Tissue Doppler echocardiography

Tissue Doppler echocardiography
Tissue Doppler echocardiography
Purpose	measures the velocity of heart muscle

Last updated June 16, 2024

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 (spectral density estimation) as pulsed Doppler^[1] and by the autocorrelation technique as colour tissue Doppler^[2] (duplex ultrasonography). While pulsed Doppler only acquires the velocity at one point at a time, colour Doppler can acquire simultaneous pixel velocity values across the whole imaging field. Pulsed Doppler on the other hand, is more robust against noise, as peak values are measured on top of the spectrum, and are unaffected of the presence of clutter (stationary reverberation noise).

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

Spectral tissue velocity curves from the mitral annulus at the septal (left) and lateral (right) points. The curves show multiple heartbeats. PwTDI.jpg — **Spectral tissue velocity curves from the mitral annulus at the septal (left) and lateral (right) points.** The curves show multiple heartbeats.

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.

Single spectral tissue velocity curve from the mitral annulus. The curve shows velocities towards the probe (positive velocity) in systole, and away from the probe (negative velocities) in diastole. The most useful measures are the peak velocities, in systole S' and in early diastole (e') and late diastole during atrial contraction (a'). PwTVI.jpg — **Single spectral tissue velocity curve from the mitral annulus.** The curve shows velocities towards the probe (positive velocity) in systole, and away from the probe (negative velocities) in diastole. The most useful measures are the peak velocities, in systole S' and in early diastole (e') and late diastole during atrial contraction (a').

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.^[12]^[13]^[14] If there is impaired relaxation (Diastolic dysfunction), the e' velocity decreases. After the early relaxation, the ventricular myocardium is passive, the late velocity peak a' is a function of atrial contraction. The ratio between e' and a' is also a measure of diastolic function, in addition to the absolute values.^{[ citation needed ]}

During the two filling phases, there is early (E) and late (A) blood flow from the atrium to the ventricle, corresponding to the annular velocity phases. The flow, is driven by the pressure difference between atrium and ventricle, this pressure difference is both a function of the pressure drop during early relaxation and the initial atrial pressure. In light diastolic dysfunction, the peak early mitral flow velocity E is reduced in proportion to the e', but if relaxation is so reduced that it causes increase in atrial pressure, E will increase again, while e', being less load dependent, remains low. Thus, the ratio E/e' is related to the atrial pressure, and can show increased filling pressure^[15]^[16] although with several reservations.^[17]^[18] In the right ventricle this is not an important principle, as the right atrial pressure is the same as central venous pressure which can easily be assessed from venous congestion.^[19]^[20]

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 ejection fraction (EF), and diastolic function by mitral flow. This led to the concept of pure "diastolic heart failure". However, In hypertrophic left ventricles with small cavity size, the systolic function is reduced although EF is not, as the EF is dependent on the relative wall thickness.^[21] This has led to the concept of "pure diastolic heart failure" being discarded.^[9] The preferred term is now heart failure with normal ejection fraction (HFNEF) or heart failure with preserved ejection fraction (HFPEF). This is common and is often seen in hypertensive heart disease, hypertrophic cardiomyopathy and aortic stenosis, and may comprise as much as 50% of the total heart failure population.^[22] The prognosis of HFPEF is the same as for heart failure with dilated hearts.^[23]

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 velocity gradient are the main measure of regional contraction, and has become the most important employment of colour tissue Doppler, in the method of strain rate imaging.^[27]

Objections

There are philosophical, methodological and applicational flaws in tissue Doppler.^[28] Doppler methodology and mensuration are suitable for flow but unsuitable for tissue application. In contrast to the regular Doppler which is High Velocity Flow Doppler (HVFD) it is better to call tissue Doppler as Low Velocity Flow Doppler (LVFD).^[29]

Thus, in tissue Doppler, velocity measurements are unscientific due to flaws in application of measurement and Doppler methodology. There is no diagnostic directional information which is vital in Doppler studies. It has poor spatial resolution and is very sensitive - resulting in false positive data. The audio output is useless. Tissue Doppler has no particular advantage in the current form but may be used to study low flow thrombogenic states like spontaneous echo contrasts.^[30]

Related Research Articles

The mitral valve, also known as the bicuspid valve or left atrioventricular valve, is one of the four heart valves. It has two cusps or flaps and lies between the left atrium and the left ventricle of the heart. The heart valves are all one-way valves allowing blood flow in just one direction. The mitral valve and the tricuspid valve are known as the atrioventricular valves because they lie between the atria and the ventricles.

