Reference Normal Absolute and Indexed Values From ECG- Gated MDCT: Left Atrial Volume, Function, and Diameter

Transcription

1 Cardiopulmonary Imaging Original Research Stojanovska et al. ECG-Gated MDCT Cardiopulmonary Imaging Original Research Jadranka Stojanovska Paul Cronin Smita Patel Barry H. Gross Hakan Oral Komal Chughtai Ella A. Kazerooni Stojanovska J, Cronin P, Patel S, et al. Keywords: atrial diameter, atrial fibrillation, atrial function, atrial volume, left atrium, MDCT DOI:./AJR..9 Received October, ; accepted after revision January 8,. Department of Radiology, Division of Cardiothoracic Radiology, University of Michigan Health System, E Medical Center Dr, UH B- Taubman/Box, Ann Arbor, MI 89-. Address correspondence to J. Stojanovska (jstoanov@umich.edu). University of Michigan Health System, Department of Internal Medicine, Cardiovascular Medicine, Cardiovascular Center, Ann Arbor, MI. AJR ; 97: X//97 6 American Roentgen Ray Society Reference Normal Absolute and Indexed Values From ECG- Gated MDCT: Left Atrial Volume, Function, and Diameter OBJECTIVE. The purpose of this study was to retrospectively determine CT-based normal reference values of left atrial volume, function, and diameter normalized by age, sex, and body surface area. MATERIALS AND METHODS. The study group consisted of 7 subjects with normal findings at ECG-gated coronary CT angiography performed with retrospective gating. Analysis of left atrial volume (end-diastolic, end-systolic, and stroke volume) and function (ejection fraction) was performed with the Simpson method. Left atrial diameter was measured in the anteroposterior dimension. General linear model analysis was performed to model the data and assess statistical significance by age group after adjustment for sex and body surface area. RESULTS. The reference range for left atrial volume, function, and diameter was normalized (indexed) to age, sex, and body surface area in healthy subjects. A statistically significant difference was noted between left atrial volume and age without adjustment for sex and body surface area, but no statistically significant difference was found after adjustment for these variables. Sex and body surface area had a significant influence on left atrial volume, function, and diameter. CONCLUSION. Left atrial volume, function, and diameter normalized to age, sex, and body surface area can be reported from CTA datasets and may provide information important for patient care. N ormal left atrial (LA) contraction plays an important role in maintaining left ventricular (LV) enddiastolic pressure and preserving LA pressure and normal blood flow through the cardiac chambers. Abnormalities in LV volume can cause changes in LA volume, function, and diameter. Knowledge of these changes relative to normal reference values is extremely important in the care of patients with atrial fibrillation, and the changes may serve as biomarkers of cardiac and cerebrovascular events [ ]. LA diameter and volume can be assessed with noninvasive imaging techniques, such as echocardiography, ECG-gated MDCT, and cardiac MRI, or with invasive imaging techniques, particularly atrial catheterization. In clinical practice, D echocardiography is the most frequently used method of assessing LA volume, function, and diameter. The principle of D echocardiography is based on geometric assumptions of shape, and true LA volume can be underestimated or overestimated compared with the MDCT and MRI findings in patients with LA remodeling []. Cardiac MRI is considered the reference standard for serial repeated measurements in the evaluation of cardiac anatomy, volume, and function []. Contrast-enhanced ECG-gated CT angiography (CTA) is an increasingly used imaging tool in the care of patients with known or suspected cardiac disease. When the technique is performed with retrospective ECG gating, images are acquired in multiple phases throughout the cardiac cycle, allowing assessment of cardiac chamber volumes and diameters throughout the cycle with no additional scanning time, radiation exposure, or IV contrast administration [6]. When CTA is performed with prospective ECG triggering, LA volume and diameter can be measured at the phases of the cardiac cycle specified at the time of acquisition, typically mid to late diastole for CTA. Mahabadi et al. [7] described excellent reproducibility of LA volume measurement on AJR:97, September 6

