congenital Heart Disease.power pointsptx

Congenital Heart diseases pathology power point

1. Congenital Heart Diseases Congenital heart disease is a general term used to describe abnormalities of the heart or the great vessels that are present from birth. Most such disorders arise from faulty embryogenesis during gestational weeks 3 through 8.

2. Pathogenesis The cause is unknown in 90% of the cases Environmental factors- E.g.- congenital rubella infection, alcohol, teratogens like thalidomide, cigarette smoking) in 10% Genetic factors as evidenced by well-defined associations with certain chromosomal anomalies (e.g. trisomies 13, 15, 18 and 21 and Turner syndrome)

3. Frequency Malformation % Ventricular septal defect 42 Atrial septal defect 10 Pulmonary stenosis 8 Patent ductus arteriosus 7 Tetralogy of Fallot 5 Coarctation of aorta 5 Aortic stenosis 4 Transposition of great arteries 4 Atrioventricular septal defect 4

4. 12 disorders account for 85% of all congenital diseases Congenital heart diseases are subdivided into 3 major groups Malformations causing left-to-right shunt Malformations causing right-to-left shunt (Cyanotic congenital heart disease) Malformations causing obstruction

5. A shunt is an abnormal communication b/n chambers or vessels Depending on the pressure relationships, shunts permit the flow of blood from the left heart to the right heart or vice versa.

6. In right-to-left shunts the pulmonary circulation is bypassed and poorly oxygenated blood enters the systemic circulation resulting in dusky blueness of the skin and mucosal membranes (cyanosis)

7. In left-to-right shunts there is increased pulmonary blood flow which initially is not associated with cyanosis However, left-to-right shunts expose the low-pressure, low-resistance pulmonary circulation to increased pressure and volume which can result in pulmonary HTN, RV hypertrophy and right sided heart failure.

8. Moreover, the muscular pulmonary arteries (<1 mm in diameter) first respond to increased pressure by medial hypertrophy and vasoconstriction which maintains normal pressure in the distal pulmonary capillaries and veins, thus preventing pulmonary edema.

9. Left-to-right shunt (late cyanosis) These represent the most common forms of congenital heart diseases They include ASD, VSD, PDA and AVSD.

10. Prolonged pulmonary arterial vasoconstriction induces irreversible obstructive intimal lesions. At some point the pulmonary vascular resistance rises and approximates that of the systemic circulation whereby there is reversal of the left-to-right shunt to right-to-left, introducing unoxygenated blood into the systemic circulation (late cyanotic congenital heart disease or Eisenmenger syndrome )

11. Atrial Septal Defect (ASD) It results from abnormalities in the development of normal atrial septation

12. Atrial Septal Defect (ASD) There are 3 types recognized a. Ostium secundum ASD (90%)- occurs when the septum secundum doesn’t enlarge sufficiently to cover the ostium secundum b. Ostium primum ASD- occurs when the septum primum and endocardial cushion fail to fuse c. Sinus venoses ASD- located near the entrance of the SVC

13. Ventricular Septal Defect (VSD) It results due to incomplete closure of the ventricular septum, allowing left-to-right shunting Most common cardiac anomaly at birth (42%) but many of these close making ASD the most common anomalies in adults.

14. The ventricular septum is normally formed by the fusion of the interventricular muscular ridge growing upward from the apex with the thinner membranous partition that grow downward from the endocardial cushion. The membranous (basal) septum is the last part to develop and is the site of 90% of VSDs.

15. In both ASD and VSD, larger defects result in P ulmonary HTN, S evere left-to-right shunting, I rreversible pulmonary vascular disease and P aradoxical embolism

16. Patent Ductus Arteriosus (PDA) The ductus arteriosus arises from the left pulmonary artery and joins the aorta distal to the origin of the left subclavian artery. During intrauterine life, the ductus arteriosus permits blood flow from the pulmonary artery to the aorta, thus bypassing the unoxygenated lung.

