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ORIGINAL RESEARCH
Year : 2019  |  Volume : 3  |  Issue : 2  |  Page : 57-62

Reproducibility of echocardiography in assessing left atrial reservoir function in rheumatic mitral valve disease


Department of Cardiology, Tanta University, Tanta, Egypt

Date of Web Publication29-Aug-2019

Correspondence Address:
Mona A Elsaidy
Department of Cardiology, Tanta University, 1 El Geish Street, Tanta, Gharbia Governorate 31111
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiae.jiae_13_19

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  Abstract 

Background: Although abnormal left atrial (LA) reservoir function had been associated with clinical events in patients with mitral valve disease, its routine assessment is not performed due to inaccuracies and difficult time-consuming measurements. Aim: The aim was to study the feasibility and reproducibility of different echocardiographic parameters for LA assessment in patients with rheumatic mitral valve disease. Methods: Two hundred and fifty-nine patients with mitral valve disease underwent full echocardiographic examination. LA reservoir function was measured by two-dimensional (2D) volumes, 3D volumes, and global longitudinal strain (LA GLS). LA GLS, volumes, and total left atrial emptying fraction values were repeated to obtain the intra- and interobserver variabilities. The latter was performed between a nonexpert and two expert examiners. Results: 3D echocardiography was highly feasible in assessing LA function, feasibility was 94%, and was performed in the shortest time (1.3 ± 0.4, ANOVA, P < 0.0001). All LA 3D measurements showed excellent intraobserver and interobserver reproducibility between the two expert readers; coefficient of variation (CV) was 7% and 8%, respectively, for LA maximal volume index (LAVImax). Although CV for interobserver variability between the expert and nonexpert readers was 12% for 3D minimal LAVI (LAVImin), assessment of 2D LA volumes had the lowest reproducibility; CV was 15% for LAVImin. Conclusion: 3-d echocardiography assessment of LA volumes and function in patients with rheumatic heart disease is highly feasible and reproducible; it is easy to learn and can be easily performed by nonexperts.

Keywords: Function, left atrium, reproducibility


How to cite this article:
Elsaidy MA, Abdalaal MA, Elsheikh AA, Elsharkawi S. Reproducibility of echocardiography in assessing left atrial reservoir function in rheumatic mitral valve disease. J Indian Acad Echocardiogr Cardiovasc Imaging 2019;3:57-62

How to cite this URL:
Elsaidy MA, Abdalaal MA, Elsheikh AA, Elsharkawi S. Reproducibility of echocardiography in assessing left atrial reservoir function in rheumatic mitral valve disease. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2019 [cited 2019 Nov 17];3:57-62. Available from: http://www.jiaecho.org/text.asp?2019/3/2/57/265746


  Introduction Top


Rheumatic heart disease is endemic in Egypt,[1] with the mitral being the most commonly affected valve.[2] Mitral valve disease is associated with left atrial (LA) remodeling, increased stiffness, and abnormal contractility.[3] There is an increasing evidence suggesting that LA function offers incremental prognostic information that occurs early in the disease processes [4],[5] and can predict clinical events in patients with both mitral stenosis [3],[6] and regurgitation.[7],[8],[9]

LA function is not routinely assessed because it is time-consuming and needs special expertise.

Recently, new echocardiographic modalities had emerged for rapid and accurate assessment of LA function as global left atrial strain (GLS)[10],[11] and real-time three-dimensional echocardiography (3DE).[12],[13]

Aim

The aim was to study the feasibility and reproducibility of different echo modalities for LA assessment in patients with rheumatic mitral valve disease.


  Methods Top


Study population

From June 2015 to June 2018, 651 patients presented to our noninvasive laboratory with rheumatic mitral valve disease were screened.

Inclusion criteria

Patients with rheumatic mitral valve disease (mitral stenosis, mitral regurgitation [MR], and mixed mitral lesions) and of all grades (mild, moderate, and severe) were included in the study.

Exclusion criteria

Significant other valvular lesions such as aortic stenosis and aortic regurgitation, atrial fibrillation or other nonsinus rhythm, left ventricular ejection fraction (LVEF <50%), and other conditions that may affect LA function as obesity, diabetes mellitus, and systemic hypertension.

All patients gave informed written consent, and the study was approved by the local ethical committee.

Echocardiography

Examinations were performed using Vivid E9 (GE Vingmed, Horten, Norway) equipped with M5S probe for 2D echocardiographic (2DE) examination and 4 V matrix-array transducer for 3DE examination. Data were stored in digital format and analyzed offline with dedicated software (EchoPAC PC 108.1.4, GE Healthcare, Horten, Norway).