2 Stojanovska et al. ECG-gated CTA images [7]. Given that such measurements can vary by age and sex, it is important to have normalized values of LA volume and function for interpretation and use of the information for patient care. Studies have shown that reference values from functional analysis of the cardiac chambers differ significantly, even when different MRI sequences are used [8]. Modality-specific reference values for LA function and LA diameter therefore are needed. The purpose of this study was to determine MDCT-based normal reference values (absolute and indexed) of LA volume, function, and diameter normalized by age, sex, and body surface area (BSA) in healthy subjects who underwent ECG-gated contrast-enhanced 6-MDCT for coronary artery evaluation and were found to have normal coronary arteries and no evidence of structural heart disease. Materials and Methods Study Design A retrospective cohort study of ECG-gated MDCT scans was performed at our institution to establish normal reference values of LA volume, function, and diameter. Study Sample The medical charts and coronary CTA reports of 6 patients evaluated in the emergency department from 6 to 9 because of atypical chest pain were retrospectively reviewed. Seventy-four subjects (6 women, 8 men) who fulfilled the inclusion criteria of being healthy without evidence of coronary artery disease (normal ECG, normal retrospectively gated coronary CTA findings) and without evidence of coronary artery disease equivalents of hypertension, hypercholesterolemia, and heart disease (normal history and physical findings, normal ECG, normal echocardiogram [available for 7 subjects]) formed the study sample. The subjects had low pretest probability of coronary artery disease according to the Framingham criteria [9] and were discharged from the emergency department with a diagnosis of chest pain of noncardiac cause (i.e., musculoskeletal or gastrointestinal origin or panic attack). A chart review was performed for all subjects through 6 months after coronary CTA to exclude those with any evidence of cardiac disease in the interval. Subjects with proven chest pain of cardiac origin, presence of coronary artery risk factors, kidney disease, and allergy to iodine contrast material were excluded. Height, weight, blood pressure, and heart rate were recorded for all subjects, and BSA was calculated according to the Mosteller formula []. Four age groups by decade were established: 9 years, 9 years, 9 years, 6 7 years. The study was approved by the institutional review board with a waiver of informed consent. ECG-Gated Cardiac CT Protocol All subjects underwent coronary CTA examinations with retrospective ECG gating on a 6-MDCT scanner (VCT, GE Healthcare). Anteroposterior and lateral topograms were followed by a prospectively ECG-triggered unenhanced calcium scoring acquisition. A timing bolus of ml of iodixanol (Visipaque, GE Healthcare) nonionic IV contrast medium was administered at a rate of ml/s and followed by a ml saline bolus at ml/s to determine peak enhancement within the aortic root. The coronary CTA acquisition was performed with a scan delay of peak plus 6 seconds with the following parameters: gantry rotation time,. second; slice thickness,.6 mm; interval,.6 mm; / kvp; ECG-modulated tube current (minimum, ma; maximum, 7 ma); FOV, cm. We used ECG modulation for all patients (% peak tube current in mid diastole, up to 8% reduction during systole) to reduce radiation exposure. The images were acquired with the patient supine with arms elevated. Iodixanol (8 ml) was administered IV with a triphasic bolus power injector (Stellant Medrad) through an antecubital vein and followed by ml of saline solution at ml/s. Image Postprocessing The images were postprocessed at a workstation (Advantage Windows version., GE Healthcare). LA volumetric and functional analysis was