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1. Congenital Heart Disease By Dr. Abu Bakarr Kanu

2. Objectives At the end of the lecture you should: Understand fetal, pulmonary and systemic circulations Understand the embryology of the heart Know malformations causing a left-to-right shunt Know malformations causing a right-to-left shunt (cyanotic congenital heart diseases); Know malformations causing obstruction

3. Fetal Circulation

4. Systemic and Pulmonary Circulation

5. Embryology of the heart

6. Embryology of the heart

7. Embryology of the heart

8. Embryology of the heart

9. Embryology of the heart

10. Embryology of the heart

11. Embryology of the heart

12. Embryology of the heart

13. Embryology of the heart

14. CONGENITAL HEART DISEASE Congenital heart disease most commonly arises from faulty embryogenesis during gestational weeks 3 through 8 , when major cardiovascular structures develop. The cause is unknown in almost 90% of cases. The accepted etiologic factors environmental exposures, congenital rubella infection , teratogens , maternal diabetes , genetic factors

15. CONGENITAL HEART DISEASE Genetic factors include specific loci implicated in familial forms of congenital heart disease certain chromosomal abnormalities trisomies 13, 15, 18, and 21, Turner syndrome

16. CONGENITAL HEART DISEASE The various structural anomalies in congenital heart disease can be assigned to three major groups based on their hemodynamic and clinical consequences : malformations causing a left-to-right shunt malformations causing a right-to-left shunt (cyanotic congenital heart diseases); malformations causing obstruction.

17. CONGENITAL HEART DISEASE A shunt is an abnormal communication between chambers or blood vessels. Depending on pressure relationships shunts permit the flow of blood from the left to the right side of the heart (or vice versa ). With right-to-left shunt a dusky blueness of the skin (cyanosis) results because the pulmonary circulation is bypassed and poorly oxygenated blood collected from the venous system enters the systemic arterial circulation.

18. CONGENITAL HEART DISEASE Left-to-right shunts increase blood flow into the pulmonary circulation not associated (at least initially) with cyanosis. However , they expose the low-pressure, low-resistance pulmonary circulation to high pressures and increased volumes; these alterations lead to adaptive changes that increase lung vascular resistance to protect the pulmonary bed, resulting in right ventricular hypertrophy and—eventually right sided— failure. With time, increased pulmonary resistance also can cause shunt reversal (right to left) and late-onset cyanosis.

19. Malformations Associated With Left-to-Right Shunts

20. Malformations Associated With Left-to-Right Shunts Disorders associated with Left-to-right shunts are the most common types of congenital cardiac malformations. They include A trial septal defects (ASDs), v entricular septal defects (VSDs), and P atent ductus arteriosus (PDA)

21. 1. Atrial Septal Defects and Patent Foramen Ovale During normal cardiac development patency is maintained between the right and left atria by a series of fenestrations ( ostium primum and ostium secundum ) that eventually become the foramen ovale. This arrangement allows oxygenated blood from the maternal circulation to flow from the right to the left atrium, thereby sustaining fetal development.

22. 1. Atrial Septal Defects and Patent Foramen Ovale At later stages of intrauterine development tissue flaps (septum primum and septum secundum ) grow to occlude the foramen ovale, in 80% of cases, the higher left-sided pressures in the heart that occur at birth permanently fuse the septa against the foramen ovale . In the remaining 20% of cases, a patent foramen ovale results

23. Atrial Septal Defects and Patent Foramen Ovale Although the flap is of adequate size to cover the foramen, the unsealed septa can allow transient right-to-left blood flow such as with a Valsalva maneuver during sneezing or straining during bowel movements. Although this typically has little significance, it occasionally manifests as paradoxical embolism,

24. Atrial Septal Defects and Patent Foramen Ovale ASD is an abnormal fixed opening in the atrial septum that allows unrestricted blood flow between the atrial chambers. A majority (90%) of ASDs are so-called “ostium secundum ” defects in which growth of the septum secundum is insufficient to occlude the second ostium.

25. Clinical Features of ASD ASDs usually are asymptomatic until adulthood. Although VSDs are more common, many close spontaneously. Consequently, ASDs—which are less likely to spontaneously close—are the most common defects to be first diagnosed in adults. Over time, however, chronic volume and pressure overloads can cause pulmonary hypertension. Surgical or intravascular ASD closure is thus performed to preempt the development of heart failure, paradoxical embolization, and irreversible pulmonary vascular disease.

26. Ventricular Septal Defects Defects in the ventricular septum allow left-to-right shunting and constitute the most common congenital cardiac anomaly at birth The ventricular septum normally is formed by muscular ridge that grows upward from the heart apex fusing with a thinner membranous partition that grows downward from the endocardial cushions. The basal (membranous) region is the last part of the septum to develop and is the site of approximately 90% of VSDs.

27. Ventricular Septal Defects Clinical Features Small VSDs may be asymptomatic; H alf of those in the muscular portion of the septum close spontaneously during infancy or childhood. Larger defects, however, result in chronic left-to-right shunting, often complicated by pulmonary hypertension and CHF.

28. Ventricular Septal Defects Progressive pulmonary hypertension, resultant reversal of the shunt and cyanosis. Early surgical correction is indicated for such lesions . Small- or medium-sized defects that produce jet lesions in the right ventricle cause endothelial damage and increase the risk for infective endocarditis.

29. Patent Ductus Arteriosus The ductus arteriosus arises from the left pulmonary artery and joins the aorta just distal to the origin of the left subclavian artery. During intrauterine life, it permits blood to flow from the pulmonary artery to the aorta, bypassing the unoxygenated lungs. Within 1 to 2 days of birth in healthy term infants the ductus constricts and closes;

30. Patent Ductus Arteriosus These changes occur in response to increased arterial oxygenation, decreased pulmonary vascular resistance, and declining local levels of prostaglandin E2. Complete obliteration occurs within the first few months of extrauterine life leaving only a strand of residual fibrous tissue known as the ligamentum arteriosum.

