ADMIXTURE PHYSIOLOGY AND LESIONS - .pptx

Detailed explanation on the physiology of admixture andf its lesions.

1. ADMIXTURE LESIONS -DR SHARATH SHANMUGAM

2. CONTENTS Definition Classification Physiology of admixture lesions Examples of admixture lesions Conclusion Take home messages

3. DEFINITION Congenital cyanotic heart disease with admixture physiology is a cardiac defect which facilitates complete mixing of the deoxygenated systemic venous blood returning from the tissues and the fully oxygenated pulmonary venous blood from the lungs in a common receiving chamber. These patients classically present with cyanosis with increased pulmonary blood flow.

4. CLASSIFICATION OF ADMIXTURE LESIONS ADMIXTURE LESIONS WITH COMPLETE MIXING: Assuming the cardiac index to be within normal range,the effective saturation of completely admixed blood will be related to amount of pulmonary blood flow.So systemic arterial saturation in an admixture lesion will reflect pulmonary blood flow. ADMIXTURE LESIONS WITH INCOMPLETE MIXING: Restrictive communications between deoxygenated and oxygenated blood eg:TGA with intact septum,restrictive interatrial communication. Selective streaming of deoxygenated and oxygenated blood as in DORV with subpulmonic VSD and no PS, Univentricular physiology.

5. LEVEL OF MIXING PRE TRICUSPID LEVEL: Venous : Total anomalous pulmonary venous connection (TAPVC) Total anomalous systemic venous connection (TASVC) Atrial : TAPVC,Single atrium,Tricuspid atresia,HLHS POST TRICUSPID LEVEL: Ventricular : Single Ventricle Arterial : Truncus arteriosus OTHER CLASSIFICATION : Mixing during systole: Truncus arteriosus, DORV. Mixing during complete cardiac cycle : TAPVC, Common atrium, Tricuspid atresia Ref:Admixture lesions in congenital cyanotic heart disease,Jaganmohan A Tharakan

6. PHYSIOLOGY OF ADMIXTURE LESIONS Simple mixing of arterial  and venous  blood channels within the atria,ventricle or great vessel  without RVOT obstruction As mixing of deoxygenated SV blood and fully oxygenated blood is simple process,the resultant mix of blood will have saturation somewhere in between that of SV blood and pulmonary venous blood oxygen saturation. A dmixture physiology facilitates complete mixing of deoxygenated and oxygenated blood resulting in equal saturation in both great arteries. The arterial saturation mainly depends on two facts ( if cardiac index normal ) A) Pulmonary blood flow B) Effect of streaming

7. In a complete admixture physiology,aorta and pulmonary artery will have equal saturation . Mostly present with frank cardiac failure and only minimal cyanosis Favourable streaming: ( Preferential streaming of pulmonary venous Blood into aorta ) Aortic saturation more than pulmonary saturation . Less cyanosis Unfavourable streaming: ( Preferential streaming of PV Blood into Pulmonary artery ) Aortic saturation less than pulmonary saturation . More cyanosis . Hence relationship of arterial oxygen saturation to pulmonary blood flow is influenced by total pulmonary blood flow and type and degree of streaming in mixing chamber. Ref:Admixture lesions in congenital cyanotic heart disease,Jaganmohan A Tharakan

8. EXAMPLES OF ADMIXTURE LESIONS Total Anomalous Pulmonary Venous Connection(TAPVC) Atresia of one of atrioventricular valves(Tricuspid atresia,Mitral atresia) Single ventricle physiology(Double Inlet ventricle) Semilunar valve atresia(Pulmonary atresia including hypoplastic right heart syndrome,aortic atresia including HLHS) DORV or DOLV Common atrium Truncus arteriosus Ref:Admixture lesions in congenital cyanotic heart disease,Jaganmohan A Tharakan

9. TOTAL ANOMALOUS PULMONARY VENOUS CONNECTION(TAPVC) All four pulmonary veins connect anomalously to a systemic venous tributary of Right atrium or to right atrium proper but have no connection to the left atrium. Admixture usually occurs at the level of Right atrium INCIDENCE: 0.5-0.9/10000 live births If not treated,85% die in 1 st year of life

10. CLASSIFICATION NEILLS CLASSIFICATION(1956) – Based on embryologic type DARLING CLASSIFICATION(1957) BURROUGHS AND EDWARD CLASSIFICATION(1960):depend on length of anastomotic channel a) Long b) Intermediate c) Short SMITH’S CLASSIFICATION(1961): a) Supradiaphragmatic type b) Infradiaphragmatic type

