Systolic and diastolic dysfunction are inextricably linked. If your canine patient has systolic dysfunction, no way does she have normal diastolic function.
Similarly, your feline patient with increased left ventricular wall thickness and diastolic dysfunction does not have normal left ventricular systolic function – despite what fractional shortening or an ejection fraction may tell you.
Even though you cannot tell the full story of a patient without some assessment of their diastolic function, so many of us avoid making it a standard part of our echocardiograms. It has been made into this impenetrable, mysterious thing, pushed into the realms of “advanced echocardiography” – unsafe for the general practitioner. Book chapters and papers on diastolic function assessment aim to be comprehensive, and quickly progress into an overwhelming amount of measurements, all linked to different components of diastolic function (filling pressures, stiffness, recoil, LV relaxation, LA pressure, and so on).
Actually, you do not need to assess all of these complex parameters to make a judgement on your patient’s diastolic function. At the general practice level, we rarely need this level of detail; the main questions are “is my patient normal?” and “if my patient isn’t normal, is her disease in its early or late stages?” You can make this judgement with just a handful of parameters, combined with what you observe from your 2D imaging. In fact, you can start using Doppler and begin to get a good impression of diastolic function without taking any measurements at all – just by looking at patterns.
Besides the B-mode signs that scream “diastolic dysfunction!” at you, the best Doppler parameters you can obtain are your mitral inflow trace, and your tissue Doppler (TDI) trace from both sides of the mitral annulus, both taken from your apical 4 chamber view.
By the time you get to your left apical views, you will have performed all of your right parasternal views and will have already formed a good impression about your patient. If their left atrium is normal in size, left ventricular systolic function is good and their wall thickness is normal, their mitral inflow is unlikely to show anything more severe than a delayed relaxation pattern, and most likely, it will be normal.
A normal mitral inflow pattern will show an early filling (E wave) velocity which is higher than the late filling (A wave) velocity. This is because early filling, powered by the suction of the left ventricle as it relaxes, should be the dominant force of diastolic filling in a healthy heart.
If you look up papers and textbooks on diastolic function assessment in echocardiography, you will find beautiful diagrams and example images of the filling patterns associated with each stage of diastolic dysfunction.
In real life, though, an animal doesn’t have normal function on Tuesday and wake up with a Grade 1 filling pattern on Wednesday – there’s a slow, steady progression. Therefore, you will often catch patients in between stages. In the early stages of diastolic dysfunction, this may mean that your patient has E and A waves of similar velocity (similar “height” on your scale).
(For more experienced readers, yes, a pseudonormalising pattern would also present with E and A waves of similar height, but the fact that the E wave is still of normal or increased duration (E wave deceleration time if you’re measuring it, but you can also use your eyes) tells you that this is not advanced diastolic dysfunction – and your imaging should be telling you this, too.)
You may never take mitral inflow traces, or you might be one of those people that does it religiously but then never interprets the result. Either way, if you are new to assessing diastolic function, you do not need to have memorised all of the grades of diastolic dysfunction and their associated mitral inflow and TDI patterns to get started. You can start now, getting into the habit of thinking about what you expect to see on your mitral inflow trace before you obtain it (rather than taking it on autopilot). If your study so far shows a young patient with a healthy heart, what do you expect your mitral inflow trace to look like? And can you explain why? If you can’t, feel free to reach out for some help.
Just beware that mitral inflow traces are sensitive to loading conditions, so definitely avoid making a judgement on diastolic function in patients with significant mitral regurgitation using mitral inflow alone. This shouldn’t be too upsetting; in a dog with severe myxomatous mitral valve disease, their diastolic function is not the most important factor to be worrying about at the general practice level.
Your Doppler traces should always complement and support your imaging. If they show something unexpected, be cautious about completely changing your diagnosis, and always talk it through with someone more experienced first. If you don’t have an echocardiography mentor of any kind, book a chat with us to find out how we can help.
If you’d like a walkthrough of all the mitral inflow and TDI patterns, I’ll be doing this via live webinar on Tuesday the 20th of August, at 7pm London (UK) time. You can register for free here.
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