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2014-08-20-22 Left isomerism © Meshkova

Left isomerism

Anna Meshkova, MD; Andrei Sleptsov, MD.

Regional Perinatal Center, Yaroslavl, Russia.


Case report

A 28-year-old woman (G1P0; pregnancy conceived by in vitro fertilization) was referred to our center at 24 weeks of gestation with suspected cervical shortening. Her personal and family history of congenital diseases was negative. Her first trimester scan at 13 and 21 weeks of gestation did not show any abnormalities.

Our ultrasound examination at 24 weeks revealed following findings:

Monochorionic diamniotic twins - in the first fetus no anomaly was found, but in the second one, the following abnormalities were seen:


• Dextroposition of the aorta;
• Atrioventricular septal defect; 
• Pulmonary stenosis;
• Interruption of the inferior vena cava with azygos continuation;
• Persistent left superior vena cava.


• Right-sided stomach;
• Symmetric liver and laminar blood flow in the umbilical vessels (less than 5 cm/s).

Cervical length was normal.

Based on the findings our presumed diagnosis was "left atrial isomerism".
The woman opted for the continuation of the pregnancy.

Following ultrasonographic examination at 30 weeks revealed intrauterine death of the affected fetus. The live fetus showed signs of impaired blood flows and bradycardia and an emergency cesarean section was indicated:

• Alive fetus: 1790 g, Apgar score 5/7/8;

• Death fetus: 1000 g without signs of maceration; autopsy confirmed the diagnosis of the left isomerism and above mentioned findings.

Images 1, 2
Image 1 shows a 4-chamber view with the heart on the left and stomach on the right side. Image 2 shows a transverse view of the abdomen with aorta and azygos vein.


Videos 1, 2, 3: The videos show: 4-chamber view of the heart with atrioventricular septal defect (video 1); 3-vessel view of the heart with stenotic pulmonary artery (video 2); and persistent left superior vena cava seen during the sweep between the four-chamber view and three-vessel view of the heart (video 3). 


Image 3 and video 4: Sagittal view of the abdomen showing prominent azygos vein running parallel and posterior to the aorta.


Image 4 and video 5: The image and video show abdominal segment of the umbilical vein with unusually straight course.


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