Mitral Valve Anatomy-important Anatomic Relationship

The functional components of the mitral valve apparatus include:

Annulus

Leaflets

Chordae

Papillary muscles

LV wall

Abnormality in any of these component will result in mitral regurgitation.

SLIDE 3 - PICTUREFIGURE 1

MITRAL VALVE

Lateral papillaryMuscle

PosteriorAnnulus

Posterolateralcommissure

Anterior Annulus Anterior leaflet Anteromedial commissure

Posterior leaflet(3 lobes)

Chordae tendinae

Medial papillarymuscle

Left mainCoronary artery

Intervalvulartrigone

Circumflexcoronary artery

Anterolateralpapillary muscle

Posterior leaflet

Left coronary

sinus

Noncoronarysinus

Anterior leaflet

SecondaryChorda tendinea

Coronary Sinus

Tertiary chordatendinea

Primary chordatendinea

Posteromedialpapillary muscle

Fiber Dimensions Calculated

Spherical LV Model (`100g)

DIASTOLE SYSTOLE

OBSERVED

DOG LV

The left ventricular wall

composed of muslce fibers,

connective tissue, fat neuro-

vascular structures and

lymphatics

Photomontages assembled from electron micrographs of dog LV cells are from control (A), congestive heart failure due to mitral regurgitation (B), and recovery state after successful mitral valve surgery (C).

Electron micrograph of adult LV canine myocardium. Long axes of several cells cross the figure from left to right. Arrows mark the location of boundaries between adjacent cells. Large open spaces are capillaries perfused with fixative.

Schematic illustration of substructure of the connective tissue matrix of the myocardium.

Myocyte

Struts

CapillaryTendon

Stranos

Myofibril

Weave

Ephysilus

Systolic Torsion of LV

Asymmetry of fiber radii, sarcomere

length and electrical activation allows

torsion of the apex relative to the base.

Model for generation of torque for LV wall. Vectors for force generation at the epicardial and endocardial surfaces could neutralize each other. The epicardial fibers at the epicardial surface have a longer radius and a more powerful moment arm. Sarcomere lengths, activation time, and infolding of the wall contribute to heterogencity of the relation between structure and function between the inner and outer regions of the wall. Differences in the total force generated are believed responsible for the LV systolic twist.

Base

Endocardium

Apex

Epicardium

Mechanism of mitral regurgitation

Classification of Structural Valve Abnormalities

Type

I Normal leaflet motion

Annular dilation

Leaflet perforation

I I Leaflet prolapse

Chordal rupture

Chordal elongation

Papillary muscle rupture

Papillary musle elongation

I I I Restricted leaflet motion

Commissure fusion

Leaflet thickening

Chordal fusion and thickening

Abnormality

Etiology I ncidence

Degenerative 87%

Endocarditis 6%

Rheumatic 4%

Miscellaneous 3%

Mechanism I ncidence

Valvular Prolapse 94%

Posterior leaflet prolapse 66%

10%

Bileaflet prolapse 18%

Ruptured chordae tendineae 74%

Anterior leaflet prolapse

Etiology of Mitral Regurgitation in Patients Undergoing Valve Repair

Pathophysiological Changes in Mitral Regurgitation

Decrease left ventricular impedance

Increase left ventricular end-diastolic volume

Increase stroke work and afterload

Decrese ejection fraction and increase left ventricular end-systolic dimension

Myocardial fibrosis and end-stage cardiomyopathy

The Natural History of Mitral Regurgitation

Mitral regurgitation is a progressive disease

With an increase on average of 7.5 ml/year for regurgitant volume and of 5.9 mm2/year for the effective regurgitant orifice.

The progression of mitral regurge also cause progression of LV remodelling at the same rate.

