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Mitral Valve Replacement William Kent CV Surgery Rounds February 13, 2009 1 Royal College Objectives 4. VALVULAR HEART DISEASE 4.1. Knowledge 4.1.1. Principles of medical and surgical management of patients with valvular heart disease. 4.1.2. Anatomy of the cardiac valves and relationships to adjacent structures. 4.1.3. Natural history of all forms valvular heart disease. 4 1 4 P i i l and use of i 4.1.4. Principles d i techniques f valvular h t di f imaging t h i for l l heart disease including cardiac auscultation, echocardiography including transesophageal echocardiography (TEE), cardiac catheterization and hemodynamic evaluation, magnetic resonance imaging (MRI). 4.1.5. Indications for medical and surgical intervention. 4.1.6. Alternative surgical approaches to cardiac valves. 4.1.7. Advantages and disadvantages of available valve repair methods/prostheses. 4.1.8. Techniques for valve surgery including methods of valve repair and replacement, aortic root enlargement, and management of complications of valve surgery. 4.1.9. Guidelines for reporting valve results including time-related multivariable analysis of morbidity/mortality. 2 Outline Historical background Indications: Mitral stenosis Mitral regurgitation Ischemic mitral regurgitation The operation: Chordal preservation techniques Valve choice: Mechanical Bioprosthetic Results Summary 3 Historical background Mechanical Valves: 1960 – first successful prosthetic mitral valve was Braunwald, implanted by Nina Braunwald age 32, at the NIH Homemade device she had designed with flexible polyurethane and teflon chordae The patient was discharged home and lived several months 4 Historical Background 1961 – St Ed d ball Starr-Edwards b ll and cage mitral valve began commercial production Albert Starr, a cardiac surgeon Edwards, and Lowell Edwards a mechanical engineer Became the “gold standard” for almost 10 yrs Function: Lateralization of forward flow with turbulence and cavitation Increased risk of thromboembolism and hemolysis 5 Historical background 1970’s – Bjork-Shiley tilting disk valve became the leading valve Better hemodynamics Opening angle: A balance between resistance to forward flow and regurgitant volume Meticulous technique is important because retained leaflets can cause subvalvular interference 6 Historical background 1980’s – Bileaflet St. Jude Medical valve Most commonly used worldwide More uniform, central and laminar flow Asynchronous closure of leaflets can result in large regurgitant volume Improved hemodynamics with more complete valve opening 7 Historical background Bioprosthetic valves: Hancock (1970) in the U.S. and Carpentier in Paris (1976) developed the first glutaraldehyde p fixed porcine aortic valve 20% failure within 10 years and ~50% at 15 years Bovine pericardial valves Pericardium mounted to fabricate a trileaflet valve Improved hemodynamic function with less flow resistance due to a more regular cone shape of the open valve 8 Diagnosis W k Workup: ECG – detection of afib or signs of ischemia Echocardiography – the most specific and sensitive method of diagnosing and quantifying severity of MS C di catheterization i no l Cardiac th t i ti is ti l longer routinely recommended: Catheterization is invasive and not as accurate as echocardiography Catheterization is indicated if there is a discordance between non-invasive findings and the clinical picture, to assess reversibility of pulmonary HTN and if there are risk factors for CAD 9 Indications: Mitral stenosis Rheumatic fever is the principle cause Ab’s to the strep M protein cross-react with endocardial tissue Pathology: Fusion of the valve leaflets at the commissures with shortening and fusion of the cordae tendinae and thickening of the leaflets from fibrosis and calcification Normal mitral valve area 4 6 cm2 4-6 Hemodynamic disturbance occurs if <2 cm2 Symptoms develop <1.5-2 cm2, severe if <1 cm 10 Indications: Mitral stenosis AHA Guidelines: JACC 2006;48:598-675 11 Indications: MR Primary (Structural): Derangement of the valve itself causing backflow, LV volume overload and LV myocardial dysfunction Secondary (Functional): V l it lf is normal. LV i d