LV Systolic Function Flashcards
1
Q
4 basic ways to assess systolic function?
A
- Fractional Shortening (>30%) 1D [distance]
- Fractional Area Change (> 50%) 2D [area]
- Ejection Fraction (>55%) 3D [volume]
- SV/CO Measurement
2
Q
What are the 6 more advanced methods to estimate systolic function?
A
- Dp/Dt
- Velocity of Circumferential Shortening (Vcf)
- End Systolic Elastance
- Preload Recruitable Stroke Work
- Strain Rate
- Tissue Doppler Peak Sysytolic Velocity
3
Q
What features are assessed in Qualitative Assessment?
A
- Visual estimation
- Wall Motion/Thickening (hypokinesis, dyskinesis, akinesis)
4
Q
How many segments in LV?
A
17
5
Q
Describe the various regions of LV
A
- Anterior: Anterior, Anterolateral and Anteroseptal Walls
- Inferior: Inferior, Inferolateral, Inferoseptal
6
Q
Describe the Blood Supply of LV
A
LMS -> LAD and LCx
LAD: anterior, anteroseptal and inferoseptal walls
LCx: lateral, anterolateral and inferolateral walls
RCA: inferior wall
7
Q
Describe the blood supply of the Inferoseptal region
A
It can either be supplied by LAD or RCA
8
Q
What does “dominance” mean in terms of Coronary Artery supply?
A
Which side (right or left) becomes the posterior descending artery
9
Q
What can give rise to RWMAs?
A
- Pacing and/or Conduction Abnormalities
- Vasospasm
- Ischaemia
10
Q
What is the eqn for Fractional Shortening?
A
FS = LV EDd - LV ESd/LV EDd
11
Q
Where and how is FS measured?
A
Just beyond the MV at the chordal level - perpendicular to the long axis of the LV - using M Mode
12
Q
What views can be used to measure FS?
A
TG mid pap view (just distal to pap muscles to exclude them) and TG 2 chamber (90)
13
Q
What is normal FS?
A
> 30%
14
Q
What are the advantages of FS?
A
- Simple to perform
- Quickly obtained
- Values not cubed (ie. Errors are not magnified)
15
Q
What are the limitations of FS?
A
- Uses only a single image so may not accurately reflect global LV function (a single systolic and diastolic dimension)
- Load dependent
16
Q
What is the formula for FAC?
A
FAC = LV EDa - LV ESa/ LV EDa
17
Q
How and where do you preform the FAC?
A
TG Mid Pap view (including the pap muscles) - trace out the area (2D)
18
Q
What is normal FAC?
A
> 50%
19
Q
Discuss automated FAC mode
A
Automated methods of real time quantification are available on some machines - acoustic amplification-> number
20
Q
What is the limitation of FAC?
A
- Endocardial borders of the lateral and septal walls can be difficult to image
21
Q
What is the eqn for EF?
A
EF = LV EDV - LV ESV/ LV EDV
22
Q
What method is used to calculate the LV Volume? How is it preformed?
A
Simpsons Method of Discs - 2 planes - in both Diastole and Systole
Trace out the area in end diastole and end systole
23
Q
What is the advantage of measuring the LV EF?
A
Widely regarded as a predictor of outcome and survival
24
Q
What are the limitations of measuring LVEF?
A
- Need very clear endocardial borders
- Errors are magnified
- Time consuming to measure
25
What is LVEF dependent on?
1. Preload
2. Contractility (not a true index of)
3. Afterload
26
How is SV/CO measured?
Volumetric calculation
Volume = area x distance
SV = cross sectional area x stroke distance
CO = SV x HR
27
Where can SV/CO be measured?
LVOT or AV
RVOT or PV
28
What does the accuracy of SV measurement depend on?
1. Parallel alignment of the US beam to the blood flow
2. Accurate determination of the vessel CSA
29
What is VTI? What does it represent?
Velocity Time Integral
'Stroke Distance' = Velocity x Time
The AUC (velocity x time) that occurs during systole (between AV opening and closing)
30
How is SV defined in terms of VTI?
SV = Area (CSA) x Stroke Distance (VTI)
31
How is SV then converted to CO?
