MV/MR assessment Flashcards
Components of MV apparatus
LA wall, mitral annulus, anterior/posterior leaflets, chordae, pap muscle, LV myocardium
Normal shape of MV
o Normally saddle shaped ellipse
Normal area of overlap/apposition = zona coapta
Some degree of annular dilation tolerated
Cause of MR
- Dysfct/altered anatomy of any component → MR
o Leaflet flexibility
o Leaflet coaptation/apposition
Chordae disruption/elongation → inadequate support of closed leaflet in systole → MR
* Severe bowing of leaflet with tip TOWARD LV apex
Chordae rupture: flail leaflet segment into LA in systole → tip of leaflet AWAY from LV apex
o Annular dilation
Normally smaller in systole vs diastole
Annular calcification → ↑ rigidity → impaired systolic contraction → MR
o Papillary muscle orientation
Ischemia → regional LV dysfct w abnormal contraction of pap muscles → restricted leaflet motion (tenting of valve in systole) → MR
Papillary muscle rupture → acute severe MR
* Partial disconnection possible
Diseases affecting leaflets
CVD
Rheumatic MR
Endocarditis
Marfan syndrome
Infiltrative dz
CVD histo
↑ mucopolysaccharides, thickening/disarray of MV leaflets
CVD gross anatomy
thick leaflets and chordaes, chordae have ↓ tensile strength and are elongated
Rheumatic MR
commissural fusion, chordal fusion shortening of chordae
Endocarditis
leaflet destruction, perforation, deformity
Marfan syndrome
long, redundant anterior leaflet sagging into LA
Infiltrative dz
irregular leaflet thickening, inadequate coaptation
Functional MR
2nd to LV dilation and systolic dysfct → normal leaflets/chordae
o Papillary muscle orientation
o Leaflet coaptation
Echo characteristics of degenerative lesions
o LV and LA dilation
o Wall and septal hypertrophy and hyperdynamic motion
o ↑ thickness of MV
o Nodularity, prolapse of one of both MV leaflets
Smooth and small lesions w club-shaped appearance in early states
* Shaggy/irregular on M-mode
* Systolic fluttering of MV on M-mode can happen
Large and irregular as dz progress
o ↑ systolic function parameters
Mechanism of MR in degenerative dz
- Lesions to valve prevent proper leaflet coaptation and closure
CVD in large breed dogs
o Large breed dogs: fewer changes to valve leaflets despite significant regurgitation
Prolapse can be observed w/o abnormal thickness
Echo characteristics of degenerative lesions: less common
o Pericardial effusion → LA rupture
o Lack of hypertrophy
o ↓ systolic function → myocardial failure
o Ruptured chordae tendineae
Anatomy of chordae tendinae
o Primary/1st order chordae: attach to tip of leaflets → pap muscles
Responsible for most of structural integrity
o Secondary, tertiary chordae: attach to midventricular portion of valve leaflets → pap muscles and ventricular wall
Chord rupture most common cause
CVD
Features of ruptured chordae tendinae
o Severe MR on color flow evaluation of regurgitant jet size
Usually eccentric jet
If present w/o LV or LA dilation → suggest acute change
o Most commonly septal leaflet, parietal leaflet less common
o Chaotic MV leaflet motion in systole + diastole
May bend in LVOT during diastole
Minor chordal rupture: may be seen in only 1 echo plane
Major chordal rupture: usually in several echo planes
Pap muscle rupture
o Abnormal mass moving in LV → portion of pap muscle attached to chordae tendinae
o Severe mitral prolapse/flail leaflets
o Visualize tip of torn muscle: abnormal appearance
Causes of MV prolapse
- Primary: from intrinsic abnormalities of MV leaflets → CVD
o Chordal rupture: body of leaflet back in LA - Secondary: w/o inherent pathologic valvular abnormalities
o Hemodynamic causes:
Volume contraction + ↓LV size
Myocardial dz → akinetic muscle and abnormal pap muscle fct
When do we see prolapse?
