© 2014, Wiley Periodicals, Inc. DOI: 10.1111/echo.12834

Echocardiography

ORIGINAL INVESTIGATION

Optimal Analysis of Left Atrial Strain by Speckle Tracking Echocardiography: P-wave versus R-wave Trigger Shuji Hayashi, M.D., Ph.D.,* Hirotsugu Yamada, M.D., Ph.D.,† Mika Bando, M.D.,† Yoshihito Saijo, M.D.,† Susumu Nishio, R.M.S.,* Yukina Hirata, M.S.,* Allan L. Klein, M.D.,‡ and Masataka Sata, M.D., Ph.D.† *Ultrasound Examination Center, Tokushima University Hospital, Tokushima, Japan; †Department of Cardiovascular Medicine, Tokushima University Hospital, Tokushima, Japan; and ‡Department of Cardiovascular Medicine, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio

Background: Left atrial (LA) strain analysis using speckle tracking echocardiography is useful for assessing LA function. However, there is no established procedure for this method. Most investigators have determined the electrocardiographic R-wave peak as the starting point for LA strain analysis. To test our hypothesis that P-wave onset should be used as the starting point, we measured LA strain using 2 different starting points and compared the strain values with the corresponding LA volume indices obtained by three-dimensional (3D) echocardiography. Methods: We enrolled 78 subjects (61  17 years, 25 males) with and without various cardiac diseases in this study and assessed global longitudinal LA strain by two-dimensional speckle tracking strain echocardiography using EchoPac software. We used either R-wave peak or P-wave onset as the starting point for determining LA strains during the reservoir (Rres, Pres), conduit (Rcon, Pcon), and booster pump (Rpump, Ppump) phases. We determined the maximum, minimum, and preatrial contraction LA volumes, and calculated the LA total, passive, and active emptying fractions using 3D echocardiography. Results: The correlation between Pres and LA total emptying fraction was better than the correlation between Rres and LA total emptying fraction (r = 0.458 vs. 0.308, P = 0.026). Pcon and Ppump exhibited better correlation with the corresponding 3D echocardiographic parameters than Rcon (r = 0.560 vs. 0.479, P = 0.133) and Rpump (r = 0.577 vs. 0.345, P = 0.003), respectively. Conclusions: LA strain in any phase should be analyzed using P-wave onset as the starting point rather than R-wave peak. (Echocardiography 2014;00:1–9) Key words: left atrium, strain, two-dimensional speckle tracking echocardiography, three-dimensional echocardiography Assessment of left atrial (LA) volume and function has become important for echocardiographic evaluation of patients with cardiac diseases. Several reports have indicated that LA parameters are useful for evaluating left ventricular (LV) diastolic function and predicting the risks of new onset of atrial fibrillation, chronic heart failure, stroke, and cardiovascular morbidity.1–5 LA function can be divided into 3 phases: a reservoir phase, in which the left atrium stores pulmonary venous return during LV contraction and isovolumetric relaxation; a conduit phase, in which the LA passively transfers blood into the Funding Source: This research was partially supported by JSPS KAKENHI through a Gant-in-Aid for Scientific Research (C) (grant number 22500437). Address for correspondence and reprint requests: Hirotsugu Yamada, M.D., Ph.D., Department of Cardiovascular Medicine, Tokushima University Hospital, 2-50-1 Kuramoto, Tokushima 770-8504, Japan. Fax: +81-88-633-7798; E-mail: [email protected]

LV; and a booster pump phase, in which the LA actively contracts during the final phase of diastole and contributes 15–30% of the LV stroke volume.4 Two-dimensional (2D) speckle tracking strain echocardiography is a novel technique for assessment of myocardial deformation. This method was originally developed for assessing regional LV myocardial function; however, it has recently been used to evaluate LA function as well.4,6–9 To determine LA strain by speckle tracking strain echocardiography, most investigators have used the analytical algorithm developed for LV myocardial strain. Thus, LA strain has been calculated from a dataset that starts from the electrocardiographic R-wave peak.7,9–12 A few researchers have calculated LA strain using P-wave onset instead of R-wave peak as the starting point.9,13,14 We speculated that the latter method may be more appropriate from a physiological viewpoint because the initial length used 1

