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ORIGINAL ARTICLE
Year : 2017  |  Volume : 30  |  Issue : 1  |  Page : 203-208

Assessment of left ventricular performance in patients with aortic regurgitation: a strain rate imaging study


Department of Cardiovascular Medicine, Faculty of Medicine, Menoufia University, Shebin El Kom, Egypt

Date of Submission26-Mar-2014
Date of Acceptance12-Jul-2014
Date of Web Publication25-Jul-2017

Correspondence Address:
Ahmed H Al Sayed Soliman
Mansoura General Hospital, Mansoura, 35517
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-2098.211530

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  Abstract 


Background
Aortic regurgitation (AR) results in left ventricular (LV) hemodynamic changes ranging from maladaptive hypertrophy and dilatation to heart failure. Conventional echocardiography and tissue doppler imaging are unable to reveal the early abnormalities in LV function caused by AR; however, two-dimensional speckle tracking echocardiography (2D STE) provides an objective way to detect subtle LV changes among AR patients.
Objective
The aim of this study was to assess functional changes in the myocardium in asymptomatic patients with AR using 2D STE-based strain and strain rate measurement, and its usefulness in early detection of subclinical LV dysfunction.
Materials and methods
Fifty asymptomatic patients with significant AR and 20 age and sex-matched healthy individuals were examined using conventional echocardiography, tissue doppler imaging, and 2D STE-based measurement of global and segmental LV systolic longitudinal strain (εsys), systolic strain rate (SRs), and early strain rate (SRe) and late (SRa) diastolic strain rates.
Results
The AR group showed significant reduction in global systolic strain (εsys) compared with the control group. Global LV longitudinal systolic SRs, diastolic SRe, and SRa were significantly reduced in the AR group in comparison with the control group. In addition, peak εsys, SRs, SRe, and SRa showed negative correlation with LV mass index in AR.
Conclusion
Patients with AR had subclinical LV dysfunction using 2D STE-based strain and strain rate imaging. The index where volume was corrected by deformation should form the basis for predicting subclinical LV dysfunction in patients with increasing LV dilatation.

Keywords: aortic regurgitation, echocardiography, strain and strain rate imaging


How to cite this article:
Abd Alaziz WF, El Noamany MF, Soltan GM, Taha MO, Al Sayed Soliman AH. Assessment of left ventricular performance in patients with aortic regurgitation: a strain rate imaging study. Menoufia Med J 2017;30:203-8

How to cite this URL:
Abd Alaziz WF, El Noamany MF, Soltan GM, Taha MO, Al Sayed Soliman AH. Assessment of left ventricular performance in patients with aortic regurgitation: a strain rate imaging study. Menoufia Med J [serial online] 2017 [cited 2019 Apr 19];30:203-8. Available from: http://www.mmj.eg.net/text.asp?2017/30/1/203/211530




  Introduction Top


The overall prevalence of chronic aortic regurgitation (AR) is ~13% in men and ~8.5% in women [1]. In general, chronic AR is well tolerated and usually asymptomatic until severe decompensation occurs [2]. Current conventional echocardiographic parameters assess only left ventricular (LV) global function. In the context of AR, when there are regional variations in wall stress, it may be important to measure regional ventricular function. Furthermore, if surgery is postponed until the patient becomes symptomatic, there may be already irreversible LV dysfunction [3],[4],[5]. Although there have been several clinical studies that have identified abnormalities in LV function in patients with AR, none of them have been able to identify subclinical LV dysfunction [6],[7]. Strain, and particularly longitudinal peak systolic strain, is a method for quantifying global and regional myocardial function [8],[9]. Two-dimensional speckle tracking echocardiography (2D STE)-based strain and strain rate (SR) imaging is a new technique that provides an insight into LV systolic and diastolic dysfunction even in patients without structural cardiac alterations and provides more information compared with tissue doppler imaging (TDI) [10].


  Aim of the Work Top


This study aimed to clarify the role of 2D STE in assessment of LV systolic and diastolic functions in AR patients.


