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Quantification of systemic right ventricle by echocardiography
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REVIEW
Quantification of systemic right ventricle by echocardiography Quantification du ventricule droit systémique par échocardiographie Xavier Iriart a,b,∗, Franc ¸ois Roubertie b,c, a,b Zakaria Jalal , Jean-Benoit Thambo a,b a
Congenital heart disease unit, Bordeaux university hospital, Pessac, France Institut de rythmologie et de modélisation LIRYC, université de Bordeaux, Inserm 1045, Bordeaux, France c Surgical centre for congenital heart disease, Bordeaux university hospital, Pessac, France b
Received 4 September 2015; received in revised form 5 November 2015; accepted 11 November 2015
KEYWORDS Systemic right ventricle; Echocardiography; Systlic function
Summary Improvements in cardiac imaging have recently focused a great interest on the right ventricle (RV). In patients with congenital heart disease, the right ventricle (RV) may support the systemic circulation (systemic RV). There are 2 different anatomic conditions providing such physiology: the congenitally corrected transposition of the great arteries (ccTGA) and the TGA surgically corrected by atrial switch. During the last decades, evidence is accumulating that progressive systemic RV failure develops leading to considerable morbidity and mortality. Various imaging modalities have been used to evaluate the systemic RV, but echocardiography is still predominantly used in clinical practice, allowing an anatomic and functional approach of the systemic RV function and the potential associated anomalies. The goal of this review is to offer a clinical perspective of the non-invasive evaluation of the systemic RV by echocardiography. © 2015 Elsevier Masson SAS. All rights reserved.
Abbreviations: 2D, two-dimensional; 2DE-KBR, 2Dechocardiography with 3D knowledge-based reconstruction; 3D, three-dimensional; ccTGA, congenitally corrected transposition of the great arteries; CHD, congenital heart disease; FAC, fractional area change; IVA, isovolumic myocardial acceleration; LV, left ventricle/ventricular; MRI, magnetic resonance imaging; RT3DE, real-time 3D echocardiography; RV, right ventricle/ventricular; RVEF, right ventricular ejection fraction; SR, strain rate; STE, speckle-tracking echocardiography; TAPSE, tricuspid annular plane systolic excursion; TDI, tissue Doppler imaging; TGA, transposition of the great arteries; TR, tricuspid regurgitation. ∗ Corresponding author at: Congenital Heart Disease Unit, Bordeaux University Hospital, Haut-Lévêque, Magellan avenue, 33600 Pessac, France. E-mail address: [email protected] (X. Iriart). http://dx.doi.org/10.1016/j.acvd.2015.11.008 1875-2136/© 2015 Elsevier Masson SAS. All rights reserved.
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MOTS CLÉS Ventricule droit systémique ; Échographie ; Fonction systolique
Résumé Les améliorations de l’imagerie cardiaque ont permis de se focaliser récemment sur l’étude du ventricule droit. Chez certains patients porteurs d’une cardiopathie congénitale, le ventricule droit peut se retrouver en position systémique. C’est le cas des patients porteurs d’une double discordance et patients porteurs d’une transposition des gros vaisseaux opérés par un switch à l’étage atrial. Durant les dernières décennies, les données scientifiques ont montré une dégradation progressive du ventricule droit systémique, qui est associée à une morbidité et une mortalité importante. Différentes modalités d’imagerie ont été utilisées pour évaluer le ventricule droit systémique mais l’échographie reste la méthode de choix dans l’activité quotidienne, permettant une analyse anatomique et fonctionnelle. L’objectif de cette revue est d’offrir une perspective clinique de l’évaluation non invasive du ventricule droit systémique par échocardiographie. © 2015 Elsevier Masson SAS. Tous droits réservés.
Introduction Improvements in cardiac imaging have recently focused great attention on the right ventricle (RV), emphasising its importance in cardiac physiology. The RV has been studied in many physiopathological conditions, such as pulmonary hypertension and heart failure related to left ventricular (LV) dysfunction. Specific congenital heart diseases (CHD) may provide an original condition where the RV is pumping through the systemic circulation. In these anatomical and haemodynamic conditions, the RV is called systemic RV (systemic meaning pumping through the systemic circulation as opposed to the pulmonary circulation). There are two different anatomical conditions that provide such physiology. The first condition is congenitally corrected transposition of the great arteries (ccTGA), where the left atrium is connected to the RV, pumping in the aorta, and where the right atrium is connected to the left ventricle (LV), pumping in the pulmonary artery branches. The other condition is related to atrial switch, which is the surgical treatment developed in the late 1950s by Ake Senning [1] and in the mid-1960s by William Mustard [2] for surgical correction of transposition of the great arteries (TGA). In terms of live birth incidence, TGA is the more common condition (TGA 1:3100 live births vs ccTGA 1:33,000), but the absolute number of Mustard and Senning patients is decreasing because atrial redirection procedures for TGA were superseded by the arterial switch operation in the 1980s. As a consequence, almost all patients with TGA and atrial redirection reach adulthood. For both populations, right ventricular (RV) failure is an important long-term concern, leading to severe late complications [3—5]. Various imaging modalities have been used to evaluate the systemic RV, including angiography, radionuclide imaging and magnetic resonance imaging (MRI) [6]. Nevertheless, in clinical practice, echocardiography is still used predominantly for the assessment of RV function, as it is non-invasive, widely available, relatively inexpensive and has no adverse side effects. However, because of complex geometry, the assessment of systemic RV function by echocardiography has remained mostly qualitative. Advances in digital echocardiography allow for a more refined assessment of the RV, as demonstrated in patients with pulmonary arterial hypertension [7] and other
clinical conditions. These novel echocardiography variables may also be valuable in the functional assessment of the systemic RV [8]. The goal of this review is to offer a clinical perspective of the non-invasive evaluation of the systemic RV by echocardiography.
Echocardiographic assessment of systolic function in the systemic RV Why the RV is different By analogy with the LV, RV ejection fraction (RVEF) is considered to be the marker of RV function. However, attempting to extend this to the RV has been problematic. The shape of the RV does not allow the use of geometric formulae to calculate the RVEF. A range of echocardiographic variables has therefore been developed to evaluate RV function in the subpulmonary position, especially simple measurements of long-axis excursion, giving rapid and unambiguous results [8—10], which has proven utility as a measure of LV function in patients with coronary artery disease, valve disease and heart failure [11,12]. The technique is equally straightforward for the RV, and is especially valid because most of the RV myocardial fibres are arranged longitudinally. These variables have been compared with other methods of calculating the RVEF, especially cardiac MRI, which is considered to be the gold standard for RV functional assessment [13]. Logically, these echocardiographic variables have been used subsequently for systemic RV functional assessment (Fig. 1).