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to calculate LA strain should not be determined from R-wave peak but from P-wave onset. However, the American Society of Echocardiography/ European Association of Echocardiography consensus statements list both P- and R-waves as the starting point for LA strain analysis but do not recommend which of these should be used as the starting point.6 Advances in three-dimensional (3D) echocardiography have enabled accurate measurement of LA volume.7,15,16 It is known that 3D echocardiographic volume assessments demonstrate extremely good agreement with magnetic resonance imaging,17,18 the gold standard for LA size assessment.19 Multidetector computed tomography, which demonstrates extremely good agreement with LA volume assessments by 3D echocardiography, has been used to validate these findings.20,21 Therefore, we compared LA strains measured using 2 different methods with the corresponding LA parameters obtained by 3D echocardiography to determine which starting point, P-wave onset or R-wave peak, is better for LA strain analysis. Methods: Study Population: Of the 672 patients who underwent echocardiography for clinical purpose at our Ultrasound Examination Center, Tokushima University Hospital from October to December 2012, 100 patients who met the following requirements were randomly selected: (1) patients who had maintained sinus rhythm without significant atrioventricular block; (2) patients who did not have mitral valve surgery. Twenty-two patients were excluded during the offline imaging analysis because of poor image quality for obtaining the LA strain and the LA volume curves. This study protocol was approved by the ethics committee of Tokushima University Hospital and informed consent was obtained from all subjects. Two-Dimensional and Doppler Echocardiography: A Vivid E9 system (GE Vingmed Ultrasound AS, Horten, Norway) was used for this study. Routine examination was performed as described in previous guidelines with a cardiac sector probe M5S-D (1.5–4.5 MHz; GE Vingmed Ultrasound AS).22,23 M-mode echocardiography was used to determined LV end-diastolic and end-systolic diameters. The thicknesses of the interventricular septal and the inferolateral walls were obtained from the short-axis view. LV volume was determined by the modified Simpson’s rule, with images recoded from apical two-chamber and four-chamber views. Pulsed Doppler parameters

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were obtained in the apical four-chamber view. The peak early and late diastolic flow velocities were obtained from recordings of transmitral flow velocity. The following parameters were determined using the pulmonary venous flow velocities: peak systolic flow velocity, peak diastolic flow velocity, and peak pulmonary venous atrial reversal flow velocity. Pulsed tissue Doppler echocardiography was performed from an apical four-chamber view to obtain the peak early diastolic mitral annular velocity of the lateral side. Subsequently, several Doppler indices were used in accordance with the guidelines of the American Society of Echocardiography/European Association of Echocardiography for grading diastolic dysfunction.23 Speckle Tracking Echocardiography: The global longitudinal LA strain was analyzed offline by the speckle tracking technique using GE EchoPAC software (EchoPAC PC 110.1.4; GE Vingmed Ultrasound AS). To increase the accuracy and the stability of LA strain measurements, we used only four-chamber view image of LA for the strain analysis. The reasons were as follows: (1) it is often difficult to obtain stable LA images in two-chamber view particularly in young subjects whose LA is small; (2) the LA in four-chamber view does not contain LA appendage and ascending aorta, where LA segmental strains are hardly determined by speckle tracking method; and (3) LA strain analysis from multiple views may increase sensitivity for detecting abnormal LA function; however, regional abnormality is less observed in LA compared with LV. We considered that LA dynamics in a four-chamber view could represent global LA function. In addition, LA analysis from one view reduced the measurement errors and the influences of image artifacts observed by multiple views. The endocardial border of LA was manually traced and a region of interest was manually adjusted to include the entire LA wall thickness. The software selected stable speckles within the LA wall and tracked these speckles frame-by-frame throughout the cardiac cycle. Thereafter, the software divided the entire LA circumference into up to 6 segments and provided the tracking quality for each segment. In segments with poor tracking, endocardial borders were readjusted until better tracking was achieved. Then, we set the starting point of strain analysis as R-wave peak (software preset) or P-wave onset. The automated software then generated traces depicting the regional longitudinal strain for each segment and calculated global strain. The starting points of R-wave peak (Rres, Rcon, and Rpump) and P-wave onset (Pres, Pcon, and Ppump) were separately used to

