Echocardiographic assessment of the right heart in adults: a practical guideline from the British Society of Echocardiography

Abbas Zaidi, MD, 1, * Daniel S Knight, MD (Res), 2, * Daniel X Augustine, MD, 3, † Allan Harkness, MSc, 4 David Oxborough, PhD, 5 Keith Pearce, 6 Liam Ring, MBBS, 7 Shaun Robinson, MSc, 8 Martin Stout, PhD, 9 James Willis, PhD, 3 Vishal Sharma, MD, 10, † and the Education Committee of the British Society of Echocardiography

Abbas Zaidi

1 University Hospital of Wales, Cardiff, UK

Daniel S Knight

2 Royal Free London NHS Foundation Trust, London, UK

Daniel X Augustine

3 Royal United Hospitals Bath NHS Foundation Trust, Bath, UK

Allan Harkness

4 East Suffolk and North Essex NHS Foundation Trust, Essex, UK

David Oxborough

5 Liverpool John Moores University, Research Institute for Sports and Exercise Science, Liverpool, UK

Keith Pearce

6 Wythenshawe Hospital, Manchester, UK

Liam Ring

7 West Suffolk Hospital NHS Foundation Trust, Bury St Edmunds, UK

Shaun Robinson

8 North West Anglia NHS Foundation Trust, Peterborough, UK

Martin Stout

9 School of Healthcare Science, Manchester Metropolitan University, Manchester, UK

James Willis

3 Royal United Hospitals Bath NHS Foundation Trust, Bath, UK

Vishal Sharma

10 Liverpool University Hospitals NHS Foundation Trust, Liverpool, UK

5 Liverpool John Moores University, Research Institute for Sports and Exercise Science, Liverpool, UK

D Oxborough and V Sharma are members of the editorial board of Echo Research and Practice. They were not involved in the review or editorial process for this paper, on which they are listed as authors.

*(A Zaidi and D S Knight contributed equally to this work and should be considered joint lead authors)

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Abstract

The structure and function of the right side of the heart is influenced by a wide range of physiological and pathological conditions. Quantification of right heart parameters is important in a variety of clinical scenarios including diagnosis, prognostication, and monitoring response to therapy. Although echocardiography remains the first-line imaging investigation for right heart assessment, published guidance is relatively sparse in comparison to that for the left ventricle. This guideline document from the British Society of Echocardiography describes the principles and practical aspects of right heart assessment by echocardiography, including quantification of chamber dimensions and function, as well as assessment of valvular function. While cut-off values for normality are included, a disease-oriented approach is advocated due to the considerable heterogeneity of structural and functional changes seen across the spectrum of diseases affecting the right heart. The complex anatomy of the right ventricle requires special considerations and echocardiographic techniques, which are set out in this document. The clinical relevance of right ventricular diastolic function is introduced, with practical guidance for its assessment. Finally, the relatively novel techniques of three-dimensional right ventricular echocardiography and right ventricular speckle tracking imaging are described. Despite these techniques holding considerable promise, issues relating to reproducibility and inter-vendor variation have limited their clinical utility to date.

Introduction

A comprehensive evaluation of the right ventricle (RV) by echocardiography is essential for the diagnosis and management of conditions affecting the right heart. Indices of right ventricular size and function are prognostic in a range of congenital and acquired diseases of both left and right heart aetiologies (1, 2, 3, 4). The British Society of Echocardiography (BSE) Education Committee has previously published a minimum dataset for a standard adult transthoracic echocardiogram (5). The present document specifically aims to review, supplement and expand on the echocardiographic assessment of right heart size and function. The variable behaviours and limitations of these parameters across the spectrum of right heart diseases give rise to a range of sensitivities and specificities for discriminating between health and disease. Consequently, there is the potential to generate contradictory and discrepant echocardiography data, and it is therefore important to undertake a detailed assessment of the right heart while taking into account the underlying pathology. This document provides a practical guide to assist with the appropriate application of echocardiography to RV pathology, with the ultimate aim of a more robust assessment of the right heart by cardiac ultrasound.

This protocol has adopted normal reference intervals for cardiac dimensions based on the results of the Normal Reference Ranges for Echocardiography (NORRE) dataset (6). These prospectively obtained data provide a more contemporary basis for reference intervals than previously available. We have also included, for the first time in a BSE protocol, measurements suggested for RV diastolic function assessment. Although this is not current routine clinical practice, the sensitivity of the RV to even minor alterations in loading conditions makes the concept of RV diastolic function at least as physiologically relevant as that of the left ventricle (LV). Indeed, there is no single parameter of RV function by any imaging modality that is truly load independent. The purpose of this part of the document is to introduce the reader to this concept and to consider the influence of the loading conditions facing the right heart on its function, rather than to necessarily mandate a routine assessment across all echocardiography studies. Finally, in order to provide a comprehensive guide to right heart assessment, quantitative assessment of right-sided native valvular heart disease will also be summarised in this document.

