2D and 3D Speckle Tracking Echocardiography

Function by 2D and 3D Echocardiography using STE

This section of the website is dedicated to the use of 3D echocardiography for functional assessment of the Right and Left Ventricle (RV and LV). We are using, in the NeoCardioLab, the Philips Epiq-7 machine with the X6-1 and X5-1 transducers (Pediatric and Adult xMatrix Array Transducers). We are also using the TomTec arena software in order to obtain LV and RV volumes. This website will not be discussing the use of 3D echocardiography for anatomical evaluation, valvular structural assessment or trans-esophageal evaluations.

Cardiac Function:

Represents the continuous process from filling of the ventricle(s) to ejection in the respective outflow tract(s)

    • Dependent on architecture of each ventricles (or of the single ventricle)

    • Dependent on afterload of outflow tract (s)

    • Cross-talk between RV-LV (disturbed in abnormal architecture)

      • Independent and shared fibers / common multi-layer septum

    • Precise activation by conducting system and fibers (synchrony vs dyssynchrony)

    • This can be altered if there is fibrosis, inflammation, ischemia

    • Coronary perfusion is essential for adequate myocardial oxygenation, as well as meeting metabolic needs - one may see an arrhythmia as demanding a lot of oxygen and energy substrates.

    • Coronary perfusion is also essential for the pathways transmitting the electric impulse. Adequate cardiac perfusion is also important for the relaxation.

    • Fibrosis/scarring may impact the diastolic function (and relaxation). These anomalies may be diffuse or circumscribed - leading to some inhomogeneity in contraction or relaxation.

    • Activation and relaxation may happen at different timepoints if there is inhomogeneity in activation or disturbed spread of electrical impuse.

    • Electrical activation usually through the interventricular septum first (left part to right right part) (if there is a septum and if it is of normal configuration). This may be altered in certain congenital heart defects (example: ccTGA). Very good article here on cardiac conduction system in ccTGA.

    • Ventricles get activated from the endocardium to the epicardium

All this results in “2 classical phases” of cardiac cycle that we divide (traditionally) between systole (which results eventually in ejection) and diastole (which results in ventricular filling). There is a phase of isovolumetric relaxation and isovolumetric contraction.

Left Ventricle

LV contracts mostly circumferentially and with torsion (wringing movement) with minor longitudinal contribution. The relaxation has been described to have the base rotate counterclockwise and apical clockwise (endocardial layer). The rate at which untwisting happens gives insight on diastolic function.

(Important references: Bansal M, Kasliwal RR. Indian heart journal 65 (2013) 117e123; Lai, W. W., Mertens, L. L., Cohen, M. S., & Geva, T. (2015). Echocardiography in pediatric and congenital heart disease: from fetus to adult. John Wiley & Sons.; Crean A et al. Journal of Cardiovascular Magnetic Resonance, 2011; J Am Soc Echocardiogr 2012;25:543-52.)

Below is a great depiction of the left ventricle in 3D by computational reconstruction. One can see the circumferential contraction, the radial thickening of the myocardium during the contraction, as well as the wringing effect (rotational properties) of the various layers of the LV. This is a YouTube video and the profile of Dr Rossi on ResearchGate can be accessed here.

Speckle Tracking Echocoardiography

  • Speckles (echodensities) form the echocardiography (ultrasound) images

    • With Speckle Tracking Echocardiography (STE), these speckles are tracked on a frame by frame to measure magnitude (or percentage) of deformation.

    • You can also use the tracking to measure:

      1. Strain (% of deformation)

      2. Strain rate (rate at which the deformation occurs - 1/second)

      3. Displacement (in degrees when assessing twisting or in millimeters for longitudinal assessment)

      4. Rotation velocity (degree/second)

      5. Time to peak of activation of each segment


  • Multiple vendors for strain assessment by STE (Tomtec, VVI of Siemens, Echopac of GE, QLab - Philips…).

    • May not have the same algorithm for tracking and Strain derived measures


  • STE allows for deformation analysis:

      1. Segmental analysis

      2. Global assessment (average of segments)

      3. Assessment in various planes: circumferential, radial, longitudinal and rotation

      4. Application to any cardiac chambers

      5. Assessment of synchrony or dys-synchrony (time 2 peak).


2D Longitudinal STE on the LV in A4C

2D Longitudinal STE on the LV in A5C

2D Longitudinal STE on the LV at apical level in the parasternal short axis view

By convention:

  • Positive values (+) when thickening, Negative values (-) when thinning

    • Example: Longitudinal systolic strain is negative, longitudinal diastolic strain is positive, radial systolic strain of the LV is positive, radial diastolic strain of the LV is negative.