Starting Point for Left Atrial Strain Analysis

calculate LA strains during the reservoir, conduit, and booster pump phases, respectively, from the LA strain curve (Fig. 1).9 In R-wave trigger method, the R-wave peak was set as zero reference. Then, the LA strain curve is composed of a predominantly positive wave that peaks at endsystole (Rres), followed by two distinct descending phases in the early diastole (Rcon) and late diastole (Rpump). Rres was considered to reflect LA reservoir function. Rcon and Rpump components to reflect conduit and booster pump function, respectively (Fig. 1, left panel).11,12 In P-wave trigger method, the P-wave onset was set as the reference point. The strain curve constructed from P-wave enabled the recognition of peak negative strain (Ppump) which corresponded to LA booster pump function, and peak positive strain (Pcon) which corresponded to LA conduit function; and the sum of these values (Pres), which corresponded to LA reservoir function (Fig. 1, right panel).13–15 Three-Dimensional Echocardiography: We obtained 3D echocardiographic datasets immediately after obtaining 2D LA images. A 4D-V cardiac probe (1.5–4 MHz; GE Vingmed Ultrasound AS) was used to perform 3D echocardiography. Acquisition was performed during

end-expiratory apnea within a breath-holding period. To measure accurately LA volume before active atrial contraction, echocardiographic data obtained by single-beat acquisition were used. The 3D echocardiographic datasets from the apical view were stored digitally and quantitative analyses were performed offline using a semiautomated contour-tracing algorithm (EchoPAC PC 110.1.4) based on manually chosen reference points. Each of the following reference points was selected at maximum and minimum LA volumes. A total of 9 reference points were selected, including 2 points on the mitral annulus and 1 point on the roof of the LA for each of the 3 views (two-, three-, and four-chamber views). We attempted to obtain images wherein the volume rate was ≥40 frames/sec by adjusting the 3D echocardiographic angle of view. This resulted in mean volume rates of 47.5  8.0 frames/sec. The following volumes were measured from the LA volume curve obtained: (1) the maximum LA volume (Vmax) at end-systole; (2) the minimum LA volume (Vmin) at end-diastole; and (3) the LA volume before active atrial contraction (Vp). The LA total emptying fraction was calculated as [(Vmax  Vmin)/Vmax] 9 100; the LA passive empting fraction was calculated as [(Vmax Vp)/ Vmax] 9 100; and the LA active emptying

Figure 1. Left atrial strain analysis by speckle tracking echocardiography. The colored lines represent left atrial (LA) strain of each segment and the white dotted line represents the global LA strain. LA strains in the reservoir, conduit, and booster pump phases were calculated from the LA strain curve either by using the starting points of R-wave peak (Rres, Rcon, and Rpump, respectively) shown in the left panel or by using the starting points of P-wave onset (Pres, Pcon, and Ppump, respectively) indicated in the right panel.

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fraction was calculated as [(Vp  Vmin)/ Vp] 9 100. Finally, the LA expansion index, a surrogate of LA reservoir function, was calculated as [(Vmax  Vmin)/Vmin] 9 100.15,24

correlation in subsequent analyses and to examine whether the sample size was adequate. Statistical significance was set at P < 0.05 for all data examined.

Statistical Analysis: Data analysis was performed using SPSS software, version 19.0 (IBM Corporation, Armonk, NY, USA). All results are expressed as mean  standard deviation (SD). Pearson’s correlation analysis and Student’s paired t-test were used to assess the agreement between R-wave trigger and P-wave trigger parameters. Correlations between the LA strain values and the corresponding 3D echocardiographic parameters were analyzed using Pearson’s method. With respect to 3D echocardiographic parameters, the Meng–Rosenthal–Rubin method, which tests for differences between paired correlations, was used to find the difference between the correlation of strain parameters for both the R-wave and P-wave. Intraclass correlation coefficients and paired Student’s paired t-test were used to assess reproducibility of echocardiographic measurements. In addition, G*Power 3.125 was used to calculate the statistical power of the

Results: Study Participants: The clinical characteristics of the study participants are presented in Table I. The study participants (age: 61  17 years; 25 males) included 59 patients with various cardiac diseases (primarily coronary artery disease) and 19 normal hearts. As noted in Table I, there was a wide spectrum of diastolic dysfunction in our patient population, which allowed observation of LA function in subjects with diseased or normal hearts. Echocardiographic characteristics are presented in Table II. Relationships between LA strains and LA Volume Parameters: Rres was greater than Pres (23.9  8.8% vs. 20.6  6.1%, P < 0.001), Rcom was greater than Pcon (12.1  7.1% vs. 9.6  5.2%, TABLE II Echocardiographic Characteristics