  Patients and Methods Top


Study population

This study was carried out in the Cardiology Department, National Heart Institute, Imbaba, for a period of 12 months from May 2012 to May 2013, and patients were enrolled in the study after their informed written consent and approval from the Ethics Committee of Menoufia University Hospitals were obtained. The study included 50 AR patients (group II; mean age 31 ± 9.2 years; 34 male patients and 16 female patients), who were compared with 20 healthy age-matched and sex-matched volunteers who constituted the control group (group I; mean age 30.1 ± 9 years; 11 male volunteers and nine female volunteers). Patients with significant chronic AR in sinus rhythm with normal LV systolic function [ejection fraction (EF)>55%] were included. Patients with the following criteria were excluded from the study: those with depressed LV function (EF<55%) or any regional wall motion abnormality, those with pericardial diseases, acute AR, or previous cardiac surgery, patients with significant cardiac arrhythmia or conduction disturbance, significant other valvular heart diseases, any febrile condition, and those with infectious diseases.

Methods

All patients had a complete clinical history taken at recruitment and then a routine physical examination, including body surface area (BSA) calculation and resting 12-lead surface ECG.

Transthoracic conventional echocardiographic doppler study, TDI, and 2D STE-based strain and SR measurement were performed using (vivid 9) a machine (GE Vingmed Ultrasound AS, Horten, Norway) equipped with a harmonic M5S variable frequency (1.7–4) phased array transducer.

All patients were examined in the left lateral decubitus position according to the recommendations of the American Society of echocardiography [11].

Using M-Mode, LV end-systolic, and LV end-diastolic dimensions, EF% was measured by modified biplane Simpson's method as the percentage change of LV chamber volumes between diastole and systole. The EF% was automatically calculated as follows [12]:



LV mass was then calculated [7] and normalized for BSA to obtain LV mass index (g/m2) (LVMI = LVM/BSA). LV hypertrophy was defined as LVMI greater than 125 g/m2 for men and more than 110 g/m2 for women [13].

Diastolic function was assessed using PW doppler of mitral inflow measurements of early diastolic peak velocity (E), late diastolic peak velocity (A), and ratio of early to late velocity peaks (E/A ratio). TDI of septal and lateral mitral annuli was performed. Three velocities were analyzed – peak systolic velocity; positive wave (Sm), early and late diastolic velocities; and negative waves (Em, Am) – and E/Em ratio was calculated.

Measurements of longitudinal strain and SR using 2D STE were taken as follows: 2D images were obtained in apical four-chamber, three-chamber, and two-chamber views with a narrow sector width to include the entire LV. The frame rate was adjusted between 40 and 90 frames/s (FPS) according to the heart rate. Three cardiac cycles were acquired. Segmental and global longitudinal systolic strain and strain rate were measured, and the results were obtained as color-coded curves and numerical values and a 17-segment model in 'bull's eye' plot.

Statistical analysis

Data were tabulated and statistical analysis was performed using SPSS v.17 using two types of statistics: descriptive statistics – mean (x–) and SD for quantitative data – and analytical statistics – the c 2-test for qualitative data. Linear regression analysis, with Pearson's correlation coefficient (r), was used to estimate the correlation between continuous variables, and a receiver operating characteristic curve was plotted [14].


  Results Top


Blood pressure

It was found that there was a statistically significant difference as regards systolic blood pressure (SBP). The SBP was higher in the AR group compared with the control group, and diastolic blood pressure was lower in the AR group compared with the control group, as shown in [Table 1].
Table 1 Comparison between the clinical data in the studied groups

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Comparing the two groups as regards conventional echocardiographic parameters (left atrial dimension, aortic root diameter, interventricular septal thickness in diastole, LV end-diastolic dimension, LV posterior wall thickness in diastole, LV end-systolic dimension, EF, and fractional shortening), it was found that the AR group had significantly higher values compared with the control group (P< 0.05), as shown in [Table 2].
Table 2 Comparison between conventional echocardiographic data in the studied group

