Download Hemodynamic Assessment ¼ π Assessment of Systolic Function

Hemodynamic Assessment
Matt M. Umland, RDCS, FASE
Aurora Medical Group
Milwaukee, WI
»Assessment
of Systolic Function Doppler Hemodynamics»
Stroke Volume
Cardiac Output
Cardiac Index
Tei Index/Index of myocardial performance (IMP)
Valve Areas
Gradients
Right heart pressures
™ Stroke Volume (SV)
¾ Can be measured through any intracardiac site
¾ Assumptions
ƒ Orifice area is circular & constant
ƒ Area and velocity measured at same site
ƒ Transducer aligned parallel to flow
ƒ Laminar flow profile
¾ LV ejects volume of blood through cylindrical aorta with each beat
¾ Base of cylinder is the cross-sectional area of the aorta
¾ Height of cylinder is the distance the average blood cell traveled during
each beat
ƒ This is expressed as the integral of the Doppler systolic time -velocity
curve (TVI)
ƒ Volume of a cylinder equals base times height; therefore, stroke volume
is CSA multiplied by TVI
Adapted from Oh.
¼π
CSA (cm2) = {diameter (cm)}2 X 0.785
SV (cc) = CSA (cm2) X TVI (cm)
1
Normal SV
60 – 90 cc/beat
™ Measurement of Left Ventricular Outflow Tract (LVOT) Stroke Volume
¾ Most frequently used location
¾ Diameter (cm) of the AV annulus
ƒ During mid-systole inner edge-to-inner edge
ƒ Measure at the annulus from the insertion point of the right coronary
cusp to the insertion point of the non-coronary cusp
ƒ Normal range = 1.8 cm – 2.2 cm
¾ TVI (cm) of LVOT
ƒ From apical long-axis using pulsed-wave Doppler, place the sample volume
the base of the aortic valve
ƒ At the same location of the measurement of the LVOT diameter
ƒ Obtain the spectral Doppler signal that includes the closing click of the
valve
ƒ Trace the leading edge of the velocity spectrum to obtain the TVI (cm)
ƒ Normal range = 16 cm – 22 cm
¾ Advantages of measuring SV in LVOT
ƒ Flow remains laminar proximal to a stenotic valve
ƒ Can be recorded in almost all patients
Adapted from Oh.
Normal CO
™ Cardiac Output (CO)
4 - 7 L/min
¾ The volume of blood ejected per minute
¾ Stroke volume multiplied by the heart rate at the time of TVI measurement
CO (L/min) =
SV (cc) X HR (bpm)
1000
2
Normal CI
2.5 – 4.5 L/min/m2
™ Cardiac Index (CI)
¾ Correcting the cardiac output to body surface area (BSA)
¾ Cardiac output divided by the patient’s BSA
CI =
CO (L/min)
BSA
™ Tei Index or Index of Myocardial Performance (IMP)
¾ Reflects global myocardial performance
¾ Includes systolic and diastolic phases
¾ Predictor of clinical outcome and functional status
¾ Independent of
ƒ Heart rate
ƒ Right venticular pressure
ƒ Pulmonary artery pressure
ƒ Loading conditions
¾ Right ventricular Index of Myocardial Performance (RIMP)
ƒ Strong predictor of survival in patients with pulmonary hypertension
ƒ RIMP > 0.82 indicates a decrease in survival
IMP =
IVCT +IVRT - ET
ET
AVCO
Ejection
Time
LV or RV
outflow
Mitral/Tricuspid
Inflow
IVCT
IMP = AVCO - ET
ET
IVRT
3
™ Valve Areas
¾ Important in the evaluation of valvular stenosis
¾ Continuity Equation
ƒ Based on the priniple of conservation of mass
ƒ “What flows in, must flow out”
ƒ Uses
• Calculation of valve areas
• Calculation of regurgitant volumes and regurgitant fractions
• Calculation of regurgitant orifice areas
• Calculation of intracardiac shunts
ƒ When flow rate (Q) is maintained, volumetric flow on each side of
narrowing is equal (Q1 = Q2)
ƒ Flow rate (Q) is equal to the mean velocity (V) times CSA
• Therefore as area decreases ,the velocity must increase to maintain a
constant flow rate
• Because flow is puslatile through the heart the volumetric flow is also
equal to the time-velocity intergal & CSA
ƒ By rearranging the equation the CSA2 can be derived
CSA1 X V1 = CSA2 X V2
CSA1 X TVI1 = CSA2 X TVI2
CSA2 =
Adapted from Oh.
