The right ventricle (RV) has, for a long time, been the neglected side of the heart. However, the impact of right ventricular (RV) systolic function on patient outcome in different cardiovascular diseases, such as left ventricular (LV) failure and pulmonary artery hypertension , has been increasingly recognized; nowadays, the assessment of RV function is a crucial issue in clinical practice. However, RV imaging is challenging, and echocardiography – the most widely available and used cardiovascular imaging technique – is hampered in particular by the location of the RV behind the sternum .

Compared with the left ventricle (LV), the shape of the thin-walled RV cavity is more complex. The RV is triangular in the sagittal plane and crescent-shaped in cross section, as a result of the concave RV free wall and convex interventricular septum wrapping around the high-pressured thick-walled bullet-shaped LV . The RV fiber arrangement is predominantly longitudinal, creating a peristaltic contraction from the inlet to the outlet and a bellows-like motion of the free wall toward the septum .

The complex RV anatomy has prevented accurate volumetric quantification of RV function by two-dimensional (2D) echocardiography because of the many assumptions required . Nevertheless, taking particular advantage of the mainly longitudinal RV fiber orientation, several reliable indexes of RV systolic function have been validated and linked to patient outcomes , and clinical guidelines for the echocardiographic assessment of the right heart in adults have been published . Data regarding the applicability of these guidelines in routine clinical practice are, however, limited.

In this issue of the journal, Peyrou et al. report their experience in RV systolic function assessment by ultrasound in routine clinical practice. In a large population of 422 consecutive patients awaiting cardiac surgery, the authors prospectively measured RV systolic function using almost all the variables described in the guidelines: RV fractional shortening (RVFAC); pulsed tissue Doppler-derived tricuspid lateral annular systolic velocity (s’); myocardial performance index; isovolumic acceleration (IVA); RV dP/dt; and longitudinal 2D strain. The combination of RVFAC and s’ was considered as the reference method. Both indexes were feasible in 413 (98%) patients; nine patients were excluded.

In accordance with the values of RVFAC and s’, the patients were classified as having normal RV systolic function if RVFAC was ≥ 35% and s’ was ≥ 10 cm/s ( n = 320, 77.5%), or abnormal RV systolic function if both indexes were below the recommended threshold values ( n = 39, 9.5%). In 54 (13%) patients, the RVFAC and s’ indexes were discordant. Receiver operating characteristic curve analysis showed that the single best variables for predicting RV systolic dysfunction were 2D longitudinal strain (area under the curve = 0.95) and IVA (area under the curve = 0.87). The feasibility of 2D longitudinal strain was better than that of IVA (94% and 84%, respectively). However, IVA appeared to be the least load-dependent variable.

The highest measure variability was observed for RVFAC; s’, 2D longitudinal strain and IVA were much more reproducible variables.

The authors are to be commended on this study, which provides strong evidence of the high feasibility of a comprehensive ultrasound assessment of RV systolic function in a routine clinical context. For a single variable RV function approach, 2D longitudinal strain and IVA appeared to be very reliable indexes. However, several study limitations should also be considered.

First, the reference method used to define normal RV function was the combination of two echocardiography variables. Patient outcomes, rather than an imaging endpoint, would have been more appropriate for assessing the clinical relevance of each ultrasound variable and answering the hypothesis that multivariable assessment is superior to a single index approach. Recent studies have demonstrated that s’ and, more recently, RV 2D longitudinal strain may be superior to RVFAC in predicting the outcome of patients with heart failure and those referred for cardiac surgery . This limitation was acknowledged by the authors; the collection of short-term and long-term prognostic data is currently ongoing.

Second, longitudinal 2D strain was reported only for the basal RV free wall segment. Even if the 2D imaging quality of the apical portion of the RV free wall is, in general, non-optimal, speckle-tracking technology is less angle dependent than tissue Doppler imaging, and provides the opportunity for a more global longitudinal function assessment of the RV free wall . It would be of interest in the future to include both regional and global longitudinal 2D strain in statistical analyses.

Finally, the study included only 34 (8%) patients with atrial fibrillation; further studies are warranted to investigate the validity of the guidelines in patients with this condition.

Transthoracic three-dimensional (3D) real-time echocardiography has emerged as a promising technique for the assessment of RV volumes and function. However, the challenge of acquiring a high-quality full-volumetric 3D data set, including the RV anterior wall and the RV apical lateral segments, in patients with poor imaging windows and/or a dilated RV is the main limitation of the method . Data on the feasibility of the method in a routine clinical context are still limited.

Cardiovascular magnetic resonance (CMR) is the second-line modality after echocardiography for comprehensive RV evaluation; both techniques provide additional and complementary information. The use of CMR should be considered, in particular, in case of an inconclusive ultrasound examination and in specific clinical situations, such as in patients suspected of having arrhythmogenic ventricular dysplasia .

Echocardiography currently offers several simple tools for quantifying RV systolic function reliably. The study by Peyrou et al. underscores the applicability of these tools in a routine clinical context. Thus, the imaging of RV should be an integral part of each echocardiographic examination. The RV needs to be imaged from several echocardiographic windows to provide several cross-sectional planes; visual assessment of RV systolic function gives the reader an initial qualitative evaluation of RV systolic function but remains insufficient. It is strongly recommended to incorporate at least one quantitative measure into the routine echocardiographic examination report. Failure to do so may result in underestimation of the severity of some patients. Emerging new technologies, such as 3D echocardiography and strain imaging , are enlarging the spectrum of pathophysiological information obtained by ultrasound. The combination of multiple ultrasound-derived and/or non–ultrasound-derived variables could enhance the diagnostic accuracy of RV imaging modalities. However, further studies are warranted to describe which variables are most valuable in combination, including 3D, and to define which patient subgroups will benefit the most from multivariable approaches.