius Acephalus Monster A case report. J Anat Soc India. 2005;54(1):26-28. Available at http://medind.nic.in/jae/t05/i1/jaet05i1p26.pdf
- Bavarian Sh et al. Acardiac Parabiotic Twin: A case report Iran J Radiol., Summer. 2007;4(4):251-253.
- Kirubamani NH. Successful pregnancy in triple with trap sequence. Indian Journal of science & Technology. Sept 2012;5(9):33043306.
- Rohilla M et al. Acardiac Acephalic Twin: A case report of 2 cases & Review of literature. Medscape J Med. 2008;10(8):200
- Athwal S et al. Twin reversed arterial perfusion (TRAP) sequence in association with VACTRERAL association: A case report. Journal of Medical Case Reports. 2010;4:411. Doi : 10.1186 / 1752 1947 4-411
- Pandey K et al. Case report - A rare case of Acardiac Acephalus twin pregnancy. J Obstet Gynecol India January / February 2010;60(1):75-76
- Callen PW. Acardiac Acephalic Twin. Ob Gyn Ultrasound Online An Interactive Text & Journal. Available at http://www.fetalsono.com/teachfiles/AcardAc.lasso
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