11. DARLING CLASSIFICATION

12. TYPE 1: Right and left pulmonary vein form a common pulmonary venous confluence that drains via a vertical vein to left innominate vein and right atrium. ASD with RT to LT shunt needed for survival. TYPE 2: Pulmonary venous confluence connects to the coronary sinus and right atrium TYPE 3: Pulmonary vein confluence drains inferiorly via a vertical vein to portal/ hepatic vein and right atrium TYPE 4: LPV drains into left innominate vein RPV drains into coronary sinus

13. SMITH’S CLASSIFICATION SUPRADIAPHRAGMATIC: Pulmonary vein Vertical vein Innominate vein SVC Right atrium INFRADIAPHRAGMATIC : Pulmonary veins portal / hepatic vein IVC Right atrium.

14. PATHOPHYSIOLOGY / HEMODYNAMICS Pulmonary veins ultimately drain into RA . Hence deoxygenated blood in RA get completely mixed with oxygenated blood from PV, and again recirculated to lung. Hence an interatrial communication is needed for survival . Hemodynamics mainly depends on PV connection whether it is obstructed or not. RA,RV,PA,LA,LV,Aorta saturations are identical. If pulmonary blood flow is markedly increased ,then aortic saturation can be high as 90% and cyanosis may be missed.

15. STREAMING IN TAPVC: In utero IVC Atrial septum Left atrium SVC Tricuspid valve RV Likewise in TAPVC: Supracardiac and cardiac have unfavourable streaming of TAPVC draining into SVC or Coronary sinus passes through tricuspid valve Infracardiac TAPVC draining into IVC selectively stream across ASD to LA( Favourable streaming ) These result in dissimilar saturations in aorta and pulmonary artery.

16. CAUSES OF LOW ARTERIAL SATURATION IN TAPVC Reduced pulmonary blood flow due to pulmonary vascular disease Due to pulmonary venous obstruction Passive pulmonary hypertension secondary to pulmonary venous hypertension Unfavourable streaming

17. TAPVC without pulmonary venous obstruction -ASD After first few weeks of life,there is decreased PVR and mixed venous blood traverses the pulmonary circuit(PBF 5 times the SBF) Dilation and hypertrophy of RV and pulmonary artery = RV FAILURE (Neonate/infant) Long term exposure leads to Medial hypertrophy and intimal proliferation in pulmonary arterioles. Pulmonary hypertension in third and fourth decades Cyanosis prominent.

18. TAPVC WITH PULMONARY VENOUS OBSTRUCTION – MITRAL STENOSIS Elevated pressure in pulmonary venous channels Pulmonary edema Right ventricular pressure and volume overload Leftward shift of interventricular septum and decrease in LV volume Systemic output decreases

19. CLINICAL PRESENTATION WITHOUT OBSTRUCTION AND LOW PVR SYMPTOMS : LARGE ASD – CCF ( dyspnea , tachypnea , diaphoresis ) Mild cyanosis SIGNS : RV impulse with PSH+ Wide fixed split loud P2 , RV S3 ESM in pulmonary area , TR , PR WITH OBSTRUCTION AND HIGH PVR SYMPTOMS : Tachycardia , tachypnea, cyanosis within hours of birth ( mimics ARDS ). Death from pulmonary edema and RV failure. SIGNS : RV apex , loud P2 , PR murmur ( Graham steel ) , liver enlargement.

20. ECG :Right axis deviation,Right ventricular volume overload(rsR’ in right sided leads) RVH(when pulmonary artery pressures elevated) CXR :Cardiomegaly with dilated RA,RV.In supracardiac type, Figure of 8 appearance seen.In obstructed TAPVC,features of Pulmonary edema seen. ECHO :RA,RV,PA dilated,look for pulmonary venous drainage,ASD(R to L shunt),look for presence or absence of obstruction All patients need surgical repair,patients with obstructive type, emergency surgery is required

21. TOTAL ANOMALOUS SYSTEMIC VENOUS DRAINAGE When SVC and IVC both connect to left atrium,mixing occur at atrial level Part of this mixture reaches LV and part passes through right heart by ASD Associated with left isomerism Associated with reduced pulmonary blood flow and normal systemic flow Clinical features:Cyanosis,clubbing,later-dyspnea Cyanosis with dominant LV ECG -70% cases have ectopic atrial rhythm with superiorly oriented axis 10% cases have complete heart block CXR -Mild to moderate cardiomegaly,midline liver Bilateral hyparterial bronchi ECHO with contrast imaging- --opacification of LA,dilated coronary sinus

