PATHOPHYSIOLOGY OF CONGENITAL CYANOTIC HEART DISEASE (2).pptx

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1. PATHOPHYSIOLOGY OF CONGENITAL CYANOTIC HEART DISEASE PRESENTED BY: DR. PALLAVI PRIYADARSHINI JR-1 Guided by: Dr. Chinmaya Sahoo Asst. professor

2. LEARNING OBJECTIVES INTRODUCTION CLASSIFICATION EMBRYOLOGY FETAL CIRCULATION HAEMODYNAMICS

3. INTRODUCTION CONGENITAL HEART DISEASE Cardiac anomalies arising due to defect in structure & function of heart & great vessels, present at birth. Either obstruct the blood flow in the heart or in the vessels, or alter the pathway of blood circulating through the heart. Clinical symptoms- cyanosis, difficult breathing, difficulty in feeding, recurrent RTI The assessment of presence of the CHD can be done using NADAS criteria

4. NADAS CRITERIA MAJOR CRITERIA MINOR CRITERIA Systolic murmur of grade 3 or more Systolic murmur less than grade 3 Diastolic murmur of any grade Abnormal second heart sound Cyanosis Abnormal ECG CHF Abnormal CXR Abnormal BP For diagnosis : 2 Major or 1 major+ 2 minor

5. PREVALENCE OF CHD IN INDIA The reported incidence of CHDs is 8-10/1000 live births according to various series from different parts of the world. Approximately 10% of the present infant mortality may be attributed to congenital heart diseases alone. Nearly 33% to 50% of these defects are critical requiring interventions in the first year of life itself. With currently available modalities, over 75% of infants born with critical heart defects can survive beyond first year of life and many can go on to lead normal lives.

6. Classification of chd (PHYSIOLOGIC) ACYANOTIC HEART DISEASE LEFT TO RIGHT SHUNTS PRETRICUSPID: Partial anomalous pulmonary venous drainage, atrial septal defect(ASD) VENTRICULAR: Ventricular septal defect(VSD) GREAT ARTERY: aortopulmonary window, Patent ductus, Ruptured sinus of Valsalva BOTH PRE & POST TRICUSPID: Atrioventricular septal defect, left ventricle to right atrial communications

7. Classification of chd (PHYSIOLOGIC) OBSTRUCTIVE LESIONS INFLOW: Obstructive lesion of mitral valve RIGHT VENTRICLE: infundibular stenosis, pulmonary valve stenosis LEFT VENTRICLE: Subaortic membrane, valvar aortic stenosis, supravalvar aortic stenosis, coarctation of aorta MISCELLANEOUS: Coronary artery abnormality, congenital mitral and tricuspid valve regurgitation

8. CLASSIFICATION OF CCHD GROUP I CCHD DECREASED PULMONARY BLOOD FLOW: PS with VSD The common lesions are- Tetralogy of fallot Pulmonary atresia with VSD Tricuspid atresia Double outlet RV(DORV), VSD, PS L-TGA, VSD, PS D-TGA, VSD, PS AV septal defect with PS Single ventricle with PS Truncus arteriosus with PS Common clinical features : Deep central cyanosis, absent features of CHF, normal or near normal cardiac size, single s2, an outflow murmur ECG RAD, and RVH without strain RAE not a feature

9. 2. GROUP II CCHD SEVERE PS; INTACT INTERVENTRICULAR SEPTUM RV dilates, develops dysfunction leading to cardiac enlargement Clinical features : central cyanosis, elevated JVP, prominent a & v waves, significant parasternal heave, single s2 or wide split with delayed P2 and s3 ECG: Severe RVH with strain pattern GROUP III DECREASED PBF with PAH Eisenmenger syndrome Can be seen in ASD, VSD, PAH, AP window Clinical features : Development od cyanosis in 2 nd – 3 rd decade, mild – moderate cyanosis, minimal to no cardiomegaly, no CHF

10. s/o PAH : parasternal heave, palpable P2, loud & single s2, ESM If with ASD : prominent JVP, cardiomegaly, hyperdynamic circulation, split s2 with loud p2 ECG RAD, RVH without strain pattern GROUP IV INCREASED PBF: PARALLEL CIRCULATION TGA a classical example Clinical features Intense early cyanosis, mild cardiomegaly, mild CHF, minimal or no murmur ECG : RVH with RAD

