Tissue Doppler echocardiography
Tissue Doppler echocardiography | |
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Purpose | measures the velocity of heart muscle |
Tissue Doppler echocardiography (TDE) is a medical ultrasound technology, specifically a form of echocardiography that measures the velocity of the heart muscle (myocardium) through the phases of one or more heartbeats by the Doppler effect (frequency shift) of the reflected ultrasound. The technique is the same as for flow Doppler echocardiography measuring flow velocities. Tissue signals, however, have higher amplitude and lower velocities, and the signals are extracted by using different filter and gain settings. The terms tissue Doppler imaging (TDI) and tissue velocity imaging (TVI) are usually synonymous with TDE because echocardiography is the main use of tissue Doppler.
Like Doppler flow, tissue Doppler can be acquired both by spectral analysis (
Pulsed tissue Doppler echocardiography
This has become a major echocardiographic tool for assessment of both systolic and diastolic ventricular function. However, as this is a spectral technique, it is important to realise that measurement of peak values is dependent on the width of the spectrum, which again is a function of gain setting.[citation needed]
Clinical use
Pulsed wave spectral tissue Doppler has become a universal tool that is part of the general echocardiographic examination. Like any other echocardiographic measurement, measures by tissue Doppler should be interpreted in the context of the whole examination. The velocity curves are in general taken from the base of the mitral annulus at the insertion of the mitral leaflets, in the septal and lateral points of the four chamber view, and eventually the anterior and inferior points of the two-chamber views. For the right ventricle it is customary to use the lateral point of the tricuspid annulus only. Averaging peak velocities from the septal and lateral point has become common, although it has been shown that averaging all four points mentioned above, gives significantly less variability[3]
The method measures annular velocities to and from the probe during the heart cycle.
Annular velocities summarize the longitudinal contraction of the ventricle during systole, and elongation during diastole. Peak velocities are commonly used.[citation needed]
Systolic function
Peak systolic annular velocity (S') of the left ventricle is as close to a contractility measure as you can get by imaging[4] (bearing in mind that any imaging method only measures the result of fibre shortening, without measuring myocyte tension). S' has become a reliable measure of global function[5][6][7][8] It shares the advantage of annular displacement, that it is reduced also in hypertrophic hearts with small ventricles and normal ejection fraction (HFNEF), which is often seen in Hypertensive heart disease, Hypertrophic cardiomyopathy and Aortic stenosis.[9]
Likewise, peak tricuspid annular systolic velocity has become a measure of the right ventricular systolic function[10][11]
Diastolic function
As the ventricle relaxes, the annulus moves towards the base of the heart, signifying the volume expansion of the ventricle. The peak mitral annular velocity during early filling, e' is a measure of left ventricular diastolic function, and has been shown to be relatively independent of left ventricular filling pressure.
During the two filling phases, there is early (E) and late (A)
Heart failure with preserved ejection fraction (HFPEF)
One of the main advantages of tissue Doppler is that diastolic and systolic function can be measured by the same tool. Before the advent of tissue Doppler, systolic function was usually assessed with
Mitral valve prolapse (MVP)
Pulsed-wave tissue Doppler can be used as a way to evaluate the severeness of arrhythmic mitral valve prolapse, by looking at the peak in the middle of the systole, which looks similar to Prussian Pickelhaube helmet, hence the name Pickelhaube spike.[24] This is one of the risk markers for malignant arrhythmias in patients with myxomatous mitral valve disease (MMVD) and bileaflet mitral valve prolapse (BMVP). It's significant when exceeds 16 cm/s. The sudden systolic overload of which Pickelhaube spike is an expression can act as a trigger for the onset of ventricular arrhythmias.[25]
Normal values and physiology
Normal gender and age related reference values For both S', e' and a' have been established in the large HUNT study, comprising 1266 subjects free of heart disease, hypertension and diabetes.[26]
This study also shows that both S' and e' values decline with age, while a' increases (fig). There is also a significant correlation between S' and e', also in healthy subjects, showing the connection between systolic and diastolic function.[citation needed]
The e'/a' ratio becomes <1 about 60 years of age, which is similar to the E/A ratio of mitral flow. Women has slightly higher S' and e' velocities than men, although the difference disappears with age. The study also did show that velocities were highest in the lateral wall, and lowest in the septum. The E/e' was thus dependent on the site of e' measurement. The ratio was also age dependent.[citation needed]
Colour tissue Doppler
Unlike spectral Doppler, colour tissue Doppler samples velocities from all points of the sector, by shooting two pulses successively, and calculating the velocity from the phase shift between them by autocorrelation. The calculation is slightly different from the true Doppler effect, but the result becomes identical. This results in a single velocity value per sample volume. The result is a velocity field of (nearly) simultaneous velocity vectors towards the probe. The advantage of colour Doppler over spectral Doppler is that all velocities can be sampled simultaneously. The disadvantage is that if there is clutter noise (stationary reverberations), the stationary echoes will be integrated in the velocity calculation, resulting in an under estimate. As pulsed wave Doppler are displayed as a spectrum, the colour Doppler values will correspond to the mean of the spectrum (in the absence of clutter), giving slightly lower values. In the HUNT study, the difference in peak systolic values were about 1.5 cm/s.[26]
The local velocities are not the result of the local function, as segments are moved by the action of neighbouring segments. Thus the velocity differences
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Further reading
- ISBN 978-90-810592-1-3.
- Marwick TH, Yu CM, Sun JP, eds. (2007). Myocardial Imaging: Tissue Doppler and Speckle Tracking. Malden, Mass.: Wiley-Blackwell. ISBN 978-1-4051-6113-8.