Chapter: The RV

RV Size RV Wall Thickness RV Function RA Pressure (E/e')

The Right Ventricle

An overview of right ventricular size and functional assessment

RIGHT VENTRICULAR SIZE

It is harder to evaluate RV size than LV size. The RV sits mostly behind the sternum, so views can be challenging. The RV shape is also complicated, with the inflow portion and the outflow portion at an angle to each other, resembling a bagpipe. The RV is first seen in the PLAX view when part of the RV outflow tract (RVOT) is seen. The normal shape of the posterior border of the RVOT in this view is a bit triangular; seeing a rounded lower border is a hint of RV troubles. Measuring the diameter of the RVOT in this view is possible but can be falsely enlarged because the cut through the RVOT is oblique. Here is a PLAX with a reasonably normal RVOT shape.

 

Next is a PLAX from a patient with RV dilation. The shape is subtly rounder, but the RVOT does not appear larger relative to the aorta or the left atria because both of these were also dilated in the patient. Thus, the 1/3, 1/3, 1/3 rule for eyeballing the RVOT, aorta, and left atrium size can fail.

The RV size is also eyeballed in the apical4 if we know that LV size is normal. The part of the RV that is seen in the apical4 should normally appear about 1/3 smaller than the LV. Use an RV enhanced view if the RV lateral wall is uncertain.  Two leaflets of the tricuspid valve need to be seen for a correct view of the RV. A normal RV is triangular shaped in the apical4, with the diameter at the base wider than the diameter at the mid-RV. However, measuring just the mid-RV diameter is good enough in most IMBUS clinical situations. Here is an apical4 of a dilated RV with severe tricuspid regurgitation. The RV was visually as large or larger than the LV and the mid-RV diameter measured 4.5 cm, which is severely enlarged (see the table below).

A good subcostal view, particularly with the patient standing, can also confirm RV dilation because of the perpendicular orientation of the beam to the RV walls. Here is a normal mid-RVEDD in SC4.

When we know that the IVS is normal in a patient, we can eyeball the RV lateral wall and see that it is less than half the diameter of the IVS.  With any uncertainty, the RV lateral wall should be measured in the subcostal4 because of the interface with the liver and the more perpendicular ultrasound beam. Here is an image from a patient with pulmonary hypertension who had hypertrophy of the lateral wall. A more precise measurement would have been obtained with a more optimized view but by eyeball, the lateral wall was as thick as the IVS.

It may be difficult to measure the RV lateral wall in patients with substantial hepatic steatosis. The right ventricle is also strongly trabeculated and including trabeculae or chordae in the measurement will falsely increase the measurement. The measurement usually needs to be made at the beginning of the basal RV, not in the mid-RV.

RV dimensions (cm)

Normal

Mild

Mod

Severe

Mid RV

1.9 - 3.5

3.5 - 3.7

3.8 - 4.1

≥ 4.2

RV lateral wall

0.1 - 0.6

 

 

 


RIGHT VENTRICULAR FUNCTION

An indicator of RV volume and pressure overload is flattening (D-ing) of the interventricular septum as relatively increased RV pressure distorts the LV. This pattern may occur just during systole (pressure overload), just during diastole (volume overload), throughout systole and diastole (volume and pressure overload), or briefly just with inspiration (classic pericardial tamponade pattern). The next PSAX shows prominent septal flattening.

RV function has a greater component of longitudinal contraction than LV function but it is still important to eyeball the radial function in parts of the RV as they are imaged. Longitudinal function of the basal RV is typically measured with tricuspid annular plane systolic excursion (TAPSE). Adjust the image to get the lateral tricuspid annulus excursion as parallel as possible to the M-mode cursor. This may require moving the annulus toward the center of the screen or the use of anatomic M-mode. As with MAPSE, find the difference between the peak and the valley. In the following patient anatomic M-mode was used to obtain a normal TAPSE.  Normal TAPSE is usually easy to eyeball after enough training.

 

 

Normal

TAPSE (cm)

1.7 - 3.1

We had thought that having the standard M-mode cursor non-parallel to the tricuspid annulus movement would always result in an under measurement of TAPSE. However, we have anecdotally noticed that if the M-mode caliper passes through part of the tricuspid valve leaflets that you can get an over measurement of TAPSE. Thus, getting the annular movement as parallel as possible to the M-mode cursor is important for accuracy and this favors the routine use of anatomic M-mode for TAPSE.

While TAPSE is a very good measure of longitudinal RV function, it is specific to the base of the RV. If RV dysfunction is localized to more distal parts of the RV, TAPSE will be falsely reassuring (see the Advanced Right Heart Disease chapter).