11. 5. GROUP V CCHD INCREASED PBF: ADMIXTURE PHYSIOLOGY Classical: single atrium, single ventricle, persistent truncus arteriosus Also includes: TAPVC and DORV, VSD and PAH Clinical feature : CHF in infancy, mild cyanosis, cardiomegaly with hyperdynamic heart, sometimes PAH ECG : RAD, RVH, RSR pattern in V1 or V3R ASD like presentation, CHF, Cyanosis TAPVC, single atrium VSD like presentation, CHF, Cyanosis Single ventricle, DORV PDA like presentation, CHF, Cyanosis Truncus

12. EMBRYOLOGY During the first 2 weeks of embryonic life, there is no heart or vascular system. Cell-to-cell diffusion provides nutrient and oxygen supply to the fetus The heart develops from two simple epithelial tubes that fuse to form a single-chambered heart that is efficiently pumping blood by the fourth week of embryonic development . Components of the Heart Tube From caudal to cranial, the following components are: Sinus venosus :  consists of right and left horns. Each horn receives blood from three important veins: the umbilical vein, the common cardinal vein, and the vitelline vein.

13. EMBRYOLOGY Paired primitive atria : will later fuse to form a common atrium Atrioventricular sulcus : divides the common atrium and the primitive ventricle Primitive ventricle : becomes the left ventricle Interventricular sulcus :  divides the primitive ventricle and the bulbus cordis Bulbus cordis :  The proximal one third-body of the right ventricle. The distal-most section ( truncus arteriosus) - aortic root and part of the ascending aorta The remaining mid-portion ( conus cordis ) and connects the primitive right ventricle to the truncus arteriosus. The conus cordis partitions to form the outflow tracts of the right and left ventricles. Aortic sac :  will give rise to the aortic arches

14. FETAL CIRCULATION

15. TRANSISTIONAL CIRCULATION RV output now flows entirely through the pulmonary circulation Pulmonary vasculature resistance becomes lower than systemic vascular resistance– shunt through ductus arteriosus reverses and becomes left to right

16. DUCT DEPENDENT LESIONS DUCT DEPENDENT PULMONARY CIRCULATION DUCT DEPENDENT SYSTEMIC CIRCULATION Pulmonary atresia with intact ventricular septum Interrupted aortic arch Pulmonary atresia with VSD Hypoplastic left heart syndrome Pulmonary atresia with single ventricle Critical aortic stenosis Critical pulmonary stenosis Critical coarctation of aorta Severe Ebstein anomaly Rare TOF with critical RVOT obstruction ADMIXTURE LESIONS Transposition of great arteries with intact interventricular septim

17. PATHOPHYSIOLOGY OF CCHD

18. CYANOSIS CYANOSIS is a bluish discoloration of the skin and mucous membrane resulting from an increased concentration of reduced hemoglobin to about 5g/100 mL in the cutaneous veins. Level of reduced hemoglobin in the blood is due to- 1. Desaturation of arterial blood( CENTRAL CYANOSIS ) 2. Increased extraction of oxygen by the peripheral tissues( PERIPHERAL CYANOSIS ) SITES - lips, fingernails, oral mucous membranes, conjunctivae, the tip of tongue

19. INFLUENCE OF HEMOGLOBIN LEVEL ON CYANOSIS Normally, about 2g/100 mL of reduced hemoglobin is present in venules, so an additional of 3g/100mL of reduced hemoglobin in the blood produces clinical cyanosis. For a normal person with hemoglobin 15g/100 mL, 3g of reduced hemoglobin results from 20% desaturation. Thus cyanosis appears at around 80% saturation in this case. In polycythemia , cyanosis is recognized at an higher level of saturation Similarly, in patients of anemia , cyanosis is recognized at a lower lever of saturation

20. CYANOSIS OF CARDIAC VERSUS PULMONARY ORIGIN The hyperoxia test helps differentiate cyanosis caused by cardiac disease from that caused by pulmonary disease. PROCEDURE & INTERPRETATION: 1. An ABG is obtained with the neonate breathing room air 2. The patient is placed on 100% FiO2 for 10 minutes 3. A repeat ABG is performed looking for an increase in PaO2 to >150 mmHg  -   If the hypoxia is secondary to a respiratory cause, the PaO2 should increase to >150 mmHg. -    If the hypoxia is secondary to a congenital cardiac lesion (i.e. secondary to a right-to-left cardiac shunt) the PaO2 is not expected to rise significantly. 