HR or measure R-R interval
32
What is Qp/Qs?
Ratio of pulmonary blood flow to systemic blood flow
or Pulmonary SV:Systemic SV
33
How is the SV of the PA or LVOT determined?
SV = Area (PA or LVOT) x VTI (PA or LVOT)
34
How do you obtain SVpa?
-Midoesophagheal SAX Aortic Valve
- Pull up probe to get Trouser Leg
- View of the PA and Branches
- Measure Diameter of PA
- Doppler down across PA (blood flow towards the probe - upward deflection on PW/CW Spectral Profile)
35
What is Dp/Dt?
change in pressure with respect to time during isovolumetric LV contraction
"isovolumetric rate of LV Pressure Rise"
36
How do you measure Dp/Dt?
Marks two points on Doppler - velocity 1m/s and 3m/s
Slope and Time Taken between points
Slope of LV pressure rise between 4-36mmHg (1m/s - 3m/s)
37
What is the normal value for Dp/Dt?
1610 +/- 290 mmHg
[1200-1400mmHg]
38
How does loading affect Dp/Dt?
relatively independent of after load
dependent on preload
requires a regurge Jet to measure
39
When can you not use Dp/Dt?
If a patient has had Mitral Valve surgery - will have decreased values
40
What are the limitations of Dp/Dt?
Angle Dependent Measurement
low velocity, high amplitude signals
influenced by tethering
translation can be used to calculate strain rate
41
What is a useful application for measuring peak systolic velocities?
Can be used to calculate strain rate
42
Strain, Strain Rate and Speckle Tracking
* Angle and load Independent
* Exempt from influence of translation
* strain is dimensionless
* speckle tracking measures strain throughout cardiac cycle
43
What is the simplified Bernoulli Eqn?
change in [P] = 4V^2
44
How is Bernoulli applied MR jet?
Change [P] = (pLV - pLA) = 4 (MR)-2
Solve for pLV
pLV = 4 (Vmr)-2 + pLA
MR 1m/s and MR 3m/s applied
36 - 4 mmHg = 32mmHg (deltaP)
Remove LA pressure as assumed stable during isovolumetric contraction
Need to then just measure deltaT (from 1m/s - 3m/s)
45
How does the slope of the MR jet reflect LV systolic function?
The steeper the slope, the faster the pressure increase generated by the LV
ie. the better the systolic function
46
What does VCF stand for?
Velocity of Circumferential Fibre shortening
47
What does VCF mean?
the fractional shortening with ejection time as the denominator
FS = (LV EDd - LV ESd)/LV EDd
VCF = (LV EDd - LV ESd)/LV EDd x ET
48
How do you measure the Ejection Time for VCF Eqn?
Continuous Wave Doppler in transgastric at 120 degrees through AV
M-Mode in mid-oesophageal at 120 degrees through AV
Time from aortic valve open to closed
49
If using M-Mode through AV valve and fluttering occurs, what is this pathognomic for?
HOCM
50
Why is VCF used vs. EF as an estimate of LV Systolic Function?
? less preload dependent than EF
51
What is End Systolic Elastance?
a true load-independent index measurement of contractility - mainly used in research
52
How is End Systolic Elastance measured?
The end-systolic point (ie. when AV closes) on the pressure/volume LV curve is plotted under varying volume conditions
Catheter in Heart while vena cavae occluded -> no load changes -> change in contractility
The slope of the line connecting these end-systolic points indicates the end-systolic elastance
The steeper the sloper -> better contractility or function
53
What is Preload Recruitable Stroke Work?
LV Pressure-Volume Loop
AUC = Stroke Work
Plot Sroke Work as Function of EDV
-> Slope Value
Another load-independent measure of systolic function
54
What is Preload Adjusted Max Power?
Used in Research
Stroke Work/(EDV)-2
Stroke Work/(EDA)-3/2
Load independent
55
How is Tissue Doppler Peak Systolic Velocity measured?
PW Doppler through lateral Mitral annulus?
Measured at the end of the QRS
Faster Systolic Velocty = Better Function
56
What is Strain?