TABLE I

n = 78

Clinical Characteristics n = 78 Age (years) Male, n (%) Body surface area (m2) Heart rate (beats/min) Systolic blood pressure (mmHg) Diastolic blood pressure (mmHg) Background disease, n (%) Coronary artery disease Hypertensive heart disease Paroxysmal atrial fibrillation Valvular disease Hypertensive heart disease Pulmonary arterial hypertension Drug-induced cardiomyopathy Dilated cardiomyopathy Hypertrophic cardiomyopathy Cardiac sarcoidosis Fabry disease Normal heart Grade of diastolic dysfunction Grade I Grade II Grade II

61  17 25 (32.1) 1.57  0.19 67  9 130  21 75  12 25 (32.1) 8 (10.3) 6 (7.7) 5 (6.4) 4 (5.1) 4 (5.1) 3 (3.8) 1 (1.3) 1 (1.3) 1 (1.3) 1 (1.3) 19 (24.4) 26 (33.3) 28 (35.9) 5 (6.4)

Data are expressed as mean  standard deviation or as number (percentage). Diastolic dysfunction was graded according to the guideline of the American Society of Echocardiography/European Association of Echocardiography.

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Two-dimensional echocardiography LV end-diastolic volume (mL) LV end-systolic volume (mL) LV ejection fraction (%) LV mass index (g/m2) Doppler echocardiography E (cm/sec) Deceleration time of E-wave velocity (msec) A (cm/sec) E/A ratio Systolic pulmonary venous flow velocity (cm/sec) Diastolic pulmonary venous flow velocity (cm/sec) Pulmonary venous atrial reversal flow velocity (cm/sec) e0 (cm/sec) E/e0 ratio Three-dimensional echocardiography LA volume before atrial active contraction (mL) Minimum LA volume at end-diastole (mL) Maximum LA volume at end-systole (mL)

87 37 60 87

   

30 26 12 24

68  22 219  59 74  23 1.0  0.5 59  17 42  15 27  8 8.5  3.4 9.3  4.7 32  18 20  14 46  21

Data are expressed as mean  standard deviation. LV = left ventricular; E = early diastolic transmitral flow velocity; A = late diastolic transmitral flow velocity; e0 = early diastolic mitral annular velocity; LA = left atrial.

Starting Point for Left Atrial Strain Analysis

P < 0.001), and Rpump was greater than Ppump (11.8  5.0% vs. 11.0  4.0%, P = 0.61). Thus, LA strain in each phase was greater when calculated from R-wave peak (R-wave trigger) than when calculated from P-wave onset (P-wave trigger), although good correlations were observed between the measurement types for each strain (Fig. 2). The LA total emptying fraction correlated better with Pres than with Rres (r = 0.458

vs. r = 0.308; Figs. 3 and 4, upper left panels). The LA expansion index correlated with Pres (r = 0.355, P = 0.001) but not with Rres (Figs. 3 and 4, lower left panels). The LA passive empting fraction correlated better with Pcon than with Rcon (r = 0.560 vs. r = 0.479; Figs. 3 and 4, upper right panels). The LA active emptying fraction correlated better with Ppump than with Rpump (r = 0.577 vs. r = 0.345; Figs. 3 and 4,

Figure 2. Correlations between left atrial strains obtained using R- and P-wave triggers in each phase.

Figure 3. Correlations between left atrial strains obtained using an R-wave trigger and atrial volumetric parameters.

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Figure 4. Correlations between left atrial strains obtained using a P-wave trigger and atrial volumetric parameters.

lower right panels). The statistical significance of the correlation coefficients of Rres and Pres for the LA total emptying fraction was 0.026. The statistical significance of the correlation coefficients of Rcon and Pcon for the LA passive empting fraction was 0.133, whereas that for Rpump and Ppump was 0.003. Reproducibility of Measurements: The reproducibility of LA volume and strain measurements was assessed in 15 randomly selected subjects. Vmax, Vmin, Vp, Rres, Rpump, Pcon, and Ppump were remeasured by the original reader and by a second reader experienced in 2D and 3D echocardiography in a blinded manner. Intra-observer intraclass correlation coefficients were 0.99 for Vmax, 0.98 for Vmin, 0.99 for Vp, 0.97 for Rres, 0.95 for Rpump, 0.98 for Pcon, and 0.95 for Ppump, respectively. The mean differences between 2 measurements were as follows: Vmax, 0.4  2.3 mL (P = 0.483); Vmin, 0.1  1.3 mL (P = 0.818); Vp, 0.4  2.3 mL (P = 0.544); Rres, 0.8  1.8% (P = 0.109); Rpump, 0.1  0.7% (P = 0.548); Pcon, 0.4  0.8% (P = 0.107); and Ppump, 0.3  0.8% (P = 0.226). Inter-observer intraclass correlation 6

coefficients were 0.97 for Vmax, 0.95 for Vmin, 0.98 for Vp, 0.96 for Rres, 0.91 for Rpump, 0.96 for Pcon, and 0.92 for Ppump. The mean differences between 2 measurements were as follows: Vmax, 1.1  3.1 mL (P = 0.175); Vmin, 0.1  2.0 mL (P = 0.792); Vp, 0.5  2.9 mL (P = 0.535); Rres, 0.2  2.5% (P = 0.744); Rpump, 0.2  0.9% (P = 0.359); Pcon, 0.4  1.4% (P = 0.272); and Ppump, 0.2  1.1% (P = 0.482). Discussion: Although the strain values calculated using different starting time correlated well in each phase, LA strain measurements based on P-wave trigger exhibited better agreement with the corresponding LA volume parameters obtained by 3D echocardiography compared with measurements based on R-wave trigger. Therefore, we recommend that P-wave onset should be used as the starting point for LA strain analysis. There were two previous studies comparing LA strains with LA volume changes obtained from 2D echocardiography. Kim et al.11 used R-wave as the starting point, whereas Saraiva et al.13 used P-wave as the starting point to conduct LA strain analysis. Both reports found significant

Starting Point for Left Atrial Strain Analysis

correlations between strain values and LA volume indices in reservoir phase and conduit phase. However, neither report found a correlation

Figure 5. Calculation of left atrial strain in the reservoir phase. When the circumferential length before atrial active contraction (Lp) is 70 mm, the minimum circumferential length (Lmin) is 60 mm and the maximum circumferential length (Lmax) is 90 mm; the left atrial reservoir strain is calculated as (90  60)/60 = 0.5. However, if the calculation starts from the R-wave, the initial length for strain calculation is not always Lmin but a slightly greater length (Lmin0 ). If Lmin0 is 62 mm, the strain in the reservoir phase is calculated as (90  62)/62 = 0.45.

between strain value and LA volume index in booster pump phase. Saraiva et al.13 determined that this was because LA volume was underestimated by 2D echocardiography. In our study, we found a significant correlation between strain value and LA volume index in booster pump phase. This may be because that LA volume evaluation with 3D echocardiography was more accurate than that with 2D echocardiography. Strain is defined as a change in length and is expressed relative to the initial length. Therefore, the initial length is very important when evaluating strain. Because the R-wave is the electrical signal of LV contraction, LA phases on R-wave peak differ among patients. Thus, the LA myocardium at R-wave peak may be in contraction or relaxation, which indicates that the LA area or volume at R-wave peak is not always the minimum volume. If one defines the initial length of the LA myocardium at R-wave peak and if the LA myocardium has already started relaxation at that instance, then the initial length for calculation of LA strain will be greater than the minimum LA length, causing an error in the calculated LA strain value (Fig. 5). As indicated in Fig. 5, if there was a slight gap in the phase, Rres would have a different value. In this study, R-wave peak coincided with Vmin in 25 (32%) subjects. Vmin was observed before R-wave peak in 28 (36%)

Figure 6. Differences in the calculation of left atrial strains using R- and P-wave triggers. Using an R-wave trigger, the initial length for strain analyses is set to the minimum left atrial (LA) circumferential length. Rcon and Rpump are calculated as presented in the left panel. Using a P-wave trigger, the initial length becomes Lp, which is greater than Lmin. Therefore, LA strains in any phase become smaller than those calculated using an R-trigger, as presented in the right panel. Abbreviations are same as the Fig. 5.

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subjects and after R-wave peak in 25 (32%) subjects. The timing gap between R-wave peak and Vmin was 10  122 msec. Theoretically, the initial length for calculating strain should be determined when the LA wall stress is at a minimum;8 therefore, it should be defined at P-wave onset and not at R-wave peak. The initial LA circumferential length used to calculate strain values differed between R- and Pwave triggers. When the length used in strain analysis is defined as L, the definitions of LA strains with an R-wave trigger are as follows: Rres = [maximum L (Lmax)  minimum L (Lmin)]/Lmin; Rpump = [L at P-wave onset (Lp)  Lmin]/Lmin; and Rcon = (Lmax  Lp)/ Lmin.11,12 On the other hand, the definitions of LA strains with a P-wave trigger are as follows: Pres = (Lmax  Lmin)/Lp; Ppump = (Lp  Lmin)/Lp; and Pcon = (Lmax  Lp)/Lp.13–15 Lp is always greater than Lmin, and LA strains calculated using an R-wave trigger are mathematically greater than those calculated using a P-wave trigger (Fig. 6). Clinical Implications: As the LA strain analysis becomes more widespread, it is necessary to standardize a method for measuring LA strain. Presently, no standard method has been established for LA strain analysis.6,9 One of the issues is which views will be designated as a global LA strain. In previous reports, the global LA stain was analyzed using two- and four-chamber views or using two-, three-, and four-chamber views.9 The other issue is the starting point for strain analysis.6,9 From our results, the global LA strain analyzed with P-wave trigger using single four-chamber view could provide similar information obtained by 3D echocardiography in terms of various LA function, and could become a simple standard method of LA strain. The standardized LA strain analysis may become a clinically useful tool for assessing LA function which can be utilized in multicenter clinical trials evaluating the effects of medication or invasive interventions for cardiac diseases. Limitations: Although our sample was not large, it was larger than that used in similar studies comparing strain analysis and changes in LA volume.11,13 Furthermore, our results were consistent with those of previous studies. In post hoc analysis, LA functional indices determined using strain values and LA volume clearly differed; thus, with an effective size of 0.5 and a critical P-value of 0.05, the statistical power of this study was 0.999. Therefore, the sample size in our study was clearly adequate. 8

Although we recommended the P-wave trigger method for measuring LA strain, this method has a few limitations. It is impossible to obtain LA strain in atrial fibrillation. In addition, current analytical software for calculating strain is customized for the R-wave trigger method, and additional manipulations and time are needed for calculating strain by the P-wave trigger method. Future improvement of the software would overcome this limitation. Recently, the vendor’s differences for strain analysis have become a huge problem.6 The detailed algorithms for speckle tracking used in the systems from vendors are proprietary, and invisible to users.26 If LA strain is to be used in a longitudinal follow-up or a cross-sectional study, the same ultrasound system should be used. Conclusions: When LA strain is used for assessing LA function, the method for LA strain measurement must be selected with care. LA strain in any phase should be analyzed from P-wave onset rather than from R-wave peak, which is the offset used in analytical software developed to determine LV strain. References 1. Tsang TS, Barnes ME, Gersh BJ, et al: Left atrial volume as a morphophysiologic expression of left ventricular diastolic dysfunction and relation to cardiovascular risk burden. Am J Cardiol 2002;90:1284–1289. 2. Tsang TS, Abhayaratna WP, Barnes ME, et al: Prediction of cardiovascular outcomes with left atrial size: Is volume superior to area or diameter? J Am Coll Cardiol 2006;47:1018–1023. 3. Takemoto Y, Barnes ME, Seward JB, et al: Usefulness of left atrial volume in predicting first congestive heart failure in patients > or = 65 years of age with well-preserved left ventricular systolic function. Am J Cardiol 2005;96:832–836. 4. Blume GG, McLeod CJ, Barnes ME, et al: Left atrial function: Physiology, assessment, and clinical implications. Eur J Echocardiogr 2011;12:421–430. 5. Bang CN, Dalsgaard M, Greve AM, et al: Left atrial size and function as predictors of new-onset of atrial fibrillation in patients with asymptomatic aortic stenosis: The simvastatin and ezetimibe in aortic stenosis study. Int J Cardiol 2013;168:2322–2327. 6. Mor-Avi V, Lang RM, Badano LP, et al: 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. J Am Soc Echocardiogr 2011;24:277–313. 7. Cameli M, Lisi M, Righini FM, et al: Novel echocardiographic techniques to assess left atrial size, anatomy and function. Cardiovasc Ultrasound 2012;10:4. 8. Todaro MC, Choudhuri I, Belohlavek M, et al: New echocardiographic techniques for evaluation of left atrial mechanics. Eur Heart J Cardiovasc Imaging 2012;13:973– 984. 9. Vieira MJ, Teixeira R, Goncalves L, et al: Left atrial mechanics: Echocardiographic assessment and clinical implications. J Am Soc Echocardiogr 2014;27:463–478. 10. Wakami K, Ohte N, Asada K, et al: Correlation between left ventricular end-diastolic pressure and peak left atrial