21. CONSEQUENCES AND COMPLICATIONS POLYCYTHEMIA PaO2 – stimulates bone marrow through EPO release from the kidneys -- red blood cells (RBCs) W hen hematocrit reaches 65% or higher , a sharp in viscosity of blood occurs, polycythemic response becomes disadvantageous , particularly if the patient has CHF N ormal hemoglobin in a cyanotic patient - relative iron deficiency state. - Although less cyanotic, these infants are more symptomatic & improve when iron therapy raises the hemoglobin.

22. COMPLICATIONS(CONTD.) CLUBBING Clubbing is caused by soft tissue growth under the nail bed as a consequence of central cyanosis.  MECHANISM - In patients with right-to-left shunts , megakaryocytes with their cytoplasm may enter the systemic circulation, become trapped in the capillaries of the digits, and release growth factors( platelet derived growth factor, transforming growth factor beta ) which in turn cause clubbing.

23. COMPLICATIONS(CONTD.) CNS COMPLICATIONS Increased risk for disorders of the CNS, such as brain abscess and vascular stroke.  The predisposition for brain abscesses - A) right-to-left intracardiac shunts may bypass the normally effective phagocytic filtering actions of the pulmonary capillary bed B) polycythemia and high viscosity of blood lead to tissue hypoxia and microinfarction of the brain, later complicated by bacterial colonization Vascular stroke caused by embolization arising from thrombus in the cardiac chamber or in the systemic veins. Cerebral venous thrombosis may occur, common in <2 years of age who have cyanosis and relative iron-deficiency anemia, because microcytosis may aggravate hyperviscosity.

24. COMPLICATIONS(CONTD.) BLEEDING DISORDERS Thrombocytopenia, defective platelet aggregation, prolonged prothrombin & partial thromboplastin time, lower level of fibrinogen, factor V & VIII HYPOXIC SPELLS SCOLIOSIS children with chronic cyanosis, most common in girls HYPERURECEMIA & GOUT

25. HYPOXIC/ HYPERCYANOTIC/TET SPELL CONCEPT: T he amount of PBF, determines the degree of cyanosis, in patients with TOF Qp /Qs is related to the ratio of resistance offered by the right ventricular outflow obstruction and the systemic vascular resistance (SVR) PR or SVR: right to left shunt, resulting in severe arterial desaturation T he role of the spasm of the RVOT as an initiating event for the hypoxic spell : CONTROVERSIAL. WHY? Pulmonary valve stenosis has a fixed resistance and does not produce spasm The infundibular stenosis, which consists of disorganized muscle fibers intermingled with fibrous tissue, is almost nonreactive to sympathetic stimulation or catecholamines  Hypoxic spell also occurs in patients with TOF with pulmonary atresia 

26. HYPOXIC SPELL (CONTD.) C hanges in the SVR plays a primary role in controlling the degree of the right-to-left shunt and the amount of PBF A decrease in the SVR increases the right-to-left shunt and decreases the PBF with a resulting increase in cyanosis I ncrease in SVR decreases the right-to-left shunt and forces more blood through the stenotic RVOT. This results in arterial oxygen saturation OTHER FACTORS LEADING TO AN INCREASE IN RIGHT-TO-LEFT SHUNT: Hypovolemia Excess tachycardia

27. HYPOXIC SPELL (CONTD.) WHEN TO SUSPECT:  Hyperpnea worsening cyanosis, disappearance of the heart murmur. Any event such as crying, defecation, or increased physical activity that suddenly lowers the SVR or produces a large right-to-left ventricular shunt may initiate the spell and, if not corrected, establishes a vicious circle of hypoxic spells.

28. MANAGEMENT AIM: To break the vicious cycle Picking up the infant in such a way that the infant assumes the knee–chest position and traps systemic venous blood in the legs ( Systemic venous return) & reduces arterial blood flow to the lower extremities ( systemic vascular resistance) Morphine sulfate suppresses the respiratory center and abolishes hyperpnea 3. Sodium bicarbonate (NaHCO 3 ) corrects acidosis and eliminates the respiratory center–stimulating effect of acidosis 4. Administration of oxygen may slightly improve arterial oxygen saturation

29. Management (contd.) Vasoconstrictors such as phenylephrine raise SVR and improve arterial oxygen saturation Ketamine is a good drug to use because it simultaneously increases SVR and sedates the patient 7. Propranolol has been used successfully in some cases of hypoxic spell, both acute and chronic

30. TETRALOGY OF FALLOT The classic description of TOF includes the following four abnormalities : Ventricular septal defect (VSD) Pulmonary stenosis Right ventricular hypertrophy Over riding of aorta FALLOT’S PHYSIOLOGY requires only two abnormalities: VSD large enough to equalize systolic pressures in both ventricles 2. S tenosis of the right ventricular outflow tract (RVOT) in the form of infundibular stenosis, valvular stenosis, or both