Background

The position of the RV within the thorax, along with its complex structure and contraction pattern, all pose additional challenges to echocardiography. The RV is the most anteriorly positioned cardiac chamber, located immediately behind the sternum. It is thin-walled with prominent trabeculations and a complex geometry. Under normal loading conditions, the RV has a triangular shape when viewed from the side, and a crescentic shape in the sagittal plane, wrapping around the conical left ventricle. The orientation of RV myofibres and their arrangement into layers is responsible for the distinct contraction pattern of this chamber, with an outer layer of circumferential subepicardial fibres, and an inner layer of longitudinal subendocardial fibres (7). These layers of differently aligned cardiomyocytes are responsible for the peristaltic, or wave-like, RV contraction pattern, starting at the inflow portion and progressing towards the infundibulum and outflow tract (8). The longitudinal motion drawing the base towards the apex is accompanied by a bellows effect of inward motion of the free wall towards the interventricular septum, which bulges into the RV cavity (9).

Despite the challenges of assessing the RV by echocardiography, it remains the most widely utilised clinical imaging modality for its assessment. A uniform approach to both data acquisition and post-processing steps is essential for ensuring the reproducibility of any imaging technique, with susceptibility to variation arising at both stages. In echocardiography, different sonographers need to acquire and post-process serial echocardiography studies in a reproducible manner in order for meaningful comparisons to be made. The standardisation of RV image acquisition is especially pertinent to echocardiography compared with cross-sectional imaging modalities, as a range of potential two-dimensional echocardiography views of this complex three-dimensional shape can be obtained. For example, foreshortening the apical window is a particular pitfall that can lead to overestimation of RV chamber size. The RV-focused view should be used to generate all apically acquired RV size and function metrics, since it has superior reproducibility for these parameters compared with the standard apical 4-chamber window (10, 11, 12). The RV-focused view can be obtained by a three-step process:

Move the transducer laterally to place the RV in the centre of the echocardiography image (instead of the conventional left heart-centred image) while ensuring that the LV outflow tract does not come into view, and that the LV apex remains central to the top of the image sector. In doing so, the entirety of the RV free wall should now be clearly visualised along with the maximal RV long axis dimension.

RV-focused apical window. Once in the apical 4-chamber view, rotating the transducer will allow the operator to obtain the maximal RV diameter (green line) while the internal LV diameter will remain relatively constant. The red line and the blue line show two variations of the standard apical 4-chamber view, optimised for the left ventricle, but failing to demonstrate maximal RV dimensions. Data from Rudski et al. (12).

Finally, although the emphasis of this document is on echocardiography of the right heart, this should not neglect a comprehensive assessment of the left heart. For example, the most common cause of pulmonary hypertension (PH), a condition which primarily affects the right heart, is disease originating from the left heart. Many conditions of the RV either share common pathology with the LV or originate from left heart disease and are readily and routinely assessed by echocardiography.

Right ventricular systolic function

The echocardiographic evaluation of RV systolic function can be performed qualitatively and quantitatively, by two- and three-dimensional methods, and by regional and global assessment. There are benefits and limitations that are inherent in all of these approaches, the significances of which should be considered relative to the pathology being investigated. Accordingly, these guidelines recommend a disease-oriented approach to RV functional assessment and recognise the specific limitations of different RV systolic functional metrics, factors which are integral to the interpretation and application of reference intervals.

The evidence-base underpinning these reference intervals for RV functional indices should also be considered. Tricuspid annular plane systolic excursion (TAPSE), pulsed Doppler S wave (S′) and fractional area change (FAC) have, by far, the most abundantly available reference data to support their use (11). Therefore, at least one of these three metrics should be routinely reported when assessing RV systolic function. Furthermore, either a measurement that incorporates radial RV function, such as FAC, or at least a qualitative statement regarding radial RV function should be routinely made, since TAPSE and S′ only reflect longitudinal RV function.