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Upon assessment of systolic LV function using conventional echocardiography, the measured EF showed a significant difference between AR patients and controls, yet within the normal range. In addition, peak systolic velocity (S wave) measured by TDI was comparable in the two groups. While using 2D STE, the measured LV longitudinal global peak systolic strain of apical four-chamber, two-chamber, and three-chamber views was markedly reduced in the AR group compared with controls (P = 0.0001) [Table 3]. In addition, global LV systolic strain rate (SRs) and cumulative peak SRs of lateral, inferior, and posterior walls were attenuated in the AR group in comparison with controls (P< 0.05) [Table 4]. Diastolic function, as evaluated by conventional doppler mitral inflow using peak E wave and E/A ratio, was markedly attenuated in the AR group compared with controls (P = 0.0001) [Table 5]. Similarly, peak Em velocity measured using TDI demonstrated a significant reduction, and the E/Em ratio showed opposite increase in controls in comparison with the AR group (P< 0.05) [Table 6]. Moreover, using 2D STE, the measured LV global early diastolic (SRe) and cumulative peak SRe of apical four-chamber and two-chamber views were reduced in the AR group in comparison with controls (P< 0.001) [Table 7].
Table 3 Comparison between the study groups with respect to LV cumulative peak systolic longitudinal strain (εsys%)

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Table 4 Comparison between the study groups with respect to cumulative peak SRs

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Table 5 Comparison between the study groups with respect to mitral doppler inflow

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Table 6 Comparison of tissue doppler echocardiographic data in the studied group

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Table 7 Comparison between the study groups with respect to cumulative LV SRe (s−1)

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A negative correlation was demonstrated between E/Em ratio and each of εsys, SRs, SRe, and SRa in AR patients. Similarly, these parameters showed an inverse correlation with LV mass index in AR patients. Receiver operating characteristic curves were constructed to explore the optimal cutoff point of peak systolic strain and strain rate that discriminates LV dysfunction between patients and controls [Table 8].
Table 8 ROC curve between patients and controls with respect to εsys, SRs, SRe, and SRa

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  Discussion Top


Patients with severe and symptomatic AR have a poor prognosis [15]. More than one-quarter of patients with this condition who die or develop systolic dysfunction do so before the onset of warning symptoms [3],[16],[17]. Patients at risk for future symptoms, LV dysfunction, or death should be identified on the basis of noninvasive testing. The optimal timing of surgical treatment is significantly associated with a reduced cardiovascular mortality rate. Therefore, early detection of LV systolic dysfunction, even in asymptomatic patients with chronic AR, should be taken into account when determining the need for further observation and clinical decision making.

Current guidelines [2] recommend aortic valve replacement even without symptoms if the left ventricular ejection fraction (LVEF) is reduced to less than 50%, the end-diastolic diameter increases to more than 75 mm, or the end-systolic diameter reaches 55 mm. However, the regular indices of LV function, such as LVEF, may be confounded by changes in preload and afterload. Therefore, volume-derived assessment has important limitations as a measure of LV function in patients with altered loading conditions, which is invariably present in severe AR. In addition, the detection of impaired LV function using LVEF presupposes dysfunction of a certain number of ventricular segments. Therefore, LVEF might be insensitive to small decrements in function associated with early changes in myocardial contraction [18]. However, strain would be expected to be a more sensitive measure in this respect, because it directly measures myocardial deformation.

Comparison between the clinical data in the studied groups showed significantly higher SBP and lower diastolic blood pressure in patients when compared with controls. This finding is supported in the study by Smedsrud et al. [19] who aimed to investigate whether global longitudinal strain measured by 2D STE could detect incipient myocardial dysfunction in patients with chronic AR. In this study, patients with AR had statistically significantly higher blood pressure when compared with controls.