performed by a CT radiology technologist with advanced training in D image processing and more than years of experience and by a single fellowship-trained cardiothoracic radiologist with years of experience. Both readers were blinded to all patient information. Left Atrial Function and Volume Semiautomated analysis (CardIQ Express and Function Software, GE Healthcare) was performed. Data from all cardiac phases were loaded into the express software. The cardiac reformat tool was used to obtain LA reformats after adjustment for the short and long planes, so that the long axis extended from the center of the mitral valve through the cardiac apex and the short axis was parallel to the mitral valve plane. Batch lines were perpendicular to the ostia of the pulmonary veins (Fig. ). A -mm slice thickness with a -mm space between the lines was used to obtain LA reformats in a sagittal oblique view. Reformats were loaded into the function software. This software automatically calculated LA function and volume by a modified Simpson method after manual tracing of the endocardial borders of approximately successive slices at ventricular end-systole (Fig. ) and end-diastole (Fig. ). These borders were previously determined by observation of cine loops of the two-chamber and short-axis views by both the Fig. 8-year-old man with normal heart findings. Long-axis coronary CT angiogram shows four chambers and batch lines perpendicular to ostia of pulmonary veins. A B Fig. 8-year-old man with normal heart findings. A, Oblique sagittal coronary CT angiogram shows left atrium (LA) at maximum volume. LVOT = left ventricular outflow tract. B, Long-axis coronary CT angiogram in two-chamber view shows left atrial (LA) cavity volume is maximum at end-systole of left ventricle (LV). 6 AJR:97, September

3 ECG-Gated MDCT technician and the radiologist. The ostia of the pulmonary veins and LA appendage were excluded from analysis. Maximal LA volume was defined at LV end-systole just before mitral valve opening, when the LA cavity was largest and the LV cavity was smallest. The minimal LA volume was defined at LV end-diastole when the LA cavity was smallest and the LV cavity largest. LA volume and function analysis took approximately minutes with the software. The following parameters were evaluated: LA maximal volume or LA enddiastolic volume (EDV), LA minimal volume or LA end-systolic volume (ESV), LA stroke volume (SV), and LA ejection fraction (EF). A Fig. 8-year-old man with normal heart findings. A, Oblique sagittal coronary CT angiogram shows left atrium (LA) at minimum volume. LV = left ventricle. B, Long-axis coronary CT angiogram in two-chamber view shows left atrial (LA) volume is minimum at enddiastole of left ventricle (LV). TABLE : Baseline Characteristics of Healthy Subjects Left Atrial Diameter An axial oblique reformatted image was obtained at the level of the aortic valve parallel to the LV outflow tract to allow measurement of LA diameter. LA diameter was measured in an anterior to posterior direction parallel to the LV outflow tract in LV end-systole when the LA cavity was the largest (Fig. ). Definitions and Measurements LA EDV was defined as LA maximal volume when the LA cavity was largest, LA ESV as LA minimal volume when the LA cavity was smallest, LA SV as the difference between EDV and ESV B Fig. 8-year-old man with normal heart findings. Long-axis coronary CT angiogram in three-chamber view shows left atrium (LA) with maximum volume, left ventricle (LV) in end-systole, and LV outflow tract (LVOT). Anteroposterior horizontal line denotes LA diameter. (SV = EDV ESV), LA EF as the fraction of EDV ejected with each heartbeat (SV / EDV), indexed LA EDV as LA maximal volume indexed to BSA, indexed LA ESV as LA minimal volume indexed to BSA, and indexed LA SV as the indexed difference between EDV and ESV indexed by BSA. Reproducibility To test for interrater variability of the LA measurements, data on 7 randomly gathered subjects were independently analyzed by a second reader year after the first reading. The second reader used the same criteria as the other two readers and was blinded to patient