22. TRICUSPID ATRESIA DEFINITION : Tricuspid Atresia is characterized by absence of tricuspid valve and hypoplastic RV. Prevalence : 0.06 / 1000 population No definitive sex distribution RA is separated from RV by a muscular floor 1 to 3% of congenital heart diseases Great arteries are normally related in 70% cases and transposed in 30% cases

23. CLASSIFICATION OF TRICUSPID ATRESIA TANDON AND EDWARD CLASSIFICATION TYPE I : TA with normally related Great arteries( 70-80% ) A) Pulmonary atresia with no VSD B) PS with VSD ( Most common) C)No PS with large VSD TYPE II: TA with D-TGA (15-25%) A) Pulmonary atresia with VSD B) PS with VSD C) No PS with large VSD TYPE III : TA with L – TGA A) PS B) Sub aortic stenosis

24. HEMODYNAMICS Imperforate Tricuspid valve Varying hypoplasia of RV Interatrial communication ( ADMIXTURE ) Systemic with pulmonary connection : VSD/ PDA

25. CLINICAL FEATURES: Cyanosis is severe from birth.Tachypnea,poor feeding present Physical findings: Single S2,VSD murmur,continuous murmur of PDA may be present ECG -Superior QRS axis,LVH,RAE or Biatrial hypertrophy CXR -Heart size normal or slightly enlarged(RA,LV).Pulmonary vascularity decreased ECHO -Absence of TV orifice,large RA,hypoplastic RV,large LA,LV,interatrial communication,VSD,PS,TGA.In TGA,look for CoA,subaortic stenosis. TREATMENT: PGE1-to maintain patency of PDA Balloon atrial septostomy CHF treatment Staged surgical procedures: 1.BT shunt/PA banding 2.Bidirectional Glenn/Hemifontan(2-6months) 3.Fontan procedure(2-5years)

26. HYPOPLASTIC LEFT HEART SYNDROME HLHS is associated with left heart anomalies like very small left ventricle with underdevelopment of mitral and aortic valves,small and hypoplastic aorta. PFO and PDA is necessary for survival Ductus dependent systemic circulation Mostly associated with CoA Pulmonary venous blood crosses the IAS and mixes with systemic venous blood in RA and from there passes to RV,PA. From PA via ductus to descending aorta and to body Retrograde flow from ductus to ascending aorta(coronaries) and cerebral circulation(associated with CNS abnormalities)

27. Timing of presentation depends on degree of atrial level obstruction,ductal patency and level of pulmonary vascular resistance After closure of ductus,symptoms of cyanosis,tachypnea,metabolic acidosis Poor peripheral perfusion,weak pulses Prominent RV impulse,single loud S2,TR murmur,flow MDM ECG -Right axis,RVH,decreased LV forces CXR -With restrictive atrial shunt-Pulmonary edema , With Nonrestrictive-cardiomegaly with increased pulmonary vascular markings ECHO -small hypoplastic LV,aorta and enlarged RA,RV,PA,look for CoA,PDA If untreated,more than 95% infants die within 1 st month of life PGE1 infusion to maintain ductal patency Atrial septostomy Staged surgical procedures: I)Norwood procedure II)BDG III)Fontan Heart transplantation

28. DOUBLE OUTLET RIGHT VENTRICLE Both great arteries are connected completely or predominantly to RV. DORV without pulmonary stenosis can have subaortic VSD or Subpulmonic VSD RV act as mixing chamber In DORV with subaortic VSD: Favourable streaming of LV blood enters aorta and RV blood enters pulmonary artery Presents as large left to right shunt at VSD level,as desaturation is mild and cyanosis is not clinically apparent

29. DORV with subpulmonic VSD :shows unfavourable streaming with LV blood enters pulmonary artery and RV blood enters aorta. Clinically presents as TGA with VSD ,with significant systemic desaturation and cyanosis despite increased pulmonary blood flow In DORV,systemic saturation may not accurately reflect pulmonary blood flow and systemic desaturation is decided by streaming and associated anomalies .

