Chapter: Tricuspid Valve

Regurgitation Valve Gradient

Tricuspid Valve

Regurgitation, RV systolic pressure assessment, and the influence on our understanding of central venous pressure.

TRICUSPID REGURGITATION (TR)

TR is the main concern with the tricuspid valve because tricuspid stenosis is rare. The tricuspid valve is more difficult to image than the mitral valve. It may take a slightly more cranial apical window to see well and the RV enhanced view may be needed in the apical4. The PSAX view of the tricuspid valve is also helpful because the view is reasonably parallel to flow. Occasionally, for various reasons, TR may even be best seen in the subcostal window. So, as with most things cardiac, multiple views are needed.

Trivial TR is common and functional TR (caused by RV dilation or pressure overload) is much more common that primary structural TR. Twenty percent of RV pacemaker leads cause TR and this can be a nidus for endocarditis. Quantification of TR is similar to AR and MR quantification.  As with other valve lesions, the preload, afterload, and contractile state of the patient will vary the apparent severity of the TR. Chronic, severe TR should have a dilated right atrium, as well as abnormal IVC and JVP. Eventually, with primary structural TR, the RV will become dilated and have reduced function because of the volume overload.

TR Classification

Mild

Moderate

Severe

Flow convergence

Minimal to none

Detectable but small

Prominent

Vena contracta cm

< 0.3

0.3 - 0.7

> 0.7

Jet area

 Small, < 20% RA area

In between

Large, > 40% RA area

This is a patient with a pacemaker and mild TR as seen in this PSAX at the level of the aortic valve.

Next is the same patient with a view from the AP4 where the TR is more impressive around the pacemaker.

And here is a final view of the TR in the same patient from an apical RV 2 chamber view achieved by fanning just anterior to the apical 3 chamber of the LV. Again, the TR nicely courses along the pacemaker lead.

This is a patient in whom the best view of the TR was the PSAX. The view of the proximal part of the jet wasn’t very good, but the jet was aliased and fairly wide, suggesting at least moderate TR.

Next is a patient in whom the subcostal view showed the best and strongest TR. The CF sector box is a little too long in this view and it needed to be a little wider in order to see the proximal part of the TR on the RV side.

The rest of the TR examples will be in the apical4 view. The first is a central TR jet that showed a definite convergence zone. To see it closer and measure its size the sector width would be decreased, the depth reduced, and magnification applied. With this view only, this is probably moderate TR. There is clearly RA enlargement (LA also).

Here is another fairly central TR jet with an appropriate CF sector that shows a larger convergence zone than the previous case and the vena contracta also appears wider. The RA is again enlarged and there may be some pericardial effusion out to the left. This TR is moderate to severe.

This next clip is the B-mode image in an apical4 that should have had less depth, but the view is nevertheless good. The thing to notice is the bulging of the RA towards the LA. This is probably a right atrial septal aneurysm.

When CF was applied, TR was seen with a large convergence zone, thick vena contracta, and a long and aliased jet moving eccentrically along the inter-atrial septum, pushing the RA into the LA during systole. This is moderate to severe TR augmenting the right atrial septal aneurysm.

This penultimate case has a large convergence zone and thick vena contracta with a strongly aliased jet. This would be entering the severe range for TR.

Finally, here is TR with a gigantic convergence zone, thick vena contracta, and a jet that fills the RA. The RA is huge and although the RV isn’t seen well in this view, it looks dilated.

 

TRICUSPID VALVE GRADIENT MEASUREMENT

Severe TR from a structural lesion does not necessarily produce severely increased RV and pulmonary artery pressures. When pulmonary hypertension develops, from what ever cause, the elevated RV pressure begins to push on the tricuspid valve, but the amount of TR may be mild despite high pressures. Nevertheless, the TR jet can be used to measure the gradient across the tricuspid valve.

A small TR jet with uniform blue color indicates low velocity flow inconsistent with a high gradient between the RV and RA. However, it is important to learn to measure this gradient well and efficiently so even mild TR jets should be analyzed.

Position the continuous wave Doppler cursor so that the focal point is right in the vena contracta of the TR and activate Doppler to get a tracing, which will look like this. The gate needs to be parallel to the TR jet flow.

It is important to see a clear enough spectrum or it isn’t worth trying to measure. FREEZE on the biggest negative spectrum and measure its depth with the caliper. In the above example, it was 2.6 m/sec. This velocity can only be underestimated, not overestimated.

Most machines use the Bernoulli equation (4 X Velocity2) to calculate the gradient across the valve, which was 26 mmHg in this first case. To calculate RV systolic pressure, which is almost always the same as systolic pulmonary artery pressure (sPAP), add the estimated RA pressure to the gradient. If sPAP is < 36, pulmonary hypertension is unlikely. The exception to this method is the rare occurrence of pulmonic stenosis.

Here is a CW spectrum from another patient in whom the peak velocity was 3.3, which was a peak gradient of 45 mmHg. Without even adding RA pressure, this is meaningful pulmonary hypertension.

In the next chapter on diastology and volume assessment, an elevated TR gradient is one of the indicators of more advanced chronic diastolic dysfunction, which is another reason to learn to measure the TR jet well.

The JVP may give a better estimate of the RA pressure than the IVC in many situations. However, the IVC is traditionally used to make an RA pressure estimate and the following grid shows how this is done. There is always concern about anything above normal with the IVC because of several issues with IVC assessment and perhaps only the top and bottom categories of the grid can be relied upon. 

RAP by IVC mmHg

IVC Diameter

Inspiration effect

0-5

small (<1.5)

collapsing

5-10

normal (1.5-2.5)

>50% reduction

10-15

dilated (>2.5)

<50% reduction

>20

dilated IVC and hepatic veins

No reduction in diameter

The most recent international standards for pulmonary hypertension are beginning to de-emphasize estimating the RA pressure because of the unreliability of most estimates. Instead, decision making is increasingly based only on the estimated gradient across the tricuspid valve.

In the most severe TR the continuous wave Doppler spectrum may be triangular shaped and unreliable for measurement. If the TR spectrum is indistinct, it is also dangerous to make the measurement.

A number of factors influence the measurement of the tricuspid gradient at any particular time. Accordingly, the only reliable diagnosis of pulmonary hypertension comes from a right heart catheter. The main utility of the IMBUS exam is to identify patients with previously undiagnosed, or newly increased, tricuspid gradients who then need to move ahead with formal echo and then right heart catheterization.