Global RV systolic function

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Introduction

The right ventricle (RV) systolic performance is of paramount importance as it defines prognosis in patients with congenital heart disease but also in patients with acquired diseases like pulmonary hypertension, myocardial infarction involving the RV, and left ventricular (LV) dysfunction.[1] The complex three dimensional geometry of the RV, the pronounced trabeculation of the inner wall contour, the anterior position just behind the sternum and the particular hemodynamic environment of the right heart are all factors that make functional assessment challenging by conventional 2D echocardiography. In this setting, multiple parameters have been developed for the comprehensive evaluation of RV systolic function. Normal RV contraction proceeds in a sequential manner, as a peristaltic wave directed from inflow tract to infundibulum with the longitudinal shortening as a major contributor to global RV performance.[2]

Contents

Conventional parameters of right systolic function

Right ventricular outflow tract shortening fraction (RVOT-SF)

RVOT-SF is obtained from a parasternal short-axis view at the base of the heart where the end-diastolic RV outflow tract diameter (EDRVOTD) and end-systolic RVOT diameter (ESRVOTD) can be measured and the shortening fraction is calculated using the formula (See also Figure 1):

RVOT-SF (%) = (EDRVOTD - ESRVOTD)/EDRVOTD (Figure 1).

Figure 1

  • It was shown to correlate well with RV longitudinal function and pulmonary acceleration time.
  • Normal values: 61±13 %.[2]
  • Care must be taken when measuring this paramenter as there are no landmarks established for orienting the image with precision and an oblique section at the level of right ventricular outflow tract may underestimate the fractional shorting value.

Right ventricular fractional area change (RVFAC)

RVFAC expresses the percentage change in RV area between end-diastole and end-systole.

It is obtained from a four-chamber view where the RV end-diastolic (RV - EDA) and end-systolic areas (RV - ESA) are measured ( it is necessary to carefully delineate the free wall beneath the trabeculation), and the RV-FAC is calculated as follows:

RV FAC (%) = (RV EDA – RV ESA)/RV EDA x 100 (See Figure 2).

Figure 2

  • Normal value for RV FAC: above 35%.[2]
  • It has been shown to correlate well with RV ejection fraction measured by magnetic resonance imaging (MRI).[3]

Tricuspid annular plane systolic excursion (TAPSE)

TAPSE represents the distance of systolic excursion of the RV annular plane towards the apex.

  • It is obtained using an M-mode cursor passed through the tricuspid lateral annulus in a four-chamber view (Figure 3) and measuring the amount of longitudinal displacement of the annulus at peak-systole.
  • Normal value for TAPSE: above 16 mm.[2]
  • It has been shown to have a good correlation with isotopic derived RVEF.[4]
  • While it is an easy and simple parameter to use in daily clinical practice it is necesary to emphasise that TAPSE measures displacement of the anular plane twords the transducer and it is therefore an angle dependent parameter and it is influenced by LV function and overall heart motion.

Figure 3

Right ventricular dp/dt

This represents the rate of pressure rise in the ventricle and it is used as a parameter of systolic function. In opposition to the LV, there are less data regarding the RV dp/dt in normals or in pathological situations and it is therefore rarely used in daily practice.

It is obtained on the continous wave Doppler envelope of the tricuspid regurgitation jet and is commonly calculated by measuring the time required for the TR jet to increase in velocity from 1 to 2 m/s. Using the simplified Bernoulli formula (see also Basic principles of non-invasive hemodynamics, volume and flow measurement) this would meen an increase from 4 to 16 mmHg resulting in the following formula for calculating dp/dt:

RV dp/dt = 1200 mmHg/ time in seconds

  • Normal values: RV dp/dt less then 400 mmHg/s is abnormal.[2]
  • Although it was shown to be highly load-dependent and not reflecting the contractile status of the the RV muscle, it may still be useful for repeated longitudinal assessments

Myocardial performance index (MPI) or Tei index

This is a global parameter of cardiac function, combining information of both systole and diastole and it is defined as the ratio of total isovolumic time divided by ejection time (ET).