30. CLINICAL FEATURES In DORV with Subaortic VSD ,PBF increases,CHF result.Clinically similar to large VSD with pulmonary hypertension and CHF Growth retardation,tachypnea,hyperactive precordium,loud P2,VSD murmur,S3,MDM may be audible ECG-RVH or BVH,superior QRS axis,1 st degree AV block CXR-cardiomegaly with prominent PA segment In DORV with Subpulmonic VSD(Taussig Bing), PBF increases,CHF result.Clinically similar to TGA with VSD. Growth retardation,severe cyanosis,loud P2,systolic murmur at upper left border. ECG-RAE,Right axis ,RVH CXR-Cardiomegaly with prominent PA segment with increased PBF VSD closure by 6months If more than 6 months ,assess for operability ASO with VSD closure by 6 weeks of age

31. SINGLE VENTRICLE It is defined as an heart with atrioventricular connection to one main ventricular chamber. The smaller ventricle may be called as an incomplete,rudimentary and outlet chamber. Prevalence-2.3/10000 live births Male predominance 3:1

32. CLASSIFICATION VAN – PRAAGH CLASSIFICATION 1) TYPE A : DOUBLE INLET LEFT VENTRICLE ( MOST COMMON ) 2) TYPE B : DOUBLE INLET RIGHT VENTRICLE 3) TYPE C : DOUBLE INLET VENTRICLE WITH MIXED MORPHOLOGY 4) TYPE D : DOUBLE INLET VENTRICLE WITH INDETERMINATE MORPHOLOGY TYPES OF DILV TYPE 1: Normally related great arteries TYPE 2: Right anterior ( d-transposition ) TYPE 3: Left anterior ( l- transposition ) (MC) TYPE 4: Left posterior ( inversus type )

33. HEMODYNAMICS The amount of pulmonary blood flow which is influenced by various factors determines the hemodynamics of single ventricle. Factors : a) Pulmonary stenosis b) Pulmonary vascular resistance c) Status of functioning ventricle d) Degree of mixing in the main chamber Admixture occur at the level of ventricle DILV with aorta arising from left sided and anterior rudimentary RV outflow chamber(inverted)---- favorable streaming DILV with aorta from right sided and anterior rudimentary RV outflow chamber(noninverted)---- Unfavorable streaming

34. CLINICAL PRESENTATION GROUP 1: MARKED CYANOSIS Mostly seen in child with severe PS or pulmonary atresia Becomes critical with closure of ductus arteriosus and ultimately die . Dies in neonatal period if untreated . GROUP 2 : MILD TO MODERATE CYANOSIS Due to mild PS with favorable streaming. Usually they reach adulthood with growth retardation like TOF In adulthood they ultimately develop Eisenmenger syndrome. GROUP 3 : CONGESTIVE CARDIAC FAILURE Usually develops CCF in infancy due to high pulmonary blood flow. Develops refractory CCF , If they have Interrupted Aortic Arch or sub aortic obstruction.

35. ECG -may have atrial arrhythmias,preexcitation,blocks CXR -cardiomegaly with pulmonary plethora(Increased PBF) Normal sized with oligemic lung fields (restricted PBF) ECHO -Anatomy and function of single ventricle,AV valve atresia,assess aortic arch Surgery is always palliative Those presenting early(neonate or 2-3 months): Timing of surgery <3months Pulmonary artery banding(Increased PBF),Systemic-PA shunt(decreased PBF) Those presenting later in life:BDG(6-12 months) followed by Fontan(4-7years of age)

36. COMMON ATRIUM Complete absence of interatrial septum <1% of congenital heart diseases Associated with isomerism Syndromes associated-Ellis van creveld syndrome,Ivemark syndrome Complete mixing of systemic venous blood and PV blood at atrial level Signs of increased pulmonary blood flow with mild desaturation Direction of flow depends on compliance of ventricles Symptoms appear earlier and progress faster than isolated ASD.

