Mitral Valve

Question 1

Mitral Valve anatomy

• Posterior annulus = 2/3 of circumference; anterior = 1/3;
• Anterior leaflet = 2/3 of mitral orifice CSA; posterior leaflet = 1/3; line of apposition = closer to posterior annulus
• the leaflets are made of a spongy layer (on top) and a fibrous layer (bottom); the fibrous layer is continuous with the annulus

Answer 1

Mitral apparatus:

1) leaflets
2) papillary muscles: a) AL pap - single head; fed by Cx; b) PM pap - multiple heads; fed by RCA
3) Chordae - a) 1ary (free edge) from pap to free edge of leaflet; b) 2ndary (strut chordae) from pap to rough ventricular surface of leaflet; c) 3ary (basal) from pap or ventricular wall to base of leaflets;
4) MV annulus - contracts with ventricular systole to reduce MV CSA by 20-40%
5) LV

Question 2

MR - natural history

• ASx for a long time before Sx; b/c chronic MR well tolerated if LV preserved;
• LV deterioration is masked by unloading of LV thru leaking valve into LA –>pseudonormal LVEF
• Sx = fatigue, weakness, dyspnea, orthopnea, PND, pulmonary HTN and right heart failure (late)

Answer 2

Poor prognostic features of MR =

• Sx > 1yr
• afib
• age >60yrs
• EF100ml/m2; LVESV >60ml/m2
• LVEDD>7cm; LVESD>5cm; normal LVEDD

Question 3

Pathology of MR

Answer 3

• Chronic LV volume overload –> eccentric hypertrophy;
• Frank-starling maintains stroke vol initially
• eventually LV contractile function decline –>increase LVESV, increased LV filling pressures, increase LA and PV pressures–> pulmonary edema and CHF
• if LVEF<60%, systolic function is present for sure as some EF goes into LA;

Question 4

Classification of MR

Answer 4

Carpentiers:

1: Normal leaflet motion (prblm at the annular plane) - annullar dilation, leaflet perforation
2: Excess leaflet motion (prblm above the annular plane)- myxomatous degen, chordal rupture;
3: Restricted leaflet motion (prblm below the annular plane)
3a: restricted opening - RF
3b: restricted closure - ischemic CM

Question 5

Chronic MR Causes

Answer 5

• MD (t2)
• RF (t3a)
• ICM (t3b and t1)

Question 6

Acute MR causes

Answer 6

Chordal rupture (t2)
Infective endocarditis (t1)
Pap rupture (t2)

Question 7

Causes of Ischemic MR

Answer 7

• acute ischemic MR caused by - infarcted, ruptures or non-ruptured pap (t2)
• chronic ischemic MR (>1month) - occurs due to 1) restricted P2 and P3 of posterior leaflets due to LV dilation displacing the papilary muscles (t3b) and 2) functional dilation of MV annulus (t1)
• also get reduced LV force due to reduced LV function and reduced contraction force of annulus results in ischemic MR

Question 8

Indications of surgery in MR

Answer 8

Class 1: Acute - symptomatic severe MR
Class 1: Chronic severe:
-Symptomatic (NYHA 2 - 4) and ABSENCE of severe LVD (LVEF55mm
-Asymptomatic with moderate LVD (30-60%) and / or LVESD ge 40mm
-Repair over replacement is preferred for patients with chronic severe MR in highly experienced centres that do repairs

Class 2a (reasonable):

• Asymptomatic severe: repair in experienced centres (liklihood of repair >90%) with normal LVEF (>60%) and normal LVESD (50mmHg rest or >60mm exercise))
• Symptomatic with severe LVD (55mm in whom repair is likely

Class 2b (can be considered):

• severe chronic MR due to severe LVD (<40 in whom repair is not likely
• isolated MV surgery in patients with mild to moderate MR

Question 9

Survival

Answer 9

1 yr mortality

no MR - 6%; mild MR - 10%; mod MR -

Question 10

Bolling Approach

Answer 10

• 30-day OR mortality = ~4.5%
• Repair - problem is that they get recurrent MR around 4-5 years due to continuing LV remodelling
• in repair - Flexible vs Rigid rings (much higher recurrence in flexible rings)

Question 11

Echo criteria of severe MR:

Answer 11

VC >0.7cm
Color jets >40% of LA area
ERO ge 0.4cm.sq
Regurgitant fraction >50%
Regurgitant volume > 60ml
LVESD >40mm
LVEF <60%
Enlarged LA