It is calculated using the following formula:

MPI = (IVRT + IVCT)/ET

  • The pulsed Doppler method: ET is determined from the parasternal short-axis view at the pulmonary valve, based on the pulsed – wave Doppler signal at the right ventricular outflow tract while isovolumic intervals are derived based on the pulsed-wave Doppler envelope of the tricuspid flow. (see Figure 4) The problem with this method is that the measurements are taken from 2 cardiac cycle and care must be taken to choose beats with similar R-R intervals for a more accurate assessment of the MPI.
  • The pulsed tissue Doppler method: has the advantage that all the times are measured from a single beat using the envelope derived from the Pulsed-wave Doppler at the tricuspid level of the right ventricular free wall. (see Figure 5)
  • Normal values: The upper reference limit for the right-sided MPI is 0.40 using the pulsed Doppler method and 0.55 using the pulsed tissue Doppler method. [2]


Figure 4 Figure 5

Novel methods

Doppler myocardial imaging in the assessment of RV systolic function

Using Doppler myocardial imaging (DMI), several global and regional parameters, such as timing, direction, amplitude of the velocity of the ventricular wall can be determined. See also Technique of Tissue Doppler Imaging Parameters derived from DMI techniques which may aid in the estimation of global RV function are tricuspid anular systolic velocity (RV S’), isovolumic relaxation time (IVRT), Tei index and isovolumic myocardial acceleration.

Velocity of the tricuspid anular systolic motion (RV S’)

Tricuspid anular motion can be assessed by pulsed tissue Doppler and color-coded tissue Doppler to measure the longitudinal velocity of excursion. This velocity has been termed the RV S’ or systolic excursion velocity.

To measure RV S’ an apical 4-chamber window is used with a tissue Doppler mode region of interest highlighting the RV free wall. The pulsed Doppler sample volume is placed at the tricuspid level of the right ventricular free wall(Figure 6). An alternative to this method is the offline analysis of the color-coded tissue Doppler images of the RV, acquired at high frame rates, by placing the region of interest in the segment to be interrogated (Figure 7). Care must be taken when interprating values obtained by colour DMI as they represent the median of the velocity spectrum and are around 25% lower than those obtained using pulsed DMI in which the maximal spectral velocity value is measured. See figure

This parameter has been validated against radionuclide angiography and has been shown to be an accurate and reproducible parameter of right ventricular systolic function. When applying a cut off for systolic annular velocity of < 11.5 cm/s, this parameter can predict right ventricular dysfunction (ejection fraction < 45%) with a sensitivity of 90% and a specificity of 85%.[5] Moreover, S’ represents a significant independent predictor of survival and event-free survival in patients with symptomatic heart failure and it has been shown to have prognostic significance also in newly-diagnosed systolic HF patient. [6]

Normal values: The lower reference limit in normal individuals is 10 cm/s. Mean annular velocities, obtained by offline analysis of Color-coded tissue Doppler acquisitions average from 8.5 to 10 cm/s. [2]

Figure 6 Figure 7

Isovolumic relaxation time (IVRT)

A normal RV that functions with preserved contractility and under normal loading conditions does not have a measurable IVRT. The end of systolic movement is immediately followed by early filling. A pressure increase in the RV leads to a sustained prolongation of the IVRT.

Tricuspid annular pulsed-wave DTI – derived IVRT correlates very strongly with invasively measured systolic pulmonary artery pressure (PASP). Therefore, it can be used to predict PASP. It can even be considered as an alternative to tricuspid regurgitation–derived PASP when tricuspid regurgitation is nonrecordable. However, caution should be taken while examining patients with significantly reduced RV function. [7]

Myocardial isovolumic acceleration time (IVA)

The myocardial acceleration during isovolumic contraction (IVA) is a DMI-derived index that is supposed to be less dependent on loading conditions in a physiological range and it is defined as the peak isovolumic myocardial velocity divided by time to peak velocity and is typically measured for the right ventricle by Doppler tissue imaging at the lateral tricuspid annulus (Figure 8)

