|Year : 2018 | Volume
| Issue : 2 | Page : 395-401
Right ventricular mechanics in patients with idiopathic dilated cardiomyopathy using strain imaging
Hala M Badran1, Naglaa F Ahmed1, Ehab E Mahdy2
1 Department of Cardiology, Menoufia University, Menoufia, Egypt
2 Department of Cardiology, Al Ahrar Teaching Hospital, Al Dakahlya, Egypt
|Date of Submission||06-Dec-2016|
|Date of Acceptance||11-Mar-2017|
|Date of Web Publication||27-Aug-2018|
Ehab E Mahdy
Department of Cardiology, Al Ahrar Teaching Hospital, Mit Ghamr, Al Dakahlya
Source of Support: None, Conflict of Interest: None
The aim of this study was to assess right ventricular (RV) mechanics in patients with idiopathic dilated cardiomyopathy (DCM) using two-dimensional (2D) strain imaging technique.
Imaging using strain and strain rate (SR) was recently applied as a promising tool to analyze global and regional myocardial function in different disease entities, including DCM. 2D strain echo would be especially useful in assessing DCM as an accurate, time-sparing method.
Patients and methods
A total of 104 patients with documented DCM as proved by echocardiography were investigated using 2D echo, and 25 age-matched and sex-matched individuals served as control. Off-line 2D strain analysis was performed for the assessment of global and regional strain of the RV, including the RV free wall and the interventricular septum.
RV deformation parameters showed loss of longitudinal systolic strain and SR base to apex gradient and significantly declined values in the DCM group. The averaged RV free wall segment systolic strain (−9.84 ± 6.73 vs. −30.86 ± 4.44%), systolic strain rate (SRsys) (−0.88 ± 0.47 vs. −1.75 ± 0.68 s−1), and early systolic strain rate (SRe) (0.67 ± 0.50 vs. 2.08 ± 1.08 s−1) were significantly reduced in the DCM group compared with the control group (P < 0.0001). These findings were also apparent in global RV deformation and gave similar significance (P < 0.0001) with the exception of late diastolic SR (P = NS). Intraventricular dyssynchrony was verified and showed a significant increase in time-to-peak standard deviation in the DCM group (75.71 ± 47.76 vs. 44.18 ± 26.72 ms, P < 0.002) compared with the control group.
In conclusion, our results suggest that the same cardiomyopathic pathology affects the RV as much as it affects the left ventricle with reduction in both RV systolic and diastolic functions. We have made an attempt to understand RV mechanics in different cardiac pathologies.
Keywords: two-dimensional strain, dilated cardiomyopathy, right ventricle
|How to cite this article:|
Badran HM, Ahmed NF, Mahdy EE. Right ventricular mechanics in patients with idiopathic dilated cardiomyopathy using strain imaging. Menoufia Med J 2018;31:395-401
|How to cite this URL:|
Badran HM, Ahmed NF, Mahdy EE. Right ventricular mechanics in patients with idiopathic dilated cardiomyopathy using strain imaging. Menoufia Med J [serial online] 2018 [cited 2018 Sep 24];31:395-401. Available from: http://www.mmj.eg.net/text.asp?2018/31/2/395/239765
| Introduction|| |
Dilated cardiomyopathy (DCM) refers to a large group of myocardial disorders that are characterized by ventricular dilation and depressed myocardial contractility in the absence of abnormal loading conditions such as hypertension or valvular disease ,.
In 1616, Sir William Harvey was the first to describe the importance of right ventricular (RV) function in his seminal treatise, De Motu Cordis: 'Thus, the right ventricle may be said to be made for the sake of transmitting blood through the lungs, not for nourishing them' ,. For many years that followed, emphasis in cardiology was placed on left ventricular (LV) physiology, overshadowing the study of the RV. In the first half of the 20th century, the study of RV function was limited to a small group of investigators who were intrigued by the hypothesis that human circulation could function adequately without RV contractile function .
For the past three decades, the LV anatomy and function has been extensively researched and studied. The RV has been ignored probably due to the technical difficulties in imaging as well as the poor understanding of its function and hemodynamics. Recent advances in medicine led to the better understanding of the role of the RV in various medical conditions .