17. Patent Ductus Arteriosus (PDA) Shortly after birth, the ductus constricts to form the ligamentum arteriosum (due to increased oxygenation, decreased vascular resistance, decline in local levels of prostaglandin E2)

18. In normal term neonates, the ductus closes in the first 1-2 days Ductal closure can be delayed in infants with hypoxia PDA can occur solitarily or in association with congenital cardiac anomalies allowing left-to-right shunt

19. However, in various congenital heart diseases (e.g. pulmonic or aortic atresia ), the PDA is the only means to provide systemic or pulmonary blood flow. Thus, ironically, PDA can be life threatening or life saving

20. Right-to-left shunts (Early cyanosis) These include Tetralogy of Fallot Transposition of the great vessels. Tricuspid atresia Total anomalous pulmonary venous connection These 2 are common

21. Clinical findings associated with severe, prolonged cyanosis include: C lubbing of the finger tips (hypertrophic osteoarthropathy ) polycythemia and hyperviscosity paradoxical embolism, IE, systemic embolism and brain abscesses (complications of right-to-left shunt)

22. Cyanosis

23. Clubbed fingernail

24. Tetralogy of Fallot ( ToF ) This is the most common cause of cyanotic congenital heart diseases

25. Tetralogy of Fallot ( ToF ) The 4 features of ToF are a. VSD b. Obstruction of the right ventricular outflow tract ( subpulmonic stenosis ) c. An aorta that overrides the VSD d. RV hypertrophy Clinical severity largely depends on the degree of pulmonary outflow obstruction

26. Morphology The heart is “boot-shaped” due to RV hypertrophy Proximal aorta is larger than normal (as it receives blood from both the LV and RV) Pulmonary trunk is diminished The aortic valve lies immediately above the VSD

27. ASD and PDA may be present and prove beneficial by allowing pulmonary blood flow If pulmonary outflow obstruction is mild the ToF resembles VSD with left-to-right shunting. Due to pulmonic obstruction the lungs are protected from hemodynamic overload and pulmonary HTN does not occur Some patients with ToF grow into adulthood

28. Transposition of the great arteries (TGA) The aorta arises from the RV and the pulmonary artery emanates from the LV However, the atrium-to-ventricle communication is normal with the right atrium emptying into the RV and the left atrium emptying into the LV

29. Transposition of the great arteries (TGA) TGA is incompatible with postnatal life unless a shunt exists for adequate mixing of blood and delivery of oxygenated blood to the aorta (e.g. VSD, ASD with PDA)

30. Obstructive lesions Congenital obstruction to blood flow can occur: A t the level of the heart valves (e.g. pulmonic valve stenosis , aortic valve stenosis or atresia ) W ithin a great vessel (e.g. coarctation of the aorta) W ithin a chamber (e.g. subpulmonic stenosis seen in ToF )

31. Aortic Coarctation ( CoA ) Coarctation (narrowing or constriction) of the aorta is a relatively common anomaly. There are 2 types: Preductal and Postductal CoA

32. Preductal (infantile) CoA There is tubular narrowing of the aorta b/n the left subclavian artery and the ductus arteriosus Usually the ductus arteriosus is patent and is the main source of oxygenated blood to the distal aorta

33. Preductal (infantile) CoA There is RV hypertrophy and pulmonary trunk dilation due to the fact that the RV is the main supplier of oxygenated blood to the body.

34. Postductal (adult) CoA The aorta is constricted by a ridge of tissue just at or distal to the ductus arteriosus which is closed. The blood vessels arising proximal to the coarctation are dilated. LV is hypertrophied

35. Postductal (adult) CoA However , due to decline in blood flow to the kidney, there is upper extremity HTN but weak pulse and pressure in the lower extremities causing claudication and coldness of the lower extremities

36. Postductal (adult) CoA Adults with CoA have extensive collateral circulation around the coarctation including markedly enlarged intercostal and internal mammary arteries.

37. Infantile coarctation of the aorta

38. Adult coarctation of the aorta

39. Coarctation of the aorta