How to measure fractional area change of the RV

Measurement of Fractional Area Change (FAC) of the Right Ventricle

Introduction

Assessment of right ventricular (RV) systolic function is an essential component of echocardiography, as RV dysfunction carries important diagnostic and prognostic implications in many cardiovascular diseases. Fractional Area Change (FAC) is a simple, reproducible, and guideline-recommended echocardiographic parameter used to quantify global RV systolic function.

What is Right Ventricular Fractional Area Change (RV FAC)?

RV FAC is a two-dimensional echocardiographic measurement that represents the percentage change in RV cavity area between end-diastole and end-systole. It reflects longitudinal and radial contraction of the RV and correlates reasonably well with RV ejection fraction measured by cardiac MRI.

Formula for RV FAC

RV FAC (%) =

[(RV End-Diastolic Area − RV End-Systolic Area) ÷ RV End-Diastolic Area] × 100

Echocardiographic View Required

• RV-focused apical four-chamber view

• The RV should be centered and maximized in the sector

• Avoid foreshortening of the RV apex

• The interventricular septum should be vertical

Step-by-Step Method of Measurement

1. Image Acquisition

• Obtain a high-quality RV-focused apical four-chamber view

• Optimize gain, depth, and sector width

• Freeze the image at true end-diastole (frame at onset of QRS or largest RV area)

• Freeze the image at true end-systole (smallest RV cavity area)

2. Endocardial Tracing

• Trace the RV endocardial border manually

• Include the RV free wall, apex, and interventricular septum

• Exclude trabeculations and papillary muscles from the cavity area

• Exclude the right atrium and the RV outflow tract

3. Area Calculation

• The machine automatically calculates RV end-diastolic area (RVEDA)

• Trace again at end-systole to obtain RV end-systolic area (RVESA)

4. FAC Calculation

• FAC is calculated automatically or manually using the standard formula

Normal Values and Interpretation

• Normal RV FAC: ≥ 35%

• Mild RV systolic dysfunction: 30–34%

• Moderate RV systolic dysfunction: 25–29%

• Severe RV systolic dysfunction: < 25%

Clinical Significance of RV FAC

RV FAC is clinically useful in:

• Pulmonary hypertension

• Right ventricular myocardial infarction

• Heart failure (HFrEF and HFpEF)

• Valvular heart disease (especially tricuspid regurgitation)

• Congenital heart disease

• Prognostic assessment in chronic lung disease and ARDS

A reduced RV FAC is associated with worse outcomes and increased mortality in several cardiovascular and pulmonary conditions.

Advantages of RV FAC

• Easy to measure

• Does not require Doppler alignment

• Reflects global RV systolic function

• Recommended by ASE and EACVI guidelines

• Useful when TAPSE is unreliable

Limitations of RV FAC

• Depends on image quality

• Limited in severe RV trabeculation

• Underestimates function in regional RV dysfunction

• Less accurate in markedly dilated or distorted RV geometry

• Two-dimensional measure of a complex three-dimensional structure

Comparison with Other RV Function Parameters

• TAPSE: Measures longitudinal RV function only

• S′ (Tissue Doppler): Angle-dependent

• RV FAC: Assesses global systolic function

• RV Strain: More sensitive but requires good image quality and software

• Cardiac MRI RVEF: Gold standard but less accessible

Guideline Recommendations

Current echocardiography guidelines recommend RV FAC as one of the core parameters for routine RV systolic function assessment, along with TAPSE, tissue Doppler S′ velocity, and RV strain when available. RV FAC should not be interpreted in isolation and must be correlated with clinical findings and other echocardiographic indices.

Practical Tips

• Always use RV-focused views

• Avoid foreshortening of the RV apex

• Measure multiple beats and average (especially in AF)

• Interpret FAC in conjunction with TAPSE and RV S′

• Ensure consistent end-diastolic and end-systolic frame selection

Conclusion

Right ventricular fractional area change is a robust, simple, and guideline-endorsed echocardiographic parameter for assessing RV systolic function. When performed correctly, it provides valuable diagnostic and prognostic information and should be part of every comprehensive echocardiographic examination.

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