31. Patent Ductus Arteriosus Ductal closure can be delayed (or even absent) in infants with hypoxia (related to respiratory distress or heart disease). PDAs account for about 7% of congenital heart lesions the great majority of these (90%) are isolated defects.

32. Clinical Features of PDA PDAs are high-pressure left-to-right shunts that produce harsh , “machinery-like” murmurs . A small PDA generally causes no symptoms Larger defects eventually can lead to Eisenmenger syndrome with cyanosis and congestive heart failure . High-pressure shunts also predispose patients to infective endocarditis .

33. Clinical Features of PDA PDAs should be closed as early in life as is feasible Preservation of ductal patency (by administering prostaglandin E) can be lifesaving when a PDA is the only means to sustain systemic or pulmonary blood flow (e.g., in infants with aortic or pulmonic atresia).

34. Malformations Associated With Right-to-Left Shunts

35. Malformations Associated With Right-to-Left Shunts Distinguished by early cyanosis. This occurs because poorly oxygenated blood from the right side of the heart flows directly into the arterial circulation.

36. Malformations Associated With Right-to-Left Shunts They include the following: Tetralogy of Fallot Transposition of the great vessels Tricuspid Atresia Total Anomalous Pulmonary Venous Return Truncus Arteriosus

37. Tetralogy of Fallot Tetralogy of Fallot is the most common cause of cyanotic congenital heart disease. The four cardinal features are: VSD Right ventricular outflow tract obstruction ( subpulmonic stenosis ) Overriding of the VSD by the aorta Right ventricular hypertrophy

38. Tetralogy of Fallot Hypertrophic osteoarthropathy and polycythemia (due to hypoxia) with attendant hyperviscosity Right-to-left shunting also increases the risk for infective endocarditis and systemic embolization.

39. Transposition of the Great Arteries Transposition of the great arteries is a discordant connection of the ventricles to their vascular outflow. The embryologic defect is an abnormal formation of the truncal and aortopulmonary septa aorta arises from the right ventricle and the pulmonary artery emanates from the left ventricle

40. Truncus arteriosus A congenital condition in which a single blood vessel called (truncus arteriosus) arises from both ventricles instead of the normal 2 vessels (pulmonary artery and aorta ). A VSD is always present, with the truncus overriding the defect and receiving blood from both the right and left ventricles

41. Truncus arteriosus

42. Tricuspid Atresia In tricuspid atresia no outlet from the right atrium to the right ventricle is present The entire systemic venous return leaves the right atrium enters the left side of the heart through the foramen ovale or, most often, an atrial septal defect (ASD)

43. Tricuspid Atresia

44. Total Anomalous Pulmonary Venous Return In TAPVR, there is no direct pulmonary venous connection into the left atrium The pulmonary veins may drain above the diaphragm into the right atrium into the coronary sinus, or into the superior vena cava by a “vertical vein ,”

45. Total Anomalous Pulmonary Venous Return This mixed right atrial blood either passes into the right ventricle and pulmonary artery or passes through an atrial septal defect (ASD) or patent foramen ovale into the left atrium, which will be the only source of systemic blood flow . The right atrium and ventricle and the pulmonary artery are generally enlarged whereas the left atrium and ventricle may be normal or small

46. Malformations Associated With Obstructive Lesions

47. Malformations Associated With Obstructive Lesions Aortic Coarctation Coarctation (narrowing, or constriction) of the aorta is a common form of obstructive congenital heart disease Males are affected twice as often as females, although females with Turner syndrome frequently have coarctation .

48. Aortic Coarctation

49. Aortic Coarctation Clinical Features Clinical manifestations depend on the severity of the narrowing and the patency of the ductus arteriosus . Preductal coarctation with a PDA usually presents early in life, classically as cyanosis localized to the lower half of the body; without intervention, most affected infants die in the neonatal period . Postductal coarctation without a PDA usually is asymptomatic, and the disease may remain unrecognized well into adult life.

50. Aortic Coarctation Classically, there is upper-extremity hypertension paired with weak pulses relative hypotension in the lower extremities, associated with symptoms of claudication and coldness. Exuberant collateral circulation “around” the coarctation often develops markedly enlarged intercostal and internal mammary arteries expansion of the flow through these vessels can lead to radiographically visible “notching” of the ribs.

51. Aortic Coarctation Balloon dilation and stent placement Surgical resection with end-to-end anastomosis replacement of the affected aortic segment by a prosthetic graft

52. ANY QUESTION(S)?

53. SUMMARY Congenital heart disease represents defects of cardiac chambers or the great vessels These either result in shunting of blood between the right- and left-sided circulation or cause outflow obstructions. Lesions range from relatively asymptomatic to rapidly fatal.

54. SUMMARY Environmental (toxic or infectious) and genetic causes both contribute . Malformations associated with Left-to-right shunts are the most common and include ASDs, VSDs, and PDA.

55. SUMMARY Shunting results in right-sided volume overload causes pulmonary hypertension with reversal of flow and right-to- left shunting, cyanosis (Eisenmenger syndrome ). Malformations associated with Right-to-left shunts include tetralogy of Fallot and transposition of the great arteries .

56. SUMMARY These lesions cause early-onset cyanosis and are associated with polycythemia, hypertrophic osteoarthropathy, and paradoxical embolization . Obstructive lesions include forms of aortic coarctation the clinical severity of these lesions depends on the degree of stenosis and the patency of the ductus arteriosus

57. THE END