Three-dimensional right ventricular ejection fraction (3D RVEF)
3D echocardiography overcomes the geometric assumptions used in 2D
echocardiography, being particularly useful for the evaluation of the
RV, which – due to its complex anatomy – cannot be comprehensively
assessed with 2D measurements only. 3D echocardiography integrates both
the longitudinal and radial components of RV contraction [19] and,
unlike bidimensional echocardiography, allows the assessment of the RVOT
as well. The images are acquired with a dedicated 3D probe using a
full-volume data set from the apical RV-focused view and they are
subsequently analysed with dedicated software (Figure 2). The 3D RV
volumes and EF have been widely validated against the gold standard
represented by CMR [56-58]. The main limitations of 3D RVEF are
load-dependency, challenges in correctly tracing the endocardial border,
image quality, stitching artefacts in case of arrhythmias, time
consumption and limited availability [19]. A 3D RVEF<45%
is considered abnormal [16].
In a population-based cohort study which enrolled 1004 elderly people,
Nochioka et al. analysed the prevalence and prognostic role of RV
dysfunction for HF with 2D and 3D echocardiography. Among patients with
no HF at baseline, 3D RVEF proved to be an independent predictor of
death or incidence of HF: each 5% decrease in 3D RVEF was associated
with a 20% increase in the hazard of death or hospitalization for HF,
independent of LVEF [59].
Magunia et al. showed that 3D RVEF is an independent predictor of
post-operative RV failure in LVAD recipients [60], which is a
well-known, common cause of mortality after LVAD implantation [61].
In a recent study, Nagata et al. investigated the long-term prognostic
value of 3D RVEF in 446 patients with various cardiovascular diseases,
who were followed during 4.1 years for a primary endpoint of cardiac
death and a secondary composite endpoint of cardiac death, ventricular
fibrillation, nonfatal myocardial infarction and hospitalization for HF
exacerbation. At the end of the follow-up period, 3D RVEF was found to
be an independent predictor of both cardiac death and of the secondary
endpoint of MACE [62].
A recent retrospective study of Surkova et al. evaluated the relative
importance of different combinations of reduced and preserved 3D LVEF
and 3D RVEF in predicting mortality in patients with different cardiac
diseases. Impaired 3D RVEF, but not LVEF, was a strong and independent
predictor of both all-cause mortality and cardiovascular mortality
[63]. Moreover, 3D RVEF was superior to conventional
echocardiographic parameters of RV performance to predict total
mortality. The group of patients with reduced LVEF and reduced RVEF had
the highest mortality in the study; interestingly, patients with reduced
LVEF and preserved RVEF had significantly better survival than patients
with reduced RVEF and preserved LVEF [63]. The results of this study
draw the attention to the potential role of therapies targeting RV
dysfunction to improve clinical outcome.