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 - Right and Left Ventricles

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. 

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.

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 

• 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

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:

Segmentation of the left ventricle

Good resource to check here: https://www.thinking3d.ac.uk/Echocardiography/ 

Important article:

Dorobantu, Dan M., et al. "The role of speckle tracking echocardiography in predicting mortality and morbidity in patients with congenital heart disease: a systematic review and meta-analysis." Journal of the American Society of Echocardiography (2023).

Speckle Tracking Echocardiography in French 

Echocardiographie par suvie de pixel en français

Presentation (PDF) on STE principles