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Assessment of Left Ventricular Systolic Function State of the Art ...

Assessment of Left Ventricular Systolic Function State of the Art ...

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## Assessment of Left Ventricular Systolic Function State of the Art ...

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**1. **Assessment of Left Ventricular Systolic FunctionState of the Art 2005

**2. **Assessment of LV Systolic Function Cardiovascular system provides tissues with oxygen, the substrate for metabolism
Delivery requires integration of the following:
Venous circulation/RV function (return)
Pulmonary circuit (oxygenation)
Left heart (delivery - bodys engine)
Peripheral circulation (tissue delivery)
Blood (fuel)
Most of circulatory disorders are due to LV abnormalities

**3. **Assessment of LV Systolic Function LV performance is dependent upon
Adequate filling (preload)
Intrinsic structure
Arrangement of individual myocytes
Normal valve and pericardial function
Acceptable resistance to ejection (afterload)
Think how severe AS affects LV
Intrinsic Contractile Function
This is the fundamental ability of myocytes to contract and generate force

**4. **Assessment of LV Systolic FunctionEjection Fraction Ratio of stroke volume to end-diastolic volume
(LVEDV - LVESV) / LVEDV
Normal resting LVEF: >50%
Most commonly used index. Why?
Easy to obtain
Visual assessment is accurate w/ experienced reader
Survival in most studies is ultimately related to EF

**7. **Calculation of Ejection Fraction Avoid foreshortening LV cavity
Horizontal long axis = Vertical long axis
Method of Discs (Biplane Simpsons)
Stack of ellipses
Volume = ?(area) x L(long axis)

**10. **Assessment of LV Systolic FunctionEjection Fraction: Limitations Disagreement between visual estimates and calculated values (cure: biplane Simpsons method)
Hard to see endocardial borders (cure: contrast)
LV is 3-dimensional; most models for calculation based on 2 dimensions (cure: 3D echo?)
These are technique limitations
Index is dependent upon:
Preload
Afterload
Heart rate
These are inherent physiologic limitations

**11. **Assessment of LV Systolic FunctionEjection Fraction: Limitations Normal LVEF: 50%
What is Lance Armstrongs resting EF? Is his heart impaired?
What if you have severe mitral regurgitation and EF 50%?
? afterload: would expect EF to ?
What if you have critical aortic stenosis and EF 50%?
? afterload: would expect EF to ?
The fundamental differences in the myocardial ability to generate force (contractility) in these examples is not reflected in the numerical value of EF

**12. **Assessment of LV Systolic FunctionEjection Fraction: Limitations LVEF is an EJECTION-PHASE INDEX
Factors that affect ejection affect the numerical value of LVEF
LVEF, while clinically useful, does not reflect the myocardial tissues ability to generate force
Are there other indices of ventricular performance?

**13. **Assessment of LV Systolic FunctionLV dP/dt What is LV dP/dt?
dP means the change in pressure, DP ? dP
dt means the change in time, Dt ? dt
The ratio of a given pressure change in a given period of time reflects the myocardiums contractility and is expressed as dP/dt

**14. **Assessment of LV Systolic FunctionLV dP/dt: An example

**15. **Assessment of LV Systolic FunctionLV dP/dt LV dP/dt is an ISOVOLUMIC INDEX
Force is generated after the mitral valve has closed and before the aortic valve has opened
Less affected by loading conditions (MR, AS)
Normal > 1000 mmHg/sec
How do we assess this by echo?

