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Non invasive haemodynamic assessment by ECHOCARDIOGRAPHY By : Dr Sunil Chhajwani (M.D)Consultant Anaesthesiologist SSSIHMS, Bangalore. Haemodynamics assessment will be discussed under following headings Assessment of systolic function
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By : Dr Sunil Chhajwani
dP/dT of the mitral regurgitant jet
2..Doppler measurement of stroke volume...and therefore cardiac output
First obtain a parasternal long axis view and place a M-mode cursor is placed through the septal and posterior LV walls just beyond the tip of the mitral leaflets.
In the resultant M-mode image take measurements of the RV internal dimension, interventricular septum thickness, LV internal dimension and LV posterior wall thickness at end-diastole (timed on ECG or point of largest LV internal dimension) and at end-systole (ECG timed or point of smallest LV internal dimension).
In this method, acquire A4C or A2C views, making sure that the endocardial borders are visualised well.
Freeze the image and scroll backward and forward to identify a frame at end diastole. This can be timed using the appearance of the ventricle - identifying a frame where the ventricle appears to have the largest volume; or with the ECG trace, where the peak of the R wave corresponds to end-diastole.
The machine will then calculate the ejection fraction by using the formula:
Ejection fraction = (LVEDV - LVESV)/LVEDV
Placement of the second cursor point on the 3m/s line: The dP/dT in this case is normal
This method is only useful in patients with enough MR to obtain a well-defined velocity curve.
LA should be compliant.
Click artifact (caused by valve closure) can obscure the descending limb of the CWD envelope, which makes measurements difficult.
Eccentric MR jets may not reflect true velocity and will result in underestimation of dp/dt unless careful colour Doppler examination of the jet is made to minimize CWD error.
A normal dp/dt maybe present in hypertension and aortic stenosis even with impaired LV function.
Although the above techniques are useful to assess the contractility of the mocardium, what is really of interest to the intensivist is the net result of myocardial stretch and contractility....the stroke volume and cardiac output.
Although cardiac output can be calculated using doppler at any of the valve orifices of the heart, the mitral or tricuspid annuli, the RVOT or the LVOT, the measurement is done most commonly at the LVOT.
Obtain the mitral inflow wave pattern on PWD and freeze the image. After selecting Dct under "Mitral Valve" in the calculations menu, the cursor is first placed at the peak of the E wave.
Typically, 2 negative waves in diastole and 1 positive wave in systole is seen. The first of the diastolic waves is the result of movement of the annulus towards the left atrium during initial filling of the LV. This wave is referred to as e'. The second diastolic wave is referred to as a'. The systolic wave is labelled s'.
place the TDI cursor over the lateral mitral annulus in the A4C view, at the base of the posterior mitral leaflet.
Repeat the above procedure for the measurement of e' (lateral)
Mitral inflow patterns:
Timing correlates of LA pressure, mitral inflow and pulmonary venous flow:
Markers of elevated LV filling pressure:
1)Mean RA pressure (mmHg)
2)RV peak systolic pressure (mmHg)
3)RV end-diastolic pressure (mmHg)
Almost same as mean RA pressure in absence of RV inflow obstruction
4)PA systolic pressure (mmHg)
Almost same as RV systolic pressure in absence of RV outflow obstruction
Figure 1: Estimation of right atrial pressure from inferior vena cava size and collapsibility with inspiration.
In the above example, estimated right pressure is 10-15 mmHg.
Figure 2: Estimation of pulmonary artery peak systolic pressure (PASP) from peak tricuspid regurgitation gradient [see text for details]. In the above example, PASP = 38 mmHg + estimated right atrial pressure.
mPAP= 0.61 X PASP (derived from TR velocity) + 2mm Hg.
In this method, mPAP is derived from the continuous wave spectral trace of pulmonary regurgitation (PR) jet using the simplified Bernoulli equation-
mPAP= 4 X (peak PR velocity)2.
mPAP= 79- [0.45 X RVOT acceleration time in milliseconds)
RVOT acceleration time is measured from the pulsed-wave Doppler interrogation of the RVOT. In the basal short axis view, place the sample volume within the RVOT and obtain the velocity trace. Time from the onset of the trace to peak velocity is the acceleration time.
: Estimation of pulmonary artery end-diastolic pressure (PAEDP) from pulmonary regurgitation (PR) jet. Addition of right atrial pressure to PR end-diastolic gradient yields PAEDP [see text for details]. In the above example, PAEDP = 18 mmHg + estimated right atrial pressure.
1) Obtain peak TR velocity as described previously.
2 )Obtain RVOT pulsed-wave Doppler recording and trace the entire spectral display to obtain velocity time integral.
3 )Use the above-mentioned equation to calculate PVR. It has been shown that PVR derived by this method is accurate and correlates well with the cardiac catheterization derived values (9).
The following measurements and indices are used for this purpose:
Figure 1: Longitudinal view of the inferior vena cava (IVC))
Place a M-mode line through the IVC 1-2cms from its junction with the right atrium
If the patient is spontaneously breathing, ask him to take a short quick inspiratory effort ("a sniff") during the M-mode recording. If the patient is mechanically ventilated, record the M-mode through 3 or 4 respiratory cycles.
Freeze the M-mode image and using calipers, measure the maximum and minimum diameter of the IVC tracing.
Physiological respiratory variations in IVC diameter in a healthy volunteer breathing quietly.
The relation pressure/IVC diameter is characterized by an initial ascending curve (arrow 1) where the compliance index (slope) does not vary, and an almost horizontal end part where the compliance index progressively decreases, because of the distension.
Respiratory variations in IVC diameter in a patient on controlled ventilation
In a patient requiring ventilatory support, the inspiratory phase induces an increase in pleural pressure, which is transmitted to the right atrium, thus reducing venous return. The result is an inversion of the cyclic changes in IVC diameter, leading to increases in the inspiratory phase and decreases in the expiratory phase.
Measuring the maximum and minimum diameters in a M-mode tracing of the IVC showing marked IVC variability
Measuring the maximum and minimum diameters in a M-mode tracing of the IVC showing insignificant IVC variability
Correct placement of the PWD cursor in the LVOT proximal to the aortic valve