One of the best uses of strain imaging is when the patient has thick left ventricular (LV) walls, or so called left ventricular hypertrophy (LVH). It is important to remember though that not all thickened LV walls are due to true hypertrophy. Infiltrative diseases, invasive tumors and hypovolumia can all cause thickening and this can be difficult to differentiate on standard 2D imaging. On this blog post I wanted to show you some cases that highlight the important uses for strain imaging to help better investigate thickened LV walls.
Case One
In this first case, you can see that the LV cavity size is increased as well as having thickened walls. You can also see that the systolic function is at the lower limits of normal with an estimated ejection fraction of ~ 50%. This may be concerning just based on this image but the addition of strain imaging allows further investigation and we can see that the strain pattern is completely normal. All regions demonstrate normal strain.
This pattern represents a case of physiological hypertrophy caused by extreme levels of exercise in a professional Australian Football (AFL) player. The thickening of the LV walls is a normal adaptation to training and is a nice example of Athlete’s heart.
Case Two
In the next case you can see that there is a mitral valve replacement but this is not the reason for the LV wall thickening but may help a bit with the diagnosis.
This patient has normal LV ejection fraction and a normal to small left ventricular cavity.
If we have a look at the strain pattern we can see a very distinctive pattern that is typical of Fabry disease.
The basal inferolateral region is reduced and this is the area where fibrosis is detected by cardiac MRI in these patients. Genetic testing confirmed that this patient has Fabry disease. Fabry disease is a rare X-linked inherited metabolic disorder, which results in a deficiency or absence of the enzyme α-galactosidase leading to the accumulation of glycosphingolipids in various cells and organs including the heart. This deposition of sphingolipids accounts for some of the wall thickening but it is thought that this process also triggers hypertrophy in the myocytes themselves. Quite often these patients also get valvular or rhythm complications so it is not uncommon to see these patients with a valve repair or replacement or a pacemaker which in some cases makes them unable to have a cardiac MRI. Fabry disease is thought to be grossly underdiagnosed in cardiac populations but if we can use strain imaging or the presence of unexplained LV wall thickening to highlight who may be at greater risk then targeted genetic testing may be undertaken. This is important because Fabry disease is treatable unlike many other infiltrative diseases that cause LV wall thickening.
Case Three
In the 3rd case you can see a normal LV cavity with only a mild degree of LV wall thickening. In fact the whole echo was fairly unremarkable other than the mild LV hypertrophy.
On strain imaging you can see that overall it is normal except for a very mild reduction in regional strain at the basal septal region. This is a typical pattern that we see early in hypertensive heart disease, the basal septal regions are affected first then if the hypertension remains uncontrolled the strain starts to reduce globally. It is thought that this occurs due to increased sheer stress at the site of the basal septum impacting on the sub-endocardial layer and reducing the longitudinal contraction. If the hypertension remains uncontrolled the strain becomes globally reduced, although often the most reduction is in this basal septal region.
Case Four
The next case may be a bit more obvious on the 2D image alone.
You can see that the walls are significantly thickened – perhaps a hypertrophic cardiomyopathy or an infiltrative disease? Well let’s see what the strain has to show us.
Any of you that use strain regularly will be able to give the diagnosis straight away but what we are seeing here is an apical sparing pattern where the strain in the distal regions are preserved with a reduction in the basal and mid wall. This is the pattern that we see in amyloid. It has been shown through histopathology studies of the whole heart at autopsy or post-transplant that there is more amyloid deposition in the basal and mid wall segments than in the distal and apical regions; hence the longitudinal strain is less affected here giving the apical sparing pattern that we see here.
Case Five
The last case I have to show you is also someone with a significant LV wall thickening – do you think that it might another infiltrative?
The strain pattern here is one that shows a significant reduction in the basal septal/ anteroseptal/ inferoseptal and mid inferoseptal regions which is where the wall was the thickest. This is a case of hypertrophic cardiomyopathy and this is the type of pattern that you see – a reduction in the most hypertrophied part of the LV.
I hope that this has helped convince you that strain is extremely useful in these patients. If you have a new patient with increased wall thickness it is a good idea to use strain imaging on them and pay particular attention to the regional strain pattern on the bull-eye. If the patient does a significant amount of high level exercise, not just a weekend warrior and their strain is normal this can be put down to athlete’s heart. If the strain is not normal then this may be caused by steroid abuse or may actually demonstrate an abnormality like a dilated or hypertrophic cardiomyopathy. If there is arterial hypertension or valve disease such as aortic stenosis then the GLS should be taken for serial follow up and to assess subclinical dysfunction, although the pattern of strain in hypertension can give you clues about the amount of time the heart has had such an increased after-load. If there is not hypertension or aortic valve disease then the bull’s eye regional strain map should be closely analysed to see if can give you any clues about what is the underlying cause of the LV wall thickening. Reduced strain in the septal regions may indicate hypertrophic cardiomyopathy, reduced strain in the basal inferolateral region may indicate Fabry disease and apical sparing pattern may indicate cardiac amyloid. Of course strain does not make the diagnosis but it may help lead the patient down the appropriate diagnostic path.
Dr Rebecca Perry is the Program Director for Medical Sonography at the University of South Australia and has an honorary position as a post-doctoral researcher in echocardiography at Flinders Medical Centre. She has been a cardiac sonographer since 1998 and has been involved in research and advanced echocardiographic techniques since 2003. She has extensive experience in advanced echocardiographic techniques such as strain and 3-D echocardiography. In 2023 she won the prestigious Australasian Sonographers Association, Pru Pratten Memorial Lifetime Achievement Award which recognises and honours a sonographer who has made a significant contribution to the profession, and the ASA, over the course of their career. She completed her PhD in 2013 and her Post-Doctoral Fellowship with the Heart Foundation through Flinders University in 2018. She is passionate about education and excellence in echocardiography and advanced imaging techniques.