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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 Function State 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 - body’s ‘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 Function Ejection 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 Simpson’s) Stack of ellipses Volume = ?(area) x L(long axis)

    10. Assessment of LV Systolic Function Ejection Fraction: Limitations Disagreement between visual estimates and calculated values (cure: biplane Simpson’s 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 Function Ejection Fraction: Limitations ‘Normal’ LVEF: 50% What is Lance Armstrong’s 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 Function Ejection 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 tissue’s ability to generate force Are there other indices of ventricular performance?

    13. Assessment of LV Systolic Function LV 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 myocardium’s contractility and is expressed as dP/dt

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

    15. Assessment of LV Systolic Function LV 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 Function LV 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 Function LV 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 Function LV dP/dt: Abnormal

    21. Assessment of LV Systolic Function LV 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 Function Myocardial 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 Function MPI

    24. Assessment of LV Systolic Function Myocardial 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 Function MPI 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 Function MPI Normal Values LV 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 Function MPI

    28. Assessment of LV Systolic Function MPI

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

    30. Assessment of LV Systolic Function MPI: 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 Function Tissue 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 Function Tissue Doppler Indices TDI Easy Reproducible Limited by tethering + extracardiac motion Strain Rate Imaging ? Myocardial Velocity/Distance Requires differences in velocity throughout segment

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