31. INCIDENCE Most common cyanotic heart defect, and most common cause of blue baby syndrome It accounts for 6-10% of all CHDs CAUSES Not clear Children born to PKU mothers are highgly susceptible, as is the history of alcohol consumption during antenatal period Genetic causes

32. TOF (CONTD.) RVH is secondary to PS, and the degree of overriding of the aorta varies widely and it is not always present The severity of the RVOT obstruction determines the direction and the magnitude of the shunt through the VSD DEPENDING UPON THE SEVERITY OF STENOSIS TOF CAN BE:- PINK OR ACYANOTIC TOF : With mild stenosis, the shunt is left to right, and the clinical picture resembles that of a VSD CYANOTIC TOF : With a more severe stenosis, the shunt is right to left, resulting in “cyanotic” TOF In the extreme form of TOF , the pulmonary valve is atretic, with right-to-left shunting of the entire systemic venous return through the VSD. Hence , the PBF is provided through PDA or multiple collateral arteries arising from the aorta 

33. ACYANOTIC OR PINK TOF small to moderate left-to-right ventricular shunt is present the systolic pressures are equal in the RV, LV, and aorta There is a mild to moderate pressure gradient between the RV and PA PA pressure may be slightly elevated (because of a less severe stenosis of the right ventricular outflow tract) the presence of the PS minimizes the magnitude of the left-to-right shunt, the heart size and the pulmonary vascularity increase only slightly to moderately ECG : RVH because the RV pressure is always high T he murmur :ejection systolic murmur of PS and a regurgitant systolic murmur of a VSD

34. Infants with acyanotic TOF become cyanotic over time, usually by 1 or 2 years of age, developing exertional dyspnea and squatting CYANOTIC TOF P resence of severe PS produces a right-to-left shunt at the ventricular level (i.e., cyanosis) with decreased PBF The PAs are small , and the LA and LV may be slightly smaller than normal because of a reduction in the pulmonary venous return to the left side of the heart CXR : normal heart size with decreased pulmonary vascularity The systolic pressures are identical in the RV, LV, and aorta The right-to-left ventricular shunt is silent , so , murmur audible in this condition originates in the PS (ejection-type murmur) The intensity and the duration of the heart murmur are proportional to the amount of blood flow through the stenotic valve

35. CYANOTIC TOF (CONTD.) A n infant with TOF does not develop CHF : No cardiac chamber under VOLUME OVERLOAD and PRESSURE OVERLOAD is placed over RV(well managed) CLINICAL CLUE: If a cyanotic infant has a large heart on CXR , with an increase in pulmonary vascularity , TOF is extremely unlikely unless the child has undergone a large systemic-to- PA shunt operation

36. EXTREME FORM OF TOF associated with  pulmonary atresia the only source of PBF is through a constricting PDA or through multiple aortic collateral arteries  A VERY SEVERE CYANOSIS: All systemic venous return is shunted right to left at the ventricular level, resulting in a marked systemic arterial desaturation markedly reduced PBF, with resulting reduction of pulmonary venous return to the left side of the heart Unless the patency of the ductus is maintained, the infant may die Heart murmur is absent , or a faint murmur of PDA is present ECG: RVH CHEST RADIOGRAPH: small heart and a markedly reduced PBF.

37. TRANSPOSITION OF GREAT VESSELS Most common cyanotic congenital heart defect in newborns, at least in Western countries PATHOLOGY D-TGA T he aorta arises from the right ventricle (RV), and the pulmonary artery (PA) arises from the left ventricle (LV) T he normal anteroposterior relationship of the great arteries is reversed , so that the aorta is anterior to the PA (transposition) but the aorta remains to the right of the PA; thus, the prefix D is used for dextroposition

38. L-TGA( CONGENITALLY CORRECTED TGA) In this anomaly, the right atrium communicates with the morphologic left ventricle , which gives rise to the pulmonary artery , while the left atrium communicates with the morphologic right ventricle, which gives rise to the aorta . Atrioventricular and ventriculoarterial discordance (double discordance) exists, and although blood flows in the normal direction, it passes through the wrong ventricular chambers. T he aorta is anterior to and to the left of the PA

