Prosthetic heart valves types physiology

Metallic & Bioprsothetic valves

1. PROSTHETIC VALVES TYPES & PHYSIOLOGY DR ASWIN RM 18.02.2020

2. HISTORY OF PROSTHETIC HEART VALVE First Mechanical valve was designed by Charles Hufna gel in 1954 ( Implanted in descending thoracic aorta for AR) Plexiglass (Methyl Methacrylate) cage & Silicone-coated nylon poppet

3. TIMELINE

4. HISTORY OF MAJOR VALVE TYPES

5. TYPES OF PROSTHETIC VALVES

6. OUTCOME AFTER VALVE REPLACEMENT

7. IDEAL VALVE

8. VALVE CHARACTERISTICS VALVE DURABILITY EOA (CM 2 ) THROMBOGENICTY AORTIC MITRAL BALL & CAGE EXCELLENT 1.2-1.6 1.4-3.1 ++++ TILTING DISC GOOD TO EXCELLENT 1.5-2.1 1.9-3.2 +++ BILEAFLET EXCELLENT 2.4-3.2 2.8-3.4 ++ HOMOGRAFT FAIR 1.0-1.7 1.3-2.7 +/++ HETEROGRAFT GOOD 3.0-4.0 NOT AVAILABLE + Vongpatanasin W, Hillis LD, Lange RA. Prosthetic Heart Valves. New England Journal of Medicine. 1996 Aug 8;335(6):407–16 .

9. MECHANICAL VALVES

10. MECHANICAL VALVES Trileaflet valve : Under trial Interactive CardioVascular and Thoracic Surgery 28 (2019) 689–694 Components made from synthetic materials Metals , alloys , polymers etc

11. STAR EDWARDS VALVE Most widely used ball & cage valve for more than 40 years (1960-2007) Large patient population still with the valve Silicone rubber ball with 2% barium sulfate Cage- Stellite alloy Sewing ring-knitted Teflon & polypropylene cloth. Circular primary orifice Ring shaped secondary orifice between the ball and the housing Tertiary orifice : In the aortic position, between equator of the ball and aorta.

12. SEP ADVANTAGES Oldest Durability up to 40 yrs DISADVANTAGES No central orifice – only lateral orifice – very high transvalvular gradient Bulky design - not suitable if small LV cavity or aortic annulus. Reduced EOA  excessive occluder -induced turbulence in the flow through and distal to the valve Thrombogenic risk is higher ie 4% to 6% per year Hemolysis - Collisions with the occluder ball causes damage to blood cells

13. UNIQUE FEATURES Occluder travels completely out of the orifice → reduces thrombus & pannus growing from the sewing ring Continuously changing points of contact of the ball → reduces the wear & tear in any one area X-ray: 3 radiopaque metal struts join at top, ball radiolucent, cage radiopaque Ball Variance

14. FLUROSCOPY

15. CAGE & DISC VALVE Introduced in mid-1960s for a better profile. Examples : Kay– Shiley , Beall , Star edwards Design similar to ball-and-cage valves - except that occluder disc instead of ball Discontinued - inferior hemodynamics

16. TILTING DISC VALVES Bjork– Shiley and Lillehei – Kaster tilting-disc valves in 1969 & 1970 respectively Over came the 2 major drawbacks of caged valves ; high profile & excessive turbulence DISC and a retaining STRUT mechanism Disc -totally occludes the valve orifice in the closed position & tilts to an angle in the open position. The disc can rotate in its axis - prevents excessive contact wear to particular region of the disc

17. 5 LANDMARK DESIGNS

18. TILTING DISC VALVE ADVANTAGES OVER BALL & CAGE Low profile Central blood flow. Decreased turbulence Reduced shear stress. Reduced Thrombotic risk DISADVANTAGES Thrombus and Pannus interfering with the motion of disc Sudden catastrophic valve thrombosis Careful orientation of disc needed during implantation

19. MEDTRONIC HALL VALVES Titanium housing, Teflon sewing ring, carbon coated disc. Single hole in the center of the disc. Goose-neck shaped central strut disk rides up and down on the strut. 2 second, smaller strut stops the motion of the disk when fully open. Opening angle: 75 degrees for aortic, 70 degrees for mitral. Approved in 1981 ,still used

20. BJORK SHILEY 2 U shaped struts Larger inlet strut Smaller outlet strut deep into the disc well- retains the disc Radiolucent occluder disc with opaque marker Disk types : Flat & concavo convex