Valve itself i l d by ischemia is damaged b i h i or dilated cardiomyopathy causing annular dilation or papillary muscle dysfunction The treatment for primary MR is straightforward e the treatment o secondary as while t e t eat e t for seco da y MR has traditionally been more controversial Carabello, B.A. (2008) JACC, 52(5): 319-26 12 Pathophysiology Primary MR: A valve problem most commonly from degenerative, prolapsing myxomatous leaflets The incompetent valve imparts a volume overload that leads to LV remodelling, myocardial dysfunction and heart failure Corrected only with restoration of valve competence There is unanimous agreement that MV repair is preferred over MVR when possible 13 Primary MR: Management AHA Practice Guidelines, JACC (2006);48(3):598 14 MV Repair vs. MVR 184 patients in Finland Primary mitral valve procedure for MR between 1992-1996 Most were degenerative pathology Non-randomized Propensity score analysis 5 yr survival: MVP: 81.2% MVR: 73.5% Jokinen et al., (2007) Ann Thorac Surg; 84:451 15 MV Repair vs. MVR Recent meta-analysis: 29 studies between 1960 and September 2005 Approximately 10 000 subjects Four groups: Ischemic, degenerative, rheumatic and mixed Survival outcome favoured repair in three disease groups (rheumatic, mixed and degenerative) No survival difference for the ischemic MR group Shuhaiber & Anderson (2007) Eur J Cardio-thoracic Surg 31:267-75 16 MV Repair vs. MVR 17 MV Repair vs. MVR Why does repair lead to better outcomes? Mitral valve is an important component of the LV Maintains LV shape and chamber contractility C ti l includes destruction f the it l Conventional MVR i l d d t ti of th mitral valve apparatus and causes a decrease in chamber contractility This realization suggested that LV systolic function might be optimized if the subvalvular apparatus was preserved 18 Annulo-Ventricular Continuity 1922 – the concept of annulo-ventricular continuity was proposed LV geometry and function are a result of a dynamic interaction between the mitral annulus and the LV wall P ill l d h d d t Papillary muscles and chordae moderate LV di t i during distension d i diastole and wall tension during systole When papillary muscles contract, the closed MV is drawn into the LV cavity decreasing it’s longitudinal axis 1964 – Lillehei introduced a technique to preserve the h d d leaflets d t d d ti in t lit chords and l fl t and reported a reduction i mortality from 37% to 14% 19 Law of Laplace In an enlarged LV the T=(P*R)/M radius increases R= radius T= tension in the wall P= transmural pressure P t l M= wall thickness To create the same pressure during ejection, larger wall tension must be developed requiring more energy 20 MVR: Choral Preservation This idea challenged the previous explanation for the low cardiac output syndrome after MVR: Elimination of systolic unloading into the low- impedance left atrium after MVR increases LV afterload and decreases LV ejection performance Concern for the potential of retained valvular apparatus interfering with the valve or limiting the size of prosthesis limited the acceptance of Lillehei’s technique 21 MVR: Chordal Preservation 1981 – By studying LV-grams in dogs, Tirone David demonstrated improved LV function after chordal preservation He went on to describe his technique is subsequent papers 1992 - Rozich and Carabello used echo to compare ejection performance before and after surgery with and without chordal preservation 2008 – Meta analysis of 24 studies including 2933 Meta-analysis patients comparing outcomes of preservation vs. non- preservation (4 were prospective, randomized) 22 MVR: Chordal Preservation Postoperative ejection fraction after mitral valve replacement with (circles) and without (squares) ti f th preservation of the chordae tendineae Ejection fraction decreases significantly without chords severed but is preserved with choral preservation. Rozich et al., (1992) Circulation 86:1718 23 MVR: Chordal Preservation Athanasiou et al. (2008) Eur J Cardio-thoracic Surg; 33:391-401 24 Technique 25 Technique Standard posterior leaflet preservation: Plication of the posterior leaflet in the l t valve sutures annular-apical connection maintained with preservation