Hemodynamics, Formulas, Prosthetics Flashcards
Valve area using PHT:
MVA = 220 / PHT
TVA = 190 / PHT
Calculate PHT using deceleration time
PHT = 0.29 x DT
What is the formuala for CO?
C0 = SV x HR
Calculate SV and CO
- E wave DT - 910 ms
- Mean diastolic mitral gradient - 17 mmHg
- Diastolic mitral inflow - VTI - 66 cm
- HR - 85 bpm
- SV = CSA (MVA) x VTI
- MVA = 220/PHT
- PHT = 0.29 x DT
- SV = 0.8 cm2 x 66 cm
- CO = 53 mL x 85 b/min = 4.5 L / min
Define ductus arteriosus (PDA)?
Explain the physiology behind a ductus arteriosus
- extracardiac shunt resulting from a communication between the descending thoracic aorta (DTA) and the proximal left pulmonary artery
- in utero, the blood that reaches the pulmonary artery from the RV cannot enter the collapsed (partially functional) lungs; instead it is diverted across the ductus arteriosus into the DTA
- Soon after birth, the pressure in the pulmonary artery falls below the pressure in DTA and blood flow in the ductus arteriosus reverses its direction –> flow from DTA into pulmonary artery
- High O2 content of the ductal blood triggers closure of the ductus arteriosus in most newborns
What is the major difference in flow calculations in pateints with PDA?
- Flow exiting LVOT (normally Qs) = Qp
- Flow exiting RVOT (normally Qp) = Qs
*****Most individuals with PDA, Qp > Qs
What is the formula for shunt flow (SF) in the setting of PDA?
SF = Qp (LVOT) - Qs (RVOT)
What is a complication of (untreated) PDA?
- Eisenmenger physiology
- R-to-L shunting of deoxygenated blood
- cyanotic lower extremities because deoxygenated blood from the PA crosses the PDA and enters the DTA past the origin of the aortic arch vessels, which supply fully oxygenated blood to the head and the arms
Explain the relationship between RAP and RVDP
can be considered equal in the absence of TS
What is the formula for pressure gradient between PADP and RVDP?
- PADP - RVDP = 4V2
- absence of TS, RVDP = RAP
- PADP - RAP = 4V2
- PADP = 4V2 + RAP
- V = Vend diastolic velocity
- RAP
- > / < 2.1 cm
- > / < 50% collapse on sniff test
- 3, 8, 15 mmHg
What are findings consistent with severe MR?
- Grades 3+ and 4+
- EROA - > 0.4 cm2
- RF - > 50%
- RV - > 60 mL
- VC - > 0.7 cm
What is the formula for instantaneous flow rate across the mitral valve?
- Calculated using PISA method
- IFR = 6.28 r2 x aliasing velocity
What is the formula for SV?
SV = 0.785 x d2 x LVOTVTI
What is the formula for regurgitant volume (RV)?
RV = EROA x VTICW
What is the formula for MVA (using PISA)?
MVA = 6.28 x V2 x aliasing velocity / Peak velocityMS x angle correction
What is the formula for LVOT gradient (using MR)?
LVOT gradient = 4VMR2 + LAP - SBP
What is Teicholz formula for LV volume / SV?
SV = (7 x LVEDD3 / 2.4 x LVEDD) x LVEF
What is the formula for projected AVA?
Projected AVA = AVA rest + [(AVApeak - AVArest) / (Qpeak - Qrest)] x (250 - Qrest)
What is the formula to calculate pulmonary artery wedge pressure?
PAWP = 4.6 + 5.27 x E / Vp
- E = mitral inflow peak velocity
- Vp = flow propagation velocity of the mitral inflow (cm/s) obtained by color M-mode
What does flow propagation velocity of mitral inflow (Vp) measure?
- measures the rate at which red blood cells reach the LV apex from the mitral valve level during early diastole
- obtained on color M-mode
- indirect measure of LV relaxation
- lower the Vp, the slower the LV relaxation and higher the LVDP
Explain the findings of mitral E and A wave in the setting of elevated LAP (or PAWP)
- Peak E wave >> A wave
- Patients will have one of two patterns:
- Pseudonormal filling pattern
- E/A between 1 - 2
- E wave deceleration time > 160 ms
- Restrictive filling pattern
- E/A > 2
- E wave deceleration time < 160 ms
- Pseudonormal filling pattern
What will be the mitral E wave to mitral annular tissue Doppler e’ wave (E/e’) be in the setting of elevated LAP and PAWP?
> 15
What is a normal Vp (propagation of mitral inflow velocity)?
- Young individuals = > 55 cm/s
- Middle-aged = > 45 cm/s
What findings are consistent with severe AR?
- Grades 3+ and 4+
- EROA >0.3 cm2
- RF > 50%
- RV > 60 mL
- VC > 0.6 cm
What measure is directly proportional to left atrial pressure?
- LAP = E/e’
- mitral E wave (inflow) to mitral annular tissue Doppler e’ wave
What measure is Doppler e’ wave directly proportional to?
- rate of LV relaxation during early diastole
- slower the LV relaxation –> higher LV diastolic pressure (LVDP)
- increased LVDP –> increased LAP and PAWP (to allow for better filling of a stiff LV)
- higher the LAP –> the taller the mitral E wave becomes
Explain what happens in regards to E and e’ as LV diastolic dysfunction worsens
- peak velocity of annular tissue e’ wave gets smaller
- mitral E wave gets higher
- E/e’ gets progressively larger –> reflecting the rising LAP and PAWP
Describe the medial E/e’ severity scale
- Normal < 8
- Indeterminate 8 - 15
- Elevated > 15
Describe the lateral E/e’ severity scale
- Indeterminate 8-12
- Elevated > 12
What is the equation to estimate LAP?
