All You Need to Know About Situs and Looping Disorders: Embryology, Anatomy, and Echocardiography Helena Gardiner Co-Director of Fetal Cardiology, The Fetal Center, University of Texas at Houston
Situs abnormalities: learning objectives Recognise and identify the spectrum of sonographic features associated with abnormalities of situs Understand the importance of extracardiac abnormalities in counselling and perinatal management
Conflicts of interest none
Why is this topic about and why is it important? Abnormalities in determining left and right affect the heart, lungs and abdominal contents major CHD pulmonary atresia, aortic coarctation biliary atresia - early Kasai procedure volvulus - short mesentery - early abdominal surgery (prophylactic Ladd s) pacing heart block (10%) Association with ciliary disorders - Kartagener EARLY SURGERY AND LONG TERM CONSEQUENCES
Some features of left atrial isomerism Interrupted IVC with azygous continuation Unusual cardiac position: 30% to right, 10% midline Bilateral left atrial appendages Bilateral long left bronchi and bi-lobed lungs The liver is usually central with right -sided stomach Polysplenia Heart block Paediatric Cardiology, 3 rd edition. Eds Anderson RH, Baker EJ, Penny DJ, Redington AN, Rigby ML, Wernovsky G. Churchill Livingstone, 2010
Abdominal situs
(Hemi)azygous in left atrial isomerism Azygous (blue) lies posterior and rightward to the aorta (red)
(Hemi)azygous in left atrial isomerism Azygous (red) lies posterior to the aorta (aorta)
Venous connections No IVC entering the atrial mass
3VT view normal azygous SVC azygous duct Normal azygous connection to right SVC
3VT in left isomerism azygous SVC duct Enlarged azygous entering RSVC
Atrial Appendages
Atrial appendages in left atrial isomerism Usual atrial arrangement in a human fetal HREM specimen at 12+5 weeks Bilateral left atrial appendages in a mouse model Liat Gindes, Hikoro Matsui, Reuven Achiron, Timothy Mohun, Siew Yen Ho, Helena Gardiner. Ultrasound Obstet Gynecol. 39(2) (2012)196-202 Paediatric Cardiology, 3 rd edition. Eds Anderson RH, Baker EJ, Penny DJ, Redington AN, Rigby ML, Wernovsky G. Churchill Livingstone, 2010
Atrial morphology with interrupted IVC R LAA Ao R PA LAA Left atrial isomerism - left AAp seen on right - heart block Left atrial isomerism - bilateral left AAp - coronal view
4 chamber and outflow tract views These may be normal
Great arteries in left atrial isomerism RSVC Usually concordant Check for coarctation arch duct LSVC
AVSD common: biventricular AV connection Right hand topology (RV on fetal right), note heart block and non-compaction identified by deep fissures into the myocardium
Unbalanced: univentricular AV connection Left atrial isomerism, atretic left AV connection with a dominant anterior right ventricle. Double outlet with malposed great arteries and pulmonary stenosis
Venous connections
Pulmonary veins forming a confluence and entering the atrial mass Venous connections
Some of the myths about left isomerism Bilateral left atrial appendages are always seen with interrupted IVC There are always bilateral long bronchi and bi-lobed lungs The liver is usually central with right -sided stomach There is invariably polysplenia Paediatric Cardiology, 3 rd edition. Eds Anderson RH, Baker EJ, Penny DJ, Redington AN, Rigby ML, Wernovsky G. Churchill Livingstone, 2010
Azygous with heart stomach heterotaxy RA R Breech position: stomach on right, azygous on right and cardiac apex to left Atrial identity right atrium on right and left atrium on left usual atrial arrangement
Right Atrial Isomerism
Some features of right atrial isomerism Aorta and IVC usually on same side of spine Bilateral right atrial appendages Bilateral short right bronchi and tri-lobed lungs The liver is usually central with small posterior stomach Asplenia Paediatric Cardiology, 3 rd edition. Eds Anderson RH, Baker EJ, Penny DJ, Redington AN, Rigby ML, Wernovsky G. Churchill Livingstone, 2010
Bilateral right atrial appendages Usual atrial arrangement in a human fetal HREM specimen at 12+5 weeks Liat Gindes, Hikoro Matsui, Reuven Achiron, Timothy Mohun, Siew Yen Ho, Helena Gardiner. Ultrasound Obstet Gynecol. 39(2) (2012)196-202
Abdominal situs
Usually aorta and IVC same side of spine R Pulmonary veins may descend below diaphragm
4 chamber and outflow tract views
Isomerism the 4 chamber view Clues L R Apex to right AVSD Symmetrical atrial wall Space behind the heart is increased (distance between spine and left atrium)
Atrioventricular junction: biventricular AV connection R Right hand topology: RV on fetal right
Great arteries in right atrial isomerism Often malposed Pulmonary atresia
Venous connections
Pulmonary venous connections Desc. vein Often a descending vein draining below diaphragm to portal sinus Here there were 2 descending veins!
RAI: LSVC draining to atrial mass 3VT has 4 vessels persistent LSVC Unlike the usual atrial arrangement this drains into the atrial mass, rather than the coronary sinus This is seen in the 4 chamber view
LAI: LSVC draining to coronary sinus
Conduction tissue Left: dysplastic node located near AV junction causing CHB in ~10% Right: dual SA nodes causing arrhythmia
Prenatal Counselling Multidisciplinary discussion of likely multiple organ involvement Karyotype likely to be normal Serial assessment for heart block/hydrops Planned delivery to manage obstructed lesions optimally pulmonary venous obstruction may be difficult to diagnose prenatally C/S if there is complete heart block
Postnatal Management Planned delivery as indicated by prenatal findings with MDT experts available Assess any obstructive lesions - CoA, PS, pulmonary veins, bowel ECG to assess heart rhythm - low atrial rhythm, ectopic, junctional - CHB (10%) drugs/pacing Exclude biliary atresia - Ladd s Infant repair of septal defects - AVSD
Conclusions: changing profile of isomerism Prenatal sonographic expertise identifies more variability in diagnostic features Prediction of obstructive lesions is improving - CoA, pulmonary veins, bowel Perinatal delivery should therefore be more organized and safer Intrinsically isomerism is a multi-organ disorder and outcomes remain guarded