STS E Book - The Mitral Valve

Question 1

What are the trigones of the mitral valve

Answer 1

The two fibrous components whose limits define the fibrous portion of the mitral annulus. Near the commissures, where the mitral meets the aortic valve.

Question 2

The right fibrous trigone of the mitral valve is part of the central fibrous body of the heart, in continuity with what structures (3)?

Answer 2

The aortic valve, the tricuspid valve, and membranous septum

Question 3

What are the important markers of the mitral valve used for annuloplasty ring sizing? Why?

Answer 3

Intertrigonal distance, because the fibrous annulus remains unchanged across the spectrum of mitral disease

Question 4

What are the papillary muscles that support the mitral valve? What is their blood supply?

Answer 4

Anterolateral - LAD and Cx
Posteromedial - PDA

Question 5

What is the usual etiology of mitral stenosis?

Answer 5

Rheumatic fever in childhood or adulthood - definitive history can be obtained in about 50-60%.

Question 6

Does rheumatic fever affect women or men more?

Answer 6

Women by a 2:1 to 3:1 ratio, usually acquired before 20, becomes evident 1-3 decades later

Question 7

What is the underlying bacteria that causes rheumatic fever and thus rheumatic mitral stenosis?

Answer 7

Group A beta-hemolytic strep -> mimicry b/w strep antigens and heart tissue proteins -> antigen cross-reactivity + high inflam cytokine + low IL-4 -> auto-immune pancarditis -> valve leaflet (MV most common), endocardium, and myocardium damage -> commissural fusion, chordial fusion and shortening, leaflet fibrosis, calcifications

Question 8

What are the physiologic adaptations of mitral stenosis?

Answer 8

Ventricular filling restriction -> LA pressure inc -> TV gradient increase during diastole -> … -> chronic and progressive stenosis -> inc PVR and pulm HTN

Question 9

What are the valve area and transvalvular gradient consistent with mitral stenosis?
Diastolic pressure half time?

Answer 9

MVA < 1.5 cm^2 (MVA < 1 is very severe)
TVG >10 mm Hg

Other dx criteria: diastolic half-time >150 ms

Will cause elevated PASP >30

Question 10

How is mitral transvalvular gradient dynamic as it relates to heart rate?

Answer 10

With increased HR -> dec duration of LV filling during diastole -> inc mean TVG and LA pressure.
This can create situations where the TVG is only significant (and thus symptomatic) during exercise.

Question 11

Why is maintenance of sinus rhythm important for mitral stenosis patients?

Answer 11

Atrial contraction augments flow through the stenotic valve, thereby helping to sustain adequate forward cardiac output

Question 12

Why does maintaining sinus rhythm become difficult for MS patients?

Answer 12

High LA pressure -> LA hypertrophy and dilation -> disorganized atrial muscle fibers -> abnormal conduction velocities -> nonhomogenous refractory periods -> inc automaticity or re-entry -> AF -> atrial thrombus and dec hemodynamic stability.

Eventually PASP >30.
MS = MVA < 1.5 or DP1/2t > 150 ms.

Question 13

Describe the pathophysiology of pHTN in MS.

Answer 13

Passive transmission of high LA pressure (w/ severe enlargement of LA) -> PV HTN, pulm arteriole constriction -> pulm vasc obliterative changes -> PA systolic P >60 -> inc impedance to RV emptying -> RHF and TR.

Elevated PASP >30 is a hemodynamic consequence of severe MS.

Question 14

How is frailty caused by MS?

Answer 14

“Cardiac cachexia” can be caused by the low CO, CHF, and lethargy associated w/ MS

Question 15

Describe the TTE findings of rheumatic mitral stenosis

Answer 15

Reduced diastolic excursion of the leaflets, thickening or calcification of the valvular and subvalvular apparatus; M-mode can show thickening, reduced motion, parallel movement of the anterior and posterior leaflets during distole

Question 16

How might a cardiac cath help with mitral stenosis workup?

Answer 16

LHC for coronary anatomy for older pts that have CAD risk; RHC for CI and pHTN.

Question 17

What are the three general pathoanatomic types of MR based on leaflet motion (Carpentier)?

Answer 17

I: normal leaflet
II: prolapse or excess motion
III: restricted motion
- a: diastole
- b: systole

Question 18

Most common cause of primary MR?

Answer 18

Myxomatous degeneration - thickened and opaque, and the degenerative process may extend down the chordae and out onto the annulus. Histologically, elastic fiber and collagen fragmentation and disorganization are present, and acid mucopolysaccharide material accumulates in the leaflets.

PICTURE: Gross view of the surgical specimen from an insufficient mitral valve represented by the anterior leaflet. A - The atrial aspect; B - The ventricular aspect. Note the diffuse thickening of the redundant leaflet with focal bulging towards the atrial aspect (asterisks) flagged as areas of valvar prolapse by the imaging exams. The chordae tendineae are also thickened. One of them shows a rounded tail end, which is characteristic of a secondary lesion due to its rupture (arrows); C and D - Photomicrography of the valve leaflet. In C, a central area of dense fibrous tissue (F) is shown, surrounded by a thick layer of loose connective tissue with myxomatous appearance (M). Hematoxylin-eosin stain, objective magnification 10X. In D, the valve section stained with Movat pentachrome is shown, revealing pale blue areas corresponding to myxomatous stroma. Black areas correspond to elastic fibers, focally disrupted (black arrowhead). Objective magnification 2.5X.