21. TILTING DISC FLUROSCOPY The base ring is radiopaque Has a characteristic curved central strut The base ring radiopaque 2 eccentric unequal “U” shaped struts Radiolucent disc with a radiopaque ring

22. TTK CHITHRA VALVE Only Indian mechanical valve Research initiated in 1976 First Human implantation in 1990 Approved in 1995 4 th generation in use now Ultra high molecular weight Polyethylene disc Cobalt chromium alloy ( Haynes-25) cage 3 struts,2 major ,1 minor strut. Machined from single block ; no welds or joints. Minimum metal exposed to blood stream Opening angle 72 deg Polyester suture ring

23. TTK - CHITHRA VALVE - FEATURES Rotatable within the sewing ring - freedom of repositioning if needed. Silent operation Low profile Most price-friendly Low thromboembolism even if poor anticoagulant compliance

24. BI LEAFLET VALVES First designed by St Jude Medical & introduced in 1978 . FDA approved in 1982 Most widely used . 2 semi-circular occluders called leaflets , which pivots about a recessed hinge. Open position – central rectangular orifice and two semi-circular lateral orifices. Closed position small gaps between the closed leaflets (b-datum gap ) and between the leaflets and the housing (periphery gap) allow some degree regurgitation. Regurgitation also occur through the hinge region

25. OTHER BI LEAFLET VALVES CarboMedics - Sorin (1993) differs from the SJM in the opening angle & shape of hinge The ATS Open Pivot valve (2000 ) inverts the hinge system change in the pivot design-protruding rather than a recessed hinge design. The On-X valve, recent introduction Length-to-diameter ratio close to native valves, Smoothed pivot recess that allows the leaflets to open at an angle of 90° relative to the valve housing 2-point landing mechanism during valve closure.

26. ADVANTAGES Largest opening angle Excellent hemodynamics even in small sizes - Lowest gradient for any given outer diameter than caged ball or tilting disc valves Low turbulence - Central laminar flow Less bulk and flat profile Easier insertion Less thrombogenicy , especially in mitral position than other mechanical valves No need for supporting struts 2 lateral , 1 central minor orifice → no chance of sudden catastrophic thrombosis

27. St. Jude Medical Valve The base ring is radiolucent. And the discs are radiopaque Carbomedics sorin bileaflet valve Both the base ring and discs are radiopaque Best seen in End on view

28. BILEAFLET VALVES the angle between the leaflets in the fully open and closed position OPENING AND CLOSING ANGLES CARDIAC CT

29. SINGLE LEAFLET – OPENING ANGLE Angle between the housing and the disc at its fully open position

30. COMMON VALVES VALVE OPENING ANGLE CLOSING ANGLE SJM <24 >130 Carbomedics <29 >148 Sorin Bicarbon <24 >135 Edwards Duromedic <13 >120 Medtronic Hall 70-75 - TTK Chithra 72 -

31. BIOPROSTHETIC VALVES

32. BIOPROSTHETIC VALVES- EVOLUTION

33. BIOPROSTHETIC VALVES Mechanical valves : life-long anticoagulation therapy and the accompanying bleeding problems. Initial approach (1962) : antibiotic- or cryo-treated human aortic valves ( homografts ) Another approach (1967) was patient’s own pulmonary valve used to replace the aortic valve ( Ross procedure) followed by homografts for pulmonary position Later occassionaly performed on mitral valves also.

34. BIOPROSTHETIC VALVES Short comings : Durability especially for homografts Availabilty of homografts Major breakthrough in 1969 Carpentier developed tissue fixation using glutaraldehyde Increased biological tissue stability and a decrease in biodegradation Inert but still biological tissue Concept of stent was also developed simulataneously New valve design, combining biological and mechanical structures to create a tissue-based valve with low thrombogenicity Term ‘ bioprosthesis ’ by Carpentier .

35. BIOPROSTHETIC HETEROGRAFTS Porcine aortic valves or pericardium Pericardium usually bovine in origin but may be porcine or equine Most of them mounted on a metallic stent Pericardial valves are almost invariably stented. 1 st , 2 nd or 3 rd generation- According to the method of tissue fixation and treatments With 3 rd gen valves offering improved freedom from structural degeneration.

36. STEPS IN DEVELOPMENT

37. PORCINE VALVES CARPENTIER -EDWARDS BIOPROSTHESIS Porcine valve tissue fixed in glutaraldehyde, Stents: Elgiloy (cobalt-nickel alloy) wire. Sewing ring : knitted Teflon X-ray Appearance: A continuous thin wire bent into 3 "U" shaped loops Others : Hancock Porcine Xenograft & Medtronic Drawbacks : a large number of valves to be harvested for appropriate size and suitable quality.