The RV can be studied with many imaging and functional modalities such as cardiac MRI, as it is increasingly used as a standard tool in the evaluation of RV structure and function. MRI is the most accurate method for the assessment of RV volume. However, in clinical practice, echocardiography is the mainstay of evaluation of RV structure and function. Compared with other modalities, it offers the advantages of versatility and availability. Moreover, Doppler-derived indices of RV function, such as the myocardial performance index and tricuspid annular isovolumic acceleration, are emerging as promising parameters of RV function .
Strain imaging is a novel method that has been developed to quantify regional myocardial function. Myocardial strain imaging was initially obtained using tissue Doppler imaging. More recently, it is being obtained with myocardial speckle tracking using two-dimensional (2D) echocardiography .
The aim of this study was to assess RV mechanics in patients with idiopathic dilated cardiomyopathy (IDC) using 2D strain imaging technique.
| Patients and Methods|| |
This was a single-center prospective study. We enrolled 104 patients with IDC on the basis of patients' clinical history, physical examination, 12-lead ECG, chest radiography, echocardiography, and coronary angiography according to the WHO criteria ; patients were recruited from Yacoub Research Unite, Menoufia University, Egypt, between January 2013 and May 2016.
The other limb of the study was the control group in which we studied 25 age-matched and sex-matched healthy individuals without a detectable cardiovascular risk factor or receiving any medication and with a normal 12-lead ECG. The study was approved by the Ethical Committee of Menoufia Faculty of Medicine. Informed consent was taken from each participant in the study.
The exclusion criteria included patients with the following:
- Systemic hypertension (>150/95 mmHg)
- Coronary artery disease (>50% in one or more major branches)
- Chronic excess alcohol (>40 g/day in women and >80 g/day in men for more than 5 years after 6-month abstinence
- Systemic disease known to cause DCM
- Pericardial diseases
- Congenital heart disease
- Cor pulmonale
- Rapid, sustained supraventricular tachycardia.
Echocardiographic examinations were performed for all participants in the left lateral decubitus position in the parasternal long, short-axis, apical two-chamber and four-chamber views using standard transducer positions. Esaote Mylab Gold ultrasound system (Esaote S.p.A, Florence, Italy) equipped with a 5 MHz phased-array transducer was utilized. RV end-diastolic diameters (basal, mid, and longitudinal) and wall thickness, left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), septum, posterior wall thickness, ejection fraction (EF%), and left atrial (LA) diameter and volume were evaluated.
Color flow mapping and continuous-wave Doppler was used to estimate pulmonary artery pressure (PAP) from tricuspid regurge velocity (simplified Bernoulli equation). The severity of mitral regurge and tricuspid regurge was graded according to the jet area method. Peak early (E) and late (A) transmitral (Em and Am) filling velocities were measured from mitral inflow velocities, and deceleration time was obtained. Peak systolic (Sa), early diastolic (E'), and atrial diastolic (A') velocities were obtained by placing a tissue Doppler Diagnostic Medical Imager (DMI) sample volume at the right ventricular free wall (RVFW) and lateral mitral annulus in the apical four-chamber view. The early mitral inflow velocity/early mitral annular velocity (Em/E'm) was calculated.
Quality, ECG signal and a frame rate (70 ± 20 frames/s), was adjusted depending on the heart rate and stored for off-line analysis using XStrain software (coMakeIT B.V., Stationsplein 62, 3743 KM Baarn., The Netherlands). Vector velocity imaging (VVI) is a dedicated software that derives longitudinal myocardial velocity, strain (ε), strain rate (SR), and displacement from the digitized 2D video clips.
Analysis of deformation
LV images were recorded and processed. Tracking and subsequent strain calculations were performed. Systolic strain (εsys), systolic strain rate (SRsys), early systolic strain rate (SRe), and atrial strain rate (SRa) in the basal, mid, and apical segments of septal, lateral, anterior, and inferior wall were measured. To reduce random noise, each sample was obtained by averaging more than one consecutive heart cycle (usually three), by averaging all previously collected data. LV Global εsys, SRsys, early diastolic strain rate (SRe dia), and diastolic atrial strain rate (SRa dia) were obtained.