of the chordae Reduction in the incidence of AV groove disruption 26 Techniques Neochordae N h d in rheumatic disease Lillehei’s technique t h i David’s technique 27 Technique: Calcified Annulus Annulo- ventricular continuity recreated using PTFE sutures as neochordae 28 Technique: Calcified Annulus Pericardial patch reconstruction after radical debridement of annular calcification 29 Technique: Calcified Annulus With dense annular f calcification, suturing the prosthesis to leaflet tissue is l i an alternative 30 Pathophysiology Secondary MR: Myocardial damage causes an anatomically normal valve to leak most commonly by annular dilation and rarely by papillary muscle dysfunction Even if the leak is corrected, the underlying cardiomyopathy still exists Central management question: Does the presence of MR in ischemic and dilated cardiomyopathy worsen prognosis? 31 Ischemic MR If MR is a cause for worsened prognosis, it should be corrected If MR is a by-product of disturbed LV geometry, correction may have little impact on outcome Traditionally, surgical treatment of IMR was associated with a high operative mortality (~20%) d thus d ( 20%) and th many advocated t d revascularization without MV intervention 32 Ischemic MR Today: Surgical risk is lower (<5% for combined CAB + MVR) It is known that revascularization alone is unlikely to improve moderate to severe MR Although not addressed by RCT’s it is accepted that RCT s, patients with severe IMR who also require CABG should have a surgical procedure The volume load associated with severe MR will further compromise LV function Mild/Moderate IMR is still controversial but retrospective data suggest a survival advantage with valve intervention 33 Ischemic MR Moderate IMR: Retrospective review of 176 patients from 1991-1996 2 groups: (repair or replacement) CABG + MVR ( i l t) CABG alone At 5 year follow-up a survival advantage was found with MVR in those with more advanced heart failure Harris et al., Ann Thorac Surg. (2003); 76(5): 1468 34 Ischemic MR Harris et al., Ann Thorac Surg. (2003); 76(5): 1468 35 Role for MVR in IMR? Many would argue NO Some suggest YES but in a specific patient population: Those with multiple, severe comorbidites – a reliable and rapid operation is in their best interest Those with a reduced chance of a successful repair: Complex jet on echo Extensive leaflet tethering Lateral wall motion abnormality Papillary muscle pathology Gillinov, A.M., Heart Fail Rev (2006); 11:231-239 36 Valve Choice Indications for mechanical valve: Young patients Patients in chronic Afib Any patient who wants to minimize the chance of reoperation Indications for a bioprosthetic valve: Considered to have better antithrombotic properties and hemorrhagic events but lack durability and thus are more suitable for older patients (>65 years) 37 Valve Choice AHA Practice Guidelines, JACC (2006);48(3):598 38 Results Over 90% of patients improve to functional class II or better Hospital mortality ranges from 5-9% in most recent series Late survival is ~50-60% at 10 years y Late morbidity: Thromboembolism is similar in bioprosthetic and mechanical valves at 1.5 – 2% per patient-year Anticoagulant hemorrhage occurs ~1-2% per patient-year Structural valve degeneration of bioprosthetic valves is ~60% at 60% 15 years Perivalvular leak occurs ~1% per patient-year Incidence of prosthetic valve endocarditis is ~1% at 5 years 39 Summary Th evolution of prosthetic valves h resulted i The l ti f th ti l has lt d in the bileaflet mechanical valve most commonly implanted in young patients and bioprostheses in older patients Operation is indicated: For symptomatic patients with mod/severe MS MVR is usually the procedure of choice For symptomatic and ASx patients with severe, structural MR MV repair is has a survival advantage over MVR For IMR if severe but controversial for moderate IMR Consider MVR in patients with multiple comorbidities 40 Summary The technique of choral preservation is important for maintaining annulo-ventricular function continuity and LV f With improved techniques and careful patient selection, outcomes continue to improve with perioperative mortality ~5% 41 Thank you 42
"Mitral Valve Replacement"