|Year : 2018 | Volume
| Issue : 3 | Page : 161-166
Evaluation of right ventricle
Sulagna Banerjee1, Soumitra Kumar2
1 Department of Cardiology, Division of Non-Invasive Cardiology, Vivekananda Institute of Medical Sciences, Kolkata, West Bengal, India
2 Department of Cardiology, Vivekananda Institute of Medical Sciences, Kolkata, West Bengal, India
|Date of Web Publication||10-Dec-2018|
Dr. Soumitra Kumar
58/1, Ballygunge Circular Road, Saptaparni, Flat - 52B, Kolkata - 700 019, West Bengal
Source of Support: None, Conflict of Interest: None
Right Ventricle (RV) has been treated as the neglected cardiac chamber for a long time. Advent of cardiac MRI and advancements in echocardiography have facilitated the understanding of RV structure and function and elucidated its role in management and prognosis of various cardiac ailments. Further refinement of three-dimensional (3D) and strain imaging and their application to study of right ventricular structural and functional abnormalities will be helpful in early identification of cardiac pathologies and their timely intervention.
Keywords: Neglected, Prognostication, RV function, Subclinical
|How to cite this article:|
Banerjee S, Kumar S. Evaluation of right ventricle. J Indian Acad Echocardiogr Cardiovasc Imaging 2018;2:161-6
| Introduction|| |
Left ventricle (LV) of the heart has always been the dominant chamber of attraction in cardiology due to obvious epidemiological and practical reasons. Myocardial infarction the most leading cause of morbidity and mortality prominently affects the LV, and hence, it has always demanded all the attention, rendering right ventricle (RV) the neglected chamber. With advent of time and advancement of technology, the right heart, and particularly the RV, has generated a lot of curiosity. With the advent of cardiac magnetic resonance imaging (C-MRI), the understanding of RV has undergone a sea-change, and the geometry and functional assessment of RV have become a lot easier, both quantitatively and qualitatively. The role of RV in management and prognosis of many cardiac ailments is being recognized. The RV function (RVF) and RV dimension (RVD) are intimately related to exercise capacity and symptom occurrence in many cases. Therefore, comprehensive and accurate evaluation of RV has become very important. Although C-MRI remains the gold standard for RV evaluation, echocardiography is the first line of investigation of choice due to its easy availability, practicability, noninvasive nature, and cost-effectiveness.
Anatomy of right ventricle
RV has a more complex geometric form compared to LV. RV is triangular, and when viewed from parasternal short-axis view, it has a crescent shape that wraps around LV. RV has three different segments: (i) the inlet area, (ii) the trabecular part, and (iii) the outflow area.
The RV has anterior, inferior, and lateral (free) wall. Echocardiographic imaging of RV is a little difficult owing to its retrosternal position, complex architecture, and anatomical peculiarities.
Functionally, RV is different from LV. Due to the structural organization of myocardial fibers, RV contraction is determined by longitudinal shortening. Its isovolumic contraction and relaxation period is very short, and also, it pumps against a low afterload. Compared to LV, RV is more sensitive to acute/chronic volume and pressure overload. The pulmonary circulation, the interventricular septum, and the pericardium make the RV and LV interdependent.
The sphericity index of the RV is assessed in the apical four-chamber view (AP4C) and is given by the ratio of the short diameter (at the mid-ventricular level) to the long diameter at end-diastole. The ratio is increased in situ ations where RV undergoes RV remodeling and dilatation. The methods to assess RVD and normal ranges are depicted in [Figure 1] and [Table 1].
|Figure 1: Linear diameters of the right ventricle measured in A4C and PSAX view. d1: Basal right ventricle diameter, d2: Right ventricle mid-cavitary diameter, d3: Base to apex right ventricle length, RVOT-2: Right ventricular outflow tract proximal, RV: Right ventricle, RA: Right atrium, LA: Left atrium, RVOT-3: Right ventricular outflow tract distal|
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|Table 1: Normal two-dimensional values of linear dimensions of right ventricle|
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Function of right ventricle
In contrast to LV, whose function is based on its contractility/pumping capacity, RVF is profoundly affected by preload and afterload. The stroke volume of RV is the same as that of LV despite decreased contractility due to decreased afterload it faces from the pulmonary circulation.
