Hemodynamic Assessment. Assessment of Systolic Function Doppler Hemodynamics

Transcription

1 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) Can be measured through any intracardiac site Assumptions Orifice area is circular & constant Area and velocity measured at same site Transducer aligned parallel to flow Laminar flow profile LV ejects volume of blood through cylindrical aorta with each beat Base of cylinder is the cross-sectional area of the aorta Height of cylinder is the distance the average blood cell traveled during each beat This is expressed as the integral of the Doppler systolic time -velocity curve (TVI) Volume of a cylinder equals base times height; therefore, stroke volume is CSA multiplied by TVI ¼ π CSA (cm 2 ) = {diameter (cm)} 2 X SV (cc) = CSA (cm 2 ) X TVI (cm) 1

2 Normal SV cc/beat Measurement of Left Ventricular Outflow Tract (LVOT) Stroke Volume Most frequently used location Diameter (cm) of the AV annulus During mid-systole inner edge-to-inner edge Measure at the annulus from the insertion point of the right coronary cusp to the insertion point of the non-coronary cusp Normal range = 1.8 cm 2.2 cm TVI (cm) of LVOT From apical long-axis using pulsed-wave Doppler, place the sample volume the base of the aortic valve At the same location of the measurement of the LVOT diameter Obtain the spectral Doppler signal that includes the closing click of the valve Trace the leading edge of the velocity spectrum to obtain the TVI (cm) Normal range = 16 cm 22 cm Advantages of measuring SV in LVOT Flow remains laminar proximal to a stenotic valve Can be recorded in almost all patients Normal CO Cardiac Output (CO) 4-7 L/min The volume of blood ejected per minute Stroke volume multiplied by the heart rate at the time of TVI measurement CO (L/min) = SV (cc) X HR (bpm)

3 Normal CI L/min/m 2 Cardiac Index (CI) Correcting the cardiac output to body surface area (BSA) Cardiac output divided by the patient s BSA CI = CO (L/min) BSA Tei Index or Index of Myocardial Performance (IMP) Reflects global myocardial performance Includes systolic and diastolic phases Predictor of clinical outcome and functional status Independent of Heart rate Right venticular pressure Pulmonary artery pressure Loading conditions Right ventricular Index of Myocardial Performance (RIMP) Strong predictor of survival in patients with pulmonary hypertension RIMP > 0.82 indicates a decrease in survival IMP = IVCT +IVRT - ET ET AVCO Ejection Time Mitral/Tricuspid Inflow LV or RV outflow IMP = AVCO - ET ET IVCT IVRT 3

4 Valve Areas Important in the evaluation of valvular stenosis Continuity Equation Based on the priniple of conservation of mass What flows in, must flow out Uses Calculation of valve areas Calculation of regurgitant volumes and regurgitant fractions Calculation of regurgitant orifice areas Calculation of intracardiac shunts When flow rate (Q) is maintained, volumetric flow on each side of narrowing is equal (Q 1 = Q 2 ) 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 By rearranging the equation the CSA 2 can be derived CSA 1 X V 1 = CSA 2 X V 2 CSA 1 X TVI 1 = CSA 2 X TVI 2 CSA 2 = CSA 1 X TVI 1 TVI 2 Limitations of the Continuity Equation CSA calculation Errors in the measurement of the diameter are reflected in the calculation of the CSA 4

5 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 TVI measurements Incorrect sample volume placement Ultrasound beam is not parallel to blood flow Over or undergaining of spectral display Incorrect filter settings CSA 2 calculation error Failure to obtain highest Doppler signal (try multiple windows and angles) Poor alignment (not parallel to blood flow) Aortic Valve Area Doppler assessment Peak aortic velocity Mean pressure gradient Aortic valve area LVOT-to-Aortic valve TVI Assessing for the maximal aortic velocity is achieved by assessing the valve from multiple windows Apical Subcostal Suprasternal Notch Right Supraclavicular Right Parasternal AVA Calculation Determine the LVOT SV using TVI Obtain the maximal aortic valve velocity and mean gradient Use continuity equation to calculate AVA 5

6 Mitral Valve Area 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 *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 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 MVA = 6.28 x r 2 x alias velocity Peak mitral inflow velocity x α 180 6

7 Gradients Doppler-derived gradients have been validated by cardiac catheterization data Bernoulli Equation Uses Measurement of maximal and mean pressure gradients across stenotic lesions Maxiaml pressure gradients across regurgitant valve lesions and shunts Intracardiac pressure estimation Conservation of energy Energy flowing in is equal to the total energy flowing out The movement of blood flow within the CV system is determined by pressure differences between 2 locations V 1 V 2 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 (V V 1 2 ) 7

8 Because flow velocity proximal to the fixed orifice (V 1 ) is much lower than the peak velocity through the orifice (V 2 ), V 1 can be ignored: P = 4V 2 Pressure Gradients Maximal pressure gradients from maximal velocity Mean pressure gradients are calculated by Digitizing the jet velocity curve (where V 1,..., V n are instantaneous velocities) Averaging the instantaneous gradients over the flow period Time (s) 0 Maximal Velocity (m/s) P max = 4V max 2 4 Vmax Time (s) 0 Maximal Velocity (m/s) 1 2 V 1 V 2 V n P mean = 4V V V V n 2 n 3 V 3 4 Right heart pressures Right systoloic pressure (RVSP) equals the pulmonary artery pressure in the absence of pulmonary stenosis Calculation of RVSP Obtain peak velocity of tricuspid regurgitation jet Estimate the right atrial pressure 8

9 Observe the inferior vena cava for Size Collapse with inspiration P TR = 4V TR 2 + RAP Systolic reversals in hepatic veins RAP Size Collapse 5 mmhg normal yes 10 mmhg normal no 15 mmhg dilated yes 20 mmhg dilated no 9

10 References Anderson, B. ECHOCARDIOGRAPHY: Normal Examination and Echocardiographic measurements. Brisbane:Fergies, Oh, JK, Seward, JB, Tajik, AJ. The Echo Manual. Boston: Little, Brown and Company, Otto CM, Pearlman AS. Textbook of Clinical Echocardiography. Philadelphia: W.B. Saunders Company, 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):