Dimensionless Index
Length is produced by the application of Stress to the Fibres
Strain = (L1 - L2) / L1
57
What is Strain Rate?
Strain/time difference
58
What is a limitation of Strain measurement?
Measured using doppler which is dependent of the angle of the US
Tissue doppler velocities are low velocity high amplitude signals
59
What do Strain and Strain Rate Assess?
the relative length of adjacent targets within the heart
60
What is Speckle Tracking?
Measures the strain and the strain rate but is INDEPENDENT of angle (no Doppler is used)
independent of translcation
limited by noise
61
What are the Load Independent Measures of LV Systolic Function?
62
What are the 4 main contributors to Heart Failure?
1. LV Systolic Dysfunction
2. LV Diastolic Dysfunction
3. RV Dysfunction
4. Pericardial Disease
63
What are the benefits of assessing LV systolic function?
1. Risk Stratification Pre Op
2. Predicting if possible difficulty weaning from CPB and need for Mechanical Support
3. Assessing cause of Instability (Fluids vs. Ionotropes)
4. Look for RWMAs
64
What 3 ways can LV Systolic Dysfunction be described?
1. Global
2. Regional
3. Cardiomyopathy in Origin
65
What are the 5 aetiologies of global LV dysfunction?
1. Impaired contractility (coronary insufficiency, cardiomyopathy)
2. Volume Overload (AR/MR, intracardiac shunt)
3. Pressure Overload (obstruction to LV ejection - mechanical AS/Coarctation or functional HTN)
4. RV Dilation
5. External Compression (tamponade, constrictive pericarditis, tumour)
66
What are the components of SV?
1. Preload
2. Contractility
3. Afterload
(4. Ventricular Geomtetry)
67
What is Preload?
the myocardial fibre stretch immediately prior to the onset of contraction
clinically: LV EDV
68
What is Contractility?
the intrinsic contractile strength of ventricles
the amount of work the heart can do under constant loading conditions (ie. preload and afterload)
69
What is Afterload?
the ventricular wall stress at the onset of ventricular contraction
70
What law applies to Afterload?
Law of Laplace
71
What causes increases and decreases in Afterload?
Increase Afterload:
- Increased LV pressure (AS/HTN)
- LV dilation from volume (AR)
Decreased Afterload:
- LV Hypertrophy
- Raised Intrathoracic Pressure (IPPV)
72
What are the two methods to assess SV?
1. Volumetric: Simpson's Biplane (LV EDV - LV ESV)
2. Doppler Method
73
What causes LV dysfunction and LV size increases?
1. Dilated Cardiomyopathy
2. Ischaemic Cardiomyopathy (chronic MIs)
3. Chronic Volume Overload
74
How does enlargement of LV affect it's function?
altered geometry; loss of cylindrical shape -> spherical shape
spherical enlargement causes systolic tethering of mitral leaflets -> MR
[MR is a cause and consequence of LV Dilation]
75
How does MI cause Dilation?
1. LV infarction (esp Anterior) -> remodelling -> LV Dilation
Global LV dilation although a regional infarct that was localised
76
What causes LV dysfunction but LV size remains normal or decreases?
1. LV Pressure Overload
2. Hypertrophic Cardiomyopathy
3. Restrictive Cardiomyopathy
77
What causes an increase in Wall Thickness/Hyperthropy?
Concentric:
- Chronic Pressure Overload
- HCM
(increased wall thickness with a normal chamber size)
Eccentric:
- chronic volume overload
(increased wall thickness and increased chamber size)
78
What causes a decrease in wall thickness?
- DCM
- Post MI Remodelling
79
How do you differentiate between Concentric and Eccentric Hypertrophy on TOE?
- assess LV at transgastric mid pap level
- 1D imaging: M-Mode
- 2D imaging: Area
"Regional Wall Thickness"
RWT: 2PWTd/ LV EDV
< 0.42 = normal or eccentric hypertrophy
>0.42 = concentric hypertrophy
80
What is "End Diastole" on TOE imaging?
first frame post MV closure or largest LV dimension
81
What is "End Systole" on TOE imaging?
first frame post AV closure or smallest LV dimension
82
Is there a good correlation between Fractional Shortening and EF?