**17. **Assessment of LV Systolic FunctionLV dP/dt CW of MR jet
1 m/s = 4 mmHg
3 m/s = 36 mmHg
DP = 32 mmHg
Dt = the time difference between 1 m/s & 3 m/s
dP/dt = 32/Dt mmHg/sec

**18. **Assessment of LV Systolic FunctionLV dP/dt Use fast sweep speed
Need crisp signal
Consider using contrast
Can calculate negative dP/dt, which is the rate of recovery of pressure, by measuring the upslope between 3 m/s and 1m/s of the MR jet
Outcome: clinical CHF and EF <50%
Best survival: dP/dt > 600 mmHg/s
Intermediate: dP/dt < 600 mmHg/s but -dP/dt > 450 mmHg/s
Worst outcome: dP/dt < 600 mmHg/s and -dP/dt < 450 mmHg/sec (Source: Kolis et al, JACC 2000; 36:1594)

**19. **Assessment of LV Systolic FunctionLV dP/dt: Abnormal

**21. **Assessment of LV Systolic FunctionLV dP/dt: Limitations What if no mitral regurgitation?
Not truly an isovolumic index, if LV is emptying volume into left atrium with mitral regurgitation
dP/dt is dependent upon the peak pressure (P) that is generated: (dP/dt/P)
Echo cannot independently assess this
Are there other useful indices?

**22. **Assessment of LV Systolic FunctionMyocardial Performance Index (MPI) Known also as the Tei index
Also called Index of Myocardial Performance: IMP
It is the sum of the isovolumic contraction time (IVCT) and the isovolumic relaxation time (IVRT) to the ejection time
(IVCT + IVRT)/Eject time
It is a dimensionless index
Principle:
The better the myocardium, the less time spent generating force (IVCT) and recovering force (IVRT) and more time spent during systole actually ejecting blood from LV
A lower value is better

**23. **Assessment of LV Systolic FunctionMPI

**24. **Assessment of LV Systolic FunctionMyocardial Performance Index (MPI) Myocardial contractility and relaxation are energy dependent events
Myocardial dysfunction results in prolongation of IVCT and IVRT
Myocardial dysfunction results in a decrease in ejection time
With LV dysfunction:
Ratio of the sum of the isovolumic events (?)
Divided by ejection time (?)
Results in a number that increases as the numerator further ?s and the denominator further ?s.
The worse the ventricular function, the more MPI ?s

**25. **Assessment of LV Systolic FunctionMPI Utility Reflects LV systolic and diastolic properties
Independent of LV geometry. No geometric assumptions.
Derived by Doppler. Image quality less vital.
Not dependent of systemic BP
If HR 50-110 bpm, MPI not influenced

**26. **Assessment of LV Systolic FunctionMPI Normal ValuesLV MPI 0.35 0.05 (Upper value < 0.40)RV MPI 0.28 0.04 (Upper value < 0.32)
Echo calcuation requiring:
Pulse Doppler mitral inflow
CW Doppler aortic flow
Crisp Doppler signals

**27. **Assessment of LV Systolic FunctionMPI

**28. **Assessment of LV Systolic FunctionMPI

**29. **Assessment of LV Systolic FunctionMPI Step 3: Calculate
[ a - b ] / b
[(IVCT + EjT + IVRT) - EjT] / EjT
Normal ValuesLV MPI 0.35 0.05 (Upper value < 0.40)RV MPI 0.28 0.04 (Upper value < 0.32)

**30. **Assessment of LV Systolic FunctionMPI: Clinical Utility MPI post MI and cardiac events (Ascione, JASE 2003;16:1019)
LV MPI > 0.47
Sensitivity 90%
Specificity 68%
Role in valvular heart disease?
Role post transplantation?
Derive RVEF from RV MPI when RV is the systemic ventricle (Salehian, Circulation 2004; 110:3229)
RVEF = 65% - (45.2 x RV MPI)
MRI validated

**32. **Assessment of LV Systolic FunctionTissue Doppler Indices High temporal and spatial resolution to provide information on regional LV function
Can measure tissue velocity or local strain

**34. **Assessment of LV Systolic FunctionTissue Doppler Indices TDI
Easy
Reproducible
Limited by tethering + extracardiac motion
Strain Rate Imaging
? Myocardial Velocity/Distance
Requires differences in velocity throughout segment