Importantly, progression is not uniform, 10% of mitral regurgitation regress spontaneously

The rate of reversal varies 6 weeks to 1 year

The Natural History of Severe Mitral Regurgitation

High morbidity at 10 year:

Atrial fibrilliation - 30%

Heart Failure - 60%

Sudden death at the rate of 1.8% per year

Timing of Surgery

What information is needed to define the timing of mitral surgery?

Symptoms-Functional Class Impact of Pre-operqtive symptoms on survival after mitral surgery

90+2

76+5

48+4

73+3

NYHA I-IINYHA III-IV

P<0.0001

100-

80-

60-

40-

20-

Su

rviv

al (

%)

N8I-II 199 192 187 184 181 169 125 95 63 42 34

III-IV 279 249 236 227 211 201 174 183 103 74 51

Figure 1. Overall postoperative survival compared between patients in NYHA Class I/II and patients in Class III/IV – Numbers at bottom indicate patients at risk.

0

0 1 2 3 4 5 6 7 8 9 10Years

Left Ventricular Function

Ejection Fraction

Left ventricular and systolic dimension

Assessed by echocardiography

Su

rviv

al (%

)

53%

32%

75%

EfEf 50-60%EF<50%P-0.0001

Years0 2 4 6 8 10

100

80

60

40

20

0

Degree of mitral regurgitation-hymodynamics Regurgitant volume (R.Vol.)

Effective regurgitant orifice (ERO)

Assessed by quantitative doppler echo

The respective thresholds for severe mitral regurgitation are (R.Vol.) > 60 ml. and ERO > 40mm2

Timing of Surgery

Translate into_when the patient seen_promptly provided no major comonbidities

The concept of waiting fro signs of early LV dysfunction is not advised

QUESTION:

Should we advise follow-up with medical treatment?

ANSWER:

NO, even if ejection fraction is low.

Operative mortality is not excessive.

Post operative complications are often delayed.

The precision of the prediction of the outcome is imperfect.

Mitral Valve Surgery

The optimal intervention for mitral surgery is valve repair.

Superior hemodynamics and ventricular function.

Less distortion of ventricular shape.

Avoidance of prosthetic valve and related complications.

Excellent long term clinical outcome.

Mitral Valve Repair

Leaflet plicationMcGoon Plication

Posterior leaflet excision [carpentier] Posterior leaflet prolapse

2 to ruptured or elongated chordae.

Posterior leaflet

Rupturedchordae

Repairleaflet

Supported repair

Repair annulus

Excise unsupportedleaflet

Subvalvar apparatus inspection with a nerve hook. The middle portion of the leaflets is identified

The central stitch is used to check the symmetricity of the orifices.

Edge-Edge Technique [Alfieri] Innovative method for mitral valve

repair.

A running suture along the free edge of the leaflets is done.

Chordal Repair Anterior leaflet prolapse

Excise unsupportedleaflet

Anteriorleaflet

Ruptured\Chordaetendineae

Posterior leaflet Mobilize apposingposterior leaflet

Transfer supportedposteior leaflet

Attach posteriorleaflet and

repair annulusCompleted repair

CONCLUSION:

Mitral regurgitation is a surgical issue.

Timing of mitral surgery still remained one of the most vexing problems of clinical cardiac science.

The concept of waiting for signs of early LV dysfunction not exists anymore.

The outlook is poor for patients who are treated medically.

Chronic severeMitral regurgitation

No symptoms Symptoms

Echocardiography Echocardiography

Left Ventricular ejectionFraction >0.60

and end-systolicDimension <45 mm

Left Ventricular ejectionFraction >0.60or end-systolic

Dimension >45 mm

Mitral valvereparable

Mitral valvenot reparable

No atrial fibrillationor pulmonaryhypertension

Atrial fibrillationor pulmonaryhypertension

Clinical andEchocardiographic

Follow-up

Mitral-valve surgery(valve repair preferredif technically feasible)

Ejection fraction>0.30

Ejection fraction>0.30

Mitral-valvereplacement

Mitral-valvereplacement

Management of Chronic Severe Mitral Regurgitation

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