Septal flattening occurs in systole when RV elongates as a result of pressure and volume overload. RV morphology can change in normal conditions, for example, in elite athletes, a bulge is seen in RV free wall, as there is increased RV end-diastolic volume compared to LV end-diastolic volume. Therefore, RVF assessment by echocardiography is extremely important and includes different methods.
Echocardiographic assessment of right ventricle function
RV evaluation by echo is faced with the following difficulties:
- RV structure is not symmetrical and well defined
- The retrosternal position of RV makes it difficult to visualize all its segments
- The visualization of RV-inflow and RV-outflow tract is difficult
- No clear landmarks are available to standardize the views, and hence, angulations can result in different measurements.
In 2010, the American Society of Echocardiography (ASE) put certain guidelines to specifically assess RV in adults, which were again updated in 2015 to include the recent advancements and technology.
Two-dimensional evaluation includes:
- Tricuspid annular plane systolic excursion (TAPSE)
- RV fractional area changes (RVFAC)
- Peak systolic tissue velocity at tricuspid annulus (S1)
- RV index of myocardial performance (RIMP).
Tricuspid annular plane systolic excursion
It measures the displacement of the tricuspid valve (TV) lateral annulus in M-mode [Figure 2]. It is measured with M-mode cursor at RV lateral annulus in AP4C view. A value <17 mm is designated as abnormal as per the guidelines of ASE in 2015. The limitation of this method is that the translational motion of the heart can overestimate the TAPSE.
|Figure 2: M.mode assessment of tricuspid annular plane systolic excursion|
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It evaluates a small segment of RV, and so, in patients with RV regional wall motion abnormality, TAPSE can be misleading.
Right ventricle fractional area change
- RV endocardium is traced in systole and diastole from a two-dimensional (2D) image of RV and RVFAC is thus calculated. A value <35% is considered to be abnormal
- The limitation of this method is the variable image quality. Even in patients with good echo window, the delineation between endocardium and trabeculations decreases the accuracy of the measurement.
Systolic tissue velocity of tricuspid valve lateral annulus
Systolic displacement of the basal-free RV wall during the cardiac cycle is measured and is thought to be accurate and reproducible. A value of <9.5 cm is considered abnormal.
Right ventricle index of myocardial performance
RIMP or Tei index is calculated on the basis of tissue Doppler velocity and pulse wave (PW) Doppler velocities from RV and given the following ratio:
As these measurements are not dependent on RV visualization and are measured by Doppler flow, they are considered to be more accurate.
However, its values are less reliable and limited in patients with atrial fibrillation (irregular heart rate) and those with raised right atrium (RA)-pressure. A value of >0.43 (by PW Doppler) and >0.53 by tissue Doppler imaging (TDI) is considered to be abnormal.
Hence, the Tei index is calculated as follows [Figure 3]:
|Figure 3: Calculation of myocardial performance index or Tei index myocardial performance index. ET: Ejection time, IVCT: Isovolumic contraction time, IVRT: Isovolumic relaxation time, E: Early filling wave of tricuspid valve, A: Late filling wave of tricuspid valve|
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Myocardial isovolumic acceleration
It is obtained by dividing peak IV myocardial velocity by the time to peak velocity. It is not currently used as an index for RVF assessment but may be useful in specific conditions such as obstructive sleep apnea, mitral stenosis, and repaired tetralogy of Fallot (TOF).
Right ventricle diastolic function
It is evaluated by placing the PW Doppler on RV inflow and on lateral TV annulus motion using TDI.