information and previous Age Group (y) Characteristic Women No Weight (lb) a 9 ± 9 (87 ± ) 6 ± (7 ± ) 6 ± (7 ± 9) ± (68 ± ) Height (in) b 6 ± (6 ± ) 6 ± (6 ± ) 6 ± (6 ± ) 6 ± (6 ± ) Body mass index c ± 6 ± 7 7 ± 9 ± 9 Body surface area (m ) ±..8 ±..8 ±..7 ±. Systolic blood pressure (mm Hg) ± 8 ± 6 ± 9 ± 9 Diastolic blood pressure (mm Hg) 7 ± 7 77 ± 77 ± 8 6 ± 8 Men No. 8 Weight (lb) a 98 ± 8 (9 ± ) 9 ± (86 ± ) ± 8 (9 ± ) 99 ± (9 ± ) Height (in) b 7 ± (8 ± ) 69 ± (7 ± ) 7 ± (8 ± 8) 7 ± (8 ± ) Body mass index c 8 ± ± ± ± Body surface area (m ) ±. ±.. ±.. ±. Systolic blood pressure (mm Hg) ± 7 ± ± ± Diastolic blood pressure (mm Hg) 7 ± 7 77 ± 8 7 ± 76 ± 8 Note Values are mean ± SD. Values in parentheses are kilograms. Values in parentheses are centimeters. c Weight in kilograms divided by the square of height in meters. AJR:97, September 6

4 Stojanovska et al. calculations, which were masked. The second reader was a fellowship-trained cardiothoracic radiologist with years of experience. Statistical Analysis All continuous variables had a normal distribution and were presented as mean ± SD. Normality of the data was confirmed with the Kolmogorov- Smirnov test. General linear model analysis was performed to model the data, construct the reference range as mean and 9% CI, and assess statistical significance between the age groups after adjustment for sex, BSA, and age as a continuous variable. Pearson correlation coefficient of the means was used to quantify relations between the two raters. Because Pearson correlation coefficient is not an assessment of variability, that is, linear error between readers, the method comparison test or difference of means test described by Bland and Altman [] was used to assess or confirm interrater agreement. Statistical significance for difference of the means for the two raters was assessed by correlation procedure. The p value obtained is the Pearson correlation coefficient and is the tool used to assess equality of precisions of two clinicians according to the Bland-Altman test. A value of p <. was considered statistically significant. All computations were performed with SAS/STAT software (version 9., SAS Institute). Results Baseline Characteristics The subjects were 7 patients (8 men, 6 women; age range, 7 years; mean, 9 years) stratified into four age groups by decade. Table summarizes the baseline characteristics of the subjects stratified by age group and sex. Table shows reference normal absolute values of LA function, volume, and diameter and values indexed to BSA and stratified by age group and sex. Table shows reference normal absolute values and values indexed to BSA for all ages and stratified by sex. Influence of Sex on Left Atrial Function, Volume, and Diameter The LA ESV (p =.), indexed ESV (p =.), and EF (p =.) of men differed significantly from those of women. No statistically significant difference between sexes was found for LA EDV, SV, or diameter. The general linear model showed significant independent influence of sex on absolute and indexed LA ESV and EF after adjustment for age and BSA. Influence of Age on Left Atrial Function, Volume, and Diameter Age as a continuous variable was found to have a significant independent effect on ESV (p =.), indexed ESV (p =.), and EF (p =.). When age groups were divided for regression analysis, a statistically significant difference of ml for EDV was found between groups and (p =.) and a statistically significant difference of ml was TABLE : Absolute and Indexed Left Atrial Function, Volume, and Diameter by Age Group Age Group (y) Measurement Women Absolute value EDV (ml) 6 ( 7) 68 (6 8) 8 (7 96) 8 (7 9) ESV (ml) ( ) ( 7) 9 ( 6) ( 9) SV (ml) 7 (9 ) 8 ( ) (7 ) ( 6) EF (%) 6 (6 6) 6 ( 6) ( ) ( 8) Diameter (mm) ( 8) 6 ( ) (8 ) (6 ) Value indexed to BSA EDV/BSA (ml/m ) (6 6) 7 ( ) ( ) 6 ( ) ESV/BSA (ml/m ) ( ) 6 ( ) (8 ) (7 ) SV/BSA (ml/m ) 9 ( ) (8 ) ( 7) ( 6) Diameter (mm) 8 (7 9) 8 (8 8) 9 (6 ) 9 (6 ) Men Absolute value EDV (ml) 79 ( 8) 8 (6 ) 9 (76 ) 9 (7 ) ESV (ml) (8 ) ( 7) ( 6) 8 ( 6) SV (ml) 7 ( ) ( 9) 9 ( 9) ( ) EF (%) 7 ( ) 7 ( ) ( ) 8 ( 6) Diameter (mm) ( 7) (7 ) (7 ) 6 (6 6) Value indexed to BSA EDV/BSA (ml/m ) 8 ( ) ( ) (7 8) ( ) ESV/BSA (ml/m ) (8 ) (6 8) ( 7) (7 9) SV/BSA (ml/m ) 8 ( ) 9 ( ) 8 ( ) (6 6) Diameter (mm) 6 ( 9) 7 ( ) 7 ( ) 7 ( ) Note Values are mean with 9% CI in parentheses. EDV = end-diastolic volume, ESV = end-systolic volume, SV = stroke volume, EF = ejection fraction, BSA = body surface area. 6 AJR:97, September