Basic longitudinal function variables The first studies focused on the analysis of longitudinal myocardial fibres using mainly tricuspid annular plane systolic excursion (TAPSE), based on the anatomical hypothesis that the majority of RV myocardial fibres originate at the apex of the heart and insert into the right atrioventricular junction, such that the main bulk of the RV myocardium is composed of longitudinally arranged fibres [14]. Derrick et al. showed that systemic RV long-axis function was notably reduced compared with that of either the normal subpulmonary RV or the systemic LV. The authors hypothesized that impaired systemic RV longitudinal function reflected the response of the longitudinally arranged
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Figure 1. Longitudinal variables commonly used for right ventricular systolic function assessment (panels A—D). A. Tricuspid annular plane systolic excursion (TAPSE) in the lateral apical four-chamber (A4C) view and M-mode. B. S’ tissue Doppler imaging (TDI) of the tricuspid ring in the lateral A4C window. C. TDI-derived strain imaging in the A4C view. D. Two-dimensional strain imaging in the A4C view.
myocardial fibres to chronic increased afterload [8], but they underlined that the systemic RVEF could remain remarkably constant over long-term follow-up [16], and that there were no ‘‘normal’’ RVEF values under these circumstances. TAPSE was further compared with cardiac MRI when the technique became the gold standard for RVEF measurement in the early 2000s. Lissin et al. [15] showed rather good correlation between TAPSE and MRI-based systemic RVEF in a small cohort of patients with TGA and previous atrial switch procedure.
Basic longitudinal function variables Tissue Doppler imaging and tissue Doppler-derived strain and strain-rate imaging Tissue Doppler imaging (TDI) is an echocardiographic technique that uses Doppler principles to measure the velocity of myocardial motion. TDI can be performed in pulsed-wave and colour modes. Pulsed-wave TDI is used to measure peak myocardial velocities, and is particularly well suited to the measurement of long-axis ventricular motion, because the longitudinally oriented endocardial fibres are most parallel to the ultrasound beam in the apical views, and it is a good surrogate measure of overall longitudinal RV contraction and relaxation. Strain and strain rate (SR) are TDI-derived modalities. SR measures the rate of deformation of a tissue segment, and is measured in s−1 . Peak systolic SR represents the maximal rate of deformation in systole. Strain is obtained by integrating the magnitude of deformation between end-diastole used as a reference
point and end-systole. Isovolumic myocardial acceleration (IVA) is also a TDI-based index of contractile function, which has been applied to RV function assessment because it was shown experimentally not only to measure contractile function accurately, but also to be relatively independent of acute changes in ventricular preload and afterload [16]. Vogel et al. confirmed reduced systolic contractile function in the systemic RV of Mustard and Senning patients. The ejection phase indexes, S wave velocity and acceleration, were both reduced [17] compared with both systemic LV and subpulmonary RV in controls. Furthermore, in a subset of 12 patients with simultaneous conductance catheter measurements, IVA correlated with the change in elastance associated with dobutamine stress [17]. These data were confirmed in a population of asymptomatic patients with ccTGA compared with subpulmonary RV in normal patients assessed by peak systolic SR and peak systolic strain [18]. Strain and SR imaging are useful for differentiating active and passive movement of myocardial segments, and to quantify and evaluate components of myocardial function, such as longitudinal myocardial shortening, which are not visually assessable; they allow comprehensive assessment of myocardial function, which is of particular importance for systemic RV assessment, considering the specific haemodynamic conditions. However, TDI-derived strain and SR have several disadvantages related to angle-dependency and the limited spatial resolution imposed by imaging at high temporal resolution. Other disadvantages of the TDI-derived strain and SR imaging techniques are the time-consuming steps for data acquisition and processing and the need for expert readers. Taking into account all of the factors mentioned
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Figure 2. Global variables for right ventricular (RV) systolic function assessment. A. Fractional area change, calculated by dividing the difference between the RV end-diastolic surface and the RV end-systolic surface in the apical four-chamber view by the RV end-diastolic surface. B. Right ventricular real time three-dimensional (3D) reconstruction using Tomtec software: top, mesh view; bottom, example of the stepwise process of RV reconstruction by 3D echocardiography, where the cavity area is optimized in the three orthogonal views and landmarks are identified. C. RV knowledge-based reconstruction model with different views enables evaluation of the 3D shape of the reconstruction. From Kutty et al. [33].
above, it is not surprising that TDI-derived strain and SR measurements are not highly reproducible [19], as with IVA, which carries even higher variability [20]. As a consequence, even if these variables are very interesting in terms of helping us to understand cardiac physiology, their applicability in clinical practice remains to be proved.
Speckle-tracking-derived two-dimensional strain imaging Speckle-tracking echocardiography (STE) is a newer technique for obtaining strain and SR measurements, which analyses motion by tracking speckles (natural acoustic markers) in the two-dimensional (2D) ultrasonic image. These markers (‘‘stable’’ speckles) within the ultrasonic image are tracked from frame to frame. Special software allows spatial and temporal image processing, with recognition and selection of such elements on ultrasound images. The geometric shift of each speckle represents local tissue movement. By tracking these speckles, strain and SR can be calculated. The advantage of this method is that it tracks in two dimensions, along the direction of the wall, not along the ultrasound beam, and thus is angle independent. STE requires only one cardiac cycle to be acquired, but strain
and SR data can be obtained only with high-resolution image quality at a high frame rate. The need for high image quality is a potential limitation to routine clinical applicability in all patients. STE was recently introduced for assessment of RV function in patients with TGA [21,22], in the context of TDI-derived strain and SR imaging, suggesting that deformation-based variables may provide incremental prognostic information over standard variables in this high-risk population. In concordance with earlier studies that used TDI [17,18], it has been reported that STE-derived deformation variables of the RV are depressed in patients with TGA and atrial switch (Fig. 2). A recent study confirmed these preliminary results, showing that systemic RV global longitudinal strain was able to discriminate TGA patients after atrial switch with and without a cardiac MRI systemic RVEF ≥ 45% [23]. The conclusions of these studies using advanced imaging technology agree with the conclusions of the first studies using basic variables. Evidently, though, there are no clear ‘‘normal’’ RVEF values under these circumstances, and longitudinal function variable values are probably different to those applied to subpulmonary RV. Furthermore, it remains uncertain whether altered markers of longitudinal function simply reflect the chronic response of the RV to its loading