Figure 8

  • Normal values: The lower reference limit by pulsed-wave Doppler tissue imaging, pooled from 10 studies, is 2.2 m/s2, with a broad 95% confidence interval of 1.4 to 3.0. Also, the normal values are age and heart rate dependent. [2]
  • Considering the wide range of normal values and concerns about its reliability and reproducibility, it is not recommended to use this parameter as a screening tool for RV systolic function in routine clinical practice. It was, however, found useful in the evaluation of patients with congenital heart diseases and after cardiac transplantation.

Myocardial deformation imaging in the assessment of RV systolic function

Doppler myocardial imaging based techniques allow not only for the evaluation of myocardial velocities but also for extracting myocardial deformation parameters (strain and strain rate). Strain (S)/strain rate (SR) represents deformation and deformation rate, respectively. Strain is defined as deformation of an object compared with its initial shape and is expressed a percentage and Strain rate or deformation rate defines the speed of the deformation and has been closely correlated with myocardial contractility in in vitro and in vivo experimental settings. (See also Technique of Tissue Doppler Imaging) (see Figures 9 and 10).

Figure 9 Figure 10


Another technique that can be employed for determining regional deformation is speckle-tracking-based myocardial deformation imaging. It is advantageous against Doppler techniques as it is relatively angle-independent but it is necessary to have good qulity images and deliniation of the endocardial border, the last being a potential problem with the RV.

Compared with the LV, strain and SR values are less homogeneously distributed in the RV and show a reverse base-to-apex gradient, reaching the highest values in the apical segment and the outflow tract.

  • Myocardial deformation parameters derived from the RV are not yet recomanded in routine clinical practice as only small populations have been investigated and normal values are yet to be established. Also, this is a complex measure with a high degree of variability that requires additional software and offline analysis. [3]
  • Nonetheless, Strain and SR correlate well with radionuclide RV EF. Cutt off points of systolic strain and SR at the basal free wall of 25% and -4 sec-1 yielded sensitivities of 81% and 85% and specificities of 82 and 88 % respectively, for the prediction of RV EF > 50%. In patients with RV dysfunction, strain and SR are reduced and delayed compared with normal RV function. [8]
  • Strain and strain-rate values of the RV ware evaluated in a number of clinical scenarios as pulmonary hypertension and RV diseases of different etiologies (RV infarction, arrhythmogenic RV dysplasia/cardiomyopathy). It has been shown that strain and SR can be a valuable tool in detecting early signs of RV involvement in pulmonary hypertension and, also, that it can detect early alteration of the RV function in patients with systemic sclerosis and normal pulmonary pressures.[9] Moreover, noninvasive assessment of RV longitudinal systolic strain and strain rate was proven to independently predict future right-sided heart failure, clinical deterioration, and mortality in patients with pulmonary arterial hypertension.

Three-dimensional echocardiography

Using 3D imaging, no geometrical assumptions are made, and thus 3D echocardiography should be more useful for the assessment of RV size and function (see Figure 11 and Video 1). Even though earlier studies have shown a weak correlation between 3D Echo-derived RVEF and MRI-derived RVEF, a more recent study has found that RT3DE is more accurate than two-dimensional approaches and reduces the test-retest variation of RV volumes and EF measurements in follow-up RV assessment.[10]

Still, there are limited normative data on 3D Echo-derived EF and there is a need for more extensive evaluation of the usefulness of this method in the evaluation of systolic function in severely dilated or dysfunctional RV.

