MVD Flashcards
Embryology
- Fusion of inferior and superior endocardial cushion → from R and L AV junctions
- Endocardial cushion on L side forms anterior MV leaflet + L and non-coronary cusps → fibrous continuity
- Protusion/growth of AV mural endocardium: mural leaflet
o Formation of valvar mesenchyme
o Apoptosis of myocardial layer - Papillary muscle: columns in trabecular layers of ventricular muscle
Gross exam MVD
- Abnormal MV leaflets
o Rolling, notching
o Short and thick leaflets
o Cleft leaflets
o Leaflet adhered to septum - Fusion/thickening or elongation of chordae tendinae
o Short and stout chordae
o Long and thin - Upward malposition of pap muscles → horizontal chordal alignment
o Atrophied (flat and small) or hypertrophied
o Direct insertion of leaflet into pap muscle
o Fusion and displacement - Diffuse endocardial fibrosis of LA is common finding
- Concurrent malformation: SAS
Pathophys MVD
- Inadequate leaflet coaptation → MR
o L sided volume overload → LAE/LVE
MVD signalment
o Mostly large breed dogs: genetic basis suspected
Bull terrier
Great Dane
German Shepherd
o Most common CHD in cats
MVD PE
o Holosystolic plateau murmur over L apex
o Systolic click if prolapse
ECG MVD
- L sided cardiomegaly:
o LV = tall R waves
o LA = prolonged P waves - Atrial arrhythmias 2nd to LAE → Afib
- Ventricular pre excitation from anomalous atrioventricular pathway reported in dogs/cats
CTX MVD
- L sided cardiomegaly
- +/- pulmonary edema
2D echo MVD
- ↑ LV end diastolic diameter, normal wall thickness
- LAE
- MV: abnormal location, shape, motion, attachment of valve apparatus
o Large MV annulus - LV function is variable, may deteriorate w time
Doppler echo MVD
o Large MR
o LVOTO reported in cats 2nd to SAM
Differentiation MR MVD from MR DCM
- Large MR jet
- Loud HM
- FS >20%
- Normal to ↑ IVS motion vs LVFW
Cardiac KT angio MVD
o LV injection of contrast → confirm MR in LA
Cardiac KT pressure study MVD
o ↑ LV end diastolic P if CHF
o ↑ mean LAP and
o LA: ↑a wave, large v wave, low of x descent
Natural hx MVD
- Generally tolerated for many years
Treatment MVD
o CHF
o B blockers if LVOTO
o MV repair
MVS gross exam
- Diffuse abnormalities of valve components
o Thickened/rolled leaflet margins
o Shortened/thickened chordae tendinea
o Fibrous obliteration of interchondral spaces
Excessive valvular tissue
o Abnormal chordal insertion
o Pap muscle hypoplasia, ↓ inter pap distance/fusion - Annular hypoplasia
- Commissural fusion
o Restriction of MV motion
o Narrowed central orifice
Common associated defect MVS
- SAS: can be present from
o Redundant MV leaflet tissue in LVOT
o Anomalous MV leaflet/chordal attachment to IVS → DLVOTO
Other types of MVD
- Double orifice MV
- Mitral arcade = hammock valve
- Parachute MV (asymmetric)
- Cleft MV
- Straddling MV
Double orifice MV
o Accessory bridge or tissue → partially/completely dived mitral inlet into 2 orifices
Unequal, smaller orifice toward anterolateral or posteromedial commissure
o Usually associated w other congenital dz
Mitral arcade
hammock valve
o Thickened MV leaflets, inserting directly into LV wall or pap muscle
o Absent/short chordae: muscularization of chordal apparatus
o Band of fibrous tissue: free margin of valve leaflets → pap muscle
Parachute MV
o Unbalanced chordal attachment to single pap muscle (single or dominant pap muscle)
Short and thick chordae
Variable pap muscle anatomy: absent, fused, single
o Absent of fused commissures
o Centrally located orifice above single pap muscle
Cleft MV
complete or tip only
Straddling MV types
o Type A: crest of IVS
o Type B: septal pap muscle of RV
o Type C: mural pap muscle of RV → ↑ override
Other defects w/ inlet obstruction
- Cor triatriatum sinister: abn insertion of PV into LA → obstruction of PV return
o LAA in DISTAL chamber - Coronary sinus obstruction
o w/ persistent LCrVC - Supravalvular mitral stenosis: ring of fibrous tissue above MV
o LAA in PROXIMAL chamber
o Male cats/Siamese overrepresented - MV atresia/hypoplasia: hypoplasia of all components of apparatus
MVS histo
- Fibrous tissue
- Myxoid dysplasia
Pathophys MVS
- Narrowed MV orifice → ↑ resistance to blood flow from LA → LV in diastole
o PG across MV
o ↑ LAP → ↑ PV and pulmonary capillary pressures → pulmonary edema
MVS c/s
L-CHF
o Syncope: ↓ LV SV
MVS PE
o Mid diastolic L apical heart murmur
o Accentuated S1
ECG MVS
- P wave prolongation
- APC
- SVT, Afib
CTX MVS
- LAE: double density sign, dorsal tracheal deviation
Echo 2D MVS
o Abnormal MV motion
↓ diastolic MV excursion
Leaflet doming toward LV in diastole
Thickened MV leaflets
o LAE
o LV: normal, ↓ or ↑ in size depending on amount of MR
M-mode echo MVS
o ↓MV motion, ↑MV opening time
o ↓EF slope
Doppler echo MVS
o Turbulent, aliased flow across MV
o Restrictive LV filling pattern
↓ peak E wave
Prolonged deceleration time of E wave
↑ A wave
o ↑ transvalvular PG
Mild 8-10mmHg
Moderate 11-15mmHg
Severe >15mmHg
* ↑ pressure ½ time
Cardiac KT MVS pressure study
o ↑ PAP and PCWP
o LAP: ↑ a wave
o Diastolic PG btw LA and LV
Cardiac KT angio MVS
hourglass shaped diastolic filling defect
Pathophys MVS
- Resistance to blood flow from LA → LV through narrowed MV orifice during diastole
o ↑LAP and pulmonary capillary pressures
o Severe disease → CHF
Clinical functional classification MVS
o Symmetric:
Normal chord distribution from each leaflet to pap muscle
Variable annular + leaflet hypoplasia
* Thick leaflets w restrictive motion/commissural fusion
* ↓ interpapillary muscle distance
* Obliterated interchordal spaces
* Centrally oriented valve orifice, smaller than annular
o Asymmetric: unbalanced chordal attachment
Tx MVS
o CHF: avoid excessive diuresis → ↓ preload since can ↓ LV filling from ↓ PG
o Surgery:
Commissurotomy, MV replacement
Balloon: risk of MR