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Quantification of systemic right ventricle by echocardiography conditions. It has been shown that RVEF, for example, can remain remarkably constant over long-term follow-up [24], and prediction of RV failure is difficult. The question of the prognostic value of deformation variables of the systemic RV in adults with TGA has been recently addressed by Kalogeropoulos et al. [25]. These authors observed that RV global longitudinal strain (with a cut-off of −10%) had the strongest association with clinical events, followed by RV global longitudinal SR and global early diastolic SR. A similar finding was reported by Diller et al. [26], who suggested that biventricular 2D longitudinal strain was reduced in adult patients with systemic RV, and was related to adverse clinical outcome in this setting (with a cut-off value of −13.3%, providing 72% sensitivity and 63% specificity in identifying patients with adverse clinical outcome). Systemic and subpulmonary myocardial functions appear to be inter-related in patients with TGA, suggesting adverse ventriculoventricular interaction, and the relationship between systemic and subpulmonary ventricular functions was found to be most pronounced in patients with ccTGA and pulmonary stenosis. A clear difference has to be made between severe longitudinal function impairment and mild impairment. Indeed, related to chronic pressure overload, severe RV dilatation and hypertrophy are observed in all patients, as an adaptive process. Pettersen et al. [27] have shown that the systemic RV contraction pattern could be shifted toward the LV contraction pattern, with predominant circumferential shortening and a relative decrease in longitudinal shortening. Based on this theory, a mild decrease in longitudinal function would be more an adaptive process than a real impairment of function. Recently, a cut-off to determine the lower limit of normal longitudinal function of the systemic RV has been proposed [25,26], and it has to be underlined that it differs from that usually used for subpulmonary RV. However, there is no doubt that severe impairment of longitudinal 2D strain is a marker of global RV function impairment, and could be used a prognostic factor in serial quantitative assessment [25,26]. This pathophysiological adaptation has also been recently demonstrated early in life in a patient with hypoplastic left heart syndrome post-Norwood stage 1 operation. Recently, others and we [28,29] tried to redefine the role of echocardiography in the functional assessment of the systemic RV in clinical practice. We confirmed an overall weak correlation of conventional echocardiographic variables of systolic RV function in adult patients with systemic RV compared with cardiac MRI-derived RVEF. For some of the well-established conventional surrogates of RV function, such as TAPSE and myocardial performance index, no significant correlation was found with cardiac MRI results in this setting [28,29]. In contrast to the study of Lissin et al. [15], who found a moderate correlation (r = 0.63) in a small number of patients (n = 18), we did not find acceptable correlation between global and longitudinal functional variables compared with MRI. Our cohort was larger than that in the study by Lissin et al., and our population was more heterogeneous in terms of anatomical distribution between complex and simple TGA. Furthermore, as demonstrated by MRI measurements, RV end-diastolic volume was larger in our population, resulting in a larger RV diameter, which can complicate echocardiographic assessment of the
5 RV. Our findings were further confirmed by Khattab et al. [29]. The main hypothesis to explain the lack of correlation between TAPSE and MRI-derived RVEF is that TAPSE and lateral tricuspid annular motion velocity are accurate for assessing systolic function in subpulmonary RVs, with myocytes predominantly oriented and contracting in the longitudinal direction. Under these circumstances, the lateral tricuspid annular motion velocity and tricuspid valve annular systolic excursion reflect an important aspect of the RV contraction pattern. In a subaortic RV, however, circumferential wall shortening might be more predominant than longitudinal shortening, leading to a systemic RV contraction pattern that resembles the contraction pattern of an anatomical LV [27]. Thus, the measures of longitudinal shortening or shortening velocity might be less likely to represent global RV function in a subaortic compared with a subpulmonary RV, especially for standard variables (TAPSE, tricuspid annulus tissue velocities) that reflect mainly the long-axis function of the laterobasal RV free wall. Global STE-longitudinal has major advantages over the above mentioned variables because it includes medial and apical segments of the systemic RV, and can differentiate between active and passive movement of myocardial segments, to better quantify myocardial longitudinal shortening. However, it has to be kept in mind that RV deformation is currently only assessed in the longitudinal direction with echocardiography, and leaves deformation in other dimensions undefined. There are very scarce data on deformation imaging of the systemic RV in the other directions by echocardiography [30], but they tend to confirm a shift from a longitudinal to a circumferential contraction pattern. The main reasons for the limited availability of this information is the difficulty in meaningfully encompassing the retrosternal and dilated RV in the short-axis view in TGA patients, and the rather poor reproducibility previously reported for the LV.
Conventional global variables The systemic RV is characterized by important remodelling, with spherical reconfiguration close to the LV shape, if we exclude the RV outflow tract. One of the first echocardiographic descriptions of systemic RV systolic function came from adult patients with Mustard baffle repair, using methods of volume and RVEF estimation derived from LV measurements (single-plane methods of ventricular volume and area estimation for RVEF calculation) compared with radionucleotide angiography [31]. The correlation with nucleotide angiography regarding RVEF was relatively weak, and the main problem identified by the authors was the difficulty in obtaining complete border detection for the entirety of complex geometric shape of the RV. One must note that the system used at that time (Hewlett-Packard Sonos 2000 echocardiography system; Agilent Technologies, Palo Alto, CA, USA) was rudimentary compared with current systems. The major improvements in ultrasound techniques together with a better understanding of systemic RV remodelling and mechanics have recently emphasized the value of global function variables. The use of fractional area change (FAC) [23,25,28] and even LV-derived global variables, such as Simpson’s method, to assess global systolic function semiquantitatively, have been applied to systolic RV function
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assessment [22,28]. FAC is measured in the four-chamber view (Fig. 2A); thus, the contribution of the RV outflow tract to global RV function is ignored. However, the circumferential and radial contraction pattern of the RV free wall is incorporated into the analysis of ventricular function. Khattab et al. [29] found that FAC had the best sensitivity (77%) for distinguishing between normal and reduced RV function among conventional variables, and was the best variable after speckle-tracking systolic and diastolic variables for predicting clinical outcome. These results were recently confirmed by Lipczynska et al. [23]. FAC has also demonstrated its value in repaired tetralogy of Fallot with a severely dilated subpulmonary RV [32].
Advanced global variables Real time three-dimensional echocardiography To overcome the problem of geometric assumptions and apical foreshortening, real-time three-dimensional echocardiography (RT3DE) was developed, allowing the fast acquisition of a pyramidal data set that contains the entire RV (TomTec Imaging Systems GmbH, Munich, Germany). In experimental settings, this imaging modality was successfully applied to calculate RV volume and RVEF in both healthy volunteers and paediatric patients with CHD. A dedicated study has yet to investigate the feasibility and reproducibility of this technique for systemic RV volume and function assessment. We have recently shown that in adult patients with repaired tetralogy of Fallot, there was good correlation between RT3DE and MRI for RVEF, but a large underestimation of RV volumes, especially in severely dilated subpulmonary RV, with great difficulties in encompassing the entire RV in the pyramidal sector size [32]. We can presume that the same limitation would be faced for systemic RV assessment with this technique (Fig. 2B).
