Assessments of RV Function
Fractional Area Change
What is the fractional area change (FAC)?
FAC is the area difference between RV end-diastolic and end-systolic areas measured through ideally RV-focused apical view
How is fractional area change (FAC) performed?
- Should be performed in the RV focused apical 4 chamber (A4C) view:
- Ensure the entire RV is contained in the imaging sector in both systole and diastole
- The RV endocardial border is manually traced in systole and diastole to give end-systolic and end-diastolic areas (cm2):
- Trace from the lateral tricuspid annulus along the free wall to the apex, and back along the interventricular septum to the medial tricuspid valve annulus
- Be sure to include the apex, entire free wall and trabeculae within the cavity
- The fractional area change (%) can then be calculated from the measured areas
What is the formula for fractional are change?
FAC (%)= (RVEDA - RVESA)/RVEDA × 100
What are the normal values for fractional area change?
Males ≥30%
Females ≥35%
What are the strengths of Fractional area change in the assessment of RV function?
- Quickly and easily obtained
- Reflects both long and radial componen
- Correlates well with cardiac MR
- Validated against cardiac MR
- Established prognostic value (shown to be an independent predictor of sudden death and mortality after PE, MI and heart failure)
What are the limitations of fractional area change in the assessment of RV function?
- Neglects the contribution of the RV outflow tract to overall systolic function.
- 2D measure so does not represent global RV function
Retest reproducibility can vary significantly.
What are the pitfalls when measuring the fractional area change?
- Avoid foreshortening of the RV
- Be sure to include the entire apex and free wall (do not trace borders of trabeculae or moderator band)
- Don’t measure what you don’t see!