The tricuspid valve is made up of three non-identical leaflets: the anterior, the septal, and the posterior one. Their sizes and positions differ between individuals, which makes identifying them on ultrasound images tricky. In this video, Cristiana Monteiro—a cardiac physiologist from the University of Oxford—explains the anatomy behind septal defects and how to diagnose them using ultrasound.
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At the end of this Medmastery lesson, you will be able to identify the characteristics that differentiate the tricuspid valve from other cardiac valves. As you know, the tricuspid valve is made up of three leaflets, these leaflets are not identical. Instead, they are each a different size. The anterior leaflet is always the largest, followed by the septal leaflet, and then the posterior leaflet.
This size relationship does not vary between individuals. But leaflets sizes and positions do vary between individuals. This variation in size and position can make distinguishing which leaflets which, very challenging on echo. There are two indicators to help identify each leaflet in the apical four chamber view. First, the septal leaflet is attached to the septum and second, the anterior leaflet is attached to the right ventricular muscle.
It is widely known that we cannot see all three leaflets at the same time using echocardiography. To understand this, let's look at the tricuspid valve in perspective, and try using different probe positions within our range of motion to demonstrate this limitation. Let's try this probe proposition to start. No luck, in this view the two dimensional image will only show a portion of the interior and septal leaflets.
Also in this view, the anterior leaflet will look shorter than a septal leaflet and we know that is just not true. So let's try again. What about this? Still no luck. This time we can see the posterior and anterior leaflets, but we can still only see two leaflets. One last try. This time a completely different perspective, same issue. In this view, again, we can only see the anterior and septal leaflets. Although the leaflet proportions are now more realistic here, we can only still see two.
So regardless of probe position, at any one time we can only see two of the three leaflets. Due to limitations of technology we can never see the tricuspid valve in full in an echocardiogram. Another distinguishing characteristic of the tricuspid valve is the fact that the tricuspid valve has three papillary muscles, unlike the mitral valve in the left heart, which has two. Each papillary muscle is associated with a corresponding leaflet to prevent prolapse of the valve during systole. This is done by a number of filaments called cordae tendineae. The whole system resembles a parachute when you think about it. In addition, the septal and anterior papillary muscles are connected by the moderator band. Good job. Now you have a better understanding of the characteristics that make the tricuspid valve so distinct from other cardiac valves.