2D echocardiography with 3D knowledge-based reconstruction 2D echocardiography with 3D knowledge-based reconstruction (2DE-KBR) has also been evaluated in the measurement of systemic RV volumes and function (VentriPoint Diagnostics Ltd., Seattle, WA, USA). This imaging tool is based on a piecewise smooth subdivision surface reconstruction technology that creates a ‘‘knowledge base’’ for the RV using image data acquired from combinations of views, and has been validated against MRI. Kutty et al. [33] recently reported on the feasibility of 2DE-KBR for the evaluation of the systemic RV, and showed the clinical feasibility of quantifying systemic RV volumes and function in adolescents and young adults with repaired TGA, and good agreement of measurements with MRI (Fig. 2C). The different echocardiographic modalities are summarized in Table 1.
Table 1 Cut-offs for systolic right ventricular function variables, based on receiver operating characteristic curve for prediction of cardiac magnetic resonance imaging-derived systemic right ventricular ejection fraction < 45% [23,29] and Cox models for prediction of clinical events [25,26]. Variable
Cut-off
TAPSE (mm) Pulsed Doppler velocity at the annulus (cm/s) IVA (m/s2 ) Systemic RV GLS (%) FAC (%) 3D RVEF (%)
< 14 [29] < 10 [29] 1.0 [17] > −10 to −14.5 [21—23] < 29.5 to 33 [23,29] < 45 [33]
3D RVEF: three-dimensional right ventricular ejection fraction; FAC: fractional area change; IVA: isovolumic acceleration; RV GLS: right ventricular global longitudinal strain; TAPSE: tricuspid annular plane systolic excursion.
systemic RV dysfunction. Several studies have demonstrated an association between the severity of TR and RV systolic dysfunction [3,5]. By comparison, patients with isolated ccTGA with minimal TR might remain asymptomatic with preserved ventricular function for decades [34]. Anatomical malformations of the tricuspid valve are the most common intracardiac abnormality associated with ccTGA. The most frequent problem is an Ebstein-like thickening of the chords that anchor the leaflets to the ventricle [35]. In other patients with a subaortic RV and more anatomically normal tricuspid valves, the tendency to develop TR might relate to anatomical differences between the mitral and tricuspid valves and their subvalvar apparatus, affecting their relative abilities to withstand systemic ventricular pressures and to maintain competence as the systemic ventricle dilates. It is also clear that tricuspid valve function in patients with ccTGA appears to be adversely affected by surgical repair of associated lesions, especially ventricular septal defect closure, which can create anatomical distortion [34]. In ccTGA, the usual vicious circle occurs whereby the inability of the RV to cope with significant TR leads to decreased contractility and annular dilation that in turn exacerbate the degree of TR, but this occurs at an accelerated rate compared with an anatomical LV with similar degrees of mitral incompetence. As a consequence, careful monitoring of TR has to be performed in the longitudinal follow-up by echocardiography. Furthermore, in the setting of systolic function assessment, the change in loading conditions related to chronic TR is an important feature to take into account.
Systemic RV dyssynchrony
Associated features for assessment of systemic RV function Tricuspid regurgitation There are extensive data supporting the concept that tricuspid regurgitation (TR) is the key driver of progressive
Intraventricular dyssynchrony in the setting of systemic RV has been studied using electromechanical and electrosystolic intraventricular delay measurement by TDI and STE-derived strain imaging [36]. The presence of dyssynchrony between the ventricles and within the systemic RV in patients with TGA after atrial redirection was previously reported by Chow et al. [21]. We found that
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Quantification of systemic right ventricle by echocardiography ventricular dyssynchrony was more dominantly present in patients receiving ventricular pacing in the non-systemic (i.e. left) ventricle [36]. As asynchronous electromechanical activation may be one cause of RV dysfunction [37], its identification should be sought during echocardiographic assessment of systemic RV function. Favourable effects of cardiac resynchronization therapy have been reported in a small series of patients with TGA [38], and echocardiography has a certain value in the management of the resynchronization, especially in patients with a pacemaker.
Systemic RV ischaemic pattern RV wall motion abnormalities have been described and linked with a reduction in systolic function [39]. The cause of wall motion abnormalities is not clear, but their presence has been described preoperatively in TGA patients [40], presumably resulting from preoperative myocardial damage. Additionally, it has been demonstrated using nuclear medicine data that resting and induced RV perfusion defects are related to global function [41,42]. Lubiszewska et al. [41] demonstrated that stress-induced perfusion abnormalities correlated with increased age, later repair and lower RVEF and LVEF. Li et al. [43] performed stress echocardiography in TGA patients with atrial redirection, and showed that systemic RV function was impaired during pharmacological stress and was related to limited exercise capacity.
Evaluation of systemic RV diastolic function The prognosis and exercise capacity of patients with systemic RV and atrial redirection are not only affected by systolic dysfunction but also by diastolic function. Riech et al. [24] showed, using radionuclide ventriculography and echocardiography, that the abnormal filling of the ventricles was not only related to impaired diastolic properties of the ventricles, but was mainly because of filling abnormalities through surgical baffles; these decrease the capacity of the systemic venous atrium and diminish the ability of atrial contraction to boost ventricular filling. This abnormal ventricular filling seems to remain constant over time [24]. The findings were in agreement with the reported diminution of early LV filling in patients after atrial redirection, assessed by jugular venous flow measurement using Doppler ultrasound [44]. This hypothesis was further confirmed by load-independent indexes of ventricular function measured by a conductance catheter during dobutamine infusion, which showed that abnormal stroke volume responses during dobutamine stress were not explained by reduced chronotropic or contractile responses, but were associated with fixed ventricular filling rates [45].
Conclusion Although the functional status of many adults with systemic RV is good, reduced exercise capacity is the norm. This finding may relate to many different factors, such as impaired systemic ventricular function, TR, impaired capacitance and conduit function of the intra-atrial baffles
7 or chronotropic incompetence. Echocardiography remains the daily-life imaging modality for systemic RV function assessment. Because of geometric changes, presumed contractility pattern shift and retrosternal position in TGA with atrial redirection, conventional echocardiographic variables are limited for RV function assessment compared with MRI. Nevertheless, echocardiography remains the technique of reference for dyssynchrony and TR assessment. New echocardiographic deformation imaging modalities have been proved to be relevant for left heart disease prognosis, and seem promising for the assessment of systemic RV function. To make a valuable estimation of RV systolic function using echocardiography, a combination of multiple variables should be performed, in association with diastolic function and TR assessment.
Disclosure of interest The authors declare that they have no competing interest.
