Anatomy and pathophysiology of tetralogy of Fallot

1. Anatomy and pathophysiology of tetralogy of Fallot Yun Hee Chang Division of Pediatric Cardiac Surgery Department of Thoracic & Cardiovascular Surgery Seoul St. Mary’s Hospital Catholic University of Korea / Catholic Medical Center

2. History

3. 1888 Fallot: La maladiebleue 1881 Widman 1846 Thomas Bevil Peacock 1816 Thaxter 1814 J.P.Farre 1812 Dorsey 4 Anatomic features Pulmonary (or RV) outflow stenosis Ventricular septal defect Aortic overriding Right ventricular hypertrophy 1797 Bell 1793 Abernethy 1785 Pulteney 1784 Willam Hunter 1777 Eduard Sandifort 1671 NielsStensen 1924 Maude Abbott: “tetralogy of Fallot”

4. Subtypes of TOF • Tetralogy of Fallot, Pulmonary stenosis • Tetralogy of Fallot, Absent pulmonary valve (3-6%) • Tetralogy of Fallot, Common atrioventricular canal (2%) • Tetralogy of Fallot, Pulmonary atresia (20%)

5. TOF with Pulmonary stenosis

6. Anatomic features Subpulmonary stenosis Overriding of the aorta Right ventricular hypertrophy Ventricular septal defect

7. Pathognomonic lesions • Van Praagh R et al. - Underdevelopment of the subpulmonary infundibulum Normal TOF

8. Anderson RH et al. - Anterocephalad deviation of the outlet septum (relative to the limb of the septomarginaltrabeculation) - Malformation of the septoparietal trabeculation TOF Normal A P

9. Hypertrophied Septoparietal trabeculation Deviated outlet septum Septal attachment of the muscular outlet septum Antero-cranial limb of TSM

10. Pulmonary outflow stenosis Subvalvar stenosis • Infundibular stenosis • - Essential part of tetralogy • - Produced by the ‘Squeeze’ between the anterocephaladmalalignment of the outlet septum and the abnormal situated septoparietal trabeculations

11. * vs. Eisenmenger type ventricular septal defect Anterocephaladmalalignment of the outlet septumwithoutabnormal situated septoparietal trabeculations

12. Additional muscular stenosis • - By hypertrophy of the moderator band or by prominent apical trabeculations. • - Often described as “two-chambered right ventricle”. Moderator band Apical trabeculations

13. Valvar stenosis • The pulmonary valve is stenotic in 75% cases • : usually caused by hypoplasia and fusion of bicuspid leaflets, supravalvar tethering. • The valve is bicuspid in ½ to 2/3 of cases. • The pulmonary valve annulus is invariably smaller than the aorta; however, it is not necessarily significant obstructive.

14. Supravalvar stenosis • The main PA is usually somewhat diffusely small and is often short. • The narrowed portion of the main pulmonary artery is often at the sinotubular junction. Sinotubular junction • Branch PA abnormalities occurred in only 10 % of cases.

15. Ventricular septal defect 3 important planes Outlet from left ventricle Interventricular plane Ventricular septal defect

16. Types of ventricular septal defect • Perimembranous defect • - In about 4/5 of Caucasian patients • - VIF stops short of the postero-caudal limb of TSM, permitting fibrous continuity to exist between the leaflets of the aortic & tricuspid valves Muscular outlet septum Ventricular infundibular fold Postero-caudal limb of TSM Right bundle branch Remnant of the interventricular membranous septum Left bundle branch AV node

17. Septoparietal trabeculation Ventricular infundibular fold Septomarginal trabeculation Aortic-tricuspid continuity

18. Muscular defect • - In about 1/5 of Caucasian patients • - Postero-caudal limb of the TSM fuses with VIF, permitting muscular continuity throughout the right ventricular margin of the defect. Hypertrophied septoparietal trabeculation Muscular outlet septum Ventricular infundibular fold Postero-caudal limb of TSM Right bundle branch Left bundle branch AV node