RV images were recorded and processed. Tracking and subsequent strain calculations were performed. Longitudinal εsys, SRsys, SRe dia, and SRa dia in the basal, mid and apical segments of the RVFW and septum were obtained. Global RV deformation was calculated from RVFW and septal segments. To estimate LV and RV mechanical dyssynchrony, myocardial contraction time was measured from regional strain curves for each ventricular segment, as time from the beginning of Q wave of ECG to the time-to-peak systolic strain. LV and RV dyssynchrony was defined as the standard deviation of the averaged time-to-peak strain (TTP-SD).
Values were presented as means ± SD or as numbers and proportions, as appropriate. The relations between qualitative variables were evaluated using the χ2-test or Fisher's exact test, as indicated. Means were compared with Student's test. Quantitative variables were correlated with the use of coefficient of correlation r. We have used Sm lateral annulus less than 9.5 as an indicator of RV dysfunction and receiver operating characteristic analysis was performed to detect suitable cutoff points for RV εsys%, SRsys, SRe, and SRa to differentiate RV dysfunction in DCM. Variables that were statistically significant in univariate analysis were introduced in a logistic regression model to detect independent predictors of RV dysfunction. All tests were bilateral and a P value of 0.05 was the limit of statistical significance. Analysis was performed using IBM SPSS for Mac (version 24) software (IBM Corp. Released 2016. Armonk, NY).
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| Results|| |
Study groups consisted of 104 patients (37 ± 17 years) (39.5% female patients) and 25 controls (24 ± 14 years) (44.0% female participants). There were no differences between the IDC and control groups in sex, body surface area, and systolic or diastolic blood pressure. Age (P < 0.001) and heart rate (P < 0.003) in the DCM group were significantly higher than that in the control group. All (104) DCM patients (39.5% female patients) were symptomatic (~7% are New York Heart Association class I, 44% class II, 28% class III, and 21% class IV).
Conventional echocardiographic data
LA dimension, volume, LVESD, LVEDD, LV mass, left ventricular mass index (LVMI), mitral regurgitation severity, tricuspid regurgitation severity, PAP, RV longitudinal and mean diameters, and RVFW thickness were significantly greater, whereas LV EF%, fractional shortening%, Em inflow deceleration time, and E'm were significantly reduced in the DCM group (P < 0.0001). LV end-diastolic pressure as estimated using Em/E'm ratio was significantly elevated in comparison with the control group (P < 0.0001). There was no significant difference among the two groups in interventricular septum and left ventricular posterior wall thickness, Em inflow velocity, Am inflow velocity, mitral E/A, and RV basal and mid diameters [Table 1].
Left ventricle global deformation analysis
In the DCM group, 2D strain analysis detected lower global and regional peak myocardial εsys, SRsys, SRa, and SRe (P < 0.0001) at the level of all analyzed segments in comparison with the control group.
Similarly, electromechanical delay was considerably prolonged in all LV segments compared with its corresponding segments in healthy individuals (P < 0.0001). Intraventricular dyssynchrony (TTP-SD) was significantly greater in the group DCM (84.79 ± 61.61) compared with the control group (29.24 ± 16.81) (P < 0.0001) [Table 2].
Regional and global right ventricular deformation analysis
Both longitudinal εsys and SR values showed a base to apex gradient in the control group. RV deformation parameters showed loss of this gradient and a significant decline in the DCM group. The averaged RVFW segments εsys (−9.84 ± 6.73 vs. −30.86 ± 4.44%), SRsys (−0.88 ± 0.47 vs. −1.75 ± 0.68 s −1), and SRe (0.67 ± 0.50 vs. 2.08 ± 1.08 s −1) were significantly reduced in the DCM group compared with the control group (P < 0.0001 for each). These findings were also apparent in global RV deformation and gave similar significance (P < 0.0001) with the exception of SRa dia (P = NS) [Table 3].
As regards electromechanical delay between RV segments, controls showed no significant difference compared with the DCM group at the level of different RV wall segments (P = NS). Intraventricular dyssynchrony was verified and showed a significant increase in TTP-SD in the DCM group (75.71 ± 47.76 vs. 44.18 ± 26.72 ms, P < 0.002) compared with the control group [Table 3].
