The right heart has jokingly been referred to as the organ's stepchild, with little attention paid to its size, function, and prognostic implications. To help with this often overlooked task, this article series reviews the proper methods to quantify the right heart for both size and function.
Judith Buckland, president of CardioServ.
We selected TAPSE and the S' wave as the initial function quantification methods to cover in our series due to their ease, reproducibility, and established prognostic value. However, TAPSE and the S' wave have limitations such as angle and load dependency. In addition, these techniques do not fully represent global RV function and are therefore susceptible to overestimation or underestimation.
FAC
In this article, we'll discuss fractional area change (FAC), another method listed by the ASE for evaluating right ventricular function. A measurement that provides an estimate of the global RV systolic function, FAC is a formula for the percentage of area change within the RV between diastole and systole. A normal value for FAC is greater than 35%. Please do not confuse FAC with the ejection fraction (EF) percentage. Based upon the area change, the value will be less than the calculated EF percentage.
Although it provides a better estimate of global RV function, fractional area change -- as is the case with most quantitative methods -- has advantages as well as limitations. FAC has an established prognostic value and can serve as an independent predictor of heart failure, sudden death, stroke, and mortality in patients after pulmonary embolectomy. It also covers both the longitudinal and radial components of RV contraction and correlates well with cardiac MRI.
On the downside, FAC neglects the contribution of the right ventricular outflow tract (RVOT) to overall RV function. In addition, it suffers from limited interobserver reproducibility. However, FAC is still a great representation of the estimated global RV systolic function.
Performing FAC correctly
This method should be performed on the RV-focused apical 4 (AP4) view, which we described in part 1 of our series. Ensure that the entire RV is contained in the imaging sector during both systole and diastole. Then trace the RV area in diastole and systole (cm2), and be sure to include the trabeculae and apex within the cavity.
It's important to be aware of several pitfalls when measuring FAC:
- Avoid foreshortening of the RV.
- Be sure to include the entire apex and free wall.
- Trace the endocardial border (see the yellow line in the image below for an example of correct tracing).
- Do not trace the borders of the moderator band and trabeculae; only trace the RV endocardial border.
- Don't measure what you don't see! Remember, there are other methods (TAPSE or S' wave) you can use for evaluating RV function.
All images courtesy of CardioServ.FAC reference values
Fractional area change can be calculated by subtracting the end systolic area (ESA) from the end diastolic area (EDA) of the RV and then dividing that result by the EDA. This is a quick and easy calculation, so don't be afraid to use a calculator if your machine does not have a measurement package.
Normal FAC values are greater than 35%; anything less than that is abnormal.
In our next article, we'll review a fourth RV quantification method: the right ventricular index of myocardial performance (RIMP).
References
Guazzi M, Bandera F, Pelissero G, et al. Tricuspid annular pane systolic excursion and pulmonary arterial systolic pressure relationship in heart failure: An index of right ventricular contractile function and prognosis. Am J Physiol Heart Circ Physiol. 2013;305(9):H1373-H1381. doi:10.1152/ajpheart.00157.2013.
Kossaify A. Echocardiographic assessment of the right ventricle, from the conventional approach to speckle training and three-dimensional imaging, and insights into the "right way" to explore the forgotten chamber. Clin Med Insights Cardiol. 2015;9:65-75. doi:10.4137/CMC.S27462.
Lang RM, Badano LP, Mor-Avi V, et al. Recommendations for cardiac chamber quantification by echocardiography in adults: An update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. American Society of Echocardiography website. http://asecho.org/wordpress/wp-content/uploads/2015/01/ChamberQuantification2015.pdf. Published 2015. Accessed March 1, 2017.
Judith Buckland is president of CardioServ, a consulting firm focused on inspiring excellence in diagnostic imaging. Judith can be reached by email at [email protected] or via CardioServ's website.
The comments and observations expressed herein do not necessarily reflect the opinions of AuntMinnie.com, nor should they be construed as an endorsement or admonishment of any particular vendor, analyst, industry consultant, or consulting group.
![Examples of ultrasound findings and techniques. (A) Images in a 39-year-old male patient with a mass in the left thigh. The mass is heterogeneous on the B-mode US image (compared with the patient in D) and showed increased microvascularity (superb microvascular imaging [SMI]) and shear-wave elastography (SWE) values. Undifferentiated pleomorphic sarcoma was diagnosed at biopsy (with pleomorphic rhabdomyosarcoma in surgical specimen). (B) Images in an 18-year-old male patient with a mass in the left leg. The mass is hypoechoic on the B-mode image, with no other findings suggestive of malignancy. The lesion is in contact with the cortex of the tibia, which is slightly irregular. CT revealed a doubtful anteromedial tibial erosion. The microvascular study demonstrated high vascularization, suggestive of malignancy. Periosteal Ewing sarcoma was diagnosed with both histologic and immunohistochemical confirmation. (C) Images in a 69-year-old female patient with a lump growing on the outside of the left leg. Multiple SWE examinations were performed (please note the high values obtained in the measurements, whereas the color map highlights the stiffness relative to adjacent tissues). SMI showed areas of increased vascularization to target for sampling. Undifferentiated spindle cell sarcoma was diagnosed at biopsy, with residual leiomyosarcoma in the surgical specimen after neoadjuvant therapy. (D) Images in a 56-year-old female patient with a mass in the right thigh. The mass is heterogeneous at both B-mode ultrasound (similar to patient A) and MRI (coronal T2-weighted spectral attenuated inversion recovery [SPAIR]; T1-weighted pre-contrast and postcontrast imaging), which even shows uptake after the administration of paramagnetic contrast material, which is traditionally suggestive of malignancy. Low values at SMI and elastography are suggestive of benignity. Spindle cell lipoma was diagnosed at biopsy, with atypical spindle cell lipomatous tumor in the surgical specimen.](https://img.auntminnie.com/mindful/smg/workspaces/default/uploads/2026/08/images-radiol250278fig2.APCFLSvX6p.jpg?auto=format%2Ccompress&dpr=2&fit=crop&h=167&q=70&w=250)