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wall strain during left ventricular systole. J Am Soc Echocardiogr 2009;22:847–851. Kim DG, Lee KJ, Lee S, et al: Feasibility of twodimensional global longitudinal strain and strain rate imaging for the assessment of left atrial function: A study in subjects with a low probability of cardiovascular disease and normal exercise capacity. Echocardiography 2009;26: 1179–1187. Matsumoto K, Tanaka H, Imanishi J, et al: Preliminary observations of prognostic value of left atrial functional reserve during dobutamine infusion in patients with dilated cardiomyopathy. J Am Soc Echocardiogr 2014;27: 430–439. Saraiva RM, Demirkol S, Buakhamsri A, et al: Left atrial strain measured by two-dimensional speckle tracking represents a new tool to evaluate left atrial function. J Am Soc Echocardiogr 2010;23:172–180. Motoki H, Alraies MC, Dahiya A, et al: Changes in left atrial mechanics following pericardiectomy for pericardial constriction. J Am Soc Echocardiogr 2013;26:640–648. To AC, Flamm SD, Marwick TH, et al: Clinical utility of multimodality LA imaging: Assessment of size, function, and structure. JACC Cardiovasc Imaging 2011;4:788–798. Vieira-Filho NG, Mancuso FJ, Oliveira WA, et al: Simplified single plane echocardiography is comparable to conventional biplane two-dimensional echocardiography in the evaluation of left atrial volume: A study validated by three-dimensional echocardiography in 143 individuals. Echocardiography 2014;31:265–272. Mor-Avi V, Yodwut C, Jenkins C, et al: Real-time 3D echocardiographic quantification of left atrial volume: Multicenter study for validation with CMR. JACC Cardiovasc Imaging 2012;5:769–777. Buechel RR, Sommer G, Leibundgut G, et al: Assessment of left atrial functional parameters using a novel dedicated analysis tool for real-time three-dimensional echocardiography: Validation in comparison to magnetic resonance imaging. Int J Cardiovasc Imaging 2013;29: 601–608.

19. Tops LF, Schalij MJ, Bax JJ: Imaging and atrial fibrillation: The role of multimodality imaging in patient evaluation and management of atrial fibrillation. Eur Heart J 2010;31:542–551. 20. Rohner A, Brinkert M, Kawel N, et al: Functional assessment of the left atrium by real-time threedimensional echocardiography using a novel dedicated analysis tool: Initial validation studies in comparison with computed tomography. Eur J Echocardiogr 2011;12: 497–505. 21. Miyasaka Y, Tsujimoto S, Maeba H, et al: Left atrial volume by real-time three-dimensional echocardiography: Validation by 64-slice multidetector computed tomography. J Am Soc Echocardiogr 2011;24:680–686. 22. Lang RM, Bierig M, Devereux RB, et al: Recommendations for chamber quantification: A report from the American Society of Echocardiography’s Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction with the European Association of Echocardiography, a branch of the European Society of Cardiology. J Am Soc Echocardiogr 2005;18:1440–1463. 23. Nagueh SF, Appleton CP, Gillebert TC, et al: Recommendations for the evaluation of left ventricular diastolic function by echocardiography. J Am Soc Echocardiogr 2009;22:107–133. 24. Delgado V, Vidal B, Sitges M, et al: Fate of left atrial function as determined by real-time three-dimensional echocardiography study after radiofrequency catheter ablation for the treatment of atrial fibrillation. Am J Cardiol 2008;101:1285–1290. 25. Faul F, Erdfelder E, Lang AG, et al: G*Power 3: A flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods 2007;39:175–191. 26. Takigiku K, Takeuchi M, Izumi C, et al: Normal range of left ventricular 2-dimensional strain: Japanese Ultrasound Speckle Tracking of the Left Ventricle (JUSTICE) study. Circ J 2012;76:2623–2632.

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Optimal Analysis of Left Atrial Strain by Speckle Tracking Echocardiography: P-wave versus R-wave Trigger.

Left atrial (LA) strain analysis using speckle tracking echocardiography is useful for assessing LA function. However, there is no established procedu...
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