HEMODYNAMIC ASSESSMENT

INTRODUCTION Conventionally hemodynamics were obtained by cardiac catheterization. It is possible to determine the same by echocardiography.

Methods M-mode & 2D echo alone can provide only indirect evidence of hemodynamic abnormalities. These signs are not highly specific / sensitive. Doppler echo is the best tool to assess intra cardiac hemodynamics.

Doppler echo & the accuracy of doppler derived hemodynamic measurements has been validated by comparison with simultaneously derived catheterization data.

Stroke volume & CO Flow across a fixed orifice is equal to the product of the cross sectional area of the orifice & flow velocity. Velocities varies during ejection in a pulsatile system, individual velocities of the doppler spectrum need to be summed(tvi or VTI). Flow rate = CSA x FLOW VELOCITY SV = CSA X TVI CO = SV X HR

STROKE VOLUME IS THE PRODUCT OF CROSS SECTIONAL AREA AND THE FLOW VELOCITY INTEGRAL.

CSA The CSA of orifices in the heart is usually assumed to be a circle and it is determined from measurement of the orifice diameter(d). CSA = (D/2) ² X = D ² X 0.785 SV = D ² X 0.785 X TVI

MEASUREMENT OF STROKE VOLUME & CARDIAC OUTPUT

Regurgitant orifice area (ROA) ESTIMATED BY PISA USING THE PRINCIPAL OF CONTINUITY EQUATION.

PISA CALCULATION

REGURGITANT ORIFICE AREA CALCULATION

REGURGITANT VOLUME VOLUME OF BLOOD THAT REGURGITATES THROUGH AN INCOMPETANT ORIFICE WITH EACH HEART BEAT RV = TOTAL FORWARD FLOW (Q) _ SYSTEMIC FLOW(Qs).

An example of regurgitant volume calculation in MR.

REGURGITANT VOLUME CALCULATION BY PISA RV = REGURGITANT ORIFICE AREA X INTEGRATED VELOCITY OF MR JET

REGURGITANT FRACTION It is simply the percentage of regurgitant volume compared to flow across the regurgitant valve. Regurgitant fraction = REG VOL Q valve flow X 100

Pulmonary to systemic flow ratio (Qp/Qs) In the presence of intracardiac shunt the flow ratio between the pulmonary & systemic circulation usually indicates the magnitude of shunt. Pulmonary flow (Qp) is calculated from the RVOT & systemic flow (Qs), from the LVOT.

RVOT TVI X RVOT CSA Qp/Qs = LVOT TVI X LVOT CSA.

DOPPLER ESTIMATION OF INTRA-CARDIAC PRESSURES

RIGHT ATRIAL PRESURE IVC diameter measurement adjacent to right atrium Subcostal view During quite respiration & forced inspiration

RV SYSTOLIC PRESSURE BY TR VELOCITY JET Reflects pressure difference between RV &RA TR present in 75% normal adults Normal velocity 2-2.5m/sec Higher velocity PS or PHT

ESTIMATION OF SYSTOLIC PAP IN THE ABSENCE OF PS PAP = 4( V TR)² + RAP systolic

ESTIMATION OF SYSTOLIC PAP IN THE PRESENCE OF PS PAP = RVSP 4(V PS) ² systolic PAP = (4 (VTR)² + RAP ) 4(V PS) ² systolic

RVOT FLOW ACCELERATION TIME Pulse wave doppler Sample volume at valve annulus Ac T=Time between beginning of flow & peak velocity Normal 120 m Sec or higher PHT Ac T Shortened

Fig. 4-43. Pulmonary artery flow in three patients with differing pulmonary artery pressures. The acceleration time (AT) becomes shorter as the pulmonary artery pressure rises.

ESTIMATION OF MEAN PAP FROM RVOT Ac T MAHAN S regression equation MPAP = 79 - ( 0.45 X Ac T)

PULMONARY REGURGITATION VELOCITY Reflects end diastolic pressure gradient between PA & RV At end diastole RV pressure = RAP Used to calculate PAEDP & mean PAP

ESIMATION OF END DIASTOLIC PAP FROM PR VELOCITY PAEDP RVEDP = 4 X PR EDV ² PAEDP = 4 X PR EDV ² + RVEDP = 4 X PR EDV ² + RAP

ESIMATION OF MEAN PAP FROM PR VELOCITY According to Masuyama Mean PAP = 4 X peak PR velocity ²

LVEDP LVEDP & LV diastolic function are closely related phenomenon. Changes in mitral flow velocities in early & late diastole reflect changes in LVEDP. In presence of AR the LVEDP is easily calculated. AR velocity reflects the diastolic pressure difference between AO & LV.

LA PRESSURE MR velocity represents the systolic pressure difference between the LV & the LA. In patients without LV outflow obstruction systolic BP is practically same as LV systolic pressure. LA pressure = SBP 4 x MRV²

Relation of PVF with LAP LAP = 35-0.39 X ( SYSTOLIC FRACTION ) SYSTOLIC FRACTION = Si X 100 Si+Di

PCWP by MITRAL & TISSUE DOPPLER PCWP = 1.24 X E + 1.9 E

LVEDP by MITRAL & TISSUE DOPPLER E > 15 E LVEDP > 12 mmhg

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