Correlation between global right ventricular systolic strain% and right ventricular free wall systolic strain% and other echocardiographic parameters in the dilated cardiomyopathy group
Both global RV εsys% and RVFW εsys% were significantly correlated with indexed LA volume, LV EF%, fractional shortening%, LVESD, LVEDD, LVMI, mitral E/A, PAP, LV global εsys%, LV TTP-SD, and LV global SRe dia (P < 0.0001). Global RV εsys% rather than RVFW εsys% had a significant correlation with LA volume and LV global SRsys (P < 0.003) for both of them. There was no significant correlation between Eam, Em inflow deceleration time, Em/Eam, Am inflow velocity, LV global SRa dia and either global RV εsys% or RVFW εsys% (P = NS).
Assessment of right ventricular dysfunction in the dilated cardiomyopathy group
A Sm lateral tricuspid annulus of less than 9.5 cm/s was taken as a cutoff value of RV dysfunction that leads to recognition of two subgroups, one with RV dysfunction (n = 46) and another with no RV dysfunction (n = 58).
Comparison between dilated cardiomyopathy patients with and those without right ventricular dysfunction
In comparison with DCM patients with no RV dysfunction, DCM patients with RV dysfunction were directly related to decreased values of LV EF% (34.60 ± 9.68 vs. 28.50 ± 8.55) (P < 0.001), LV global εsys% (−6.87 ± 4.51 vs. 4.48 ± 3.25) (P < 0.003), LV global SRe dia (0.45 ± 0.32 vs. 0.33 ± 0.24) (P < 0.04), LV global late SR dia (0.39 ± 0.36 vs. 0.24 ± 0.14) (P < 0.008), εsys% global RV (−10.36 ± 6.05 vs. −7.15 ± 4.17) (P < 0.003), RV global SRsys (0.93 ± 0.44 vs. 0.69 ± 0.33) (P < 0.002), global RV SRe dia (0.73 ± 0.48 vs. 0.48 ± 0.27) (P < 0.002), RV global late SR dia (0.70 ± 0.39 vs. 0.41 ± 0.21) (P < 0.0001), early diastolic myocardial velocity lateral annulus (12.40 ± 4.01 vs. 8.29 ± 6.51) (P < 0.0001), late diastolic myocardial velocity latanulus (13.84 ± 5.38 vs. 7.64 ± 6.21) (P < 0.0001), mean displacement (3.92 ± 2.35 vs. 2.74 ± 2.05) (P < 0.009), and RV EF (29.92 ± 12.89 vs. 24.38 ± 12.97) (P < 0.03) [Table 4].
|Table 4: Comparison between dilated cardiomyopathy patients with and those without RV dysfunction according to different echocardiographic parameters|
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However, RV dysfunction was directly related to increased values of indexed LA volume (34.03 ± 16.65 vs. 42.73 ± 18.48) (P < 0.015), LVESD (52.61 ± 12.97 vs. 58.63 ± 12.13) (P < 0.017), LVMI (174.91 ± 65.23 vs. 208.49 ± 80.26) (P < 0.023), RV longitudinal diameter (60.97 ± 13.19 vs. 66.37 ± 11.37) (P < 0.03), RV mean diameter (41.28 ± 8.58 vs. 44.94 ± 6.72) (P < 0.019), and RV thickness (6.17 ± 1.58 vs. 6.97 ± 1.31) (P < 0.007) [Table 4].
To explore the cutoff point that discriminates RV dysfunction, we constructed receiver operating characteristic curves for RV ∈sys, SRsys, SRe, and SRa in the DCM group. For global ∈sys% a cutoff value of −8.7% shows 63% sensitivity, 60.3% specificity, and area under the curve (AUC) of 0.653 [confidence interval (CI): 0.548–0.757, P < 0.008]. For global SRsys, a cutoff value of −0.76% shows 71.7% sensitivity and 60.3% specificity with AUC of 0.683 (CI: 0.580–0.787, P < 0.001) [Table 4].
For diastolic function, RV global SRe cutoff value of 0.53 shows 62.2% sensitivity, 60.3% specificity, and an AUC of 0.659 (CI: 0.555–0.764, P < 0.006). In addition, RV global SRa cutoff value of 0.58 shows 73.3% sensitivity, 60.3% specificity, and AUC of 0.731 (CI: 0.635–0.827, P < 0.0001) [Table 4].