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REVIEW
Quantification of systemic right ventricle by echocardiography Quantification du ventricule droit systémique par échocardiographie Xavier Iriart a,b,∗, Franc ¸ois Roubertie b,c, a,b Zakaria Jalal , Jean-Benoit Thambo a,b a
Congenital heart disease unit, Bordeaux university hospital, Pessac, France Institut de rythmologie et de modélisation LIRYC, université de Bordeaux, Inserm 1045, Bordeaux, France c Surgical centre for congenital heart disease, Bordeaux university hospital, Pessac, France b
Received 4 September 2015; received in revised form 5 November 2015; accepted 11 November 2015
KEYWORDS Systemic right ventricle; Echocardiography; Systlic function
Summary Improvements in cardiac imaging have recently focused a great interest on the right ventricle (RV). In patients with congenital heart disease, the right ventricle (RV) may support the systemic circulation (systemic RV). There are 2 different anatomic conditions providing such physiology: the congenitally corrected transposition of the great arteries (ccTGA) and the TGA surgically corrected by atrial switch. During the last decades, evidence is accumulating that progressive systemic RV failure develops leading to considerable morbidity and mortality. Various imaging modalities have been used to evaluate the systemic RV, but echocardiography is still predominantly used in clinical practice, allowing an anatomic and functional approach of the systemic RV function and the potential associated anomalies. The goal of this review is to offer a clinical perspective of the non-invasive evaluation of the systemic RV by echocardiography. © 2015 Elsevier Masson SAS. All rights reserved.
Abbreviations: 2D, two-dimensional; 2DE-KBR, 2Dechocardiography with 3D knowledge-based reconstruction; 3D, three-dimensional; ccTGA, congenitally corrected transposition of the great arteries; CHD, congenital heart disease; FAC, fractional area change; IVA, isovolumic myocardial acceleration; LV, left ventricle/ventricular; MRI, magnetic resonance imaging; RT3DE, real-time 3D echocardiography; RV, right ventricle/ventricular; RVEF, right ventricular ejection fraction; SR, strain rate; STE, speckle-tracking echocardiography; TAPSE, tricuspid annular plane systolic excursion; TDI, tissue Doppler imaging; TGA, transposition of the great arteries; TR, tricuspid regurgitation. ∗ Corresponding author at: Congenital Heart Disease Unit, Bordeaux University Hospital, Haut-Lévêque, Magellan avenue, 33600 Pessac, France. E-mail address: [email protected] (X. Iriart). http://dx.doi.org/10.1016/j.acvd.2015.11.008 1875-2136/© 2015 Elsevier Masson SAS. All rights reserved.
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MOTS CLÉS Ventricule droit systémique ; Échographie ; Fonction systolique
Résumé Les améliorations de l’imagerie cardiaque ont permis de se focaliser récemment sur l’étude du ventricule droit. Chez certains patients porteurs d’une cardiopathie congénitale, le ventricule droit peut se retrouver en position systémique. C’est le cas des patients porteurs d’une double discordance et patients porteurs d’une transposition des gros vaisseaux opérés par un switch à l’étage atrial. Durant les dernières décennies, les données scientifiques ont montré une dégradation progressive du ventricule droit systémique, qui est associée à une morbidité et une mortalité importante. Différentes modalités d’imagerie ont été utilisées pour évaluer le ventricule droit systémique mais l’échographie reste la méthode de choix dans l’activité quotidienne, permettant une analyse anatomique et fonctionnelle. L’objectif de cette revue est d’offrir une perspective clinique de l’évaluation non invasive du ventricule droit systémique par échocardiographie. © 2015 Elsevier Masson SAS. Tous droits réservés.
Introduction Improvements in cardiac imaging have recently focused great attention on the right ventricle (RV), emphasising its importance in cardiac physiology. The RV has been studied in many physiopathological conditions, such as pulmonary hypertension and heart failure related to left ventricular (LV) dysfunction. Specific congenital heart diseases (CHD) may provide an original condition where the RV is pumping through the systemic circulation. In these anatomical and haemodynamic conditions, the RV is called systemic RV (systemic meaning pumping through the systemic circulation as opposed to the pulmonary circulation). There are two different anatomical conditions that provide such physiology. The first condition is congenitally corrected transposition of the great arteries (ccTGA), where the left atrium is connected to the RV, pumping in the aorta, and where the right atrium is connected to the left ventricle (LV), pumping in the pulmonary artery branches. The other condition is related to atrial switch, which is the surgical treatment developed in the late 1950s by Ake Senning [1] and in the mid-1960s by William Mustard [2] for surgical correction of transposition of the great arteries (TGA). In terms of live birth incidence, TGA is the more common condition (TGA 1:3100 live births vs ccTGA 1:33,000), but the absolute number of Mustard and Senning patients is decreasing because atrial redirection procedures for TGA were superseded by the arterial switch operation in the 1980s. As a consequence, almost all patients with TGA and atrial redirection reach adulthood. For both populations, right ventricular (RV) failure is an important long-term concern, leading to severe late complications [3—5]. Various imaging modalities have been used to evaluate the systemic RV, including angiography, radionuclide imaging and magnetic resonance imaging (MRI) [6]. Nevertheless, in clinical practice, echocardiography is still used predominantly for the assessment of RV function, as it is non-invasive, widely available, relatively inexpensive and has no adverse side effects. However, because of complex geometry, the assessment of systemic RV function by echocardiography has remained mostly qualitative. Advances in digital echocardiography allow for a more refined assessment of the RV, as demonstrated in patients with pulmonary arterial hypertension [7] and other
clinical conditions. These novel echocardiography variables may also be valuable in the functional assessment of the systemic RV [8]. The goal of this review is to offer a clinical perspective of the non-invasive evaluation of the systemic RV by echocardiography.
Echocardiographic assessment of systolic function in the systemic RV Why the RV is different By analogy with the LV, RV ejection fraction (RVEF) is considered to be the marker of RV function. However, attempting to extend this to the RV has been problematic. The shape of the RV does not allow the use of geometric formulae to calculate the RVEF. A range of echocardiographic variables has therefore been developed to evaluate RV function in the subpulmonary position, especially simple measurements of long-axis excursion, giving rapid and unambiguous results [8—10], which has proven utility as a measure of LV function in patients with coronary artery disease, valve disease and heart failure [11,12]. The technique is equally straightforward for the RV, and is especially valid because most of the RV myocardial fibres are arranged longitudinally. These variables have been compared with other methods of calculating the RVEF, especially cardiac MRI, which is considered to be the gold standard for RV functional assessment [13]. Logically, these echocardiographic variables have been used subsequently for systemic RV functional assessment (Fig. 1).