      • If shortening during systole (longitudinal and circumferential), strain and strain rate values are negative

      • Lengthening (diastolic relaxation) or thickening (radial contraction) = positive.

  • Rotational mechanics of the LV can be assessed in 3D and in 2D.

    • When assessed at the base, contraction is usually a clockwise rotation as viewed from the apex and expressed in negative values

    • When assessed at the apex, it is usually counterclockwise as viewed from the apex and expressed in positive values

    • Twist = Rotation at Apex – Rotation at the base

    • One may also evaluate the untwisting rate during diastole

Rotation analysis from a 3D Echocardiography by TomTec - Apex (blue), Base (Red), Torsion (Orange) from NeoCardioLab.

Rotation analysis from 2D Echocardiography by TomTec (NeoCardioLab participant). When doing rotation analysis by 2D, one needs to ensure that the images are sequentially obtained to avoid variation in loading conditions, as well as heart rate. The base and apex need to be acquired by facing the structure and not sweeping with an angle.

Important terminology:

  • "Bull's eye": representation of the various segments of the left ventricle. The map can be used to outline the strain results, as well as the strain rate, displacement, time to peak of contraction, circumferential strain, radial strain, etc.

  • Circumferential: One is looking at the circumferential contraction when evaluating the contraction towards the inside of the LV cavity (along its circular perimeter)

  • Longitudinal: Base-To-Apex axis

  • Radial: Refers to the thickening or thinking of the myocardium during contraction and relaxation

  • Strain: Myocardial deformation in % - Distance modification between two points

  • Strain rate: Speed of myocardial deformation (velocity) in 1 per second. Speed at which strain occurs

  • Twist: The difference between the Apex and Base rotation

  • Torsion: Twist normalized to the length of the LV (Base to Apex). As such, at the peak of systole - normalized to the distance Base-to-Apex in systole, at peak of diastole - normalized to the distance Base-to-Apex in diastole

Bull's eye of the LV for Strain assessment. ©Neocardiolab

  • Electrocardiogram gating is necessary with the highest frame-rate. We usually aim in the lab to be at a minimum of 70 frame per second. Ideally, one should narrow the sector around the structure of interest and save the clips in raw data.

    • Typical PACS will integrate ECHO images at a compressed 20-30 FPS despite recording at a higher Frame Rate. Need to ensure the setup of the machine.

    • Raw images are rarely sent via PACS but are essential for STE quality.

    • If no ECG available, may use the M-Mode in order to time the various periods of the cardiac cycle.

  • EF might be preserved despite abnormal regional deformation in subclinical disease

    • Myocardial infarction: local area of decreased contractility tethered by more healthy myocardium and move during systole, despite not actively participating to the efficient contraction

  • Auto-tracking gives you FAC and EF evaluation; as well as estimated LV volumes

  • For analysis, requires:

    • ECG gating or M-Mode traced by the software to time End Systole and End Diastole.

  • For Peak global longitudinal SYSTOLIC strain and strain rate, needs:

    • Time from R wave to Aortic valve closure for LV

      • PW of LVOT in 3 chamber

    • Time from R wave to Pulmonary valve closure for RV

      • PW of RVOT either by anterior sweep in apical, or in PSA

  • For Peak GLS (global longitudinal strain):

    • A2C, A3C and Apical 4 chambers with good view of LV – 2-3 beats

    • If only A4C: Peak Longitudinal Strain: lateral and septal wall.

    • PSA: view at valvular level, mid-papillary (typical) and apex for LV


Summary:

The LV contracts in a wringing (in french, we say: "essorage") motion (the apex and the base will rotate in different directions; with a gradient from the endocardium to the epicardium) and with a contraction towards the inside of the cavity (circumferential). The longitudinal aspect of contraction is not as pronounced as the longitudinal contraction of the RV.

The RV, which has fibrous discontinuity between the AV valve (usually a tricuspid) and the Outflow tract (usually a pulmonary valve), will contract in a bellow motion with the inflow going towards the outflow, the free wall going towards the septum and the septum going towards the free wall (assuming there is no increase RV afterload, there is adequate spread of electrical activation and the conformation is as expected - ie: no VSD, etc).

When we look at the LV, we can look at the global circumferential strain (% deformation towards the inside of the cavity) and torsion (gradience of difference of degrees of rotation from Apex to base of LV).

