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Mitral Valve Disease

Mitral Valve Disease

1. Surgical Anatomy of the Mitral Valve

A. Leaflet
1) Anterior leaflet inserts on about 1/3 of the annulus
2) Posterior leaflet inserts into about 2/3 of the annulus
3) Posterior leaflet area is significantly larger than anterior leaflet area
4) The combined leaflet area is twice the mitral orifice
B. Chordae
1) Primary attachment to free margin
2) Secondary & tertiary attachment away from free margin
C. Papillary Muscles
1) Anterolateral and posteromedial supplying both leaflets

2. Mitral Stenosis

A. Etiology
1) Rheumatic
B. History
1) Dyspnea, fatigue, palpitations, hemoptysis
C. Physical exam: for mitral stenosis
1) Loud 1st heart sound, diastolic, rumble, opening snap
D. Chest X-Ray
1) Left atrial and right ventricular enlargement

3. Cardiac Catheterization

A. Mitral valve area = diastolic flow %pressure gradient (Gorlin formula)
1) Normal Mitral valve area 4.0-5.0 cm2
2) Symptomatic mitral stenosis 1.4-2.5 cm2
3) Critical mitral stenosis <1.0 cm2

4. Natural History

A. Mitral Stenosis
1) Continuous progressive, life-long disease
2) Slow, stable early course, latent period of 20-40 years from Rheumatic fever to onset of sypmtoms
3) Onset of symptoms to disability- 10 years
4) Atrial fibrillation 30-40%
4) More common in older patients
B. 10 year survival-- Overall 50-60%
1) Asymptomatic => 80% (60% no progression of symptoms)
2) Symptomatic 0-15%
3) Severe pulmonary hypertension <3%
4) Older patients with atrial fibrillation 25%
5) Normal sinus rhythm 46%
C. Causes of death
1) CHF 60-70%
2) Systemic embolism 20-30%
3) Pulmonary embolism 10%
4) Infection 1-5%

5. Indications for Intervention

A. Mitral stenosis- reparable valve
1) Prominent opening snap, no calcification
2) Pliable leaflets, commissural fusion
3) Chordae and papillary muscle normal
B. Balloon valvuloplasty vs open commissurotomy
1) Experience of operator
2) Left atrial thrombus or mitral insufficiency = open commissurotomy
C. Symptomatic patients (NYHA Functional Class III or IV)
1) MV area ə.5 cm2
2) PA pressure > 50 mmHg at rest- >60 mmHg exercise
D. Asymptomatic patients
1) New atrial fibrillation
2) Left atrial thrombus or embolism after anticoagulation

6. Indications for Surgery

A. Mitral valve stenosis- Mitral valve replacement
B. Symptomatic patients
1) NYHA functional class III-IV
2) MV area >1.5 cm2
C. Asymptomatic patients
1) PA pressure >60 mmHg at rest

7. Mitral Incompetence

A. Etiology
1) Myxomatous degenerations
2) Mitral valve prolapse
3) Ruptured chordae
B. History
1) Asymptomatic
2) Dyspnea on exertion
3) Congestive heart failure
C. Physical exam
1) Holosystolic at apex radiates to axilla
D. Chest X-Ray
1) LV and LA enlargement
2) Echocardiography
E. Best diagnostic tool or Mitral valve prolapse
F. Quantitative regurgitation
G. Direction of jet
1) Anterior (septal) = posterior leaflet prolapse
2) Cardiac Catheterization
H. Quantitative regurgitation
I. Assess function of pulmonary hypertension
1) ? Exercise
J. Coronary angiography
K. Natural history
L. Mitral valve prolapse is most common form of valvular heart disease
1) Affecting 2-6% of population
2) Probably overdiagnosed
M. Gradual progression of Mitral regurgitation results in enlarged LA and LV
N. Enlarged LA may result in atrial fibrillation
O. Moderate to severe Mitral regurgitation results in LV dysfunction, CHF, pulmonary hypertension
P. Prolonged asymptomatic phase accelerated phase, ruptured chordae tendinae
Q. Men age >45 are subject to complications
R. Sudden death rare <1% per year
S. Infective endocarditis- incidence extremely low, risk controversial, antibiotic prophylaxis advised
T. Occasionally presents as acute sever Mitral regurgitation requiring urgent operation

8. Mitral Incompetence- Indications for Operation

A. Acute symptomatic mitral regurgitation
B. Symptomatic or Asymptomatic Patients with LV Dysfunction
TYPEEFSystolic Dimension
Mild0.5-0.640-50 mm
Moderate0.3-0.550-55 mm
Severe<0.3>55 mm
C. LV dysfunction will persist, symptoms diminish, risk increase
D. Asymptomatic patients with atrial fibrillation or pulmonary hypertension
1) PA = >50 mmHg at rest, >60 mmHg exercise