More contemporary techniques such as 3-dimensional (3D) and speckle tracking (STE) echocardiography offer novel insights into RV function assessment, but with the caveats of less validation data and standardization across vendor platforms. These limitations should not hinder their development and dissemination in both clinical and academic echocardiography, but should nevertheless be taken into account to ensure the standardization of data acquisition, post-processing and interpretation. Consequently, this document places emphasis on recommending how to perform these techniques systematically and homogeneously in order to allow their reproducible application for assessing RV systolic function.

Right ventricular diastolic function

In comparison with LV diastolic function, there is a lack of guidance for the assessment and quantification of RV diastolic function, and these measures do not typically form part of a standard clinical echocardiographic study. However, a large number of conditions have been shown to be associated with RV diastolic dysfunction, including congenital heart diseases, cardiomyopathies, left-sided valvular heart diseases, and systemic conditions such as diabetes, rheumatoid arthritis and various vasculitides. Table 1 gives examples from the published literature of the utility of RV diastolic function assessment in diagnosis, prognostication, and in monitoring therapeutic response, in a broad range of clinical conditions.

Table 1

Clinical utility of RV diastolic function assessment.

Right ventricular diastole commences with closure of the pulmonary valve. There then ensues a brief period of RV isovolumic relaxation, followed by opening of the tricuspid valve which allows RV filling. Analogous to LV filling, RV filling consists of an early passive phase, and a late active phase driven by right atrial contraction. When RV pressure increases above that of right atrial (RA) pressure, the tricuspid valve closes marking the end of RV diastole. Echocardiographic assessment of RV diastolic function involves four main components:

Two-dimensional morphological assessment of the right heart and inferior vena cava (IVC): Significant elevation of right-sided filling pressure is unlikely in the presence of normal RV and RA dimensions, normal IVC size and inspiratory collapse, and normal RV free wall thickness.

Doppler interrogation of tricuspid inflow: Early (E) and late (A) trans-tricuspid inflow velocities, E/A ratio, and E deceleration time are recorded using pulsed wave Doppler at the tricuspid leaflet tips. The imaging plane should be optimised to align the beam with tricuspid inflow. Trans-tricuspid flow is highly sensitive to preload and afterload, and also to respiratory phase. Therefore, averaging over 5 consecutive beats, or measurement in held expiration, is recommended. The utility of these measurements will be reduced by the presence of moderate or severe tricuspid regurgitation (TR), and in atrial fibrillation (absent A wave).

Tissue Doppler at the lateral tricuspid annulus: RV isovolumic relaxation time (IVRT), E′, A′, and E′/A′ should be measured. This also permits calculation of the RV E/E′ ratio, and the myocardial performance index (RIMP or Tei index) which is described in detail in Table 2 . RV tissue Doppler indices are less load dependent than pulsed wave inflow measurements.