Question 19

Affecting 2-3% of the population, MR can be congenital/heritable or acquired. What is the congenital/heritable type?

Answer 19

Barlow valve in younger pts (A). Tend to have more myxomatous changes - thick, opaque.

Question 20

Affecting 2-3% of the population, MR can be congenital/heritable or acquired. What is the acquired type?

Answer 20

fibroelastic deficiency in older pts

Question 21

A minority of pts w/ MVP progress to sx mitral insufficiency (5-10%). What are the general etiologies of the mitral insufficiency in these pts?

Answer 21

chordal rupture and/or annular dilation

Question 22

What is the most common chordal rupture for the mitral valve?

Answer 22

P2.

Question 23

What is the difference in hemodynamic pathophysiology b/w acute MR and chronic MR?

Answer 23

Acute: LA is not as compliant -> high LA pressure -> rapid pulm edema and sx.
Chronic: compensatory changes inc LA and pulm bed venous compliance -> sx may not occur for years.

Question 24

How does MR affect preload and afterload?

Answer 24

preload is increased because of the backwards volume, and afterload is decreased d/t a parallel outflow track across the MV -> inc LV EF, inc LV EDV

Question 25

What EF in the presence of severe MR would indicate an advanced degree of myocardial dysfunction?

Answer 25

<55%

Question 26

Does atrial fibrillation occur more often in MR or MS?

Answer 26

MS

Question 27

What is the prognosis of those with rheumatic anterior leaflet MR as opposed to those with posterior?

Answer 27

Anterior rheumatic MR tends to improve with medical mgmt.

Question 28

How did Replogle subclassify ischemic mitral regurgitation?

Answer 28

1) sudden onset insufficiency d/t acute MI and papillary muscle rupture w/ or w/o LV wall dysfx
2) MR assd w/ CAD w/ normal leaflets
3) MR caused by end-stage ischemic dilated CM

Question 29

Boltwood found that in patients with nonischemic cardiomyopathy and mean EF of 25%, what echo measurement was the chief determinant mitral insufficiency?

Answer 29

Annular size, especially in the septal-lateral dimension correlates with the degree of LV systolic dysfunction in those with dilated cardiomyopathy

Question 30

What represents the sum effect of annular and subvalvular geometric deformations on leaflet coaption and is consistently identified in FMR and iMR as the main predictor of MR severity?

Answer 30

Leaflet tenting

Question 31

What is the trend seen in the difference in MR caused by anterior vs inferior MI?

Answer 31

Anterior MI:
More significant LV dysfunction and dilation - more like idiopathic dilated cardiomyopathy with leaflets widely tethered toward the ventricle with greater LV and mitral dilation.
Infarction of the anterior wall and the anterior papillary muscle does not result in MR until advanced LV dilatation and systolic dysfunction develop.

Inferior MI:
More localized tethering, more substantial perturbation of the mitral valve apparatus.
Systolic dysfunction of the posterior/inferior LV wall inclusive of the posterior papillary muscle with subsequent leaflet tethering appears to be the prerequisite lesion for the evolution of experimental IMR.

Question 32

In a recent report from the Cardiothoracic Surgical Trials Network of 301 patients with moderate IMR randomized to coronary artery bypass grafting alone or combined coronary artery bypass grafting with valve repair, the rate of death was 7.3% and 6.7% at 1 year, respectively.
What were some of the other outcomes?
What are the likely determinants of outcomes?

Answer 32

The combined group had longer bypass time, longer hospital stays, and more neurologic events.
In terms of the best type of valve surgery for patients with IMR, it is likely that the patient clinical condition and LV functional status are more powerful determinants of outcome, as opposed to whether a patient undergoes repair or replacement.

Question 33

The Cardiothoracic Surgical Trials Network multi-institutional randomized trial of 251 patients with severe IMR comparing complete rigid or semi-rigid ring annuloplasty with mitral valve replacement demonstrated what?

Answer 33

no difference in LV reverse remodeling or survival at 12 months

Question 34

Pt has severe symptomatic MS with AF and LA thrombus. What do you do?

Answer 34

Surgery.
PMBC is normally first line, but not in pts with LA thrombus and moderate to severe thrombus.

Question 35

Pt has severe symptomatic MS with moderate MR, and AF. What do you do?

Answer 35

Surgery.
PMBC is normally first line, but not in pts with LA thrombus and moderate to severe regurgitation.

Question 36

In the context of rheumatic mitral stenosis, the morphologic favorability of a stenotic valve for PMBC can be assessed using what?

Answer 36

the Wilkins Score

Question 37

What is the Wilkins Score (context of MS)?

Answer 37

Score to predict PMBC success when evaluating favorable valve anatomy. Consists of degree of leaflet mobility, valve thickness, subvalvular thickening, and valvular calcification are evaluated by echocardiography and each scored from 0 to 4.
Using this system, a total score of 8 or less is predictive of successful PMBC, with 72% sensitivity and 73% specificity.