9. Surgical approaches to the Mitral Valve

A. Left thoracotomy
1) Rarely used, redo
B. Right thoracotomy
1) For isolated redo MVR
C. Median sternotomy
1) Traditional through Waterston's groove
2) Through Waterston's groove with SVC detachment
3) Superior via dome of left atrium transseptal
D. Partial/mini-sternotomy

10. Surgical Procedures for Mitral Valve Disease

A. Stenosis
1) Closed mitral commissurotomy
2) Open mitral commissurotomy
3) Mitral valve replacement-- likely with thick anterior leaflet, calcification, mitral regurgitation, thick short chordal
B. Regurgitation
C. Mitral valve repair
1) Repair likely with posterior leaflet prolapse or ruptured chordal
2) Repair less likely with anterior leaflet prolapse
D. Mitral valve replacement with preservation of chordae tendinae
1) Mechanical bioprosthesis
2) Bioprosthesis (stented porcine aortic)
3) Mitral homograft

11. Risk Factors for Mitral Valve Replacement

A. Type of prosthesis is not a risk factor
B. Previous valvotomy or commissurotomy not a risk factor
C. NYHA Class (MR, LV size, LA size)
D. Age
E. Tricuspid valve disease
F. Coronary artery disease (3 x risk)
G. Chordal preservation reduces risk

EXTENDED OUTLINE

1. Structure and Pathology

A. crucial to understand the anatomy of the mitral valve in order or perform valve repair
B. mitral valve is composed of five separate components
1) valvular leaflets
2) annulus
3) chordae tendinae
4) papillary muscles
5) left ventricular wall

2. Ischemic Mitral Valve Disease

A. myocardial ischemia from coronary artery disease affects mitral valve function in many ways
1) ischemia leads to loss of contractility which affects mitral valve competence
2) lateral ventricle wall and papillary muscle dysfunction
a) anterior papillary muscle is supplied usually by the LAD but can be from a diagonal, ramus or proximal marginal arteries
b) posterior papillary muscle is usually supplied by RCA or distal CX
c) ischemia in these distributions can lead to papillary muscle dysfunction
3) papillary muscle necrosis and rupture leads to acute cardiac decompensation
4) left ventricular aneurysm may lead to valvular incompetence
5) the chordae tendinae and valve leaflets are avascular and not directly affected by ischemia
6) annular dilatation can lead to MV incompetence
a) up to 20% of patients undergoing surgery for CAD will have some MV regurgitation
b) often with correction of underlying CAD with improve MV regurgitation

3. Rheumatic Disease

A. mitral leaflets are the most common structures involved
B. mitral stenosis occurs distant from initial episode
C. rheumatic heart disease can manifest itself as mitral stenosis, insufficiency or both
D. rheumatic process includes:
1) leaflet thickening, calcification and retraction
2) periannular calcification with limitation of annular motion
3) leaflet fusion (esp. at the commussural regions) and “fish-mouthing”
4) chordal thickening , shortening, and fusion
5) papillary muscle inflammation

4. Myxomatous Degeneration

A. primarily affects the chordae and leaflets in older patients
B. chordae elongate leading to MV regurgitation
C. myxomatous degeneration with prolapse is a common cause for mitral valve operation

5. Endocarditis

A. leaflet tissue is commonly involved resulting in vegetations and destruction of leaflet
B. may result in annular or periannular abscess
C. destruction of leaflets, chordae, or papillary muscle may result in rupture and massive MV regurgitation
D. annular involvement of one valve may result in involvement of the other valve (aortic)
Symptoms

6. Mitral Stenosis

A. rheumatic fever is most common cause
B. symptoms are usually insidious occurring over several years after infection
C. symptoms include decreased exercise tolerance, dyspnea, orthopnea and PND
D. pulmonary edema is a late sign
E. hemoptysis
F. the onset of atrial fibrillation often worsens the symptoms of mitral stenosis
1) thromboembolism occurs in 20% patients
2) may occur without presence of atrial fibrillation
3) incidence of thromboembolism correlates with size of the left atrial appendage
G. pulmonary hypertension can occur and is usually reversible after valve replacement

7. Mitral Regurgitation

A. symptoms depend on the acuteness of onset
B. if acute in onset secondary to papillary muscle rupture or leaflet disruption then patient will present with pulmonary edema and right heart failure
C. patients with chronic mitral regurgitation with remain aymptomatic for several years until left ventricular failure develops at which time dyspnea occurs
Physical Examination