Yes
83
When is Fractional Shortening not reliable?
If RWMAs present;
underestimation of LV function if RWMA at site of interrogation
overestimation of LV function if RWMA distant from region
84
How does Simpson's Biplane method estimate LV Volume?
conversion of area -> volume estimation
method of discs
biplane disk summation method taken at orthogonal views (4C and 2C) in End Systole and End Diastole
85
What are the advantages of Simpson's Biplane?
1. Few geometric Assumptions
2. Accounts for shape disstortion (if seen in 2 views)
86
What are the limitations of Simpson's Biplane?
1. Foreshortening (esp in 4C view)
- disproportionally decreased LV ESV vs. LV EDV -> overestimation of LV EF
87
How is LV EF related to preload and afterload?
-relatively independent of Preload; slope of the ventricular function curve, relatively linear over the working range of the LV
- sensitive to changes in Afterload; especially when systolic function is impaired (increased afterload -> decreased LV EF)
88
What are the ranges of LV EF?
1. normal > 55%
2. mildly abnormal 40 - 50%
3. moderately abnormal 30 - 40%
4. severely abnormal < 30%
89
How does FAC relate to EF?
FAC is about 10% < LV EF
90
What are the Reference Ranges for FAC?
FAC: 40-60%
LV EDA: 12- 16cm2
LV ESA: 4- 8cm2
91
What factors affect LV Size?
1. Systolic LV function
2. LV Diastolic function (compliance)
3. Preload
4. Afterload
5. RV Function
92
What is the relationship between SV and LVEF?
they do not always change in parallel - they are related by LV EDV
EF: SV/LV EDV
93
Why are EF and SV/CO assesed?
LV EF = prognosticator (cardiology)
SV/CO = tissue O2 delivery (anaes/ICU)
94
Compare Chronic and Acute HF in terms of EF and SV
Chronic HF:
- low EF
- SV may be normal (if afterload is kept low) as LV EDV is high
Acute HF:
- both EF and SV will be low as LV EDV normal (heart hasn't compensated/dilated yet)
95
Discuss EF and SV in terms of Hypovolaemia.
SV will be low (hypovolaemic)
EF will be normal or increased (total LV EDV low)
96
What is TDI?
Tissue Doppler Imaging
97
How does TDI work?
measures myocardial velocity
PW or Colour modes
98
How does myocardial tissue velocity compare to blood velocity during the cardiac cycle?
Myocardial velocities (<15cm/s)
Blood velocity (>50cm/s)
99
How do PW and Colour mode TDI differ?
PW TDI measures peak instantaneous velocity
- produces a standard velocity-time curve, no further processing
Colour TDI measures mean velocity (approx 20% lower)
- need offline processing afterwards to calculate strain and strain rate curves
100
What can TDI not distinguish between in terms of motion during cardiac cycle?
cannot distinguish between active cardiac contraction and motion due to tethering
101
What is Speckle Tracking?
- a technique for measuring myocardial velocity strain and SR
- based on tracking the movement of naturally occurring speckles on 2D grayscale
- tracks location of speckles from end diastole to end systole
102
What are the advantages of Speckle Tracking?
- the measurements can be in any direction (vs. TDI)
- independent of angle
103
What is a disadvantage of Speckle Tracking?
- not instantaneous
- performed offline on stored 2D images (not feasible in OT?)
104
What is Strain?
the functional change in length of a myocardial segment
it is dimensionless and usually expressed as a positive or negative change (%)
negative when myocardium shortens (below baseline on strain-trime curve)
105
What is Strain Rate?
the rate of change of strain
the difference in velocity at the two sample points, divided by the distance between them
V1 - V2 / d
SR = slope of strain curve (steeper = more positive strain)
106
What is an advantage of Strain/SR over Velocity Tissue Measurements?
Strain and SR can distinguish between active and passive contraction
107
What is a "normal" value for strain?
Values > -20% in TTE applied for TOE
108
What is a normal value for PW TDI?
Lateral Mitral Annulus >7.5m/s
Simple global measure of LV systolic function