For the RV, we can look at the RV free wall and septal longitudinal strain.

Global just means we take free wall and septal together.

Knowing that the LV is bullet shape, we often talk about "peak global longitudinal strain" (pGLS) when assessing the deformation in the longitudinal planes of all the standard views in 2D (A2C, A3C, A4C) or in full 3D volume.

We talk about "peak longitudinal strain" (pLS) when we have only one plane (example: A4C).

We talk about "peak" (pGLS, pGCS - circumferential, pGRS - radial, pEDSR - peak early diastolic strain rate, pGLSR - peak GLS rate) - when we assess the peak at the contraction or relaxation.

We talk about "pGLSs" (systolic) when we match the curves with the aortic valve opening and closure.

"Deformation analysis" encompasses the assessment of % (strain), speed (strain rate), displacement (distance of movement), degrees (torsional properties) of the deformational properties of the ventricles. These properties can be assessed for segments, for global ventricle, in systole and in diastole.

Although theoretically STE is less influenced by preload status compared to other standard measure of functions using 2D ECHO, TDI, M-Mode, etc... all these measures are realistically influenced by preload for the RV or the LV.

This article is key at explaining the Twisting mechanics of the LV

Here is the screenshot of a deformation analysis done by TomTec for the LV in parasternal short axis view at the mid-papillary muscle area. Here are selected the Strain-Rate curves. The LV is divided in segments and each segment is represented by a curve. There is a systolic and diastolic phase to the contraction. One may see the radial and circumferential curves, as well as summary table of the peak of strain rate for each segment, as well as the average. The radial strain rate is positive during contraction. The circumferential strain rate is negative during contraction. The curves can also outline the strain rage in diastole (positive for the circumferential strain rate, and negative for the radial one). The time to peak gives a sense of the dysynchrony of activation. ©Neocardiolab

This is the summary panel that TomTEC provides for 2D analysis of the longitudinal deformation of the LV when inputing the apical 2,3 and 3 chamber views. There is a Bull's eye depicting the strain values for each segments. There is also a 3D remodelling from the 2D acquisition, with estimated end diastolic and systolic volumes. ©Neocardiolab

These are the curves for each segment in the A4C related to the longitudinal strain in %. The peak appears for each segment in the summary table, as well as the average % of each peak. The measurements are done for the endocardium. One may also ask from the software to do the same measurements of the epicardium and myocardium. Typically, in the literature, values are reported for measurements taken at the endocardial layer. ©Neocardiolab

Longitudinal strain rate in Apical 4 Chamber view for the LV. One may also obtain values from the average curve on the early diastolic strain rate peak. ©Neocardiolab

3D volume obtained from the apex in a premature newborn (1 kg). ©Neocardiolab

LV 3D - STE. Here the software tracks the endocardial layer. One may also obtain the LV mass by STE when applying the epicardial layer tracking algorithm. ©Neocardiolab

From the 3D analysis, one may obtain end diastolic and systolic volumes, ejection fraction, stroke volume, peak circumferential/longitudinal strain, twist and torsion. ©Neocardiolab

Time to peak of contraction analysis to detect dys-synchrony of segments. ©Neocardiolab

Longitudinal strain by segment. ©Neocardiolab

3D STE for the RV in a premature newborn. © NeoCardioLab

From the 3D RV volume, one may obtain the estimated end-diastolic and systolic volumes, ejection fraction and stoke volume. The algorithm also provides the longitudinal strain of the RV free wall and septum. ©Neocardiolab

This is an exceptional publication available from the American Society of Echocardiography website and from the European Association of Echocardiography. This article is available on the web, by clicking here. The online PDF is linked here:

EAE-ASE-recommendation-image-acquisition-3D-echo.pdf

These are 2 presentations in PDF that are publicly available on the website of the ASE. You can access them by clicking here and here. The presentations are from Dr Wendy Tsang, from the University of Toronto at Toronto General Hospital. They are among the best presentations available on the web teaching on the use of 3D echocardiography. Please make sure to visit the UofT website on Virtual TEE. You can find the ResearchGate profile of Dr Tsang here. I have put the linked PDF from the ASE website available here:

ASE-EchoFlorida-2017-3D-Cropping-Acquisition-and-Display-finalv3.pdf
Tsang-NO-ANSWERS-When-Does-3D-Echo-Make-a-Difference.pdf

Created by Gabriel Altit - Neonatologist / Créé par Gabriel Altit (néonatalogiste) - © NeoCardioLab - 2020 - Contact us / Contactez-nous