Basic longitudinal function variables The first studies focused on the analysis of longitudinal myocardial fibres using mainly tricuspid annular plane systolic excursion (TAPSE), based on the anatomical hypothesis that the majority of RV myocardial fibres originate at the apex of the heart and insert into the right atrioventricular junction, such that the main bulk of the RV myocardium is composed of longitudinally arranged fibres [14]. Derrick et al. showed that systemic RV long-axis function was notably reduced compared with that of either the normal subpulmonary RV or the systemic LV. The authors hypothesized that impaired systemic RV longitudinal function reflected the response of the longitudinally arranged
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Figure 1. Longitudinal variables commonly used for right ventricular systolic function assessment (panels A—D). A. Tricuspid annular plane systolic excursion (TAPSE) in the lateral apical four-chamber (A4C) view and M-mode. B. S’ tissue Doppler imaging (TDI) of the tricuspid ring in the lateral A4C window. C. TDI-derived strain imaging in the A4C view. D. Two-dimensional strain imaging in the A4C view.
myocardial fibres to chronic increased afterload [8], but they underlined that the systemic RVEF could remain remarkably constant over long-term follow-up [16], and that there were no ‘‘normal’’ RVEF values under these circumstances. TAPSE was further compared with cardiac MRI when the technique became the gold standard for RVEF measurement in the early 2000s. Lissin et al. [15] showed rather good correlation between TAPSE and MRI-based systemic RVEF in a small cohort of patients with TGA and previous atrial switch procedure.
Basic longitudinal function variables Tissue Doppler imaging and tissue Doppler-derived strain and strain-rate imaging Tissue Doppler imaging (TDI) is an echocardiographic technique that uses Doppler principles to measure the velocity of myocardial motion. TDI can be performed in pulsed-wave and colour modes. Pulsed-wave TDI is used to measure peak myocardial velocities, and is particularly well suited to the measurement of long-axis ventricular motion, because the longitudinally oriented endocardial fibres are most parallel to the ultrasound beam in the apical views, and it is a good surrogate measure of overall longitudinal RV contraction and relaxation. Strain and strain rate (SR) are TDI-derived modalities. SR measures the rate of deformation of a tissue segment, and is measured in s−1 . Peak systolic SR represents the maximal rate of deformation in systole. Strain is obtained by integrating the magnitude of deformation between end-diastole used as a reference
point and end-systole. Isovolumic myocardial acceleration (IVA) is also a TDI-based index of contractile function, which has been applied to RV function assessment because it was shown experimentally not only to measure contractile function accurately, but also to be relatively independent of acute changes in ventricular preload and afterload [16]. Vogel et al. confirmed reduced systolic contractile function in the systemic RV of Mustard and Senning patients. The ejection phase indexes, S wave velocity and acceleration, were both reduced [17] compared with both systemic LV and subpulmonary RV in controls. Furthermore, in a subset of 12 patients with simultaneous conductance catheter measurements, IVA correlated with the change in elastance associated with dobutamine stress [17]. These data were confirmed in a population of asymptomatic patients with ccTGA compared with subpulmonary RV in normal patients assessed by peak systolic SR and peak systolic strain [18]. Strain and SR imaging are useful for differentiating active and passive movement of myocardial segments, and to quantify and evaluate components of myocardial function, such as longitudinal myocardial shortening, which are not visually assessable; they allow comprehensive assessment of myocardial function, which is of particular importance for systemic RV assessment, considering the specific haemodynamic conditions. However, TDI-derived strain and SR have several disadvantages related to angle-dependency and the limited spatial resolution imposed by imaging at high temporal resolution. Other disadvantages of the TDI-derived strain and SR imaging techniques are the time-consuming steps for data acquisition and processing and the need for expert readers. Taking into account all of the factors mentioned
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Figure 2. Global variables for right ventricular (RV) systolic function assessment. A. Fractional area change, calculated by dividing the difference between the RV end-diastolic surface and the RV end-systolic surface in the apical four-chamber view by the RV end-diastolic surface. B. Right ventricular real time three-dimensional (3D) reconstruction using Tomtec software: top, mesh view; bottom, example of the stepwise process of RV reconstruction by 3D echocardiography, where the cavity area is optimized in the three orthogonal views and landmarks are identified. C. RV knowledge-based reconstruction model with different views enables evaluation of the 3D shape of the reconstruction. From Kutty et al. [33].
above, it is not surprising that TDI-derived strain and SR measurements are not highly reproducible [19], as with IVA, which carries even higher variability [20]. As a consequence, even if these variables are very interesting in terms of helping us to understand cardiac physiology, their applicability in clinical practice remains to be proved.
Speckle-tracking-derived two-dimensional strain imaging Speckle-tracking echocardiography (STE) is a newer technique for obtaining strain and SR measurements, which analyses motion by tracking speckles (natural acoustic markers) in the two-dimensional (2D) ultrasonic image. These markers (‘‘stable’’ speckles) within the ultrasonic image are tracked from frame to frame. Special software allows spatial and temporal image processing, with recognition and selection of such elements on ultrasound images. The geometric shift of each speckle represents local tissue movement. By tracking these speckles, strain and SR can be calculated. The advantage of this method is that it tracks in two dimensions, along the direction of the wall, not along the ultrasound beam, and thus is angle independent. STE requires only one cardiac cycle to be acquired, but strain
and SR data can be obtained only with high-resolution image quality at a high frame rate. The need for high image quality is a potential limitation to routine clinical applicability in all patients. STE was recently introduced for assessment of RV function in patients with TGA [21,22], in the context of TDI-derived strain and SR imaging, suggesting that deformation-based variables may provide incremental prognostic information over standard variables in this high-risk population. In concordance with earlier studies that used TDI [17,18], it has been reported that STE-derived deformation variables of the RV are depressed in patients with TGA and atrial switch (Fig. 2). A recent study confirmed these preliminary results, showing that systemic RV global longitudinal strain was able to discriminate TGA patients after atrial switch with and without a cardiac MRI systemic RVEF ≥ 45% [23]. The conclusions of these studies using advanced imaging technology agree with the conclusions of the first studies using basic variables. Evidently, though, there are no clear ‘‘normal’’ RVEF values under these circumstances, and longitudinal function variable values are probably different to those applied to subpulmonary RV. Furthermore, it remains uncertain whether altered markers of longitudinal function simply reflect the chronic response of the RV to its loading
