What is RV Fractional Area Change?

This is much easier to do away from the patient on your machine/echo workstation software, on a saved loop.

Your machine may have a package for FAC- if not, you can work it out yourself by plugging your end-diastolic and end-systolic areas into the above formula

SO WHAT IS NORMAL FAC?

A FAC of more than 35% is considered normal. <25% is considered severely impaired.

SO WHAT ARE THE ADVANTAGES OF FAC?

The main advantage of FAC over TAPSE and S’ is that it includes the contribution of the RV free wall- so it increases your sensitivity for detecting RV dysfunction. 

Remember the examples of RV dysfunction I showed in both the TAPSE and S’ post with preserved longitudinal but impaired radial function? FAC in that case was <25%, correlating with severe RV dysfunction.

WHAT ARE ITS PITFALLS?

Sadly there are a lot.

1. You need a REALLY good view of the RV, including the free wall. In critically unwell patients this can be very difficult.
2. Because of the need for tracing and a clear view, it means that this measurement is significantly user-dependent- more so than TAPSE or S’.
3. Because part of the tracing includes the interventricular septum, a particularly hyperdynamic LV can give a false positive for a well-functioning RV.
4. In the same vein, a stunned septum (i.e post-cardiac surgery) can make the RV appear worse than it actually is.
5. It doesn’t include the right ventricular outflow tract in its assessment and may miss RV dysfunction localized there.

SO NOW I HAVE 3 TOOLS TO MEASURE THE RV- GREAT! WHAT HAPPENS IF I ASSESS AN RV AND GET NON-MATCHING VALUES?

I’d get a senior echocardiographer to have a look. Either there’s been user error, or you’ve got a very complex RV with dissimilar contraction between segments (post-cardiac surgery, post-infarction, bundle branch block).