Assessing left ventricular global systolic function (LVF) with echo

In this video from our Echocardiography Essentials course, you will learn how to recognize normal, hyperkinetic, and hypokinetic function of the left ventricle with the help of transthoracic echo.

After completing this course, you’ll be able to perform a basic transthoracic echo (TTE) exam without the help of a more senior colleague. Using practical demos, we’ll teach you echo anatomy and show you how to operate the machine, obtain the standard TTE views, differentiate normal from abnormal, and confidently assess and report anything you find!

[00:00:00] The heart is a pump. Well actually, it's two parallel pumps. The left ventricle and the right ventricle. We often want to know how well either or both of the pumps are working. We usually want to know how well they are pumping out and we can think of this as global systolic function. But obviously, a pump needs to be filled and the best pump in the world will be useless if it doesn't contain anything. So, we can see how diastolic function or filling also matters. But for now, let's just think about LV systolic function and

[00:00:30] how our heart is pumping out. We usually assess the function of the left ventricle using the ejection fraction, which is exactly what is says. It's the amount of blood ejected from the left ventricle, expressed as a percentage of its maximum volume. It's normally around 60% but in a severely impaired ventricle, it could be 30% or less. So, we can use Simpson's method like we've got here or we can use 3D or we may eyeball it and give an estimate. Ejection fraction is popular but it's controversial.

[00:01:00] Not all departments use it and those that do should quality assure their work against an independent standard. Centers that don't use ejection fraction tend to use qualitative terms but the same applies, they need to be sure that all of their echocardiographers are reporting similarly. Contrast agents can be used to improve endocardial definition, if a really accurate ejection fraction is essential. Another way to describe LV systolic function is to view it in terms of how much blood is ejected, rather than using the change in the size of the

[00:01:30] left ventricle and Doppler echo can be really useful for this. There are three commonly used measures, the stroke distance, the stroke volume, and the cardiac output. Let's start with stroke distance. As you can see, we've got a pulse wave signal that we've measured in the outflow tract of the left ventricle. So, we know we've got time against velocity. So, if we integrate our waveform, as in we take its area, we're going to get the measure called the velocity time integral. So, for this wave form, the velocity time integral is 15 cm.

[00:02:00] And what that says is that that little bunch of red blood cells will travel 15 cm along the aorta with that particular systole. Velocity time integral and stroke distance are the same thing and the terms tend to be used interchangeably. So, let's move on to stroke volume. So, what we're doing here is we're measuring the diameter in the left ventricular outflow tract. This gives me 2.2 and we're using that to work out the cross-sectional area using Pi r2 and multiplying it by the stroke

[00:02:30] distance and your echo machine will do this for you automatically. So, for this case, it's giving us a stroke volume of 57 mL. So normally, it's about 60 to 100 mL, so this is a sort of a borderline measurement. So, another really useful measurement we can calculate using Doppler echo is the cardiac output. This will convert our stroke volume to cardiac output. And again, your echo machines will do this for you. If it doesn't have the capability, you can use a phone app or you can be really old school and get out a calculator.

[00:03:00] So, what we're going to do is multiply our stroke volume by our heart rate and we divide it by a thousand to sort out our units. So, we know our stroke volume was 57. In our patient, we've been looking out if they had a heart rate of 83 and that's going to give us a cardiac output of 4.7 L / min. So, that's a really useful measurement. There's a lot of enthusiasm for this sort of measurement on intensive care and sometimes there, you'll find they'll use a continuous wave Doppler through the aortic valve rather than the pulse

[00:03:30] wave of the outflow tract but it's very useful for monitoring.