Diastolic dysfunction is graded as (i) Type I or mild when tricuspid E/A <0.8, (ii) Type II moderate when (E/A is 0.8–2.1 and E/E' >6 or diastolic flow predominance is hepatic veins), (iii) Type III or severe when E/A >2.1, Deceleration time (DT) <120 ms (restrictive pattern).,,
Of multiple forms of strain measurements, the longitudinal strain imaging is the most useful clinically used technique. It is the measurement of the percentage of systolic shortening of long axis RV-free wall compared with diastole. It can be measured by speckle tracking or Doppler tissue imaging. Global longitudinal strain (GLS) is the average strain of RV-free wall and septal segments. They are assessed in the AP4C. The RV myocardium is divided into six segments. The lateral and septal RV wall is divided into basal, middle, and apical segments each. Regional strain and strain rate values are generated; the GLS of RV is then derived and expressed as mean ± standard deviation [Figure 4].
Although no clear reference data/guidelines are available, Kannan et al. reported that a GLS >25% allows the prediction of RV ejection fraction (RVEF) >50% with a sensitivity of 81%. Guendouz et al. reported the following findings based on absolute GLS values: GLS <21% in patients with congestive heart failure (HF) are at high risk for cardiac events.
Similarly, Motoji et al. and Fukuda et al. reported that GLS <19.4% in patients with pulmonary arterial hypertension (PAH) are at high risk of adverse cardiovascular events.,
Compared to 2D echocardiography (2DE), 3D echocardiography (3DE) provides a better anatomical delineation of the RV and is validated as optimal modality in few conditions such as RV cardiomyopathy, Ebstein's anomaly, and TOF. RVEF can be calculated by 3DE using volumetric semiautomated border detection method, and normal RV systolic function is set as a value >45%., However, such measurements are limited by suboptimal sonographic signal and irregular rhythm. With current technique, volumetric measurements of 3DE evaluation of the RV correlate with C-MRI measurements.
Other parameters relevant to right ventricle assessment
A comprehensive assessment of RV includes the evaluation of:
- RA size and RA pressure (RAP)
- Tricuspid flow and pulmonary artery pressure (PAP).
Right atrium - Dimensions and pressure
- RA - Quantification is done in AP4C view with the following measurements [Figure 5]
- RA - Minor diameter - measured from the lateral border of RA to the IAS (upper reference limits: 4.4 cm)
- RA - Major diameter - measured from the bottom of RA to the TV annulus (upper reference limits: 5.3 cm)
- RA - Area - the upper reference limit is 18 cm2, measured by 2DE at the end of systole
- RA - Volume - the reference values are 25 ± 7 ml/m2 in M-mode and 21 ± 6 ml/m2 in F-mode
- RA - Pressure - it is estimated by measuring the diameter of inferior venacava (IVC) in subcostal view and assessing its collapsibility.
|Figure 5: Right atrial linear dimensions. d1: Transverse diameter, d2: Longitudinal diameter|
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Inferior venacava - Diameter
- Normal diameter is 1.5–2.1 cm, with >50% collapsibility with sniff suggests normal RA pressure (RAP) (0–5 mmHg)
- A diameter of >2.1 cm with <50% collapsibility with sniff suggests raised RAP of (>15 mmHg)
- In indeterminate cases, where the diameter and collapsibility do not fit such parameters, a value of 8 mmHg is taken.
- Mild tricuspid regurgitation (TR) is seen in most normal subjects
- However, when it is moderate/severe, it is pathological and correlated with RA/RV abnormalities (both structural and functional)
- TR - jet area
- <5 cm2 = Mild TR
- 6–10 cm2 = Moderate TR
- >10 cm2 = Severe TR.
TR vena contracta – width >6.5 cm is associated with severe TR.
TR pressure gradient (PG) is used to measure the pulmonary artery systolic pressure (PASP/SPAP), when no intrinsic organic TV disease is present [Figure 6].
|Figure 6: Doppler assessment of tricuspid regurgitation peak pressure gradient|
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PAP: Pulmonary hypertension is defined when the mean PAP is >25 mmHg.
- The PASP is calculated by adding RAP to TR peak pressure gradient (RAP is assessed using IVC collapsibility described previously)
- The pulmonary acceleration time (PAT): PAT is also used to assess mean PAP when TR-PG is not found to be reliable. The normal value of PAT is 120 ms. A value <105 ms suggests PAH.