8. Mitral Stenosis

A. loud first heart sound, diastolic murmur, and sometimes
B. an opening snap murmur is best heard over the apex
C. opening snap occurs when the leaflets are mobile
D. when leaflets are rigid and calcified there is no opening snap
E. may be evidence of peripheral arterial embolism
F. signs of right ventricular failure may be present
1) RV heave
2) triscupid regurgitation
3) hepatomegaly, ascites
G. normal sized ventricle

9. Mitral Regurgitation

A. left ventricular enlargement
B. high pitched apical systolic murmur that radiates to the axilla
C. in a prosthetic valvular leak, the murmur may radiate in any direction
D. holosystolic murmurs are indicative of severe MR
E. in ischemic regurgitation the murmur may vary in intensity depending on the presence of ischemia and papillary muscle dysfunction
F. findings of right ventricular failure may occur in advanced disease

10. Laboratory Examinations

A. EKG may reveal atrial fibrillation and/or enlargement
B. CXR may reveal ventricular enlargement, pulmonary edema or annular calcification
C. ECHO- mainstay of mitral valvalur pathology diagnosis
1) reveals leaflet thickening and abnormal excursion
2) doppler ECHO can estimate transvalvular gradient
3) detection of atrial thrombi and valvular vegetations
D. cardiac catheterization
1) completed if coronary artery disease is suspected
2) can calculate valve area utilizing the Gorlin formula
Indications for Operation

11. Mitral Stenosis

A. asymptomatic patients are generally not recommended for operation
B. patients with few symptoms that are otherwise healthy should undergo operation
C. patients with severe mitral stenosis should undergo operation
1) normal orifice is 4-6 cm2
2) 2-4 cm2 is mild
3) < 1 cm2 is severe

12. Mitral Regurgitation

A. indications for operation are more complex than mitral stenosis
B. endocarditis and acute ischemic mitral regurgitation are clear indications
C. patients with MR secondary to myxoid degeneration or rheumatic disease typically have an insidious onset of symptoms after several years of quiescent disease
1) patients with MR become symptomatic only after left ventricular function has been irreversibly damaged at which time, results are less favorable
2) ejection fraction is a poor measure of function because it may be preserved even after irreversible LV failure has occurred
3) when the ejection fraction is 40% the left ventricular function is severely impaired
4) it is important to assess status of the LV for prognostic reasons and to determine optimal timing for operation
a) measurements of end-systolic volume or diameter have been found to be reliable indices for LV function
b) patients with end-systolic volume <30 mL/m2 or an end-systolic diameter of < 40 mm will have normal LV function post-op
c) patients with end-systolic volume > 90 mL/m2 or end-systolic diameter > 50 mm LV function is irreversibly impaired and surgical mortality is higher

13. Operation General Considerations

A. three classes of techniques
1) valve repair
2) valve replacement
3) transcatheter
B. patient-specific considerations
1) presence of cardiogenic shock
2) is valve repair is feasible
3) presence of atrial fibrillation
4) ability to take anticoagulants

14. Choice of Incision and Cannulation

A. median sternotomy- most common
B. right thoracotomy
C. left thoracotomy
D. dual or single caval cannulation
E. antegrade or retrograde cardioplegia

15. Left Atrial Incision

A. “standard approach” - incision parallel to intraatrial groove in to lateral atrium posterior to SVC and IVC
B. superior septal- incision in roof of left atrium between aorta and SVC
C. transseptal- incision in right atrium and through intraatrial septum

16. Chordal Preservation

A. controversy exist on how to deal with native mitral vavle tissue
B. in endocarditis with infected tissue, or with heavily calcified valvular apparatus, complete excision is necessary
C. there is some evidence to suggest preservation of chordae and the posterior leaflet is important in maintaining the annuloventricular apparatus and normal left ventricular function
D. techniques
1) preservation of posterior valve
2) elliptical excision of the anterior leaflet
3) excision and re-attachment of the chordae

17. Atrioventricular Groove Disruption

A. occurs with over aggressive resection of valvular apparatus
B. usually a fatal complication
C. requires re-institution of bypass, removal of valve, repair of disruption and valve replacement
D. retention of the posterior leaflet had decreased the incidence

18. Associated Operations

A. when coronary bypass is also required, the distal anastamoses are completed first followed by valve replacement in order to avoid atrioventricular disruption
B. when triscupid valve procedures must be completed then a transseptal approach can be utilized
1) the triscupid procedure can be completed after the mitral valve has been replaced and the left atrium closed with the aortic cross clamp removed
C. with combined aortic valve replacement, care must be taken when excising the intra-annular region to avoid damaging the aortic annulus
Choice of Valve

