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Mitral Valve Replacement

VIEWS: 91 PAGES: 42

									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

								
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