Fetal Chest and Heart

1. Fetal Chest and Heart

2. Normal Imaging of the Chest • Heart: • ¼ to 1/3 of thoracic cavity • Apex to left • Cardiac axis approximately 45° • Lungs • Homogenous, intermediate echogenicity • Echogenicity increases with age • Volume of right greater than left, lobar anatomy not appreciable • Diaphragm • Continuous hypoechoic band between pleural and peritoneal cavities

3. Fetal Heart

4. Normal Lungs and Diaphragm

7. CONGENITAL DIAPHRAGM HERNIA Bochdalek - 90% on left; most unilat All should have amniocentesis and dedicated echo Secondary pulmonary hypoplasia is major cause of mortality Findings Polyhydramnios Stomach/bowel/liver adjacent to heart Absent stomach bubble in normal spot Peristalsis in chest Mediastinal shift Absent gastric bubble Reduced abdominal circumference compared to rest of fetal biometry

8. Associated anomalies Aneuploidy (T18, T21); NTD; CHD; malrotation, omphalocele DDX CCAM Other cystic masses such as foregut duplication cysts are rare

10. CCAM Most common fetal lung mass (75%) Types I-III Types I and II macroscopic cysts >5mm with good prognosis and hydrops is rare Small risk of malignant degeneration (rhabdomyosarcoma) Imaging Macroscopic types appear cystic Microscopic types appear solid (echogenic) Pulmonary hypoplasia of normal lung - degree determines prognosis Mediastinal shift - cardiac compromise causes polyhydramnios (impaired swallowing) and hydrops Associations (type II) Cardiac anomalies Pulmonary sequestration Pectusexcavatum Jejunal atresia Renal agenesis, prune-belly syndrome Pathology Hamartomatous proliferation of terminal bronchioles Cysts lined by respiratory epithelium and communicate with airways at birth Vasc supply from pulmonary artery

11. CCAM

13. EXTRALOBAR SEQUESTRATION More common in males (4:1) 90% LLL or below diaphragm Always airless as it has its own pleural envelope and no communication with bronchial tree Systemic arterial supply - Aorta 80% Systemic venous drainage - IVC, azygos, portal v Imaging Findings Solid hyperechogenic mass Look for systemic arterial supply on Doppler Polyhydramnios Hydrops Associations 65% CDH Cardiac GI, Renal, Vertebral anomalies Often regress in utero DDX CCAM Congential lobar emphysema (initially filled with fetal fluid) Neuroblastoma

14. Bronchopulmonary Sequestration

15. Teratoma • Neoplasm composed of all three germ cell layers • In the thorax, most originate from the mediastinum or pericardium, primary lung teratomas are rare • Variable size but typically large, may grow rapidly • Appears as heterogenous mass with solid and cystic components, calcification is the most specific feature but is not always present, no feeder vessel • Mediastinal • Typically occur anteriorly and may cross midline • Difficult to distinguish from lung mass • Pericardial • May be intra or extra pericardial. Intracardiac nearly always have a pericardial effusion and are at risk of tamponade

16. Pericardial Mass

17. PULMONARY HYPOPLASIA Agenesis – complete absence of one or both lungs (airways, alveoli, and vessels) Aplasia – absence of lung except for a rudimentary bronchus that ends in a blind pouch Hypoplasia – decrease in number and size of airways and alveoli Primary Secondary Bilateral - Oligohydramnios (Potter’s sequence); Skeletal dysplasia Unilateral - CCAM; Sequestration; CDH; Hydrothorax Imaging Reduced thoracic circumference (<2SD) is suggestive Fetal lung maturity best sssessed with lecithin:sphingomyelin ratio in amniotic fluid Echogenic pattern unreliable marker for maturity

18. Pulmonary Hypoplasia • Oligohydramnios • Renal conditions (agenesis, obstruction, polycystic disease) • PROM • IUGR (placental insufficiency, aneuploidy) • Cardiac Malformations • Right sided obstruction decreasing pulmonary blood flow • Pulmonary atresia or stenosis • Hypoplastic right heart • Neuromuscular Abnormalities • Decreased fetal breathing and poor lung development • Thoracic cavity mechanical problems • Small or deformed thoracic cavity – osteogenesis imperfecta, achondrogenesis, asphyxiating thoracic dystrophy etc.

19. Pulmonary Hypoplasia • Imaging • No universally accepted diagnostic criteria • Many measurements and ratios • Thoracic circumference – correlate with GA or as ratio with another growth parameter, particularly AC. TC/AC ratio > 0.80 • Lung head ratio – mainly in CDH – measure contralateral lung volume and divide by HC to give LHR - <1.0 poor, >1.4 good • Peripheral pulmonary artery resistance (Doppler) – increased in hypoplasia but non specific • Pulmonary artery Doppler of acceleration time/ejection time (AT/ET). • Normal ‘spike and dome’ pattern with reversal of flow at diastole due to closure of pulmonary valve • Normal ratios are 0.17 on right, 0.15 left, low ratio suggestive of hypoplasia

20. Normal Pulmonary Artery

21. Fetal Heart Normal View • 4 chamber view • Atrial and ventricular septa, mitral and tricuspid valves • Axis 45°-50° • Foramen ovale interrupts atrial septum, with the flap of the foramen opening towards the left atrium • Ventricles are approximately same size • Right ventricle characterised by moderator band, and lower septal attachments of tricuspid valve • Base of heart • Left and Right ventricular outflow tracts • Aortic ‘candy cane’