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Quantification of systemic right ventricle by echocardiography conditions. It has been shown that RVEF, for example, can remain remarkably constant over long-term follow-up [24], and prediction of RV failure is difficult. The question of the prognostic value of deformation variables of the systemic RV in adults with TGA has been recently addressed by Kalogeropoulos et al. [25]. These authors observed that RV global longitudinal strain (with a cut-off of −10%) had the strongest association with clinical events, followed by RV global longitudinal SR and global early diastolic SR. A similar finding was reported by Diller et al. [26], who suggested that biventricular 2D longitudinal strain was reduced in adult patients with systemic RV, and was related to adverse clinical outcome in this setting (with a cut-off value of −13.3%, providing 72% sensitivity and 63% specificity in identifying patients with adverse clinical outcome). Systemic and subpulmonary myocardial functions appear to be inter-related in patients with TGA, suggesting adverse ventriculoventricular interaction, and the relationship between systemic and subpulmonary ventricular functions was found to be most pronounced in patients with ccTGA and pulmonary stenosis. A clear difference has to be made between severe longitudinal function impairment and mild impairment. Indeed, related to chronic pressure overload, severe RV dilatation and hypertrophy are observed in all patients, as an adaptive process. Pettersen et al. [27] have shown that the systemic RV contraction pattern could be shifted toward the LV contraction pattern, with predominant circumferential shortening and a relative decrease in longitudinal shortening. Based on this theory, a mild decrease in longitudinal function would be more an adaptive process than a real impairment of function. Recently, a cut-off to determine the lower limit of normal longitudinal function of the systemic RV has been proposed [25,26], and it has to be underlined that it differs from that usually used for subpulmonary RV. However, there is no doubt that severe impairment of longitudinal 2D strain is a marker of global RV function impairment, and could be used a prognostic factor in serial quantitative assessment [25,26]. This pathophysiological adaptation has also been recently demonstrated early in life in a patient with hypoplastic left heart syndrome post-Norwood stage 1 operation. Recently, others and we [28,29] tried to redefine the role of echocardiography in the functional assessment of the systemic RV in clinical practice. We confirmed an overall weak correlation of conventional echocardiographic variables of systolic RV function in adult patients with systemic RV compared with cardiac MRI-derived RVEF. For some of the well-established conventional surrogates of RV function, such as TAPSE and myocardial performance index, no significant correlation was found with cardiac MRI results in this setting [28,29]. In contrast to the study of Lissin et al. [15], who found a moderate correlation (r = 0.63) in a small number of patients (n = 18), we did not find acceptable correlation between global and longitudinal functional variables compared with MRI. Our cohort was larger than that in the study by Lissin et al., and our population was more heterogeneous in terms of anatomical distribution between complex and simple TGA. Furthermore, as demonstrated by MRI measurements, RV end-diastolic volume was larger in our population, resulting in a larger RV diameter, which can complicate echocardiographic assessment of the
5 RV. Our findings were further confirmed by Khattab et al. [29]. The main hypothesis to explain the lack of correlation between TAPSE and MRI-derived RVEF is that TAPSE and lateral tricuspid annular motion velocity are accurate for assessing systolic function in subpulmonary RVs, with myocytes predominantly oriented and contracting in the longitudinal direction. Under these circumstances, the lateral tricuspid annular motion velocity and tricuspid valve annular systolic excursion reflect an important aspect of the RV contraction pattern. In a subaortic RV, however, circumferential wall shortening might be more predominant than longitudinal shortening, leading to a systemic RV contraction pattern that resembles the contraction pattern of an anatomical LV [27]. Thus, the measures of longitudinal shortening or shortening velocity might be less likely to represent global RV function in a subaortic compared with a subpulmonary RV, especially for standard variables (TAPSE, tricuspid annulus tissue velocities) that reflect mainly the long-axis function of the laterobasal RV free wall. Global STE-longitudinal has major advantages over the above mentioned variables because it includes medial and apical segments of the systemic RV, and can differentiate between active and passive movement of myocardial segments, to better quantify myocardial longitudinal shortening. However, it has to be kept in mind that RV deformation is currently only assessed in the longitudinal direction with echocardiography, and leaves deformation in other dimensions undefined. There are very scarce data on deformation imaging of the systemic RV in the other directions by echocardiography [30], but they tend to confirm a shift from a longitudinal to a circumferential contraction pattern. The main reasons for the limited availability of this information is the difficulty in meaningfully encompassing the retrosternal and dilated RV in the short-axis view in TGA patients, and the rather poor reproducibility previously reported for the LV.
Conventional global variables The systemic RV is characterized by important remodelling, with spherical reconfiguration close to the LV shape, if we exclude the RV outflow tract. One of the first echocardiographic descriptions of systemic RV systolic function came from adult patients with Mustard baffle repair, using methods of volume and RVEF estimation derived from LV measurements (single-plane methods of ventricular volume and area estimation for RVEF calculation) compared with radionucleotide angiography [31]. The correlation with nucleotide angiography regarding RVEF was relatively weak, and the main problem identified by the authors was the difficulty in obtaining complete border detection for the entirety of complex geometric shape of the RV. One must note that the system used at that time (Hewlett-Packard Sonos 2000 echocardiography system; Agilent Technologies, Palo Alto, CA, USA) was rudimentary compared with current systems. The major improvements in ultrasound techniques together with a better understanding of systemic RV remodelling and mechanics have recently emphasized the value of global function variables. The use of fractional area change (FAC) [23,25,28] and even LV-derived global variables, such as Simpson’s method, to assess global systolic function semiquantitatively, have been applied to systolic RV function
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assessment [22,28]. FAC is measured in the four-chamber view (Fig. 2A); thus, the contribution of the RV outflow tract to global RV function is ignored. However, the circumferential and radial contraction pattern of the RV free wall is incorporated into the analysis of ventricular function. Khattab et al. [29] found that FAC had the best sensitivity (77%) for distinguishing between normal and reduced RV function among conventional variables, and was the best variable after speckle-tracking systolic and diastolic variables for predicting clinical outcome. These results were recently confirmed by Lipczynska et al. [23]. FAC has also demonstrated its value in repaired tetralogy of Fallot with a severely dilated subpulmonary RV [32].
Advanced global variables Real time three-dimensional echocardiography To overcome the problem of geometric assumptions and apical foreshortening, real-time three-dimensional echocardiography (RT3DE) was developed, allowing the fast acquisition of a pyramidal data set that contains the entire RV (TomTec Imaging Systems GmbH, Munich, Germany). In experimental settings, this imaging modality was successfully applied to calculate RV volume and RVEF in both healthy volunteers and paediatric patients with CHD. A dedicated study has yet to investigate the feasibility and reproducibility of this technique for systemic RV volume and function assessment. We have recently shown that in adult patients with repaired tetralogy of Fallot, there was good correlation between RT3DE and MRI for RVEF, but a large underestimation of RV volumes, especially in severely dilated subpulmonary RV, with great difficulties in encompassing the entire RV in the pyramidal sector size [32]. We can presume that the same limitation would be faced for systemic RV assessment with this technique (Fig. 2B).