Standard transthoracic echocardiography

A complete study was performed in all patients; LA diameter was measured during systole. The maximum LA volume index (LAVImax) and the minimum LA volume index (LAVImin) were calculated from apical four- and two-chamber-zoomed views of the LA using the biplane area-length method [14] and were indexed to the body surface area.[15]

The difference between LAVImax and LAVImin divided by LAVImax was used as an index of atrial total emptying (ejection) fraction representing LA reservoir function [Figure 1].
Figure 1: Two-dimensional echocardiography volume assessment of left atrial minimal volume using area/length in a patient with mitral lesion

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Left ventricular global systolic function was evaluated by ejection fraction (EF) using the biplane Simpson's method. Right ventricle systolic function was evaluated by tricuspid annular plane systolic excursion, and estimated systolic pulmonary arterial pressure was assessed from the tricuspid regurgitation velocity.[14] Mitral valve area was evaluated using the 2D planimetry and pressure half-time methods.[16]

The degree of MR was determined according to the 2017 European Society of Cardiology (ESC) Guidelines for the management of valvular heart disease.[17] A lesion is considered significant if more than moderate.

Three beats in each view were analyzed and averaged.

Speckle-tracking GLS

It was performed using Q-analysis; apical four- and two-chamber views were obtained using 2D grayscale echocardiography for speckle-tracking analysis. The frame rate was set between 60 and 80 frames/s. The endocardial surface of the LA was traced manually in both four- and two-chamber views. The system then automatically generated an epicardial surface tracing. A region of interest (ROI) was created and adjusted manually to fit LA wall. The software divided the ROI into six segments in the two-chamber and the four-chamber views. It then generated the longitudinal strain curves for each segment, and a global strain curve manifested as a dotted white line [Figure 2].
Figure 2: Global longitudinal strain of the left atrium (white-dotted line) in a patient with mitral stenosis

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Three-dimensional echocardiography

Images were acquired with increased all over gain in large multislice (12 slices), multibeat (4–6) mode, and the frame rate was adjusted to be 45% of the resting heart rate, focus was laid on the most optimal image of the LA, angulation was avoided, and the images were obtained and transferred to the EchoPac for the analysis by 4D Auto Left Ventricular Quantification (LVQ) tool.

4D Auto LVQ was activated by manually obtaining LA volumes at end ventricular systole (maximal) and at end diastole (minimal); two anatomical landmarks were identified manually at the center of the mitral valve annulus and the center of the posterior wall. Then, manual adjustments of the endocardial surface were performed in all traces using attractor points to exclude atrial appendages and pulmonary veins, and finally, left atrial emptying fraction (LAEF) was automatically generated [Figure 3].
Figure 3: Three-dimensional echo assessment of left atrial volumes and total emptying fraction in a patient with mitral stenosis using four-dimensional auto left ventricular quantification tool

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3D analysis was done 24 h after the 2D measurement. Measurements were randomly assigned to two expert investigators.

The time needed to complete each measurement (2D, GLS, and LVQ) was assessed.

Intra- and interobserver agreement

2D and 3DE volume measurements and GLS measurements were repeated in 20 randomly selected cases by the same investigator to analyze the intraobserver agreement and by the second expert investigator to analyze the interobserver agreement. Measurements were performed within 2 weeks of the first reading. The readers used the same cycle, and they were blinded to previous measurements.

Expert versus nonexpert agreement

Twenty randomly selected patients were assessed for 2DE LA volumes, GLS, and 3D volumetric measurement by a nonexpert cardiologist and were compared to an expert investigator for the agreement.

The expert investigators have more than 3-year experience in using 3DE and strain in both clinical and research purposes, whereas the nonexpert investigator is a cardiologist with proficiency in echocardiography interpretation, but no prior experience in performing LA strain analysis or volume assessment. She received a 20-min training session on LA assessment before proceeding with the measurements.

Statistical analysis

Statistical analysis was carried out using Microsoft Excel 2011 sheet.

Quantitative data were expressed as mean ± standard deviation (SD), and qualitative data were expressed as numbers and percentages. Differences between LA volumes and EF during 2DE and 3DE studies were evaluated using Student's t-test of equal variance. Comparison of the time needed to complete the measurement of each parameter was evaluated using ANOVA test.

The intra- and interobserver and expert versus nonexpert variability of repeated measurements had been expressed as coefficient of variation (CV). The CV was calculated as SD of the differences divided by the mean of the variable under consideration. Differences were considered statistically significant when P < 0.05.


  Results Top


We screened 651 patients with rheumatic mitral valve disease; however, only 269 (41%) met the inclusion criteria as 340 patients had atrial fibrillation, 25 were obese, 9 showed atrial tachycardia, 6 had EF <50%, and 2 were diabetics.