Heart murmurs are unique heart sounds produced when blood flows across a heart valve or blood vessel. This occurs when turbulent blood flow creates a sound loud enough to hear with a stethoscope. The sound differs from normal heart sounds by their characteristics. For example, heart murmurs may have a distinct pitch, duration and timing. The major way health care providers examine the heart on physical exam is heart auscultation; another clinical technique is palpation, which can detect by touch when such turbulence causes the vibrations called cardiac thrill. A murmur is a sign found during the cardiac exam. Murmurs are of various types and are important in the detection of cardiac and valvular pathologies.

A ventricle is one of two large chambers located toward the bottom of the heart that collect and expel blood towards the peripheral beds within the body and lungs. The blood pumped by a ventricle is supplied by an atrium, an adjacent chamber in the upper heart that is smaller than a ventricle. Interventricular means between the ventricles, while intraventricular means within one ventricle.

Echocardiography, also known as cardiac ultrasound, is the use of ultrasound to examine the heart. It is a type of medical imaging, using standard ultrasound or Doppler ultrasound. The visual image formed using this technique is called an echocardiogram, a cardiac echo, or simply an echo.

An ejection fraction (EF) is the volumetric fraction of fluid ejected from a chamber with each contraction. It can refer to the cardiac atrium, ventricle, gall bladder, or leg veins, although if unspecified it usually refers to the left ventricle of the heart. EF is widely used as a measure of the pumping efficiency of the heart and is used to classify heart failure types. It is also used as an indicator of the severity of heart failure, although it has recognized limitations.

Afterload is the pressure that the heart must work against to eject blood during systole. Afterload is proportional to the average arterial pressure. As aortic and pulmonary pressures increase, the afterload increases on the left and right ventricles respectively. Afterload changes to adapt to the continually changing demands on an animal's cardiovascular system. Afterload is proportional to mean systolic blood pressure and is measured in millimeters of mercury.

Diastole is the relaxed phase of the cardiac cycle when the chambers of the heart are refilling with blood. The contrasting phase is systole when the heart chambers are contracting. Atrial diastole is the relaxing of the atria, and ventricular diastole the relaxing of the ventricles.

Mitral stenosis is a valvular heart disease characterized by the narrowing of the opening of the mitral valve of the heart. It is almost always caused by rheumatic valvular heart disease. Normally, the mitral valve is about 5 cm² during diastole. Any decrease in area below 2 cm² causes mitral stenosis. Early diagnosis of mitral stenosis in pregnancy is very important as the heart cannot tolerate increased cardiac output demand as in the case of exercise and pregnancy. Atrial fibrillation is a common complication of resulting left atrial enlargement, which can lead to systemic thromboembolic complications such as stroke.

Aortic regurgitation (AR), also known as aortic insufficiency (AI), is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle. As a consequence, the cardiac muscle is forced to work harder than normal.

Mitral regurgitation (MR), also known as mitral insufficiency or mitral incompetence, is a form of valvular heart disease in which the mitral valve is insufficient and does not close properly when the heart pumps out blood. It is the abnormal leaking of blood backwards – regurgitation from the left ventricle, through the mitral valve, into the left atrium, when the left ventricle contracts. Mitral regurgitation is the most common form of valvular heart disease.

In cardiac physiology, preload is the amount of sarcomere stretch experienced by cardiac muscle cells, called cardiomyocytes, at the end of ventricular filling during diastole. Preload is directly related to ventricular filling. As the relaxed ventricle fills during diastole, the walls are stretched and the length of sarcomeres increases. Sarcomere length can be approximated by the volume of the ventricle because each shape has a conserved surface-area-to-volume ratio. This is useful clinically because measuring the sarcomere length is destructive to heart tissue. It requires cutting out a piece of cardiac muscle to look at the sarcomeres under a microscope. It is currently not possible to directly measure preload in the beating heart of a living animal. Preload is estimated from end-diastolic ventricular pressure and is measured in millimeters of mercury (mmHg).