22. FETAL HEART Technique Abdominal situs view 4-chamber view LVOT Posterior/central to RVOT Runs left to right RVOT Anterior to LVOT Runs right to left Bifurcates early: DA and RPA Check for antegrade flow in DA Anatomical trifurcation: DA, RPA, LPA 3-vessel view amniocentesis indicated in all abnormal: 15-40% will have chromosomal anomalies ventricles/atria are of roughly same size as other ventricle/atria 3 in 1 rule: heart fills 1/3 of axial chest Cardiac circumference 1/2 chest circumference Length atrial septum: ventricular septum 1:2 Normal HR: 120-160bpm, SR

23. Best seen on Four-Chamber View Septal defect Endocardial cushion defect (AVSD) Hypoplastic left heart Ebstein’s anomaly Critical AS Coarctation

24. 4 chamber view

25. 3-VESSEL VIEW

26. Base of Heart

27. Base of Heart

28. VOT

29. Aorta – candy cane

31. Pericardial Effusion • Pericardial fluid >2mm in depth is abnormal • Multiple causes: • Cardiac abnormality • Structural • CMO • Arrhythmia • As a feature of hydrops • Congenital infection – TORCH • High output state • tumour • AVM • anaemia • TTTS

32. VSD • Most common cardiac anomaly (20-40%) congenital heart defect, and 50% are associated with another anomaly • Location • Membranous 80% - associated with tetralogy, truncus • Muscular 10% • Outlet 5% - often associated with aortic insufficiency • Inlet 5% - component of AVSD or endocardial cushion defect • Karyotype if associated extra-cardiac anomaly (trisomy, Holt Oram) • Monitor growth • Many are undetected, and only appreciable at birth or beyond • 50% close spontaneously, may need surgical closure especially if large with shunting

33. Title

34. VSD • Imaging findings: • May see defect in b mode – echogenic edge • Needs to be seen in 2 planes • Doppler – may be only clue • Bi directional shunt as right and left ventricular pressures similar in fetus • If unidirectional, look for other cardiac anomaly altering ventricular pressures

35. VSD

36. VSD

37. VSD

38. AVSD/Endocardial Cushion Defect • EC forms lower atrial septum, superior ventricular septum, anterior MV leaflet and septal TV leaflet • Central heart defect involving • Atrial septum • Ventricular septum • Atrioventricular valves • Conducting system • Spectrum – partial more common than complete in newborns • 2-7% of congenital heart defects • High association with aneuploidy • 40% have trisomy 21

39. AVSD • Imaging findings • Single AV valve makes solid line across heart in systole (normally there is an offset of 2mm between valves) • Atrial and ventricular septal defect – b mode and Doppler • Arrhythmia – especially CHB • Additional cardiac malformations are common • Tetralogy of fallot • Pulmonary stenosis • Left heart/LVOT obstruction • AV regurgitation • Fetal heart failure and hydrops (poor prognosis)

40. AVSD/Endocardial Cushion Defect

41. Ebstein’s Anomaly Septal and posterior leaflets of tricuspid valve prolapse and are integrated into RV wall Atrialisation of RV Large RA due to massive regurg Maternal lithium is a risk factor

42. Hypoplastic Left Heart Syndrome • Small/hypoplastic left ventricle, associated with • Aortic atresia/stenosis • Mitral atresia/stenosis • Hypoplastic ascending aorta • 9% of congenital heart defects • Associated with chromosomal abnormalities in 2-10%, particularly Turner’s, karyotype should be considered • Prognosis: 20% fetal demise, long term survival 30years with surgical treatment, otherwise rapidly (weeks) fatal • Imaging: • Small left ventricle with poor contraction (4 chamber) • Normal right ventricle • Bowing of atrial septa to right, minimal flow across mitral valve • Small ascending aorta with minimal flow across aortic valve

43. Hypoplastic Left Heart Syndrome

44. LVOTO • Obstruction to flow across the aortic valve • Valvular • Subvalvular • Supravalvular • 2-3% of congenital heart defects • Associated with chromosomal abnormalities, particularly supravalvular (Turner’s, William’s syndrome) • Prognosis depends on severity and surgical intervention, in extreme cases may consider fetal balloon valvuloplasty

45. LVOTO • Imaging features • Variable size of left ventricle, usually with reduced function • May see RV hypertrophy to compensate • Turbulent Doppler flow across LVOT • MR from increased LV pressure • Left to right flow (shunting) across foramen ovale • Subvalvular • Muscular: asymmetrical septal hypertrophy • Membranous: membrane from septum to mitral valve • Valvular • Thickened valve leaflets (often bicuspid) • Supravalvular • Narrow/stenosis in proximal ascending aorta

46. Pulmonary Atresia Hypoplastic RA and RV Pulmonary artery calibre may be normal Reversed flow in DA

47. Persistent Truncus Arteriosus • Single vessel overriding outflow valves and feeding aorta and pulmonary artery • 1% of congenital heart defects • Almost always associated with a VSD, right sided arch in 30% of cases • Needs early surgical correction to avoid pulmonary HTN, excellent prognosis with surgery • High association with 22q11 deletion – karyotype for recurrence risk • Association with maternal diabetes • Imaging • Failure of normal crossing of great vessels • Single truncus vessel dividing into aorta and pulmonary artery

48. Truncus Arteriosus

49. Transposition of Great Vessels • 5 % of congenital heart defects • Rare association with aneuploidy • There is an association with maternal diabetes • Excellent prognosis • Imaging • Careful orientation required • Failure of vessels to cross • Vessels arising from either side of the septum

50. Transposition of Great Vessels Aorta arises from RV and pulmonary trunk from LV Aorta and pulmonary artery are parallel instead of perpendicular to each other