38. PERICARDIAL VALVES Ionescu– Shiley pericardial xenograft first one to be marketed (1976) discontinued owing to structural failure. The Carpentier –Edwards pericardial valve introduced - 1981 & approved for commercial use in 1991 Superior haemodynamic performance with better durability Mitroflow valve by Sorin Group Latest approval (2007)

39. STENT LESS VALVES Stent major hindrance to hemodynamic profile in Bioprosthetic valves Porcine aortic root or Dacron cloth instead of stent Larger EOA Useful for small aortic roots More physiological flow & low transvalvular gradients. In aortic position - distributes mechanical stresses into the aortic tissue than on the leaflet tissue near the stents of traditional bio prostheses. Early post op gradients very low

40. STENTLESS VALVES Two types – Sub coronary & root inclusion Coronary reattachment may be required in later Technically challenging & longer bypass time , approved for AVR only at present

41. PERCUTANEOUS VALVES - AORTIC BALLOON EXPANDABLE EDWARD SAPIEN SERIES (Edwards Lifesciences, CA) SAPEIN , SAPIEN XT SAPIEN 3 MYVAL ( MERIL )

42. PERCUTANEOUS VALVES SELF EXPANDING EVOLUT -R & EVOLUT PRO ( MEDTRONIC) ACCURATE NEO ( SYMENTIS ) PORTICO (ABBOTT VASCULAR) ALLEGRA ( NVT AG) JENA VALVE MECHANICALY EXPANDING LOTUS VALVE (BOSTON SCIENTIFIC CORPORATION)

43. PERCUTANEOUS PULMONARY VALVES Bonhoeffer - first performed transcatheter PV implantation in 2000 MELODY VALVE Bovine jugular vein Platinum-iridium stent. EDWARDS SAPIEN PULMONIC TRANSCATHETER HEART VALVE Bovine pericardium Stainless steel stent.

44. TRICUSPID VALVE CAVI ( CAVAL VALVE IMPLANATATION ) IVC or Bi caval Balloon expndable TAVI devices Dedicated self-expandable CAVI devices ( TricValve ) TRICVALVE Self-expandable pericardial valve mounted on a nitinol belly-shaped stent with little radial force, specially designed for low-pressure circulation First case of TTVR in a human native TV was reported in 2014 by Kefer et al – Edward Sapiens valve The NaviGate bioprosthesis - currently the only available dedicated device allowing fully orthotopic TTVR in humans

45. SUTURELESS VALVES Initially developed in 1960s & abandoned High rates of complications such as paravalvular leaks and thromboembolic events. Now being reintroduced for aortic position Reduces procedural time

46. VALVE PHYSIOLOGY The type and size of prosthesis determines what is considered normal function (Gradients, EOA , and degree regurgitation) for that valve for that patient. ALL PROSTHETIC VALVES ARE

47. VALVE AORTIC MITRAL VELOCITY MEAN GR VELOCITY MEAN GR Starr Edward 3.1 ±0.5 24±4 1.8 ±0.5 7±2 St Jude 3.0±0.8 11±6 1.5±0.3 5±2 Medtronic Hall 2.6±0.3 12±3 1.6±0.3 5±2 Aortic Homograft 0.8±0.4 7±3 1.5±0.4 4±2 Hancock 2.4±0.4 11±2 1.5±0.3 5±2 Carpentier’s 2.4±0.5 14±6 1.5±0.3 5±2

48. OPENING CLICK SYSTOLIC MURMUR IN MVR DIASTOLIC MURMUR IN AVR CAGED BALL LOUDER THAN CLOSING Grade 1 or 2 - TILTING DISK FAINT - Grade 1 or 2 BI LEAFLET FAINT . ABSENT - Grade 1 or 2 BIOPROSTHESIS 50% - HEARD Grade 1 or 2 -

49. FORWARD FLOW

50. COMPLICATIONS Non-physiological blood flow patterns in the vicinity of heart valves. High shear stress – mechanical damage - haemolysis and platelet activation Recirculation and flow stagnation – abnormal contact time between activated platelets, Elevated shear stress in tissue valves - leaflet calcification and tearing in tissue

51. REGURGITATION CLOSURE BACK FLOW Small displacement of blood caused by the motion of the occlude LEAKAGE BACK FLOW : true trivial or mild regurgitation at hinges & peripheries of the occluder . Prevents blood stasis and thrombus formation