Table 2

View (modality)	Measurement	Explanatory notes	Image
PLAX (2D)	Qualitative regional wall motion analysis of the anterior wall of the RVOT. Visual assessment for RWMA; akinesia, dyskinesia or aneurysm.
RVOTPLAX	At end-diastole, at a similar level to PSAX RVOT1 measurement. Adjust depth and focal zone to visualise the RVOT. Ideally should form a perpendicular line from the RVOT wall to the junction between the interventricular septum and aortic valve. RVOTPLAX ≤43 mm (males) or ≤40 mm (females) is considered normal. RV RWMA + RVOTPLAX ≥32 mm, or ≥19 mm/m 2 = major criterion for ARVC. RV RWMA + RVOTPLAX ≥29 mm to See BSE ARVC protocol (24).
PLAX RV inflow (2D)	Qualitative regional wall motion analysis of the anterior and inferior walls of the RV. Ensure the ventricular septum has been excluded and the true inferior wall is seen (diaphragm and liver in view).
PLAX RV inflow (CFM)	Assessment of TR severity (see A4C CFM for details).
PLAX RV inflow (CW)	TR Vmax	See A4C CW for details.
PSAX Base (2D)	Qualitative assessment of RV structure and function at basal level. Regional wall motion analysis of inferior, lateral, and anterior walls of RV in PSAX at base (mitral valve) level.
PSAX Mid (2D)	Qualitative assessment of RV structure and function at LV papillary muscle level. Regional wall motion analysis of inferior, lateral, and anterior walls of RV in PSAX at mid (LV papillary muscle) level.
Eccentricity index	Measure from PSAX view at mid LV level between papillary muscle and tips of mitral valve leaflets, at end-systole and end-diastole. RV volume overload causes eccentricity in diastole only. RV pressure overload causes eccentricity in systole also. Left ventricular eccentricity index (D2/D1) >1.1 is considered abnormal. See BSE Pulmonary Hypertension protocol for details (25).
PSAX Apex (2D)	Qualitative assessment of RV structure and function at the apex. Regional wall motion analysis of inferior and superior walls of RV in PSAX at apical level.
PSAX RVOT (2D)	Qualitative assessment of RVOT structure and function. Regional wall motion analysis of the anterior wall of the RVOT.
RVOT1 (proximal RVOT)	End-diastolic. Anterior aortic wall directly up to the RVOT free wall (at the level of the aortic valve). The PSAX view is more reproducible than RVOT PLAX. RVOT1 ≤44 mm (males) or ≤42 mm (females) is considered normal (6). RV RWMA + RVOT1 ≥36 mm, or ≥21 mm/m 2 = major criterion for ARVC. RV RWMA + RVOT1 ≥32 mm to
PSAX RVOT (2D)	Qualitative assessment of RVOT structure and function. Regional wall motion analysis of the infundibulum of the RV.
RVOT2 (distal RVOT)	End-diastolic. Measured just proximal to the PV. RVOT2 ≤29 mm (males) or ≤28 mm (females) is considered normal (6).
PSAX PA (2D)	Qualitative assessment of pulmonary valve (PV) leaflet morphology, leaflet thickening, coaptation, prolapse, or presence of supravalvular stenosis.
Pulmonary artery (PA) diameter	PA dimension is measured in end-diastole, halfway between the PV and bifurcation of main PA (12), or 1 cm distal to the PV. A diameter >25 mm is considered abnormal (26).
PSAX RVOT (CFM)	Qualitative assessment of pulmonary regurgitation (PR). Mild PR is likely if the jet has a narrow origin and is
PR jet width/RVOT width	Jet width >65% of the RVOT width (RVOT2) is an indicator of severe PR (27).
PR vena contracta (VC)/PV annular ratio	VC/PV annulus ratio >50% is an indicator of severe PR (28).
PSAX RVOT (CW)	Qualitative inspection of the CW signal morphology. Right atrial contraction may be seen as late diastolic forward flow in the CW Doppler profile through the RVOT/PA (yellow arrow). This signal may be more prominent during inspiration and is a marker of restrictive RV physiology. Visual assessment of PR severity. Mild PR has a soft Doppler envelope with slow deceleration. Severe PR has a dense CW envelope with a triangular envelope.
PA Vmax	4 m/s severe pulmonary stenosis (29). Visual assessment (2D) and PW Doppler are used to differentiate subvalvular, valvular and supravalvular PS.
PR early velocity	CW Doppler measurement through the pulmonary valve in line with the PR jet. An early PR velocity >2.2 m/s is considered a marker of raised mean PA pressure (26). See BSE Pulmonary Hypertension protocol for details (25).
PR end-diastolic velocity	Can be used to estimate PA diastolic pressure, as 4 × (velocity) 2 + RA pressure. RA pressure is estimated from IVC size and collapse (see below).
PR pressure half time	PR pressure half time
PR index	The duration of the CW PR jet as a proportion of the whole of diastole. PR index
PSAX RVOT (PW)	RV outflow tract (RVOT) acceleration time	Can be used to determine the level of obstruction (subvalvular, valvular or supravalvular) if PA Vmax is elevated. A pulsed wave (PW) Doppler measurement taken after positioning the sample volume just below the pulmonic cusp on the RV side in the RV outflow tract. Measure at end-expiration from the onset of flow to peak flow velocity. Acceleration time
A4C (2D)	Right atrial area (RAA)	Measure at the end of ventricular systole on the frame just prior to tricuspid valve (TV) opening. Trace the RA from the plane of the TV annulus along the interatrial septum, superior and lateral walls of RA. RAA ≤22 cm 2 (≤11 cm 2 /m 2 ) in males, or ≤19 cm2 (≤11 cm2/m2) in females is considered normal (6).
A4C (2D)	Qualitative assessment of RV structure, radial and longitudinal function. Detection of regional RV akinesia, dyskinesia or aneurysms. See BSE ARVC protocol (24).
RV/LV basal diameter ratio	This is measured from the standard A4C view without foreshortening. Measurement is taken at end-diastole. A ratio of >1 measured at end-diastole suggests RV dilatation (26).
A4C (2D)	RVD1, RVD2, RVD3	All measurements taken at end-diastole in the RV-focused view. RV size may be underestimated due to the crescentic RV shape. RVD1: Basal RV diameter. Measured at the maximal transverse diameter in the basal one third of the RV. RVD1 ≤47 mm in males, or ≤43 mm in females, is considered normal (6). RVD2: Mid RV diameter measured at the level of the LV papillary muscles. RVD2 ≤42 mm in males, or ≤35 mm in females, is considered normal (6). RVD3: RV length, from the plane of the tricuspid annulus to the RV apex. RVD3 ≤87 mm in males, or ≤80 mm in females, is considered normal (6).
A4C (2D)	Fractional area change (FAC)	Manual tracing of the RV endocardial border, from the lateral tricuspid annulus along the free wall to the apex, and back along the interventricular septum to the medial tricuspid valve annulus. Repeated at end-diastole and end-systole. A disadvantage of this measure is that it neglects the contribution of the RV outflow tract to overall systolic function. FAC = (RVAdiastole − RVAsystole)/RVAdiastole × 100. RV FAC ≥30% in males, or ≥35% in females, is considered normal (6).