2D echocardiography with 3D knowledge-based reconstruction 2D echocardiography with 3D knowledge-based reconstruction (2DE-KBR) has also been evaluated in the measurement of systemic RV volumes and function (VentriPoint Diagnostics Ltd., Seattle, WA, USA). This imaging tool is based on a piecewise smooth subdivision surface reconstruction technology that creates a ‘‘knowledge base’’ for the RV using image data acquired from combinations of views, and has been validated against MRI. Kutty et al. [33] recently reported on the feasibility of 2DE-KBR for the evaluation of the systemic RV, and showed the clinical feasibility of quantifying systemic RV volumes and function in adolescents and young adults with repaired TGA, and good agreement of measurements with MRI (Fig. 2C). The different echocardiographic modalities are summarized in Table 1.
Table 1 Cut-offs for systolic right ventricular function variables, based on receiver operating characteristic curve for prediction of cardiac magnetic resonance imaging-derived systemic right ventricular ejection fraction < 45% [23,29] and Cox models for prediction of clinical events [25,26]. Variable
Cut-off
TAPSE (mm) Pulsed Doppler velocity at the annulus (cm/s) IVA (m/s2 ) Systemic RV GLS (%) FAC (%) 3D RVEF (%)
< 14 [29] < 10 [29] 1.0 [17] > −10 to −14.5 [21—23] < 29.5 to 33 [23,29] < 45 [33]
3D RVEF: three-dimensional right ventricular ejection fraction; FAC: fractional area change; IVA: isovolumic acceleration; RV GLS: right ventricular global longitudinal strain; TAPSE: tricuspid annular plane systolic excursion.
systemic RV dysfunction. Several studies have demonstrated an association between the severity of TR and RV systolic dysfunction [3,5]. By comparison, patients with isolated ccTGA with minimal TR might remain asymptomatic with preserved ventricular function for decades [34]. Anatomical malformations of the tricuspid valve are the most common intracardiac abnormality associated with ccTGA. The most frequent problem is an Ebstein-like thickening of the chords that anchor the leaflets to the ventricle [35]. In other patients with a subaortic RV and more anatomically normal tricuspid valves, the tendency to develop TR might relate to anatomical differences between the mitral and tricuspid valves and their subvalvar apparatus, affecting their relative abilities to withstand systemic ventricular pressures and to maintain competence as the systemic ventricle dilates. It is also clear that tricuspid valve function in patients with ccTGA appears to be adversely affected by surgical repair of associated lesions, especially ventricular septal defect closure, which can create anatomical distortion [34]. In ccTGA, the usual vicious circle occurs whereby the inability of the RV to cope with significant TR leads to decreased contractility and annular dilation that in turn exacerbate the degree of TR, but this occurs at an accelerated rate compared with an anatomical LV with similar degrees of mitral incompetence. As a consequence, careful monitoring of TR has to be performed in the longitudinal follow-up by echocardiography. Furthermore, in the setting of systolic function assessment, the change in loading conditions related to chronic TR is an important feature to take into account.
Systemic RV dyssynchrony
Associated features for assessment of systemic RV function Tricuspid regurgitation There are extensive data supporting the concept that tricuspid regurgitation (TR) is the key driver of progressive
Intraventricular dyssynchrony in the setting of systemic RV has been studied using electromechanical and electrosystolic intraventricular delay measurement by TDI and STE-derived strain imaging [36]. The presence of dyssynchrony between the ventricles and within the systemic RV in patients with TGA after atrial redirection was previously reported by Chow et al. [21]. We found that
Please cite this article in press as: Iriart X, et al. Quantification of systemic right ventricle by echocardiography. Arch Cardiovasc Dis (2016), http://dx.doi.org/10.1016/j.acvd.2015.11.008
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Quantification of systemic right ventricle by echocardiography ventricular dyssynchrony was more dominantly present in patients receiving ventricular pacing in the non-systemic (i.e. left) ventricle [36]. As asynchronous electromechanical activation may be one cause of RV dysfunction [37], its identification should be sought during echocardiographic assessment of systemic RV function. Favourable effects of cardiac resynchronization therapy have been reported in a small series of patients with TGA [38], and echocardiography has a certain value in the management of the resynchronization, especially in patients with a pacemaker.
Systemic RV ischaemic pattern RV wall motion abnormalities have been described and linked with a reduction in systolic function [39]. The cause of wall motion abnormalities is not clear, but their presence has been described preoperatively in TGA patients [40], presumably resulting from preoperative myocardial damage. Additionally, it has been demonstrated using nuclear medicine data that resting and induced RV perfusion defects are related to global function [41,42]. Lubiszewska et al. [41] demonstrated that stress-induced perfusion abnormalities correlated with increased age, later repair and lower RVEF and LVEF. Li et al. [43] performed stress echocardiography in TGA patients with atrial redirection, and showed that systemic RV function was impaired during pharmacological stress and was related to limited exercise capacity.
Evaluation of systemic RV diastolic function The prognosis and exercise capacity of patients with systemic RV and atrial redirection are not only affected by systolic dysfunction but also by diastolic function. Riech et al. [24] showed, using radionuclide ventriculography and echocardiography, that the abnormal filling of the ventricles was not only related to impaired diastolic properties of the ventricles, but was mainly because of filling abnormalities through surgical baffles; these decrease the capacity of the systemic venous atrium and diminish the ability of atrial contraction to boost ventricular filling. This abnormal ventricular filling seems to remain constant over time [24]. The findings were in agreement with the reported diminution of early LV filling in patients after atrial redirection, assessed by jugular venous flow measurement using Doppler ultrasound [44]. This hypothesis was further confirmed by load-independent indexes of ventricular function measured by a conductance catheter during dobutamine infusion, which showed that abnormal stroke volume responses during dobutamine stress were not explained by reduced chronotropic or contractile responses, but were associated with fixed ventricular filling rates [45].
Conclusion Although the functional status of many adults with systemic RV is good, reduced exercise capacity is the norm. This finding may relate to many different factors, such as impaired systemic ventricular function, TR, impaired capacitance and conduit function of the intra-atrial baffles
7 or chronotropic incompetence. Echocardiography remains the daily-life imaging modality for systemic RV function assessment. Because of geometric changes, presumed contractility pattern shift and retrosternal position in TGA with atrial redirection, conventional echocardiographic variables are limited for RV function assessment compared with MRI. Nevertheless, echocardiography remains the technique of reference for dyssynchrony and TR assessment. New echocardiographic deformation imaging modalities have been proved to be relevant for left heart disease prognosis, and seem promising for the assessment of systemic RV function. To make a valuable estimation of RV systolic function using echocardiography, a combination of multiple variables should be performed, in association with diastolic function and TR assessment.
Disclosure of interest The authors declare that they have no competing interest.
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Please cite this article in press as: Iriart X, et al. Quantification of systemic right ventricle by echocardiography. Arch Cardiovasc Dis (2016), http://dx.doi.org/10.1016/j.acvd.2015.11.008