CSA1 X TVI1
TVI2
¾ Limitations of the Continuity Equation
ƒ CSA calculation
• Errors in the measurement of the diameter are reflected in the
calculation of the CSA
4
Erroneuous diameter measure is magnified in area because the
diameter is squared in calculation of CSA
• Measurements must be made at the site at the time of flow through
site
♦ Measurements of CSA of aortic valve are made during systole
♦ Measurements of CSA of mitral valve are made during diastole
ƒ TVI measurements
• Incorrect sample volume placement
• Ultrasound beam is not parallel to blood flow
• Over or undergaining of spectral display
• Incorrect filter settings
ƒ CSA2 calculation error
• Failure to obtain highest Doppler signal (try multiple windows and
angles)
• Poor alignment (not parallel to blood flow)
¾ Aortic Valve Area
ƒ Doppler assessment
• Peak aortic velocity
• Mean pressure gradient
• Aortic valve area
• LVOT-to-Aortic valve TVI
ƒ Assessing for the maximal aortic velocity is achieved by assessing the
valve from multiple windows
• Apical
• Subcostal
• Suprasternal Notch
• Right Supraclavicular
• Right Parasternal
ƒ AVA Calculation
• Determine the LVOT SV using TVI
• Obtain the maximal aortic valve velocity and
mean gradient
• Use continuity equation to calculate AVA
•
Adapted from Oh.
Adapted from Oh.
5
¾ Mitral Valve Area
ƒ Doppler Assessment
• Determine the SV using the LVOT diameter and TVI
• Obtain the maximal mitral valve velocity using continuous-wave
Doppler
• Trace the mitral inflow velocity to obtain the mean gradient and TVI
• Use continuity equation
Adapted from Oh.
*Cannot be used if there
is significant AR or MR*
Measure the Pressure halftime (PHT)
♦ Time interval for the peak pressure to
reach its half level
♦ PHT = Deceleration Time x 0.29
Adapted from Oh.
♦ MVA = 220/PHT
MVA by PISA Method
• Zoom on the mitral valve from the Apical 4-chamber view
• Use color-flow imaging to assess the inflow jet
• Shift the color baseline up (30 – 45 cm/sec aliasing velocity)
• Freeze color-flow images and cine to optimal frame to measure radius
(r) of PISA in left atrium
• Determine the angle (α) between the 2 mitral leaflets at the atrial
surface
•
ƒ
Adapted from Oh.
MVA =
6.28 x r2 x alias velocity
Peak mitral inflow velocity
x
6
α°
180°
™ Gradients
¾ Doppler-derived gradients have been validated by cardiac catheterization
data
¾ Bernoulli Equation
ƒ Uses
• Measurement of maximal and mean pressure gradients across
stenotic lesions
• Maxiaml pressure gradients across regurgitant valve lesions and
shunts
• Intracardiac pressure estimation
ƒ Conservation of energy
ƒ Energy flowing in is equal to the total energy flowing out
ƒ The movement of blood flow within the CV system is determined by
pressure differences between 2 locations
• V1
• V2
Adapted from Oh.
ƒ
ƒ
Assumptions
• Flow acceleration can be ignored as at peak velocities, acceleration is
zero
• Viscuos friction is negligible as the flow profile within the curve of
the lumen is generally flat and losses are minimal toward the center
of the vessel
• Mass density (1/2 ρ) for normal blood equals 4
• There is conservation of energy; that is, there is no energy transfer
Therefore, the Bernoulli’s Equation can be simplified to:
∆P = 4 (V22 - V12)
7
ƒ
Because flow velocity proximal to the fixed orifice (V1) is much lower
than the peak velocity through the orifice (V2), V1 can be ignored:
∆P = 4V2
¾ Pressure Gradients
ƒ Maximal pressure gradients from maximal velocity
ƒ Mean pressure gradients are calculated by
• Digitizing the jet velocity curve (where V1, . . . , Vn are instantaneous
velocities)
• Averaging the instantaneous gradients over the flow period
Time (s)
0
1
∆Pmax = 4Vmax2
Maximal
2
Velocity (m/s)
3
4
Vmax
Time (s)
0
1
Maximal
Velocity (m/s)
2
3
V1
Vn
V2
∆Pmean =
4V12 + 4V12 + 4V12 + ··· + 4Vn2
n
V3
4
™ Right heart pressures
¾ Right systoloic pressure (RVSP) equals the pulmonary artery pressure in the
absence of pulmonary stenosis
¾ Calculation of RVSP
ƒ Obtain peak velocity of tricuspid regurgitation jet
ƒ Estimate the right atrial pressure
8
•
Observe the inferior vena cava for
♦ Size
♦ Collapse with inspiration
∆PTR = 4VTR2 + RAP
Systolic
reversals in
hepatic veins
RAP
5 mmHg
10 mmHg
15 mmHg
20 mmHg
Size
normal
normal
dilated
dilated
Collapse
yes
no
yes
no
9
References
Anderson, B. ECHOCARDIOGRAPHY: Normal Examination and Echocardiographic
measurements. Brisbane:Fergies, 2000.
Oh, JK, Seward, JB, Tajik, AJ. The Echo Manual. Boston: Little, Brown and
Company, 1994.
Otto CM, Pearlman AS. Textbook of Clinical Echocardiography. Philadelphia: W.B.
Saunders Company, 1995.
Tei C, et al. New index of combined systolic and diastolic myocardial performance: a
simple and reproducable measure of cardiac function—a study in normals and
dilated cardiomyopahty. JACC. 26(6): 357-66.
10