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Radiology
Atrial Isomerism
Built from Obstetric Imaging
What’s inside
6 sections · 50 slides
Overview
- What this topic covers
What isomerism is
The body normally has a left side and a right side that are built differently
- Your body is not a mirror image
- What isomerism means
- Heterotaxy: the bigger family
- Four names for the same condition
- Three ways the organs can sit
- Normal, mirrored and ambiguous organ layouts
- How the two types are named
- The two types at a glance
- 4%
Right atrial isomerism
Two right sides: no spleen, three-lobed lungs on both sides, and a badly malformed heart
- Right isomerism: the pattern
- Right isomerism: heart and great vessels
Left atrial isomerism
Two left sides: many small spleens, two-lobed lungs, an interrupted vena cava and heart block
- Left isomerism: the pattern
- Normal organ layout compared with left isomerism
- Multiple small spleens seen in cross-section
- Left isomerism: what the heart shows
- Left isomerism, all in one picture
- Interrupted vena cava, explained
- Where the azygos vein runs
- The double-vessel sign
- Double-vessel sign on a sagittal fetal view
- Double-vessel sign confirmed with colour Doppler
- Right versus left isomerism
Finding it on the scan
Situs ambiguus plus a congenital heart defect is almost proof of atrial isomerism
- When it is picked up
- Typical ultrasound signs
- Pulmonary veins in the wrong place
- Pulmonary veins entering the middle of both atria
- Pulmonary veins draining into the right atrium
- Do not skip the abdomen
- What the scan can still miss
- Which heart defects go with which type?
- Prevalence of Associated Intracardiac Anomalies in Fetuses Diagnosed Prenatally With Left or Right Atrial Isomerism
- Prevalence of Associated Intracardiac Anomalies in Fetuses Diagnosed Prenatally With Left or Right Atrial Isomerism (continued)
- Reading that table
- Fetal MRI adds detail
- “
Chromosomes, outlook and care
The heart defect sets the prognosis - but the abdomen decides the long term
- Is it a chromosome problem?
- What drives the outlook
- A mild heart defect is not reassuring
- >90%
- Right does worse than left
- What decides the outcome
- After birth
- Why the abdomen now matters more
- What the referring physician needs to know
- Key points
- References
- References (continued)
- Suggested readings
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition