Hemodynamic Calculations Flashcards
What is volume equal to?
Area x Distance
What is the stroke volume equal to?
Cross sectional area (CSA) x Stroke Distance
Where is stroke volume calculated? (2 places)
LVOT or Aortic Valve
What does the accuracy of the stroke volume determination depend on?
- Parallel Alignment of U/S beam to blood flow
- Accurate determinations of vessel cross sectional area (CSA)
How do we calculate Stroke Volume?
Stroke Volume = (Area at LVOT or Aortic Valve) x Stroke Distance
Said another way:
SV = Area x Stroke Distance = CSA x TVI
Stroke distance = TVI (Time Velocity Intergral) = VTI
How would we measure CSA of LVOT to measure stroke volume?
Deep Transgastric Long Axis view with U/S Beam through Aortic Valve
- Measure LVOT
- Use (pi)*r2
How do you calculate Stroke Distance Logistically?
- Deep TG with doppler through Aortic Valve
- Measure negative deflection
- This will give you TVI = Stroke Distance
What is Qp / Qs mean?
Qp = Flow through Right side of heart (p = pulmonary)
Qs = Flow through the Left side of the heart (s = systemic)
How do we calculate Qp/Qs on echo?
SVPA / SVLVOT
SVPA = APA x TVIPA
SVLVOT = ALVOT x TVILVOT
What TEE view do we use to calculate the Stroke Volume through the PA?
Mid-Esophageal Ascending Aorta Short Axis
What TEE view do we use to calculate Stroke Volume of the LVOT?
Mid Esophageal Long Axis to get Area of the LVOT
Deep TG Short Axis to get TVILVOT
How close do you want to measure the LVOT from the aortic valve?
Stay within 1 cm (Distance changes the further you go away from that)
What is the derivation to arrive at the Regurgitant Volume equation?
Volume in = Volume out
Diastolic LV inflow = Systolic LV outflow = (SV forward + Regurgitant Volume)
SVMV inflow = SVAV + Regurgitant VolumeMV
Regurgitant VolumeMV = SVAV - SVMV inflow
How do you calculate SVMV?
AMV x TVIMV
What is the cutoff for Mild MR based on Regurgitant Volume?
<30 mL
What is the cutoff for Moderate MR based on Regurgitant Volume?
30 - 59 mL
What is the cutoff for Severe MR based on Regurgitant Volume?
> 60 mL
What is the formula for regurgitant volume?
SVMV - SVLVOT
SV<strong>MV</strong> = AMV x TVI MV inflow
SVLVOT = ALVOT x TVILVOT
What are all the ways that the Area of the Mitral valve can be calculated in order to obtain SVMV?
220 / Pressure Half Time
760 / Decelaration TIme
PISA
Continuity Equation
Pi * r2
What is the regurgitant fraction?
What is the equation for this?
Backwards Flow / Total Flow
Regurgitant Fraction (RF) = Regurgitant Volume / SVMV Inflow
What is the cutoff for Mild MR based on Regurgitant Fraction?
<30%
What is the cutoff for Moderate MR based on Regurgitant Fraction?
30-49%
What is the cutoff for Severe MR based on Regurgitant Fraction?
>50%
What is the regurgitant orifice area?
Area of the hole through which regurgitation occurs
regurgitant orifice area equation
Volume = Area x Distance
Regurgitant Orifice Area = Regurgitant Volume / TVI Mitral Valve
What is the cutoff for Mild MR based on Regurgitant Orifice Area?
< 0.2 cm2
What is the cutoff for Moderate MR based on Regurgitant Orifice Area?
0.2 - 0.39 cm2
What is the cutoff for Severe MR based on Regurgitant Orifice Area?
> 0.4 cm2
What do we use to calculate intracardiac pressures?
Change in Pressure (Delta) = 4V2
How do you estimate RA pressure?
IVC size
What is the estimated Right Atrial Pressure for an IVC of <1.5 cm and Collapses with Sniff?
0 - 5 mmHg
What is the estimated Right Atrial Pressure for an IVC of 1.5-2.5 cm and Decreases >50%?
5 - 10 mmHg
What is the estimated Right Atrial Pressure for an IVC of 1.5-2.5 cm and Decreases <50%?
10 - 15 mmHg
What is the estimated Right Atrial Pressure for an IVC of >2.5 cm and Decreases <50%?
15 - 20 mmHg
What is the estimated Right Atrial Pressure for an IVC of >2.5 cm and No change with Sniff?
>20 mmHg
What is the RV Diastolic Pressure going to equal?
RVDP = RAP
*Unless Tricuspid Stenosis is present
To calculate RVSP, What view do we use?
Mid-esophageal 4 chamber with U/S beam through tricuspid valve
What is the equation for RVSP?
Change in Pressure = 4*V2
RVSP - RAP = 4 (Velocity of Max TR Jet)2
*Rearrange equation*
RVSP = 4 (Velocity of Max TR Jet)2 + RAP
What is the equation for Pulmonary Artery Systolic Pressure?
*What is the caveat*
PASP = RVSP - Change in Pressure (Pulmonic Stenosis)
*Caveat is Pulmonic Stenosis in which you have to subtract the gradient across the pulmonic valve
How do we calculate the Main Pulmonary Artery Mean Pressures?
Not done often**
Change in P = 4 V2
PAMP - RVDP = 4 (VPI early)2
PAMP = 4 (VPI early)2 + RVDP
PAMP = 4 (VPI early)2 + RAP
When do you use VPI early and when do you use VPI late?
Early = PA Mean
PAMP = 4 (VPI Early)2 + RAP
Late = PA Diastolic
PADP = 4 (VPI Late)2 + RAP
How do we estimate Left Atrial Pressure?
Equation
Measure this from the velocity of an MR Jet
Change in Pressure = 4 V2
LVSP - LAP = 4 (VMR)2
*LVSP can be substituted by SBP*
LAP = SBP - 4 (VMR)2
If you have a VSD, How do you calculate RVSP?
Change in Pressure = 4V2
LVSP - RVSP = 4 (VVSD)2
RVSP = LVSP - 4 (VVSD)2
What is Dp/Dt?
Isovolumetric rate of LV Pressure rise
Said another way:
Rate of LV pressure rise during isovolumetric contraction of the LV
What is Dp/Dt calculated as?
Slope of LV Pressure rise from 4-36 mmHg (VMR = 1 to VMR = 3 m/s)
What is Dp/Dt dependent on?
Preload
What is Dp/Dt independent of?
Afterload
What is the equation for calculating Dp/Dt?
Use Change in Pressure = 4V2
With Mitral Regurgitation: Change in P = (PLV - PLA) = 4 (VMR)2
PLV = 4 (VMR)2 + PLA
Then substitute
VMR 1 = 4 so PLV = 4 + PLA
VMR 3 = 36 so PLV = 36 + PLA
Change in P / Change in T = 32/ Change in T
What is the Dp/Dt for this picture?
Change in Time is 0.06
Change in P = 32 / 0.06
533 mmHg
The peak velocity is 280 cm/sec
Given BP of 120/80, Calculate RVSP
- Convert 280 cm/sec = 2.8 m/sec
- Realize its a VSD
- RVSP = LVSP - 4 (VVSD)2
- RVSP = 120 - 31 = 88 mmHg
What Tricuspid Valve Leaflets are seen here?
Left = Septal / Posterior
Right = Anterior
What is the green circle at?
Right Atrial Appendage
What pressure can be calculated from this?
This is the Tricuspid valve shown here with an U/S beam through it.
You can calculate:
RVSP using Bernoulli (Change in Pressure) = 4 * (VTR JET)2 + RAP
RV Systolic Pressure = Pulmonary Systolic Pressure in the absence of what?
Pulmonic Stenosis
What TR peak velocity is indicative of elevated Left Atrial Pressure?
What TR peak velocity is indicative of elevated Diastolic Dysfunction?
>2.8 m/sec
*Commit to memory*