EC Gynaecology

Objectives: To evaluate the normal tick shaped orientation of the arches in first trimester fetuses and to propose the use of this sign, the alteration of which has a significant role in diagnosing cardiac anomalies especially the transposition of great arteries in the first trimester.

Methods: This was a retrospective study from November 2010 to April 2013 conducted in fetal medicine unit, Mediscan systems, Chennai, Tamil Nadu, India. All the fetuses who had first trimester scan followed by target scan in our center were included in our study. Fetal cardiac examination was standardized by including the Color four chamber and the “tick sign” as a part of our mandatory anatomy. The operators were trained adequately before they start independent imaging.

Results: A total of 178 normal fetuses were reviewed, the peculiar “tick” shaped arches were seen in 58 (32%) of the fetuses. Out of these, 3 (5%) were 11 - 12 weeks, 33 (56%) were 12 - 13 weeks, and 22 (37%) were 13 - 14 weeks. All the fetuses with normal “tick sign” had normal echocardiography at target scan. Two fetuses who were diagnosed with transposition of great arteries at target scan, when we retrospectively reviewed the images at 11 - 14 weeks scan, the “arches view” showed abnormal orientation of the two arches. Including the tick sign as part of mandatory anatomy in first trimester, a case of transposition of great arteries was picked in the first trimester.

Conclusion: The “tick sign” is consistently reproducible in normal fetuses in 11 - 14 weeks scan especially between 12 - 14 weeks. Alteration of this normal orientation is useful to suspect and diagnose cardiac anomalies especially outflow tract anomalies even in first trimester. We recommend inclusion of arches view (“Tick sign”) as part of mandatory anatomy in first trimester scan.

Keywords: Fetus; Ultrasound; First Trimester Screening; Echocardiography; “Tick Sign”

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