Faculty of Medicine and Health Sciences
Department of Circulation and medical imaging

Strain rate imaging.

Myocardial deformation mechanics.

Revised edition 2023

by

Asbjørn Støylen, Professor, Dr. Med

asbjorn.stoylen@ntnu.no
@strain_rate.bsky.social

Portal to deformation imaging and myocardial mechanics for the novice researcher and curious clinician

1. Imaging measures shortening, not contraction, nor contractility. There is not a direct correspondence between contraction (tension) / relaxation (tension devolution) and shortening / lengthening.
2. Length and velocity are both related to volume changes, and are the resultant of tension vs. load. 
3. Strain and strain rate are measures related to relative volume changes (EF), and are thus functions of tension vs. load, and not measures of contraction ( tension) nor contractility. 
   
1. Global systolic longitudinal strain is inversely related to BSA, while MAPSE is not, which means that BSA is a confounder for reduced GLS, but not for reduced MAPSE

1. MAPSE is proportional to stroke volume, and the ratio of MAPSE to SV is constant across both BSA and Age.
2. Both E and e' are related to tension vs load, and e' is not the cause of early pressure changes.
3. The concept that the E/e' ratio is due to the fact that e' is the cause of pressures, while flow is the result, is erroneous. The discrepancy is due to the fact that while flow velocity is related to pressure gradients, tissue velocity is related to volume flow, and thus to early compliance.

Welcome to the revised strain rate website

Animations will still be in *.GIF format, so they will run on web browsers, and can be embedded in presentations. Pictures and animations are still free to use, with due credit. 


Strain and strain rate are the concepts of myocardial deformation. My basic views are still that 

• Any imaging method deals with myocyte shortening, myocyte shortening is always a function of tension versus load, and thus any imaging method and measure is load dependent, including deformation and deformation derived measures.
• The three strain components are only coordinates of the total three dimensional deformation of one object - the myocardium, and thus interdependent, but also meaning that longitudinal strain carries most of the information
• Longitudinal strain is method dependent, so there is no gold standard
• Gradient of longitudinal layer strain, is just an artefact of speckle tracking, tracking the inward motion, which increases towards the endocardium.
• Gradient of circumferential and transmural strain are just a function of inward expansion into a progressively smaller space toward the center of the left ventricle, i.e. geometry, not differential layer function.
• For global function, annular motion (displacement and velocity are basically as useful as global strain and strain rate, 
• Except in the right ventricle where deformation is superior,
• But when there is regional dysfunction, annular motion is not enough, deformation imaging is necessary, but as an adjunct method to B-mode.
• Peak values are less useful, qualitative and semi-qualitative information is more important: curve shapes or colour M-mode, the typical acute ischemic segmental pattern is:     
• Delayed onset of shortening    
• Reduced rate and amount of shortening    
• post systolic shortening   
•  

Website index:

Basic ultrasound

This section replaces the sections on 

• Basic ultrasound
• Doppler
• Strain ultrasound
• Problems and pitfalls 

Basic concepts of motion and deformation 

This section replaces the two old sections:

• Basic concepts of motion and deformation
• Basic concepts in myocardial strain and strain rate

Basic physiology

This section deals with the basic physiology as seen with various echo methods, and replaces most of

• Basic physiological concepts in strain and strain rate - What does strain and strain rate actually measure?
• Global systolic functional imaging
• Regional systolic functional imaging.
• Diastolic functional imaging

In the physiological aspects, as these were largely overlapping anyway.

References

have been updated, but will still be revised, especially for the basic ultrasound section.