Proper echo views were not possible in 10/269, so adequate 2D views were possible in 259/269 (96%) of the patients.

Among 259 patients with rheumatic mitral valve disease, 174 (68%) had isolated mitral stenosis (MR, if present was not significant), 80 (30%) had mixed significant lesions (both mitral stenosis and regurgitation), and finally, 5 (2%) had isolated MR (mitral stenosis was not significant).

  • Baseline characteristics – Women constituted 49% of the study patients with the mean age of 35 ± 2 years [Table 1]
  • 2DE versus 3DE – Echocardiographic criteria are shown in [Table 2]


  • All 2DE volumes were significantly lower than 3DE volumes: 2DE LAVImax was 50 ± 12 ml/m 2 and 3DE was 61 ± 8, P < 0.001 and 2DE LAVImin was 23 ± 4 versus 29 ± 9, P = 0.012, whereas LAEF did not differ significantly; 41 ± 8% versus 43 ± 17, P = 0.9 [Table 2].

  • GLS – It ranged from 9% to 25% with the mean of 17 ± 4.
Table 1: Baseline characteristics of the study patients

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Table 2: Echo parameters of the study patients

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Feasibility

Measurement of 2D GLS was feasible in 251/259 (96%) patients as four patients showed huge LA dilatation with severe thinning of LA wall and inability to encompass ROI in the wall. Image acquisition for 3DE processing was feasible in 246/259 (94%) patients as 9 patients could not hold their breath and 4 patients had huge LA dilatation [Figure 4].
Figure 4: Feasibility of different echo parameters for measuring left atrial function. 2DE: Two-dimensional echocardiography, GLS: Global longitudinal strain, 4DLVQ: Three-dimensional echocardiography using 4D auto left ventricular quantification tool. P is significant if < 0.05

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Time

The least time needed was that to measure 3DE volumes and LAEF (it ranged from 0.5 to 2 min with the mean of 1.3 ± 0.4) ANOVA, P < 0.0001. The time needed to complete measurement of 2D volumes ranged from 2 to 8 min with the mean of 5 ± 1.5, whereas the time needed for GLS ranged from 1 to 3 min with the mean of 2 ± 0.4.

The time needed to complete 3D volume study by the nonexpert reader was not significantly different from the expert reader (1.8 ± 0.6 versus 1.3 ± 0.4, P = 0.153); however, the nonexpert reader took a significantly longer time in measuring 2D volumes and GLS compared to the experts [Table 3].
Table 3: Time (in minutes) needed to complete different measurements by expert versus nonexpert readers

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Reproducibility

All measurements showed excellent intraobserver and interobserver reproducibility between the two expert readers. However, assessment of 2DE LA volumes and function showed the least agreement for the nonexpert reader; CV was 15% for LAVImin [Table 4].
Table 4: Coefficient of variation of intra- and interobserver measurement, and expert versus nonexpert

Click here to view



  Discussion Top


Abnormal LA reservoir function can predict symptoms development and events in patients with rheumatic mitral valve disease,[3],[6] and the 2017 ESC [17] Guidelines had used LAVI >60 ml/m 2 as a Class IIa indication for surgical intervention in asymptomatic patients with severe MR who do not meet the recommended criteria for surgery. However, LA function assessment is not included in the routine echocardiographic examination because it is time-consuming, needs special expertise, and could be inaccurate because of volume assumption and foreshortening of the LA during 2D examination.[18] Although 3DE volumetric measurement correlated well with cardiac magnetic resonance (CMR),[19] its use had been restricted as a research tool used only by the experts in the field because the analysis consists of many steps, requires multiple adjustments, and is considered time-consuming.

4-D Auto LVQ tool, a semiautomated real-time 3D quantification tool, had been introduced initially as a left ventricular assessment software, but for quite some time, had been used for LA volumes measurement for being simpler, easier, and requires less time for the analysis than the other available 3D quantification tools.[20] Recently, it had been validated against CMR and proved to be accurately equivalent to CMR, especially on short-axis plane.[13]

This study aimed to evaluate the feasibility and reproducibility of three echocardiographic modalities to evaluate LA function in patients with rheumatic mitral valve disease and to test how a nonexpert cardiologist can fair using these parameters.

Two-dimensional echocardiography

Although assessment of LA volumes by 2DE had an excellent feasibility of 96% as ten patients had inadequate echo window, it took a significantly longer time for the analysis as it needs proper image acquisition to avoid foreshortening in both apical four- and two-chamber views, manual border delineation, minor axis measurement in both views, compare, and take the smaller of them, and then, applying the formula of area/length method for both LAVI max and LAVI min, and finally, measuring LA total emptying fraction. It was also highly reproducible for the same reader and both expert readers.