- Can be seen w/o insufficiency.
o Genetically influenced in CKCS, Spaniels, Dachshunds
o Prolapse can happen as early as 3y/o
No c/s or murmur
High incidence of insufficiency later in life
Features on echo of MV prolapse
o Both leaflets buckle back toward LA in systole
o MV annulus: base of AoV → point of attachment of parietal MV leaflet
o Avoid apical 4 chamber view for dx
Normal curving of anterior leaflet in LA
Posterior leaflet buckling always abnormal in any plane
LV assessment for MV disease
LV size
LV fct
LV size evaluation
- Hemodynamically significant chronic MR result in LV and LA dilation
o Degree of LAE = indicator of HF stage
Correlate with severity of MR
LA/Ao >1.7 = poor px indicator for survival
Eq: 4 chamber LAX view → LAD > 13.5cm
o Significant insufficiency w/o LAE suggest acute process (chordal rupture)
o LV remodeling: ↑sphericity and hyperkinetic
Accuracy of LA/Ao w/ CVD progression
- As MR ↑, LA/Ao may not accurately reflect ↑ LA size
o Ao size will ↓ with ↓ forward flow or ↓ circulating blood volume
LA rupture
o Inter atrial septum → ASD
o Free wall → pericardial effusion
Presence of thrombus in effusion or LA = confirm atrial splitting
* Linear layer of hyperechoic material that conform to the shape of the heart
MV motion can reflect ↑ LV diastolic pressures
* Delayed closure of MV after atrial contraction
* B bump (LVP >30mmHg)
↑ septal motion: affected to greater extent by volume changes in RV and LV
Mechanisms of LV function w/ CVD
o LV systolic contraction → mvt of blood to low pressure LA → ↓ needs for LVH compensation for MR volume overload
Thin LV walls = compliant → allow ↑ ventricular filling and ↑ SV
* MR hearts: lowest mass to volume ratio
o CHF is 2nd to severe MR and volume overload (not myocardial failure)
FS% with MR
measure of myocardial motion
o Should be elevated with MR → ↑ preload, ↓ afterload, ↑ contractility
Normal contractility = normal LV end systolic dimension event if volume overload
FS > normal with normal myocardial contractility
FS in normal range (33-45%) with impaired contractility
↓ FS = myocardial failure
Systolic index equation
Systolic index = (End systolic volume)/BSA
Myocardial failure indices in dogs w/ MR
- FS, end systolic dimensions, systolic index can detect myocardial failure in dogs w MR
o End systolic dimensions and systolic index = not affected by preload
Normal systolic index in dogs <30ml/m2
* Severe myocardial failure >100ml/m2
* Moderate reduction in contractility = 70-100ml/m2 (mean 73)
* Mild myocardial impairment = 34-70 ml/m2 (52±6)
o Expected end systolic dimensions (ESDe): based on allometric ratio
Ratio of ESD/ESDe >1.13 in large breed dogs, >0.89 in small breeds
o Large breed tend to develop myocardial failure more frequently (vs small breeds)
Lack of adequate hypertrophy 2nd to volume overload → ↓ myocardial fct
- LA dimension normalized to BW: 76%sens, 81%spe to identify myocardial failure for LA size >1.55
Wall stress equation and changes w/ MR
ratio of radius to wall thickness
o MR → eccentric hypertrophy → normal to high wall stress (limited hypertrophy)
o > ratio = ↓ wall stress
Wall stress = (P x r)/h
Diastolic Lv dimension
o LV end diastolic radius
o Wall thickness: normal = 0.47 ± 0.11 in large breeds (>20kg), 0.53 ± 0.11 in small breeds.
Color flow Doppler eval of MR
Jet size/area
PISA
Vena contracta
Jet size/area of MR
- Semiquantitative assessment:
o Size of regurgitant jet w/I atria (largest jet in any plane): Hu → ratio RJarea/LAarea
Mild insufficiency: <20% of LA (Hu)
Moderate insufficiency: 20-40% of LA
Severe insufficiency: >50% of LA
Dogs: mild <30%, moderate 30-70%, severe >70% in L apical 4 chamber view
o Regurgitant jet area correlates well with jet volume
o LA area correlates well with RF% (not if ruptured chordae)
Pitfalls of semiquatitative eval of jet size area
o Poorest method: lot of factors can influence.