Stepwise forward, multiple linear regression analyses that were performed in DCM patients showed that SRa dia global RV was an independent predictor of RV dysfunction (P < 0.01).
| Discussion|| |
Current research in clinical cardiac mechanics is moving from LV short-axis and EF to long-axis function and from global to regional deformation abnormalities in different myocardial diseases. Measurement of longitudinal SR in the RV can be regarded as a reliable measure for (global) RV myocardial function and EF, even more than that in the LV, as 80% of total stroke volume is generated by longitudinal shortening .
This study with special focus on the RV provides new insights into mechanical alteration in the RV using feature tracking. Quantitative RV functional evaluation revealed a reduction in systolic and diastolic deformation, which is strongly correlated with LV function in DCM. The most important finding of this study was that RVFW mechanics was closely related to global RV deformation and gave the same clinical correlates. The former might consequently be used as an alternative measure of RV pump function.
Previous experimental and clinical studies indicate that the septum is the lion of RV function, and the fiber orientation and septal architecture and function are essential for RV ejection and suction for rapid filling .
In the present study, despite septal and myocardial dysfunction due to involvement by myopathic process, the RVFW still playing important role in overall RV performance. Both RVFW and global RV longitudinal deformation were firmly parallel and were directly related to LV systolic and diastolic function.
In previous reports analyzing the RV Doppler inflow, Lazzaret et al.  described slow deceleration of rapid filling wave and an increase in the lengthening of atrial contraction.
The present study verified RV myocardial diastolic dysfunction in DCM, as RV global εsys and regional 2D SRe and SRa peaks were significantly impaired; however, clinical evidence of RV failure does not exist.
Integration of the new evidence in basic science and evolution in imaging technology must be matched with a new understanding of cardiac mechanics to provide insights into disease that can lead to new therapy .
Many of the recent efforts to assess RV function have used tissue velocity (Doppler) signals to assess velocity at the tricuspid annulus ,.
Researchers have demonstrated the ability of the diffusion tensor imaging (DTI) to characterize global and regional myocardial motion or deformation with high temporal resolution, but the angle dependency of Doppler, high noise-to-signal ratio, and interobserver variability are unavoidable limitations . Conversely, the alternative method for motion estimation proposed here is based on 2D feature tracking using VVI processing, a novel approach that is inherently 2D and independent of both cardiac translation and interrogation angle as it tracks speckle patterns (acoustic markers) within serial B-mode sector scans .
RV global function as estimated by εsys determines the total amount of local deformation of RV wall segments, whereas SR reflects the rate of myocardial deformation, developed by estimating the spatial gradients in myocardial velocities. VVI echocardiography represents a simplified and angle-independent modality for the quantification of regional RV and LV myocardial deformation; longitudinal strain and SR are more sensitive in the assessment of subclinical systolic and diastolic dysfunction of the heart ,.
To the best of our knowledge, this is one of the first studies to analyze RV regional deformation by the use of feature tracking VVI technology in patients affected by DCM.
The present study found an RV and LV myocardial systolic and diastolic dysfunction at global and regional level using VVI and that loss of base to apex gradient is concordant with LV EF.
Besides, our result highlights a systolic asynchronicity involving the RVFW and septum in DCM. The electromechanical delay between RV segments and prevalence of perceived stress scale (PSS) and diminished RV myocardial deformation might be explained on the grounds of a direct involvement of the RV wall by myopathic process.
However, the lower LV myocardial deformation indexes and its close correlation with RV dysfunction suggest ventricular interaction as further explanation of impairment in RV function in DCM. Ventricular interaction is an expression of close anatomic association between the two ventricles. this is strengthened and well scored in our study by the close relation between deterioration of RV deformation and the aggressiveness of LV dysfunction.
Interestingly, the present study sights the existence of extreme RV myocardial systolic nonuniformity and dyssynchrony in DCM as evidenced by increased values of RV TTP-SD, even in the absence of intraventricular conduction delay.
RV deformation was strongly related to intraventricular asynchrony, which is the most powerful predictor of sudden cardiac arrest .
Additional longitudinal studies using 2D strain analyses are warranted to advance our understanding of the natural history of RV myocardial deformation in DCM, the extent of reversibility of RV dysfunction with medical therapy, and the possible long-term impact of such changes on patient outcomes.
| Conclusion|| |
In conclusion, our results suggest that the same cardiomyopathic pathology affects the RV as much as it affects the LV with reduction of both RV systolic and diastolic functions as well as global and RVFW function.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]