A transthoracic echocardiogram (TTE) is the most common type of echocardiogram, which is a still or moving image of the internal parts of the heart using ultrasound. In this case, the probe is placed on the chest or abdomen of the subject to get various views of the heart. It is used as a non-invasive assessment of the overall health of the heart, including a patient's heart valves and degree of heart muscle contraction. The images are displayed on a monitor for real-time viewing and then recorded.

Doppler echocardiography is a procedure that uses Doppler ultrasonography to examine the heart. An echocardiogram uses high frequency sound waves to create an image of the heart while the use of Doppler technology allows determination of the speed and direction of blood flow by utilizing the Doppler effect.

The E/A ratio is a marker of the function of the left ventricle of the heart. It represents the ratio of peak velocity blood flow from left ventricular relaxation in early diastole to peak velocity flow in late diastole caused by atrial contraction. It is calculated using Doppler echocardiography, an ultrasound-based cardiac imaging modality. Abnormalities in the E/A ratio suggest that the left ventricle, which pumps blood into the systemic circulation, cannot fill with blood properly in the period between contractions. This phenomenon is referred to as diastolic dysfunction and can eventually lead to the symptoms of heart failure.

A plot of a system's pressure versus volume has long been used to measure the work done by the system and its efficiency. This analysis can be applied to heat engines and pumps, including the heart. A considerable amount of information on cardiac performance can be determined from the pressure vs. volume plot. A number of methods have been determined for measuring PV-loop values experimentally.

<span class="mw-page-title-main">Speckle tracking echocardiography</span>

In the fields of cardiology and medical imaging, speckle tracking echocardiography (STE) is an echocardiographic imaging technique. It analyzes the motion of tissues in the heart by using the naturally occurring speckle pattern in the myocardium.

$<span class="mw-page-title-main">Heart failure with preserved ejection fraction</span> Medical condition$

Heart failure with preserved ejection fraction (HFpEF) is a form of heart failure in which the ejection fraction – the percentage of the volume of blood ejected from the left ventricle with each heartbeat divided by the volume of blood when the left ventricle is maximally filled – is normal, defined as greater than 50%; this may be measured by echocardiography or cardiac catheterization. Approximately half of people with heart failure have preserved ejection fraction, while the other half have a reduction in ejection fraction, called heart failure with reduced ejection fraction (HFrEF).

<span class="mw-page-title-main">Doppler ultrasonography</span> Ultrasound imaging of the movement of tissues and body fluids using the Doppler effect

Doppler ultrasonography is medical ultrasonography that employs the Doppler effect to perform imaging of the movement of tissues and body fluids, and their relative velocity to the probe. By calculating the frequency shift of a particular sample volume, for example, flow in an artery or a jet of blood flow over a heart valve, its speed and direction can be determined and visualized.

<span class="mw-page-title-main">Strain rate imaging</span>

Strain rate imaging is a method in echocardiography for measuring regional or global deformation of the myocardium. The term "deformation" refers to the myocardium changing shape and dimensions during the cardiac cycle. If there is myocardial ischemia, or there has been a myocardial infarction, in part of the heart muscle, this part is weakened and shows reduced and altered systolic function. Also in regional asynchrony, as in bundle branch block, there is regional heterogeneity of systolic function. By strain rate imaging, the simultaneous function of different regions can be displayed and measured. The method was first based on colour tissue Doppler. by using the longitudinal myocardial velocity gradient, already in use transmurally. Later, the regional deformation has also been available by speckle tracking echocardiography, both methods having some, but different methodological weaknesses. Both methods, however, will acquire the same data, and also can be displayed by the same type of display.

In clinical cardiology the term "diastolic function" is most commonly referred as how the heart fills. Parallel to "diastolic function", the term "systolic function" is usually referenced in terms of the left ventricular ejection fraction (LVEF), which is the ratio of stroke volume and end-diastolic volume. Due to the epidemic of heart failure, particularly the cases determined as diastolic heart failure, it is increasingly urgent and crucial to understand the meaning of “diastolic function”. Unlike "systolic function", which can be simply evaluated by LVEF, there are no established dimensionless parameters for "diastolic function" assessment. Hence to further study "diastolic function" the complicated and speculative physiology must be taken into consideration.

References

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