CHD.pptx
- 2. Abnormalities of the heart or great vessels that are present at birth Gestational weeks 3 through 8
- 3. Incidence up to 0.5% among the most prevalent birth defects and are the most common type of pediatric heart disease.
- 4. Cardiac Development. caused by errors during cardiac morphogenesis. precursors originate --- lateral mesoderm and move to midline in two migratory waves to create ----- first and second heart fields by about day 15. Both fields contain multipotent progenitor cells that can produce all of the major cell types of the heart: endocardium, myocardium, and smooth muscle cells. each heart field is differentially marked by the expression of distinct gene sets. first heart field expresses -- transcription factor H and 1 second heart field expresses --- transcription factor Hand2 and the secreted protein fibroblast growth factor-10.
- 5. each heart field --give rise to particular portions of the heart. left ventricle largely first heart field second heart field become the outflow tract, right ventricle, and most of the atria By day 20--- beating tube, which loops to the right andbegins to form the basic heart chambers two other critical events occur: (1) neural crestderived cells migrate into the outflow tract -- formation of the aortic arches (2) interstitial connective tissue --- enlarges to produce swellings known as endocardial cushions. By day 50, further septation of the ventricles, atria, and atrioventricular valves produces a four-chambered heart.
- 6. depends on a network of transcription factors ---- regulated by --signaling pathways, the Wnt, hedgehog, (VEGF), bone morphogenetic factor, TGF硫, FGF, and Notch pathways In addition hemodynamic forces play an important role in cardiac development
- 9. inherited defects that involve genes that encode transcription factors; transient environmental stresses during the first trimester
- 10. Etiology and Pathogenesis Sporadic genetic abnormalities are the major known causes of congenital heart disease. single gene mutations, small chromosomal losses, and additions or deletions of whole chromosomes (trisomies and monosomies). In the GATA4, TBX5, and NKX2-5---- atrial and ventricular septal defects
- 12. deletion 22q11.2----- DiGeorge syndrome syndrome, the fourth branchial arch , third and fourth pharyngeal pouches (thymus, parathyroids, and heart) develop abnormally. The syndrome --- multiple deficits CATCH-22: cardiac abnormality, abnormal facies, thymic aplasia, cleft palate, and hypocalcemia
- 13. Turner syndrome (monosomy X) and trisomies 13, 18, and 21. 40% of patients with Down syndrome have CHD environmental factors, congenital rubella infection, gestational diabetes teratogen exposure Nutritional factors --- folate supplementation during early pregnancy may reduce congenital heart disease risk. alcohol
- 14. Clinical Features. Three major categories: Malformations causing a left-to-right shunt Malformations causing a right-to-left shunt Malformations causing an obstruction Malpositions of heart
- 15. A shunt is an abnormal communication between chambers or blood vessels pressure gradients from the left (systemic) side to the right (pulmonary) side of the circulation or vice versa. right-to-left shunt--- hypoxemia and cyanosis ---- result because the pulmonary circulation is bypassed Right to- left shunts can allow emboli -- paradoxical embolism clubbing of the tips of the fingers and toes as well as polycythemia.
- 16. left-to-right shunts increase pulmonary blood flow, but are not initially associated with cyanosis. elevate both volume and pressure in the normally low- pressure, low-resistance pulmonary circulation. Muscular pulmonary arteries ---- medial hypertrophy and vasoconstriction. prolonged pulmonary arterial vasoconstriction stimulates the development of irreversible obstructive intimal lesions --- frank atherosclerotic lesions. The right ventricle --- hypertrophy. Eventually, pulmonary vascular resistance = systemic levels--- right-to-left shunt --- poorly oxygenated blood into the systemic circulation (Eisenmenger syndrome).
- 18. Obstructive congenital heart disease occurs when there is abnormal narrowing of chambers, valves, or blood vessels. A complete obstruction --- atresia.
- 20. Left-to-Right Shunts Pink babies most common CHD ASD, VSD, and PDA. ASD increases volumes, VSD and PDA--- both flow and pressure.
- 22. Atrial Septal Defect abnormal, fixed openings in the atrial septum caused by incomplete tissue formation Communication of blood between the left and right atria ASDs -- usually asymptomatic until adulthood ASD should not be confused with patent foramen ovale , which represents the failure to close a foramen (hole) that is part of normal development.
