Right ventricular fractional area change (RV FAC)
FAC is a bidimensional marker of RV systolic function obtained from the apical 4 chamber view by manually tracing the endocardial border of the RV in end-diastole and end-systole, while including the trabeculations in the cavity. It is calculated as: (end-diastolic area – end-systolic area)/ end-diastolic area x 100% [16]. This parameter reflects both the longitudinal and radial contraction of the RV, but it neglects the contraction of the outflow tract [16, 19]. It has shown good correlation with the RV ejection fraction (RVEF) determined by CMR [33], but it is load-dependent and potentially difficult to acquire in case of poor endocardial definition [19, 34]. A RV FAC<35% reflects RV dysfunction [16, 18].
Zornoff et al. found that RV FAC is an independent predictor of total mortality, cardiovascular mortality and development of HF in patients with LV systolic dysfunction following a myocardial infarction (MI), each 5% decrease in FAC being associated with a 16% increase in odds of cardiovascular mortality [35]. Similar findings were reported by Anavekar et al., who found RV FAC to be an independent predictor of all-cause mortality, cardiovascular death, sudden death, HF and stroke in patients with MI and LV dysfunction [36].
A small retrospective study found that RV FAC<26.7% is predictive of death or LV assist device implantation in patients with DCM, providing better prognostic information than other RV functional parameters such as TAPSE and S’ wave velocity [37]. Merlo et al. found that RV FAC<35% was an independent predictor of death or heart transplantation in patients with idiopathic DCM; moreover, RV FAC had stronger predictive value than other well-known prognostic factors such as LV dimensions and New York Heart Association (NYHA) functional class [38].