Sunday, November 29, 2009

Assessment of the Left ventricular function in the presence of mitral regurge

The assessment of the rate of rise of LV pressure (dP/dt) can predict the intrinsic left vemtricular systolic function in a load-independent from. Thus it can be used in the assessment of left ventricular systolic function in the presence of mitral regurge. In fact, this method is under utilized in the daily practice.
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To take this measure you must have good picture of the maximum regurgitant jet. Then take a continuous wave doppler spectral profile with high sweep speed (100mm/sec or more). Then measure the time taken for the velocity to rise from 1m/sec to 3m/sec. From Bernolli equation: the pressure change in this time is 32mmHg (4(3)2 – 4(1) 2 = 36 – 4 = 32). Then dP/dt = 32/the measured time in seconds. Normally this value is > 1200. A dP/dt value from 800-1200 suggests mild systolic impairment. A dP/dt value <800>
LV systolic function
dP/dt
Time taken by LV to generate 32 mmHg
Normal
>1200
<27 br="" msec="">
Mild-moderate impairment
800 – 1200
27 – 40 msec
Sever impairment
<800 o:p="">

>40 msec


(click on the images to view full size)

The major advantage of this method is that it is independent from changes in the afterload as the measures are taken in the isovolumetric contraction phase (before the opening of the aortic valve. Also, this method is well-validated in comparison with cardiac catheterization results. Unfortunately this method is unreliable in cases of left ventricular dysynchrony as in cases of LBBB. Also, it is affected by left atrial compliance. So, it can not be used in cases of acute mitral regurge as the left atrial pressure is elevated and the left atrium is noncompliant. If the regurgitant jet is eccentric, excess care should be taken to make the cursor line at the direction of the jet and at its center to avoid false measurements. However sever aortic stenosis and systemic hypertension was found to affect the reliability of this method.
The dP/dt was found to have prognostic value in the course of chronic heart failure. It is also used to predict the postoperative left ventricular function before valve repair and replacement.
The same principle can be used in the assessment of the right ventricular systolic function with some modification. On the tricuspid valve the time is measured time interval is between the velocities 0 and 2 m/sec (due to the lower pressures on the right side). Thus the dP/dt value on the right side is calculated by dividing 16 on the time interval taken to raise the tricuspid regurge velocity from 0 to 2 m/sec. But this method is not well-validated to assess RV systolic function.
On the opposite side the –ve dP/dt, which is the rate of decline of left ventricular pressure, can be used as a measure for diastolic dysfunction.


References:
2- Feigenbaum's Echocardiography, 6th Edition
3- Echocardiography: the normal examination and echocardiographic measurements, by Bonita Anderson 2002.
4- The practice of clinical echocardiography, by Catherine M. Otto, 2007
5- Echocardiography Review Guide, by Catherine M. Otto and Rebecca Gibbons Schwaegler, 2007
6- Doppler-derived dP/dt and –dP/dt predict survival in congestive heart failure, Theodore J. Kolias, Keith D. Aaronson, and William F. Armstrong, 2000;36;1594-1599 J. Am. Coll. Cardiol.
7- A new method for estimating left ventricular dP/dt by continuous wave Doppler-echocardiography. Validation studies at cardiac catheterization, GS Bargiggia, C Bertucci, F Recusani, A Raisaro, S de Servi, LM Valdes-Cruz, DJ Sahn and L Tronconi, 1989;80;1287-1292 Circulation

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