A4C (M-mode)	Tricuspid annular plane systolic excursion (TAPSE)	This is an angle dependent measurement and therefore it is important to align the M-Mode cursor along the direction of the lateral tricuspid annulus. Select a fast sweep speed. Measure total excursion of the tricuspid annulus. The measurement should be a vertical line as shown in the figure, using the leading-edge to leading-edge technique. A measure of longitudinal RV systolic function. TAPSE
A4C (CFM)	Assessment of TR severity.
TR VC width	The width of the TR jet at its narrowest point immediately after the regurgitant orifice (white line). VC >0.7 cm is consistent with severe TR (28).
Proximal isovelocity surface area (PISA) radius	The Nyquist limit is adjusted in the direction of the TR jet. The PISA radius is measured from the centre of the TV to the furthest point of the proximal flow convergence zone (red line). PISA radius 0.9 cm severe TR (28).
A4C (CW)	Qualitative assessment of TR severity. Mild TR has a soft jet density and parabolic contour. Severe TR has a dense CW jet and early peaking or triangular CW envelope.
Peak TR velocity	TR Vmax is measured by CW Doppler across the tricuspid valve. Multiple views may need to be taken to obtain the optimal window. These include the RV inflow, parasternal short axis (PSAX), apical 4-chamber (A4C) view, subcostal view, or a modified view between the PSAX and A4C. Ensure the CW Doppler flow angle is correctly aligned. Eccentric jets can lead to incomplete Doppler envelopes and underestimation of TR velocity. A high sweep speed (100 mm/s) can help to differentiate between true velocities and artefact (12). TR velocity can be underestimated in severe/free TR and should be stated in the report if present. Measure from a complete TR envelope. Choose the highest velocity (average of 5 beats in atrial fibrillation). TR Vmax
TR effective regurgitant orifice area (EROA)	Calculated from the PISA radius, aliaising velocity, and peak TR velocity. EROA ≥0.4 cm 2 is considered to indicate severe TR (28).
TR regurgitant volume	Calculated from the EROA multiplied by the TR VTI (red outline in figure). Regurgitant volume ≥45 mL is considered to indicate severe TR (28).
A4C (PW)	The view should be optimised in order to align the ultrasound beam with tricuspid inflow. This may require an unconventional/oblique angulation. Tricuspid inflow velocities vary with respiration, hence averaging should be performed over 5 beats. Note also that the values below are highly sensitive to preload and afterload, and should be interpreted with caution in the presence of moderate or severe TR.
TV E wave velocity	E
TV A wave velocity	Normal range 21-58 cm/s (12).
TV E/A ratio	Normal range = 0.8-2.1. TV E/A 2.1 may indicate restrictive RV filling (12).
TV E wave deceleration time	Normal range = 120-229 ms. TV EDT >229 ms may indicate impaired RV relaxation. EDT
A4C (tissue Doppler)	PW tissue Doppler S′ wave measurement taken at the lateral tricuspid annulus in systole. It is important to ensure the basal RV free wall segment and the lateral tricuspid annulus are aligned with the Doppler cursor to avoid velocity underestimation. RV S′ is closely correlated with TAPSE, and these two measures should be concordant if measured correctly. A disadvantage of this measure is that it assumes that the function of a single segment represents the function of the entire ventricle, which is not likely in conditions that include regionality such as RV infarction (30).
RV S′	Sʹ wave velocity ≥9 cm/s indicates normal RV long axis systolic function (11).
RV E′ and A′	E′ 6 suggests elevated RA pressure (12).
RV IVRT	RV IVRT is often not visible in normal hearts. IVRT >73 ms may indicate impaired RV filling (12).
A4C (tissue Doppler)	Right ventricular index of myocardial performance (RIMP)	RIMP (also known as the Tei index) is an index of global RV performance. The isovolumic contraction time (IVCT), isovolumic relaxation time (IVRT) and ejection time intervals can be measured using tissue Doppler or pulsed wave Doppler. Pulsed wave Doppler or tissue Doppler methods require a sample positioned at the lateral tricuspid valve annulus. However, RIMP derived from pulsed wave Doppler also requires an additional sample from the RVOT and both pulse wave samples need to have near-identical R-R intervals (i.e. heart rate). Tissue Doppler is preferred as it is derived from a single sample. RIMP >0.43 by pulsed wave Doppler, or >0.54 by tissue Doppler, indicates RV dysfunction (11). RIMP >0.64 is associated with a worse prognosis in pulmonary hypertension (25).
Subcostal (2D)	IVC diameter	Diameter is measured perpendicular to the IVC long axis, 1–2 cm from the RA junction at end-expiration. Assess size and percentage reduction in diameter with sniffing or quiet inspiration. (12, 26) IVC diameter ≤21 mm, with >50% collapse with sniff suggests normal RA pressure (0-5 mmHg) IVC diameter ≤21 mm with 21 mm with >50% collapse with sniff suggests intermediate RA pressure (5-10 mmHg) IVC diameter >21 mm, with NB Intermediate can be upgraded to high RA pressure if minimal IVC collapse with sniff (<35%), and secondary indices of elevated RA pressure are present (restrictive filling, RV E/e′ >6, or diastolic flow reversal in the hepatic veins). Intermediate can be downgraded to normal RA pressure if no secondary indices are present.
Subcostal (2D)	Qualitative regional wall motion analysis of the inferior wall of the RV. Visual assessment for akinesia, dyskinesia or aneurysm.
RV wall thickness	At end-diastole. Do not include trabeculations and papillary muscles. Use reduced depth to improve resolution and measurement accuracy. RV wall thickness >5 mm is consistent with RV hypertrophy (12).
Subcostal (CFM)	Qualitative inspection of TR.
Subcostal (CW)	Assessment of TR severity and TR Vmax	See A4C (CW). May be performed if good Doppler alignment with TR jet.
Subcostal (PW) of hepatic veins	Note that there is significant respiratory variation in these parameters, hence averaging over 5 beats should be performed. See the ‘Right ventricular diastolic function’ section for explanation of different HV waveforms.
HV S/D ratio	S/D
HV systolic filling fraction (HVSFF)	HVSFF is calculated as the S velocity/(S velocity + D velocity) × 100. HVSFF
HV systolic and atrial reversal waves	Prominent systolic and/or atrial reversal waves which are amplified during inspiration, are in keeping with raised RA pressure (32). Caution, as these may also be seen in the presence of severe TR.