Comparison between tissue doppler echocardiographic data in the studied groups had shown impaired diastolic and systolic function parameters. This is in accordance with the results of Mizarienė et al. [20] who reported impaired tissue doppler parameters in AR patients when compared with controls.

Moreover, this was supported by a study carried out by Mizarienė et al. [21] that showed that tissue doppler S¢ velocity was reduced in all patient groups and subgroups with AR in comparison with normal individuals.

We found a significant reduction in global longitudinal systolic strain in the AR group compared with the control group. This was supported by a study conducted by Smedsrud et al. [19] that aimed to investigate whether global longitudinal strain measured using 2D STE could detect incipient myocardial dysfunction in patients with chronic ARAR. They selected 47 patients referred for aortic valve replacement because of chronic AR, along with 31 healthy controls. Myocardial deformation as determined by longitudinal, circumferential, and radial strain was calculated using 2D STE, in addition to LV volumes, dimensions, and EF. Global systolic longitudinal strain was significantly lower in patients with AR before surgery compared with healthy controls (−17.5 ± 3.1 vs. −22.1 ± 1.8%, P< 0.01), whereas global circumferential strain and LVEF did not differ (−21.7 ± 3.4 vs. −22.6 ± 2.5%, P = 0.22, and 59 ± 5 vs. 59 ± 6%, P = 0.59, respectively). However, differences between patients and controls were evident for both longitudinal and circumferential strain when normalized to end-diastolic volume (−0.09 ± 0.04 vs. −0.23 ± 0.08, P< 0.01, and −0.11 ± 0.05 vs. −0.24 ± 0.08, P< 0.01, respectively). The study demonstrated reduced global longitudinal strain in patients with chronic AR with preserved LVEFs.

In our study, we did not measure radial strain, as there was evidence that the radial function of the heart is less affected compared with longitudinal axis function in chronic AR patients [21]. Moreover, we did not measure circumferential strain, as circumferential LV function is less sensitive to chronic volume overload in AR and thereby remains near the normal ranges as in other heart diseases with preserved LVEF [22],[23],[24].

Limitations

A limitation of this study is the small size of the sample that may have influenced the results; this was dependent on the inclusion of highly selected AR patients with exclusion of those with a poor acoustic window. A further limitation is that we have included patients treated at different time points, at different doses, and with different types of vasodilator drugs for the assessment of LV mechanics. In addition, our results were based only on 2D-mode echocardiographic technique and measurements; although accepted for clinical investigation, this method is inferior to reference 3D echocardiographic or magnetic resonance-based measurements of LV mass.

At present, the optimal frame rate for speckle tracking seems to be 50–70 FPS, which is lower compared with TDI (>180 FPS). This could result in undersampling, especially in patients with tachycardia, in which rapid events during the cardiac cycle, particularly in isovolumic phases and in early diastole, may disappear altogether, and peak SR and velocity values may be reduced. Higher frame rates could reduce the undersampling problem, although this will result in a reduction of spatial resolution and considerable noise in the SR signal.


  Conclusion Top


2D speckle tracking-derived strain and strain rate are good methods to detect subtle or substantial reduction in LV systolic and diastolic function in AR patients [Figure 1] and [Figure 2].
Figure 1: A speckle-tracking echocardiographic measurement of longitudinal strain in apical four-chamber view in a control individual (normal values) .The myocardium is divided into six segments that are color coded, peak longitudinal strain is the peak negative value obtained at or before aortic valve closure, displayed graphically, with each segment represented by matching color as strain curves and numeric values. AVC, aortic valve closure.

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Figure 2: Two-dimensional speckle tracking echocardiography measurement of longitudinal strain in apical three-chamber view in a patient with aortic regurgitation showing reduction of peak longitudinal strain value of basal and midsegments of anteroseptal wall (εsys = −13.2, −13.7%, respectively) but normal peak longitudinal strain of the remaining myocardial segments. APLAX, apical long axis view; AVC, aortic valve closure.

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  Acknowledgements Top


Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]



 

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Introduction
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