Abnormal systemic pressures: driving pressure affect velocity and area of flow
* ↓ systemic BP → large jet despite mild MR
↓ systemic and ↑LAP → small jet area despite severe MR
HR: fast HR underestimate jet area
Eccentric regurgitant jet: limit accuracy → jet directed toward LA wall and prevent its dispersion in LA → underestimation of severity = Coanda effect
Influenced by transducer frequency and gain
Qualitative eval of jet size/area
o Eccentric jet suggest pathologic regurgitation
Abnormal posterior leaflet → anterior jet
Abnormal anterior leaflet + pap muscle dysfct → posterior jet
o Central jet suggest physiologic regurgitation
LV/MV annulus dilation
Mild MR
What is PISA a
- Area of flow acceleration/convergence proximal to MV
o Lack of flow convergence area consistent with mild MR vs large area = severe MR
PISA assumption
Assume that flow accelerates in concentric hemispheres approaching the small orifice on ventricular side
PISA: echo
o Apical 4 chamber view
o Centrally directed MR
o Flow convergence, vena contracta, jet expansion
o Nyquist limit 40-70cm/s
o Largest MR in mid systole: use zoom, adjust baseline and then Nyquist limit to 18-40cm/s
Visualize flow convergence: as close as possible to perfect hemisphere
Echo measures PISA
o Radius of hemisphere of proximal flow convergence (r in cm)
Hemicircles too close to MV underestimate radius (flat)
Hemicircles too far to MV overestimare radius (>parabole)
o Peak MR velocity (MRvmax in cm/s)
o MR VTI (in cm)
Effective regurgitant orifice area normals, equation
o Mild insufficiency <0.2cm2
o Moderate insufficiency = 0.2-0.39cm2
o Severe insufficiency = >0.4cm2
EROA (cm2) = 〖Flow rate〗_MR/〖MR〗_vmax
Regurgitant fraction classification (kittleson)
o Severe MR: >75% of LV volume move to LA
o Moderate MR: 45-75%
o Mild MR: <45%
Limitations of PISA
o More accurate with central jets: if eccentric, regurgitant flow rate can be overestimated
o Needs holosystolic jet
o Contour of convergence zone changes w stage of regurgitation
Smaller zone flattened
Larger zone elliptical
o Measure radius in the center of convergent zone, where flow is// to radius
Vena contracta def
Smallest regurgitant color flow jet at MV orifice
Vena contracta measure
- Echo: use multiple planes and small color sector to optimize lateral and temporal resolution
o Parasternal LAX
o See flow convergence, vena contracta and jet expansion → zoom in - No affected by driving pressures/flow rate
Spectral doppler evaluation
Jet area
Reg volume and fraction
Transmitral valve flows
Spectral Doppler eval of jet area
PW gate at various depth in LA → provide information on how wide/deep MR extends
Spectral Doppler eval of regurgitant volume/fraction
- Regurgitant volume: total ventricular volume (through MV) - forward SV through Ao
- Regurgitant fraction: % of total SV flowing back into LA
- Calculated with CSA and VTI (discussed above)
o The valve used for normal SV should not be insufficient
RV (ml) = Total SV MV – Forward SV Ao
RF (%) = (Total SV MV-Forward SV Ao)/(Total SV MV)
Transmitral valve flows changes MR
- E wave >1.2cm/s = significant regurgitation
o Predictive of poor survival time
o Affected by LAP and LVP - Rapid E wave deceleration correlated with poor px in Hu and dogs (<80ms w DCM)
E>1.25m/s
E/E’>12
IVRT<45ms
E/IVRT>2.5
LAP evaluation w/ transmitral valve flows
- Evaluation of LAP (↑LAP>20mmHg)
o Mean LAP calculation from E:Ea
E:Ea < 6 → predicts MLAP <20mmHg
E:Ea > 9 → predicts MLAPD >20 mmHg
o ↑LAP → ↓IVRT, ↑E/E’, E/IVRT
MLAP = 6.38 x E:Ea -28.3
MR flow profile
- Peak velocity: no information regarding severity of MR
- Flow profile: usually symmetrical
o V wave on deceleration portion: suggest rapid ↑LAP 2nd to regurgitation
o Asymmetric: high LAP and compliant chamber
Seen w acute severe MR
Triangluar shape indicates ↑LAP
o Dense flow profile: significant regurgitant volume
Changes in PV flow w/ severe MR
- Changes with severe MR
o ↓ S wave velocity ± reversal of flow - If LA severely enlarged and compliant: excess volume contained in LA and no flow reversal
- Reversal of flow can also happen with
o Eccentric jet directed into PV
o Arrhythmia with loss of atrial contraction or AV asynchrony
o Other physiologic factors: respiratory phase, cardiac phase/rhythm, atrial/venous compliance, age, diastolic filling
PH 2nd to CVD
- Pressure gradient from TR with Bernoulli equation = systolic PAP
o Added RA pressure
Normal <5mmHg
RA dilation, no R-CHF, 50% collapse of CaVC = 10 mmHg
RA dilation, R-CHF, <CaVC mvt = 15mmHg - Pressure gradient from PI = mean PAP
- LA/Ao positively correlates with sPAP/mPAP
o PAP ↑ passively 2nd to ↑LAP
o PVR can ↑ in chronic ↑ LAP
Diastolic MR causes
- Seen with AV conduction abnormalities
o 1st, 2nd , 3rd AVB and retrograde P waves
Diastolic MR features on echo
- Late diastole → atrial contraction not followed by appropriate ventricular contraction → normally closes MV
- Hemodynamically insignificant