37. Symptoms like dyspnea,failure to thrive RV type apical impulse,wide fixed split S2,flow MDM ,cleft mitral leaflet(associated MR) ECG -like Primum ASD,left or superior axis ,rsR’ in V1,QRS notched in 2,3,avF CXR -cardiomegaly,RA enlarged,RV apex ECHO -absence of IAS,look for abnormal venous drainage Treatment : Symptomatic treatment-Diuretics Early surgery-pericardial patch reconstruction of IAS(6-12months)

38. TRUNCUS ARTERIOSUS Truncus arteriosus accounts for <1% of CHD Prevalence-0.07/1000 live births Classified under conotruncal anomalies a) A common arterial trunk from base of heart b ) Common arterial trunk giving rise to aorta , pulmonary artery and coronaries Associated with 22q11.2 microdeletion(40% cases)

39. COLLETT AND EDWARDS CLASSIFICATION (1949): Type I : The main pulmonary is from truncus and bifurcates into the left and right pulmonary arteries Type II : The right and left branches arise adjacent to each other from the posterolateral segment of the common trunk Type III : The right and left branches originate separately from the right and left lateral segments of the common trunk. Type IV : Neither of the branches arise from the common trunk, but are perfused by aortopulmonary collaterals. This type is now categorized as a form of pulmonary atresia with a ventricular septal defect rather than TA( PSEUDOTRUNCUS )   VAN PRAAGH CLASSIFICATION(1965): Type A1 : The main pulmonary is present and bifurcates into the left and right pulmonary arteries (same as Collette and Edwards classification). Type A2 : The right and left branch pulmonary arteries arise from the common trunk. Type A3 : One branch pulmonary artery (typically the right) arises from the common trunk and the other arises from a PDA or the aorta. Type A4 : This type is defined by presence of aortic arch hypoplasia, coarctation or interrupted aortic arch and a large PDA.

40. HEMODYNAMICS AND PHYSIOLOGY Admixture happens at the level of major vessel . Streaming is well documented in truncus arteriosus and can result in substantial difference in aortic and pulmonary arterial saturation. Due to large left to right shunt ( systemic pressure exposure to pulmonary circulation), neonates usually presents with Congestive cardiac failure which ultimately results in death. Children with significant pulmonary stenosis , usually do not develop CCF and in later stages can develop Eisenmenger syndrome. Physiologic consequences depends on size of pulmonary arteries and on PVR,with truncal valve regurgitation/stenosis add to hemodynamic burden on ventricles

41. CLINICAL PRESENTATION Heart failure in the first few weeks of life. Most often they present with acute precipitation of heart failure following closure of PDA . Cyanosis may be present in neonatal period due to increased pulmonary vascular resistance and pulmonary ostial stenosis, which will improve as the PVR reduces. As the child grows , usually presents with CCF. Survival rate-35% at 6months ,10% at 1 year SIGNS - Wide pulse pressure ,hyperdynamic precordium,LV type apical impulse,ejection click,S2 single and loud ESM in pulmonary area.EDM(Truncal valve regurgitation) ECG -QRS axis is normal or right axis,BVH,LAE CXR -Cardiomegaly with increased pulmonary vascularity and prominent ascending aortic shadow.Right Aortic Arch in 30% cases ECHO :Single arterial trunk,look for truncal valve,VSD,PDA Uncontrolled HF-Early surgery,Controlled HF-Surgery at 3-6weeks Surgery-Removing PA from truncus,patch closure of VSD and RV-PA conduit placement Truncal valve repair or replacement(when truncal valve is dysfunctional)

42. SURGERY IN CONGENITAL HEART DISEASE WITH ADMIXTURE PHYSIOLOGY In patients with pulmonary hypertension and pulmonary vascular disease,guidelines for surgery are generally similar to isolated VSD with pulmonary vascular disease PVRI less than 4woodunits m2 have favourable outcome PVRI>8woodunitsm2 have poor outcome PVRI drop to 6-8wum2 on 100% oxygen /NO also referred for surgical correction Patients with Qp:Qs ratio >1.8(PVR:SVR ratio <0.7)may be offered surgery even when PA and aortic systolic pressures are identical.

43. CONCLUSION CCHD with admixture physiology accounts for nearly 50% of all cyanotic CHD. Though admixture lesions are discussed separately,bulk of them  actually represent cyanosis with increased pulmonary blood flow situations . The  net pulmonary blood flow is much more important than the quantum  of admixture in determining the degree cyanosis. The aortic saturation reflects the amount of pulmonary blood flow, but streaming is an important component of admixture lesions resulting in minor to significant difference.

44. TAKE HOME MESSAGES Admixture lesions are basically cyanotic heart diseases with increased pulmonary blood flow. They predominantly present with CCF with minimal cyanosis. They are net left to right shunt resulting in cyanosis. Role of streaming is very much important in admixture lesions. There can also be a combination of admixture lesions with obstructive RVOT components(tricuspid atresia+ pulmonary stenosis).

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