52. NORMAL REGURGITATION Bjork- Shiley valve : small jets inside sewing ring, where the closed disc meets the housing Medtronic Hall valve : same jets + single large jet through central hole Bileaflet : Gaps around perimeter of valve between disc and valve housing and centrally, bileaflets meet – maximum regurgitation Tissue Valves : Nearly zero regurgitation

53. Paravalvular – always pathological Bioprosthetic pathological MR asessement difficult – acoustic shadows Suspect occult prosthetic mitral regurgitation Flow convergence downstream of the prosthesis during systole Increased mitral peak E-wave velocity (2 m/s) and/or mean gradient (5 to 7 mm Hg) DVI <0.45 Unexplained or new worsening of pulmonary arterial hypertension. ABNORMAL REGURGITATION

54. PRESSURE RECOVERY Sudden drop in pressure just proximal to valve – reagained only in distal aorta Over estimation of Valve gradients More pronounced in narrower aortas PR= 4v²× 2EOA/ AoA (1-EOA/ AoA )

55. EOA Calculated by the continuity equation ( PHT not reliable) is a better index of valve function than gradient alone In-vitro prosthetic area < native valve EOA for given prosthetic size differs between valves & normal reference range described for most of the valves for both positions Ratio of EOA to GOA known as coefficient of contraction ( usually 0.90 to 0.71) In-vivo prosthetic area further reduced by IVS hypertrophy, progressive endothelialization and tissue ingrowth  

56. PATIENT PROSTHETIC MISMATCH Normally functioning valve But EOA too small for the body surface area ( BSA = C.O requirement) Results in abnormally high post OP gradients Diagnosis  Calculating EOA indexed to BSA Threshold Values of Indexed Prosthetic Valve EOA for the Quantification of PPM Mild or Not Clinically Significant, cm 2 /m 2 Moderate, cm 2 /m 2 Severe, cm 2 /m 2 Aortic >0.85 (0.8–0.9) ≤0.85 (0.8–0.9) ≤0.65 (0.6–0.7) Mitral >1.2 (1.2–1.3) ≤1.2 (1.2–1.3) ≤0.9 (0.9)

57. PATIENT PROSTHETIC MISMATCH Moderate PPM → Frequent in both the aortic (20% to 70%) and mitral (30% to 70%) positions Prevalence of severe PPM ranges from 2% to 10% in both positions No improvement in functional class Reduced exercise capacity Reduced survival AV  no regression of LVH , MV  Persistent PAH & increased incidence of CCF

58. Normal Reference Values of EOAs for the Aortic Prostheses

59. Normal Reference Values of EOAs for the Mitral Prostheses

60. CHOICE OF PROSTHETIC VALVE

61. CHOICE OF PROSTHETIC VALVE REPAIR VS REPLACEMENT ? MECHANICAL VS BIOPROSTHETIC ? SURGICAL VS TRANSCATHETER ?

62. In younger patients (< 45 years) the ross procedure can be performed in a reference center (IIb C) A mechanical rosthesis may be considered if the patient is already on long-term anticoagulation (IIb C)

63. ANTICOAGULATION & ANTITHROMBOTIC TREATMENT

64. CXR / FLOUROSCOPY Carina Apex AV MV

65. CXR / FLOUROSCOPY - AP Aortic valve: Intersection of these two lines. Mitral valve: lower left quadrant (patient’s left). Tricuspid valve: lower right corner) Pulmonic valve: upper left corner LESS RELIABLE

66. CXR – DIRECTION OF FLOW INFERIOR  SUPERIOR : AORTIC SUPERIOR  INFERIOR : MITRAL

67. FLUROSCOPY Normal motion varies with each valve model and with each patient. Aortic prosthesis  RAO caudal and LAO cranial angles, Mitral prosthesis : visualised better in RAO cranial position PA view (0) and lateral (90) view - in-situ orientation of valve In profile projection - radiographic beam parallel to both the valve ring plane and the tilting axis of disc , allowing calculation of opening and closing angles en face projection - radiographic beam parallel to the valve outflow tract which is utilized only for mitral prostheses.

68. VALVE DEHISCENCE Rocking and tilting of the base ring of the prosthesis. >10° in the case of the mitral valve & > 6° in the case of aortic valve is highly suggestive of dehiscence. At least 40% of the circumference involved to be apparent in fluro – better identified in doppler

69. BIOPROSTHETIC VALVES Limited Utility The detection of calcium on the leaflets of a tissue valve is diagnostic of degeneration Does not allow assessment of its hemodynamic impact.

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