- 23. The septum primum -- sits posteriorly between the right and left atria and partially separates them----- anterior opening, called the ostium primum---- fetal development. Before the growing septum primum completely obliterates the ostium primum, it develops a second posterior opening called the ostium secundum. The septum secundum is a subsequent membranous ingrowth located to the right and anterior of the septum primum. As the septum secundum grows-- opening called the foramen ovale --- continuous with the ostium secundum The septum secundum enlarge -- FLAP--- covers the foramen ovale on its left side
- 24. the valve opens only when the pressure is greater in the right atrium. In fetal life--- pulmonary circulation pressure is greater than that of the systemic circulation--- foramen ovale is normally open. At birth----pulmonary vascular pressures drop---- the valve of the foramen ovale closes
- 25. MORPHOLOGY classified according to -- location. Secundum ASD (90% of all ASD) These are usually not associated with other anomalies may be of any size, multiple or fenestrated. Primum anomalies (5% of ASD) Associated with AV valve abnormalities and/or a VSD. Sinus venosus defects (5%) are located near the entrance of the superior vena cava
- 27. Clinical Features Infant tires easily when feeding left-to-right shunt---- pulmonary vascular resistance is less and compliance of right ventricle is much greater Pulmonary blood -- two to four times normal A murmur --- excessive flow through the pulmonary valve. ASDs -- well tolerated till age 30 Surgical or catheter-based closure
- 28. Patent Foramen Ovale small hole created by an open flap of tissue in the atrial septum at the oval fossa. at birth -- flap closes -- 80% of people. 20% of people-- flap can open when there is more pressure on the right side of the heart sustained pulmonary hypertension or even transient increases in right-sided pressures-- during a bowel movement, coughing, or sneezing- brief periods of right-to-left shunting
- 29. Ventricular Septal Defect incomplete closures -- ventricular septum, free communication -- left to right ventricles
- 30. classified --- size and location Most are size of the aortic valve orifice 90%occur in the region of the membranous septum (membranous VSD) The remainder occur below the pulmonary valve (infundibular VSD) or within the muscular septum. Single Muscular septum may be multiple so-called Swiss- cheese septum
- 33. Clinical Features. depend on the size and associated with right-sided malformations. Large --- difficulties from birth smaller -- well tolerated for years 50% of small muscular VSDs close spontaneously Large defects are usually membranous or infundibular, left-to-right shunting--- right ventricular hypertrophy and pulmonary hypertension ---- ultimately resulting in shunt reversal, cyanosis, and death. Surgical or catheter-based closure
- 34. Patent Ductus Arteriosus The ductus arteriosus arises from the pulmonary artery and joins the aorta Intrauterine blood flow from the pulmonary artery to the aorta--- bypassing the lungs. functionally closed after 1 to 2 days increased arterial oxygenation---- decreased pulmonary vascular resistance--- declining prostaglandin E2. ligamentum arteriosum. Ductal closure is often delayed (or even absent) in infants with hypoxia (due to respiratory distress or heart disease), PDAs account for about 7% of cases of congenital heart disease
- 36. continuous harsh machinery-like murmur. PDA is usually asymptomatic at birth Upto -- 2cm long, 1 cm dia large shunts, the additional volume and pressure overloads eventually produce obstructive changes in small pulmonary arteries, leading to reversal of flow and its associated consequences.
- 37. Right-to-Left Shunts Blue babies cyanosis (cyanotic congenital heart disease) Tetralogy of Fallot the most common in this group transposition of the great arteries The others include persistent truncus arteriosus, tricuspid atresia, and total anomalous pulmonary venous connection.
- 38. Tetralogy of Fallot (1) VSD (2) obstruction of the right ventricular outflow tract (subpulmonary stenosis) (3) an aorta that overrides the VSD (4) right ventricular hypertrophy anterosuperior displacement of the infundibular septum.
- 41. Morphology. heart -- enlarged -- boot-shaped The aortic valve forms the superior border of the VSD, thereby overriding the defect and both ventricular chambers. The obstruction to right ventricular outflow --- due to narrowing of the infundibulum (subpulmonic stenosis) can be accompanied by pulmonary valvular stenosis. Aortic valve insufficiency or an ASD may also be present; a right aortic arch is present in about 25% of cases.
- 42. Clinical Features. survive into adult life; depend primarily on the severity of the subpulmonary stenosis, since this determines the direction of blood flow. If mild--- resembles an isolated VSD, and the shunt may be left-to-right, without cyanosis (so-called pink tetralogy). severe obstruction, right-sided pressures approach or exceed left-sided pressures-- right-to-left shunting --- cyanosis (classic TOF). The more severe the subpulmonic stenosis, the more hypoplastic are the pulmonary arteries (i.e., smaller and thinner-walled), and the larger is the overriding aorta.
- 43. Transposition of the Great Arteries TGA produces ventriculoarterial discordance. aorta -- arises from right ventricle pulmonary artery --- from the left ventricle. atrium-to-ventricle connections are normal (concordant), Embryologic defect ----abnormal formation of the truncal and aortopulmonary septa. Separation of the systemic and pulmonary circulations incompatible with life unless a shunt
- 46. . Patients with TGA and a VSD (approximately 35%) often have a stable shunt. patent foramen ovale or ductus arteriosus for blood mixing (approximately 65%) is problematic.
- 47. Tricuspid Atresia complete occlusion of the tricuspid valve orifice. the mitral valve is larger than normal right ventricular hypoplasia circulation can be maintained by right-to-left shunting through an interatrial communication (ASD or patent foramen ovale), in addition to a VSD
- 48. Obstructive Lesions Congenital obstruction can occur at the level of the heart valves or within a great vessel. Common examples include aortic or pulmonary valve stenosis or atresia, and coarctation of the aorta.
- 49. Coarctation of the Aorta common structural anomalies. twice as common in M There are two classic forms: (1) an infantile formoften symptomatic in early childhoodtubular hypoplasia (2) an adult form --- ridgelike infolding of the aorta just opposite the closed ductus arteriosus (ligamentum arteriosum) solitary defect or is accompanied by a bicuspid aortic valve
- 51. Clinical manifestations ---severity of the narrowing and the patency of the ductus arteriosus. Coarctation of the aorta with a PDA usually manifests early in life; the delivery of unsaturated blood through the PDA produces cyanosis localized to the lower half of the body. coarctation of the aorta without a PDA--- . Most children are asymptomatic Hypertension in the upper extremities with weak pulses and hypotension in the lower extremities--- claudication and coldness Development of collateral circulation -- through enlarged intercostal and internal mammary arteries------- visible erosions (notching) of the undersurfaces of the ribs. murmurs -- throughout systole; sometimes thrill long-standing pressure -- left ventricular hypertrophy.
- 52. Pulmonary Stenosis and Atresia obstruction at the level of the pulmonary valve. This can be mild to severe isolated or part of a more complex anomaly either TOF or TGA Right ventricular hypertrophy typically develops,
- 53. Aortic Stenosis and Atresia obstruction of the aortic valve can occur at three locations: valvular, subvalvular, and supravalvular. hypoplasia of the left ventricle and ascending aorta The ductus must be open to allow blood flow to the aorta and coronary arteries