39. HEMODYNAMICS Circuit in parallel instead of being in series Incompatible , communication present can be- ASD, VSD, PDA M/C in D-TGA, only a small communication exists between the atria, usually a patent foramen ovale (PFO) Cyanotic since birth with SpO2 30-50%( pO2 20-30 mm Hg) , leading to anaerobic glycolysis, hence, metabolic acidosis Post natal decrease in pulmonary vascular resistance (PVR) results in increased pulmonary blood flow (PBF) and volume overload to the LA and LV IF UNCORRECTED- Hypoxia and acidosis stimulate the carotid and cerebral chemoreceptors, causing hyperventilation and a low Pco 2  in the pulmonary circulation H ypoglycemia, secondary to pancreatic islet hypertrophy and hyperinsulinism, and a tendency toward hypothermia

40. Hemodynamics (contd.) When a large ASD is present, infants have good arterial oxygen saturation (as high as 80% to 90%) because of good mixing.   Ventricular septal defect (VSD), only minimal arterial desaturation is present, and cyanosis may be missed Metabolic acidosis does not develop L eft-sided heart failure results within the first few weeks of life( PVR) VSD is associated with pulmonary stenosis (PS) in infants with TGA- VSD helps good mixing, but the volume of fully saturated blood returning from the lungs is inadequate. infants have severe hypoxia and acidosis and may succumb early in life

41. CLINICAL CLUE-  A deeply cyanotic newborn with increased pulmonary vascular markings and cardiomegaly without heart murmur , single S2 can be considered to have TGA until proved otherwise.

42. PERSISTENT TRUNCUS ARTERIOSUS & SINGLE VENTRICLE PATHOLOGY A single arterial blood vessel (truncus arteriosus) arises from the heart The PA or its branches arise from the truncus arteriosus, and the truncus continues as the aorta A large VSD is always present in this condition

43. In single ventricle, two atrioventricular (AV) valves empty into a single ventricular chamber from which a great artery (either the aorta or PA) arises. The other great artery arises from a rudimentary ventricular chamber attached to the main ventricle. No ventricular septum of significance is present- small opening present called-”BULBOVENTRICULAR FORAMEN”

44. HEMODYNAMICS The following similarities exist between persistent truncus arteriosus and single ventricle from a hemodynamic point of view: 1. There is almost complete mixing of systemic and pulmonary venous blood in the ventricle, and the oxygen saturation of blood in the two great arteries is similar. 2. Pressures in both ventricles are identical. 3. The level of oxygen saturation in the systemic circulation is proportional to the magnitude of PBF. FACTORS DETERMINING PBF IN BOTH CASES: PERSISTENT TA- PVR & caliber of PA SINGLE VENTRICLE- Presence / absence of PS - The size of VSD

45. When the PBF is large , the patient is minimally cyanotic but may develop CHF because of an excessive volume overload placed on the ventricle. W hen the PBF is small , the patient is severely cyanotic and does not develop CHF because there is no volume overload.( same picture as TOF)

46. TRICUSPID ATRESIA PATHOLOGY T he tricuspid valve and a portion of the RV do not exist Because no direct communication exists between the RA and RV, systemic venous return to the RA must be shunted first to the LA through an ASD or PFO There is usually a VSD (or PDA) for the pulmonary arteries to receive some blood for survival

47. hemodynamics For the right-to-left shunt to occur, the RA pressure is elevated in excess of the LA pressure, RA size The LA and LV receive both systemic and pulmonary venous returns and thereby dilate  The volume overload placed on the LV is unopposed by the hypoplastic RV, with resulting LVH Anatomically, two types: TA WITH NORMALLY RELATED GREAT VESSELS(70%):  the PBF is generally reduced because it comes through a small VSD, hypoplastic RV, or small PAs. arterial oxygen saturation is low, and infant is notably cyanotic

48. hemodynamics TA WITH TRANSPOSED GREAT VESSELS(30%) T he PBF is usually increased M ildly cyanotic; their heart size is large, and their pulmonary vascular markings are increased The magnitude of PBF determines not only the level of arterial oxygen saturation but also the degree of enlargement of the cardiac chambers. CLINICAL HINT: T ricuspid atresia is the most likely diagnosis if a cyanotic infant has an ECG that shows a “superior” QRS axis, RAH, and LVH and chest radiographic films that show enlargement of the RA (with or without left atrial enlargement), a concave PA segment, and decreased pulmonary vascularity.

