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Rong et al. Vessel Plus 2019;3:18 I http://dx.doi.org/10.20517/2574-1209.2019.007 Page 3 of 15

EVALUATION OF THE LEFT VENTRICLE
Subjective interpretation of left ventricular (LV) volumes and function has long been recognized as one of
[8]
the greatest limitations of mono- and bi-dimensional echocardiography . Accurate interpretation of LV
volumes and function becomes even more difficult in the not uncommon case of patients with regional
LV wall motion abnormalities, including aneurysmal LV for which conventional 2D echo has been
demonstrated as not accurate in determining absolute LV volumes and ejection fraction (EF) because of LV
[9]
asymmetry .

Validation of echo against cardiac magnetic resonance imaging (MRI) (regarded as the gold-standard),
nuclear imaging, and computed tomography (CT) has consistently shown 3D echo to be more accurate
[10]
and reproducible compared to conventional 2D evaluation . In a meta-analysis including 23 studies
[11]
(1,638 echocardiograms), Dorosz et al. showed that 3D echo, as compared to cardiac MRI, systematically
underestimates volumes and has wide limits of agreement; its performance, however, remains better than
traditional 2D methods. Of note, greater magnitude of bias was reported in patients with poor quality
data sets and/or large ventricles, likely due to the known difficulty to include larger structures within the
3D pyramidal dataset. Similar results have been obtained in other series , confirming the systematic
[12]
underestimation of MRI-derived volumes by 3D echo.

These concepts have been incorporated into the latest edition of the American Society of Echocardiography
(ASE) guidelines on chamber quantification, which now recommend different cutoffs to define normal LV
[6]
3D parameters .
A certain degree of underestimation by 3D echo has also been demonstrated with regard to LV mass
assessment as compared to cardiac MRI, although improvements in terms of accuracy have been achieved
[13]
more recently. In a meta-analysis including 25 studies comparing 3D echo vs. cardiac MRI, Shimada et al.
2
found that papers published in or before 2004 reported high heterogeneity (I = 69%) and significant
underestimation of LV mass by 3D echo [-5.7 g, 95% confidence interval (95%CI) -11.3 to -0.2, P = 0.04],
papers published from 2005 to 2007 were still heterogeneous (I = 60%) but showed less systematic bias (-0.5
2
2
g, 95%CI -2.5 to 1.5, P = 0.63). In contrast, studies published in or after 2008 were highly homogenous (I =
3%) and reported excellent accuracy (-0.1 g, 95%CI -2.2 to 1.9, P = 0.90).

EVALUATION OF THE RIGHT VENTRICLE
The complex and highly asymmetric anatomy of the right ventricle (RV) has traditionally represented a
challenge for quantitative evaluation by echocardiography. Its trabeculations, along with the retrosternal
position and its unique shape (defying any easy geometric approximation) explains the difficult task of RV
assessment. Nonetheless, RV size and function have been shown to be important predictors of cardiovascular
[14]
morbidity and mortality in patients with various conditions .
Conventional 2D echo lacks the possibility to encompass the whole RV structure (inflow, outflow, and apical
trabecular area); consistently, RV evaluation must be pursued by means of acquisitions via multiple acoustic
[6]
windows, as recommended by international guidelines .
Nowadays, different imaging modalities can offer better understanding of the RV anatomy (e.g., cardiac
MRI, CT scan) but their use is limited by local availability, higher costs, complexity and greater time-
[14]
consumption compared to echocardiography .

The previously described ability of 3D echo to acquire the whole structure of interest has opened to new
possibilities to overcome the challenges encountered with conventional echocardiography when it comes to
[15]
exploring “the forgotten ventricle” [Figure 1] .