LAP = 1.9 + 1.24 x E/e’
Simplified: LAP = 4 + E/e’
What is the formula to calculate LVSP (in presence of MR)?
LVSP = 4VMR2 + LAP
- VMR = peak systolic gradient of the MR jet
What is the formula to calculate peak-to-peak gradient of AS?
P2P = LVSP - SBP
****P2P gradient is not a physiologic one because it represents a pressure difference at separate points in time
What is normal dP/dt?
dP/dt = 1661 + 323
What is the formula to calculated LVEDP using DBP?
- DBP - LVEDP = 4V2
- LVEDP = DBP - 4Vend diastolic velocity2
What PHT indicates severe AR?
PHT < 300 ms
What is the relationship between LVSP and SBP in patients with AS?
peak LVSP is always higher than peak SBP
- LVSP becomes progressively higher as AS becomes more severe
Can the continuity equation be used in the evaluation of AS in the presence of significant AR?
Yes
- increased flow will proportionally effect VTI of both LVOT and AV
What is one factor that can preclude an ASD closure?
Increased PVR
- not pulmonary hypertension alone
What is the formula to calculate RVSP and PASP from VSD?
What information must be known?
What cannot be present?
- RVSP = SBP - Vpeak systolic VSD gradient
- RVSP = SBP - 4V2
- SBP must be known
- no LVOT obstruction can be present
What is the formula to calculate PASP if RVSP is known?
- PASP = RVSP
- if no PS is present
- PASP = RVSP - Peak PS gradient
What is the formula to calculate RVEDP in the setting of VSD?
What must be provided?
- RVEDP = LVEDP - Vend-diastolic gradient
- RVEDP = LVEDP - 4V2
- LVEDP must be provided
How do you calculate RVOT SV in the setting of an ASD (L-to-R shunt)?
SVRVOT = SVLVOT + SVASD
What is the formula to calculate Qp (in setting of ASD)?
Qp = Qs + ASDshunt flow
Describe dP/dt
- a measure of left ventricle systolic function
- dP - rate of pressure rise in the left ventricle
- dt - time
What is the formula used to calculate dP/dt?
- dP/dt = ΔP / RTI
- RTI = relative time interval (measured in seconds) between MR jet velocities
- change in pressure (ΔP) - represents the pressure difference between the left ventricular to LAP gradients at V2 and V1
Calculate dP/dt
- dP/dt = ΔP / RTI
- ΔP = 4V22 - 4V12
- ΔP = 36 - 4 = 32 mmHg
- RTI = Time at V2 - Time at V1 = 25 - 5 = 20 ms –> 0.02s
- dP/dt = 32mmHg / 0.02s –> 1,600 mmHg/s
What is the expected peak E velocity when severe (native) MR is present?
> 1.5 m/s
What is the expected peak E velocity when severe (prosthetic) MR is present?
> 2.0 m/s
Calculate LAP
- LVSP = ΔP + LAP
- LAP = LVSP - ΔP
- SBP can be substituted for LVSP in the absence of LVOTO or AS
- LAP = 95 mmHg - 4(4)2
- LAP = 95 mmHg - 64 mmHg
- LAP = 31 mmHg
What is normal dP/dt?
1661 + 323 mmHg/s
- 900 mmHg/s –> indicates markedly diminished LV systolic function as seen in cardiogenic shock
What are findings consistent with very severe MS?
- MVA < 1.0 cm2
- PHT > 200 ms
- MG > 10 mmHg
What findings are consistent with severe MS?
- MVA 1.0 - 1.5 cm2
- PHT 150-220 ms
- MG 5-10 mmHg
What findings are consistent with Progressive MS?
- MVA > 1.5 cm2
- PHT < 150 ms
Calculate LAP
- LAP = MG in diastole + Early LV diastolic pressure
- LAP = 21 mmHg + 7 mmHg = 28 mmHg
What is the relationship between velocity and area of an orifice?
inversely related
- V = 1 / CSA (or MVA in setting of MS)
- smaller or more severe the stenosis, the higher the velocity (E wave velocity)
Why is PHT (assessment of MS) not reliable after PMBV?
- PHT method assumes LV pressure and compliance are normal
- PMBV –> sudden increase in mitral orifice area leading to an increase in the SV delivered to the LV in early diastole
- Because LV compliance cannot acutely change, the LVDP increases
- Increase in LVDP –> diastolic gradient between the LA and LV decreases and the mitral PHT shortens (above and beyond what would be expected by an increase in the MVA alone after valvuloplasty)
- PHT method –> erroneously large MVA
What are two ways to utilize diminsionless index (in assessment of AS)?
VTILVOT / VTIAV
or
PVLVOT / PVAV
Calculate AVA
- AVA = CSALVOT x VTILVOT / VTIAV
- AVA = CSALVOT x DI
- DI can be calculated using VTI or PV
- AVA = 0.785 (1.9)2 x (1 m/s) / (5 m/s)
- AVA = 2.84 cm2 x 0.2
- AVA = 0.6 cm2
Calculate SV
- SV = CSALVOT x VTILVOT
- SV = 0.785 (1.9)2 x 20 cm
- SV = 57 mL/beat