19. Septoparietal trabeculation Ventricular infundibular fold Septomarginal trabeculation

20. Doubly committed & juxta-arterial defect • - Commoner in the Far East and South America • - Consequence of failure of formation of a complete muscular subpulmonary infundibulum Fibrous continuity between the leaflets of the arterial valves Ventricular infundibular fold Postero-caudal limb of TSM

21. Pathophysiology Normal or low PA pressure Unobstructed but relatively high-resistance systemic vascular bed Obstructed pulmonary outflow tract Anatomic route of balance between the two circulatory beds RV hypertension

22. Hypercyanotic spell Catecholamine State of low intravascular volume state Crying /feeding, etc

23. TOF with Pulmonary atresia

24. Anatomic features

26. Atretic arterial segment - Can be recognized as a solid elastic cord in about ¾ - Rarely only the PV is imperforate. - Confluent or non-confluent. - Confluent in about 2/3 of the cases - The caliber of the central PAs varies : When the ductus or collateral arteries connect proximally to the central PAs or their lobar branches, the central vessels may be only mildly hypoplastic or even normal in size. • The central right & left PAs

27. The blood supply to the lungs • “Entirely from the systemic circulation”. • - Ductus arteriosus • - Systemic-to - pulmonary collateral arteries • - Coronary artery • - Plexus of bronchial or pleural arteries

28. * Ductal & collateral sources may coexist in the same patients but only rarely coexist in the same lung segment. Systemic-to-pulmonary collateral arteries Patent ductus arteriosus Pulmonary arteries Pulmonary atreisia

29. Ductus arteriosus • - Usually is a unilateral structure • - Associated with confluent PAs in > 80% of cases • - Rarely, bilateral ductus may occur with non-confluent arteries • - Because the ductus is widely patent during fetal life, the PAs may be a normal size at birth. • - Normal postnatal ductal narrowing usually occurs and produce distal stenosis in 35-50% of cases. Patent ductus arteriosus Pulmonary coarctation

30. Collateral arteries • - Most commonly from the descending thoracic aorta • - Less commonly the subclavian arteries • - Rarely from the abdominal aorta • - Their number varies from 1 to 6 • - Their diameter ranges from 1 to 20mm • - More stable source of pulmonary blood flow

31. - Anastomoses between the central PAs (or their branches) and the collateral arteries • : About 40% of subjects • : May occur at the hilum or within the lung • : In the remaining 60%, the collateral arteries enter the pulmonary hilum, travel with the bronchi as PAs

32. - Stenosis • : nearly 60% of collateral arteries • : tend to occur near the aortic or intrapulmonary anastomosis • : may be discrete or segmental • : may be congenital or acquired

33. Intrapulmonary artery distribution • - Ductus supplies confluent central PAs • : Intra-PAs of both lungs are normal • - Ductus supplies one of the non-confluent central PAs • : Contra-lateral lung usually has arborization abnormalities • - Ductus is absent • : Both lungs have arborization abnormalities

34. Classification • There is no standard classification system for PAVSD, but several have been proposed. • Most classification schemes focus on the patterns of pulmonary blood flow. Congenital Heart Surgery Nomenclature and Database Project

35. Boston group IIIa. Central pulmonary artery Z – score > -2.5 IIIb. Central pulmonary artery Z – score < -2.5

36. Pathophysiology • One of Three • Marked heart failure because of lung overflow • Cyanotic because of reduced lung flow • Fairly well balancedwith systemic oxygen saturation in the high 70s to low 80s Extrapulmonary collateral Obstruction Intrapulmonary collateral has thin-walled elastic media Collateral stenosis

37. TOF with Absent Pulmonary Valve

38. Anatomic features Dilated pulmonary arterial trees Absence of ductusarteriosus Rudimentary leaflets of PV Pulmonary annular hypoplasia Deviated muscular outlet septum

39. Pathophysiology • Free pulmonary regurgitation throughout fetal life • - Transmission of chronic volume load of the RV to PAs Normal TOF with APV Airway compression PA Proximal PA : aneurismal dilatation

40. Common atrioventricular canal

41. Anatomic features Pulmonary trunk Aorta Outlet septum Septoparietal trabeculations Common atrioventricular valve Anterior papillary muscle