Pulsed wave (PW) Doppler sampling of hepatic vein flow: Hepatic vein flow assessment is analogous to the measurement of pulmonary vein flow during left heart diastolic function assessment. The PW Doppler beam is aligned with a hepatic vein from the subcostal window. There is significant respiratory variation in flow, with greater velocities seen during inspiration. Averaging should therefore be performed across 5 consecutive beats. The main components of the hepatic vein waveform are the systolic wave (S), systolic reversal wave (SR), diastolic wave (D), and atrial reversal wave (AR). Systolic flow (S) predominance is normally seen, as the IVC rapidly fills the empty RA during ventricular systole. A small SR wave may be seen in late systole but is usually indiscernible in the presence of normal right-sided filling pressures. A low velocity D wave follows, as the RA empties passively into the RV during ventricular diastole. A small AR wave is seen in late diastole as atrial contraction completes RV filling and a small amount of flow is reflected back towards the liver. Impaired right heart filling manifests as diastolic flow predominance (S/D reversal) and increased reversal wave velocities, particularly during inspiration, as detailed in Table 2 .

As with the assessment of LV diastolic function, no single measure should be interpreted in isolation. Assessment of RV diastolic function requires the integration of data from different echocardiographic views and modalities (primarily 2-dimensional, PW, and tissue Doppler). We have not attempted to be too rigid in defining grades of RV diastolic dysfunction in this document. Rather, we would encourage the echo practitioner as a minimum to consider whether RV diastolic function is likely to be normal or abnormal. Figure 2 summarises key indices in the echocardiographic assessment of RV diastolic function.