Quantification of AR Severity Flashcards
Definition of Regurgitant Volume (RV)
Volume of blood through the leaky valve
Definition of Regurgitant Fraction (RF)
- Regurgitant volume divided by total volume
- % of stroke volume through the leaky valve
Definition of Regurgitant Orifice Area (EROA)
Size of ‘hole’ in the leaky valve
Which calculations can be derived via stroke volume method?
- RV
- RF
- EROA
(All can be derived via SV method)
Which calculations can be derived via PISA?
- RV
2. EROA
Concept for stroke volume through the LVOT in the presence of AR?
- In diastole, regurgitant volume (RV) enters LV and combines with inflow stroke volume coming through MV
- Therefore, SV LVOT = SV MV + RV
Stroke Volume Method: Formula to calculate AR Regurgitant Volume?
RV(AR) = SV LVOT - SV MV
Stroke Volume Method: Formula to calculate SV LVOT
SV LVOT = LVOT area x LVOT VTI
Stroke Volume Method: Formula to calculate mitral annular SV
SV MV = MV area x MV VTI
Stroke Volume Method: How to measure mitral annular diameter?
- Zoomed view of A4V
- MV measured in early diastole (open valve leaflets) at leaflet insertion (inner edge to inner edge)
Stroke Volume Method: How to measure MV VTI?
- Different to normal
- Cursor placed at MV annulus level with 1-2mm sample volume
- Trace modal velocity (dense part of signal) and avoid ‘fluffy’ bits
Normal mitral annulus diameter
3.0 - 3.5cm
Normal mitral annulus VTI
10 - 13cm
Normal LVOTd
1.8 - 2.2cm
Normal LVOT VTI
18 - 22cm
Stroke Volume Method: RVol formula for AR
RV (mL) = SV LVOT – SV MV
Stroke Volume Method: RF formula
RF (%) = (RV / SV regurgitant valve) x 100
Stroke Volume Method: EROA formula
EROA (cm2) = RV / VTI regurgitant valve
Limitations of Stroke Volume Methods
- Diameter measurement errors
- VTI measurement errors
- Assumptions of calculation
- Significant learning curve in performing calculation - especially mitral annular stroke volume
Assumptions of Stroke Volume Method Calculations
- Assumes flow occurs in a rigid, circular tube
- Assumes uniform velocity across vessel
- Assumes circular annulus areas
PISA Method Principles/Assumptions
- Assumes flow proximal to a narrowed orifice must flow through the narrowed orifice (continuity principle)
- Assumes as flow converges towards narrowed orifice, it conforms concentric hemispheric shells
- Assumes flow rate proximal to narrowed opening (Q1) = flow rate through narrowed opening (Q2)
PISA Method: Equation for EROA
EROA= (2πr^2×VN)/VRJ
VN = Nyquist limit VRJ = peak velocity of regurgitant jet (CW Doppler)
PISA Technique
- Zoom in on AV
- Move colour baseline in direction of AR jet
- Cine to find optimal hemispheric PISA dome
- Measure PISA dome radius from regurgitant orifice to 1st aliased zone (red-blue interface)
Which Nyquist limit to note when performing PISA calculation?
- If flow towards the Tx (red), note top of colour bar
2. If flow away from Tx (blue), note bottom of colour bar
Which direction do you move colour baseline for PISA?
- Always move baseline in the direction of flow
- If flow is towards from the Tx, move baseline upwards (regurgitant flow is red)
- If flow is away from the Tx, move baseline down (regurgitant flow is blue)
Equation for Regurgitant Volume via PISA?
RV = EROA x VTI AR
Is RV or EROA more useful in the assessment of AR?
RV because AR occurs in diastole and flow varies over the diastolic period
Assumptions of PISA Method (Limitations)
Assumes that:
- Radius is consistent over flow period
- Regurgitant orifice is circular
- EROA is consistent over the flow period
PISA Method Limitations
- Multiple jets (not additive)
- Aortic valve calcification
- Under-estimation possible with aortic root aneurysms
SV vs PISA Method: Which is preferred and why?
- PISA method is preferred as there are less measurements
- The less measurements we have to do, the more reliable the method will be