The other parameters that can be integrated to assess SPAP include indexed RA volume >34 ml/m2 in men and 27 ml/m2 in women, RVFAC <32%, RV-IVRT >75 ms, TAPSE <16 mm and tissue velocity at IV lateral annulus of <0.09 ms.
The pulmonary Doppler flow envelope can give clue regarding origin of PAH. A mid or late systolic notch suggests association of pulmonary vascular disease.
Congenital heart disease
Although C-MRI is considered to be the gold standard in RV evaluation, 3DE has shown a promising future. However, in patients with repaired TOF and systemic RVs, it underestimates RV volume compared to C-MRI. In patients with corrected D-transportation of arteries, RIMP assessed by echo appears to have a better predictive value of patient's work capacity by stress test compared to RVEF assessment of C-MRI.
Arrhythmogenic right ventricle dysfunction
Echo may play an important role in risk stratification in patients with arrhythmogenic RV dysfunction. RV-GLS mechanical dispersion and RV diameter appear to predict an increased risk of arrhythmia in these conditions.
Effects of chemotherapy
Instead of safely relying on LV function and LV strain, RV end-diastolic volume, TAPSE, and RVFAC are considered to be significant markers in patients of breast malignancy, receiving anthracycline chemotherapy. Before any detectable changes in RV and LV size, TAPSE and RVFAC significantly decrease, in patients of breast cancer under chemotherapy.
In patients of chronic pulmonary hypertension of multiple etiology, assessment of RV-3D ejection fraction and RV-GLS were found to be independent predictors of mortality in 2 years. Assessment of TAPSE and RV global strain is considered to be better predictors than RV-S' and RV-FAC for judging the outcome of therapy.
Chronic heart failure and tricuspid regurgitation
RV diameter, TR volume, and RA area are the predictors of all-cause mortality at 1 year in patients with chronic HF and functional TR.
In patients of nonischemic dilated cardiomyopathy (DCM), RV dysfunction is an important predictor of outcome and provides significant prognostic data.
Patients with DCM with LV ejection fraction around 32% are associated with RV dysfunction (in 20% cases). In cases, where there was an improvement of RVF, considerable LV remodeling was found to be present.
In patients with ischemic cardiomyopathy, RVF is an important predictor of mortality. Every 10% decrease in RV ejection fraction corresponds to 17% increase in mortality. RV dysfunction is also associated with heart transplantation and death.
Left ventricular assisted-device
RVF assessment by echocardiography is of paramount significance as LV-assisted devices rely on adequate RVF. Lam et al. showed that echo can be used to assess RVF in their group of patients.
Diagnostic ability of right ventricle assessment
RV assessment by echocardiography is of utmost importance in patients with acute cardiac conditions such as:
- Pulmonary embolism (PE): Acute HF
- Cardiogenic shock
- Cardiac tamponade
- Acute valvular dysfunction.
TAPSE was found to be the least user dependent and easily reproducible parameter in PE. Descotes et al. reported that there was a significant reduction of GLS in patients with intermediate to high-risk PE.
Susland et al. noted McConnell's sign in patients with acute PE which showed akinesia of mid-RVF wall and normal motion of RV apex.
A common sign of cardiac tamponade is collapse of RA and RV. Atrial collapse is observed more than ventricular collapse (longer than one-third of the cardiac cycle) has been defined as 100% sensitive and specific sign of clinical cardiac tamponade. RV-free wall collapse is commonly observed in diastole (at the end of T wave), initially in expiration and later through out respiratory cycle. Longer the duration of RV-free wall collapse, more severe is the tamponade as assessed by M-mode with electrocardiography gating.
| Conclusion, Future Direction|| |
RV assessment requires use of multiple echocardiographic techniques and acoustic windows. It is always advisable to perform a complete comprehensive examination after considering all clinical information. No single guideline or accepted approach is available right now for RV assessment. However, both qualitative and quantitative assessment is required to yield definite prognostic information. With continuous advances in technology, echocardiography is well poised to become the primary tool for evaluation of RV. 3DE and strain imaging will allow echocardiography to overcome the challenges of a conventional echo, and hopefully, monitoring RV myocardial function and early detection of subclinical dysfunction will help in better risk stratification and timely therapy.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]