TABLE 1.

Selected open questions or future directions for the assessment of the right heart

Right heart diastolic performance	What are the best metrics that define right heart diastolic performance? More recently, right atrial strain and volume measures or peak lateral tricuspid annulus systolic velocity/right atrial area index ratio have emerged as promising. In addition, a greater emphasis is placed on systemic venous volume, e.g. portal, hepatic and renal venous flow patterns.
Integrated right heart profiles	Can we further develop better metrics (multimodality) of right heart adaptation in PH that integrate systolic and diastolic performance?
Diagnostic algorithms	Which parameters of right heart structure function best inform diagnostic algorithms in PH? The focus should shift to early detection of PH and multimodality approaches.
Prognostic algorithms	How do imaging metrics best complement clinical prognostic scores?
Surrogate end-point research	Validate in different cohorts the most robust surrogate end-point for PH research. Efforts will also evolve toward defining consistent right heart response profiles in PH.
Indexing of right heart measures	Validate the optimal scaling metrics for right heart dimensions and function beyond body surface area. These metrics may include parameters of body mass, height, age and sex as well as cardiac time periods and physical activity levels. Moreover, indexing may require different scaling depending on the measures, i.e. volumes, areas, linear dimensions.
Standardisation of right heart measures	How best to define the diastolic and systolic phase to measure both right atrium and ventricle size? This may be particularly challenging in the presence of abnormal septal motion. Can we define a more informative internal reference, e.g. centre line, for the RV that takes into account the geometrical complexity of the RV? Should measurements be performed at the compacted or noncompacted region, and should volumes always be inclusive of trabecular muscle? How best to ensure reliable implementation of three-dimensional right heart echocardiography in routine clinical practice?
Reporting	Can we develop a consistent grading system for right heart dysfunction? Can we improve reporting for the right heart by ensuring comments on pulmonary flow profiles including pulmonary regurgitation, septal curvature and geometry of the heart? Can we standardise/integrate comments on image quality? Understand how imaging metrics require contextualisation based on individual patient characteristics.
Defining reference change values	How best to define meaningful changes for right heart measures considering analytic and biological variation?
Molecular imaging	Can we use right heart imaging profiles to gain better insights on mechanism of right heart adaptation? Imaging would benefit from molecular and tissue characterisation-based technology. This can be also useful to test specific targeted therapeutics.
Deep learning	How best to ensure PRIME checklist for deep learning development? How best to implement right heart-related deep learning in practice?
Right heart-specific targets to combat RV failure	What molecular targets are the most promising to allow for right heart specific effects? How will we stratify RV physiological (evaluating right atrial and RV systolic function, diastolic function and volume changes) or molecular (metabolic disruptions or pro-inflammatory/fibrotic changes) to enrich populations for new interventions in the future?

RV: right ventricle; PH: pulmonary hypertension; PRIME: Proposed Requirements for Cardiovascular Imaging-Related Machine Learning Evaluation.