LA GLS was feasible in 96% of patients as five patients had huge LA dilatation with inability to encompass the whole LA wall since more than two segments could not be visualized. The measurement took about 2 min to be completed and showed excellent reproducibility.

All studies [21],[22],[23] examining the reproducibility of GLS in LA assessment also found excellent reproducibility; however, Caso et al.[6] found that CV for tissue Doppler imaging (TDI)-gained strain was 11% and 17% for intra and interobserver variabilities, respectively, but we found it to be better of 4% and 7% because TDI has the limitation of being angle dependent and technically challenging, as signal-to-noise ratios may be problematic.[18]

Three-dimensional echocardiography

It has perfect feasibility of 94% but insignificantly less than the other two modalities, as it depends on the quality of 2D images and needs patients' cooperation to hold their breath, which could be really difficult in patients suffering from dyspnea. It took the least time to complete the measurement since it is semiautomated (provides a simple user interface and an efficient workflow), the analysis needs few steps and minimal adjustment (eliminating the need for manual tracing with delineation of the border with only 2 points), with automatic generation of LAVImax, LAVImin, and LAEF. It also showed excellent reproducibility for LAVImax, LAVImin, and LAEF. Other studies [12],[24],[25] found excellent reproducibility for LAVImax and poorer agreement for LAVImin; this may be attributed to the fact that during the end ventricular diastole, the LA is at its smallest size with difficult identification of the endocardial border; however, this difficulty was not seen in the current study as the majority of our patients had marked LA dilatation, while other studies enrolled patients with normal LA dimensions.

Expert versus nonexpert

The nonexpert investigator took 1.8 ± 0.6 minutes to complete the measurement of LA volumes using LVQ, which was not significantly different from the time needed by the expert reader of 1.3 ± 0.4, P = 0.153 [Table 3].

The nonexpert showed very good reproducibility for LA GLS assessment and that was also shown in previous studies.[25],[26]

Two-dimensional echocardiography versus three-dimensional echocardiography volume values

All volume values by 3DE were significantly higher than those obtained by 2DE because the LA is an asymmetrical cavity; therefore, 2DE may underestimate the volume due to its inability to detect the whole LA borders, especially when it is dilated. This was also found by Artang et al.[12] and Badano et al.[25]

The current study is a novel, as it is the first to examine feasibility and reproducibility of 3D echo for LA volume assessment using LVQ software in patients with rheumatic heart disease. However, Ojaghi-Haghighi et al.[27] examined the LA reservoir function in patients with rheumatic mitral disease as well, using tissue Doppler-based strain, while we used speckle-tracking-based GLS, Badano et al.[25] studied reproducibility of 3D echo volumetric analysis of LA function using TomTec software (TomTec Imaging Systems, Unterschleissheim, Germany) in normal healthy individuals, and while we used LVQ software in patients with rheumatic heart disease, Deng, et al.[28] studied the reproducibility of 3DE using QLab version 8 in patients with rheumatic mitral stenosis only, before and after balloon mitral valvuloplasty.

Limitations of the study and future direction

  1. All three-phasic LA volumes could not be measured automatically by LVQ because of software timing limitation as it was intended for LV assessment; however, conduit and pump function could be assessed manually from the time/volume curve, but a longer time is needed
  2. Few patients were included in the study as most of the patients with mitral valve disease had atrial fibrillation.



  Conclusion Top


LA reservoir function assessment by 3DE using 4D Auto LVQ is feasible, easy to learn, rapid, and reproducible in patients with mitral valve disease. Given the clinical importance of LA function and the ease of measuring its 3DE-derived volume and function, routine acquisition of these parameters should be recommended, especially in busy echocardiography laboratories receiving a lot of patients with rheumatic mitral valve disease.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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Caso P, Ancona R, Di Salvo G, Comenale Pinto S, Macrino M, Di Palma V, et al. Atrial reservoir function by strain rate imaging in asymptomatic mitral stenosis: Prognostic value at 3 year follow-up. Eur J Echocardiogr 2009;10:753-9.  Back to cited text no. 3
    
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Mondillo S, Cameli M, Caputo ML, Lisi M, Palmerini E, Padeletti M, et al. Early detection of left atrial strain abnormalities by speckle-tracking in hypertensive and diabetic patients with normal left atrial size. J Am Soc Echocardiogr 2011;24:898-908.  Back to cited text no. 4
    
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Genovese D, Singh A, Volpato V, Kruse E, Weinert L, Yamat M, et al. Load dependency of left atrial strain in normal subjects. J Am Soc Echocardiogr 2018;31:1221-8.  Back to cited text no. 22
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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