49. PULMONARY ATRESIA PATHOLOGY Direct communication between the RV cavity and the PA does not exist; the PDA (or collateral arteries) is the major source of blood flow to the lungs The systemic venous return to the RA must go to the LA through an ASD or a PFO

50. HEMODYNAMICS The RA enlarges and hypertrophies to maintain a right-to-left atrial shunt The RV is usually hypoplastic with a thick ventricular wall or RV if of normal size present with TR Systemic and pulmonary venous returns mix in the LA and go to the LV to supply the body and the lungs  The volume load placed on the left side of the heart (i.e., LA and LV) is proportionally related to the magnitude of PBF PDA is the major source of PBF and it may close after birth, the PBF is usually decreased. When multiple collateral arteries are the only source of PBF, they are usually not adequate and PBF is reduced, so infant severely cyanotic &  S2 is single

51. CLINICAL HINT A severely cyanotic newborn with decreased pulmonary vascularity and normal or slightly enlarged heart size on chest radiographic films and RAH or biatrial hypertrophy (BAH) and LVH on the ECG with QRS axis normal, may have pulmonary atresia.

52. TOTAL ANOMALOUS PULMONARY VENOUS RETURN PATHOLOGY T he pulmonary veins drain abnormally to the RA, either directly or indirectly through its venous tributaries An ASD is usually present to send blood from the RA to the LA and LV. Depending on the drainage site, TAPVR may be divided into three types.

53. classification BASED ON SITE OF DRAINAGE( DARLING’S CLASSIFIACTION) TYPE I : SUPRACARDIAC TYPE (most common): The common pulmonary vein drains to the superior vena cava through the vertical vein and the left innominate vein. TYPE II : CARDIAC TYPE : The pulmonary veins empty into the RA directly or indirectly through the coronary sinus. TYPE III : INFRACARDIAC/SUBDIAPHRAGMATIC TYPE : The common pulmonary vein traverses the diaphragm and drains into the portal or hepatic vein or the inferior vena cava TYPE IV : MIXED TYPE ( least common) PHYSIOLOGIC CLASSIFICATION( BASED ON OBSTRUCTION TO PV RETURN) Obstructive Non-obstructive

54. HEMODYNAMICS NON-OBSTRUCTED TYPED OF TAPVR S imilar to those of a large ASD The amount of blood that goes to the LA through the ASD, is determined by the size of the interatrial communication and the relative compliance of the ventricles R ight ventricular compliance normally increases after birth, with a rapid fall in PVR, and the ASD may be inadequate in size, more blood enters the RV than the LA volume overload of the right side of the heart and the pulmonary circulation results, with enlargement of the RA, RV, PA, and pulmonary veins C omplete mixing of systemic and pulmonary venous blood in the RA, oxygen saturation values are almost identical in the aorta and the PA

55. HEMODYNAMICS (CONTD.) CARDIAC EXAMINATION : ejection systolic murmur of PS  diastolic murmur of tricuspid stenosis S2 splits widely Characteristic “quadruple” rhythm of TAPVR, which consists of an S1, a widely split S2, and an S3 or S4 CHEST RADIOGRAPH : There i s an enlargement of the RA and RV, a prominent PA segment, and increased pulmonary vascular markings

56. HEMODYNAMICS (CONTD) OBSTRUCTED TYPE OF TAPVR P ulmonary venous hypertension and secondary PA and RV hypertension Pulmonary edema As long as a large ASD permits a right-to-left shunt, the RV cavity remains relatively small.  This is because the RV hypertension prevents the RV compliance from increasing, and the PVR remains elevated. COMPLETE MIXING PHYSIOLOGY : sp02 of aorta & PA equal but lower than non-obstructed type

57. Hemodynamics(contd.) CHEST RADIOGRAPH S mall heart and characteristic patterns of pulmonary venous congestion or pulmonary edema (i.e., “ground-glass” appearance) The degree of arterial desaturation or cyanosis inversely relates to the amount of PBF The pulmonary valve closure sound (P2) is loud because of pulmonary hypertension, which results in a single, loud S2

58. TAKE HOME MESSAGE For a given defect, an  increase  in the magnitude of PBF results in a rise in the systemic arterial oxygen saturation;  a decrease  in PBF results in a decrease in the arterial oxygen saturation Conversely, infants with a single ventricle may be in CHF from a large PBF but not be cyanotic, CHF improves after a PA banding operation, but the arterial oxygen saturation usually decreases, and cyanosis may appear.

59. BIBLIOGRAPHY GHAI ESSENTIAL PAEDIATRICS (9 TH EDITION) NELSON TEXTBOOK OF PAEDIATRICS AIIMS NICU PROTOCOLS PARK’S PEDIATRIC CARDIOLOGY PIYUSH GUPTA TEXTBOOK OF PEDIATRICS