19. Bioprosthetic Valves

A. low incidence of thromboembolism
B. average durability is 10-15 years
C. porcine valves may be chosen in females who desire to become pregnant
D. glutaraldehyde-preserved stented porcine tissue valves are the most common
E. bovine pericardial valves were found to degenerate rapidly
F. structural deterioration
1) mitral stenosis secondary to calcification, esp. in young patients
2) mitral insufficiency form cuspal tearing and detachment
G. when bioprosthetic valve degeneration is detected, repair shoud be completed before the onset of symptoms due to the possibility of rupture and embolism
H. some recommend patients should receive 3 months of anticoagulation therapy until endocardial healing is completed

20. Mechanical Valves

A. durable with valve life up to 20 years
B. requires anticoagulation (INR 2.5 -3.0)
C. usually indicated in young patients or patients with chronic atrial fibrillation
D. three types of mechanical valves
1) caged- ball (Starr-Edwards)
a) first implanted in 1965
b) incidence of thromboembolism is higher than bileaflet vavles
c) long-term durability
d) high profile and contraindicated in patients with a small left ventricle
2) tilting disc (Medtronic, Omniscience)
a) low profile and useful in patients with small ventricles
b) orifice larger than caged- ball
c) meticulous surgical technique is required during implantation to avoid subvalvular interference
3) bileaflet (St. Jude, Carbomedics)
a) most common mechanical valve used in the U.S.
b) surgical technique important - no subvalvular interference
c) incidence of valve thrombosis is low
Results

21. Hospital Mortality

A. higher mortality than aortic valve replacement
B. the Society of Thoracic Surgeons National Cardiac Surgery Database is the largest database of cardiac surgical procedures in the U.S.
1) contains 345,000 cases with 9,000 mitral valve replacements
2) results of univariate analysis of the Database with the 1991 to 1993 experience (3625 patients)
a) operative mortality 2.5% for males and 3.9% for females for first time elective cases
b) coincident CAD increases operative risk (mortality 6.1% men, 12.2% women)
c) left ventricular end-systolic diameter is the most sensitive indicator of irreversible LV dysfunction from mitral regurgitation and predicts mortality

22. Overall Survival and Function

A. two most important factors are postoperative left ventricular function and age of patient
B. patients with impaired left ventricular function have decreased long-term survival
C. actuarial 5-year survival after mitral valve replacement in recent series is 80%, with a 10 year survival between 50 and 87%
D. a recent study demonstrated that in patients with combined coronary bypass and mitral valve replacement the actuarial 5-year survival to be 66% and 10-year survival of 31%

23. Bioprosthetic Valve Failure

A. a major risk is structural valve failure
B. infants, children and patients with chronic renal failure have a high incidence of structural failure
C. valves in the mitral position degenerate faster than those in the aortic position
D. follow-up is important to detect any structural failure
E. the two most common valves (Hancock and Carpentier-Edwards) show no difference in structural failure at 10 years with freedom from failure at 10 years between 60 and 78%
F. at 14 years, freedom from operation is between 27 and 43%

24. Thromboembolism and Bleeding

A. the percentage of patients free from thromboembolism at 10 years is similar whether mechanical or bioprosthetic valves are implanted with a rate of 1.6 to 2.9% per patient year
B. thromboembolism is higher with Starr-Edwards valves with only 55% of patients free of thromboembolism at 10 years
C. the incidence of anticoagulant-related hemorrhage is between 0.18 and 2.2 per patient year
D. bleeding is most common in the CNS, GI and GU tracts

25. Mechanical Valve Thrombosis and Structural Failure

A. the tilting disc valve is most susceptible to valve thrombosis
B. Bjork-Shiley valve has a thrombosis rate of 0.28% per patient year
C. St. Jude valve has a thrombosis rate between 0.09 and 0.3%
D. structural failure is rare in mechanical valves with three studies demonstrating no structural failure with St. Jude valves in a 10-year follow-up

26. Paravalvular Leak

A. presence of active native valve endocarditis is a risk for developing a paravalvular leak
B. patients with annular and atrial wall calcifications also have a higher incidence of leak
C. prosthetic valve hemolysis is most often related to paravalvular leaks
D. some valves (Bjork-Shiley) have a higher basal state of hemolysis
E. bileaflet valves have been found to be relatively free of chronic hemolysis

27. Prosthetic Valve Endocarditis

A. most important factor is the presence of native valve endocarditis
B. several series have reported rates of endocarditis of 0.06 to 0.4%
C. early mortality as high as 75%
D. indications for prosthetic valve rereplacement include septic emboli, persistent sepsis, and hemodynamic instability
E. infections caused by Staphylococcus aureus, gram negative organisms, and Candida albicans should lead to early consideration of valve rereplacement