Figure 11

References

  1. Haddad F, Doyle R, Murph DJ,Hunt SA. Right ventricular function in cardiovascular disease, part II: Pathophysiology, Clinical Importance, and Management of Right Ventricular Failure. Circulation: 2008, 117; 1717-1731
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Rudski LG, Lai WW, Afilalo J, Hua L, Handschumacher MD,Chandrasekaran K, Solomon SD, Louie EK, Schiller NB. Guidelines for the echocardiographic assessment of the right heart in adults: a report from the American Society of Echocardiography endorsed by the European Association of Echocardiography, a registered branch of the European Society of Cardiology, and the Canadian Society of Echocardiography. J Am Soc Echocardiogr: 2010, 23(7);685-713;
  3. 3.0 3.1 Anavekar NS, Gerson D, Skali H, Kwong RY, Yucel EK, Solomon SD. Two-dimensional assessment of right ventricular function: an echocardiographic-MRI correlative study. Echocardiography 2007;24: 452-6.
  4. Kaul S, Tei C, Hopkins JM, Shah PM. Assessment of right ventricular function using two-dimensional echocardiography. Am Heart J 1984;107:526–31.
  5. Meluzin J, Spinarova L, Bakala J, Toman J, Krejci J, Hude P, Kara T, Soucek M. Pulsed Doppler tissue imaging of the velocity of tricuspid annular systolic motion; a new, rapid, and non-invasive method of evaluating right ventricular systolic function. Eur Heart J 2001;22:340-8.
  6. Chrysohoou C, Antoniou CK, Kotrogiannis I, Metallinos G, Aggelis A, Andreou I, Brili S, Pitsavos C, Stefanadis C. Role of Right Ventricular Systolic Function on Long-Term Outcome in Patients With Newly Diagnosed Systolic Heart Failure. Circulation Journal Vol. 75 (2011) No. 9 p. 2176-2181
  7. Dambrauskaite V, Delcroix M, Claus P, Herbots L, Palecek T, D'hooge J, Bijnens B, Rademakers F, Sutherland GR. The evaluation of pulmonary hypertension using right ventricular myocardial isovolumic relaxation time. J Am Soc Echocardiogr. 2005 Nov;18(11):1113-20.
  8. Vitarelli A, Conde Y, Cimino E, Stellato S, D'orazio S, D’Angeli I, Nguyen BL, Padella V, Caranci F, Petroianni A, D’Antoni L, Terzano C. Assessment of right ventricular function by strain rate imaging in chronic obstructive pulmonary disease. Eur Respir J 2006;27:268-75.
  9. Borges AC, Knebel F, Eddicks S, Panda A, Schattke S, Witt C, Baumann G. Right ventricular function assessed by two-dimensional strain and tissue Doppler echocardiography in patients with pulmonary arterial hypertension and effect of vasodilator therapy. Am J Cardiol 2006;98:530-4.
  10. Jenkins C, Chan J,Bricknell C, Strudwick M, Marwick TH. Reproducibility of right ventricular volumes and ejection fraction using real-time three-dimensional echocardiography: Comparison with cardiac MRI. CHEST.2007;131(6):1844-1851

Further reading

  1. Rudski LG, Lai WW, Afilalo J, Hua L, Handschumacher MD,Chandrasekaran K, Solomon SD, Louie EK, Schiller NB . Guidelines for the echocardiographic assessment of the right heart in adults: a report from the American Society of Echocardiography endorsed by the European Association of Echocardiography, a registered branch of the European Society of Cardiology, and the Canadian Society of Echocardiography. J Am Soc Echocardiogr: 2010, 23(7);685-713;
  2. Mor-Avi V, Lang RM, Badano LP, Belohlavek M, Cardim NM, Derumeaux G, Galderisi M, Marwick TH, Nagueh SF, Sengupta PP, Sicar Ri, Smiseth OA, Smulevitz B, Takeuchi M, Thomas JD, Vannan M, Voigt JU, Zamorano JL. Current and evolving echocardiographic techniques for the quantitative evaluation of cardiac mechanics: ASE/EAE consensus statement on methodology and indications endorsed by the Japanese Society of Echocardiography. Eur J Echocardiogr: 2011, 12(3);167-205
  3. Jurcut R, Giusca S, Gherche A, Vasile S, Ginghina C, Voigt JU. The echocardiographic assessment of the right ventricle: what to do in 2010? Eur J Echocardiogr: 2010, 11; 81-9;
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