5 ECG-Gated MDCT TABLE : Left Atrial Volume, Function, and Diameter for All Ages Measurement All Subjects (n = 7) Women (n = 6) Men (n = 8) Absolute value EDV (ml) 8 ± (76 8) 7 ± 8 (68 8) 86 ± (79 9) ESV (ml) ± (7 ) ± ( 8) 6 ± ( ) SV (ml) ± (8 ) ± 9 (7 ) ± (6 ) EF (%) ± 9 (8 ) ± 8 ( 7) 6 ± 8 ( 8) Diameter (mm) ± ( 6) ± ( 6) ± ( 6) Indexed value EDV/BSA (ml/m ) ± 9 (9 ) ± 9 (7 ) ± (8 ) ESV/BSA (ml/m ) ± 6 (9 ) 8 ± 6 (6 ) ± 6 ( ) SV/BSA (ml/m ) ± (9 ) ± ( ) 9 ± 6 (7 ) Diameter/BSA (mm/m ) 8 ± (7 9) 8 ± (7 9) 7 ± (6 8) Note Values are mean ± SD with 9% CI in parentheses. EDV = end-diastolic volume, ESV = end-systolic volume, SV = stroke volume, EF = ejection fraction, BSA = body surface area found between groups and (p =.), with an expected mean EDV of 7 ml. For ESV, a statistically significant difference of ml was found between groups and (p =.), and a statistically significant difference of 9 ml was found between groups and (p =.), with an expected mean ESV of ml. After adjustment for other covariates, such as sex and BSA, no significant differences were found between age groups A with respect to EDV and ESV; a significant difference of mm was found for LA diameter between groups and (p =.) with an expected mean LA diameter of mm. Significant differences were found for indexed EDV between groups and (p =.) and groups and (p =.8), for indexed ESV between groups and (p =.) and groups and (p =.), and for indexed SV between groups and (p =.). However after adjustment for sex, heart rate, and body mass index, no significant differences were found between the age groups with respect to indexed EDV, indexed ESV, or indexed SV. Influence of Body Surface Area on Left Atrial Function, Volume, and Diameter LA diameter (p <.), SV (p =.), ESV (p =.), and EDV (p <.) were found to differ significantly in relation to BSA. A general linear model showed significant independent influence of BSA on LA EDV, ESV, SV, and diameter B Fig. Bland-Altman plots. A, Mean difference between two readers for left atrial end-diastolic volume. B, Mean difference between two readers for left atrial ejection fraction. C, Mean difference between two readers for left atrial end-systolic volume. D, Mean difference between two readers for left atrial stroke volume. C D AJR:97, September 6

6 Stojanovska et al. Reproducibility The Pearson correlation coefficient indicated a statistically significant linear relation of mean LA volume and function between the first and second readers. This finding was confirmed with Bland-Altman analysis, which is used to test interrater variability (Figs. A D) and calculate mean differences between two readers (Table ). Discussion Our results show that all parameters of LA volume and diameter were significantly influenced by BSA and that absolute LA ESV, indexed LA ESV, and EF were significantly influenced by sex and age as continuous variables. With division into age groups, some of the values of LA volume and diameter were influenced by age group. After adjustment for other covariates (sex and BSA), no significant differences were found between the age groups and LA volumes. The only significant difference after adjustment for other variables was LA diameter. To our knowledge, there has been no report of a previous study in which reference normal LA volume, function, and diameter values were normalized to age, sex, and BSA for CT. We believe our data may have substantial influence on current and future research regarding the role of CT parameters in clinical practice. The American Society of Echocardiography in conjunction with European Association of Echocardiography recommend the use of either the ellipsoid model (biplane area-length method) or the Simpson method for evaluation of LA volume and function []. The Simpson method is preferred because it does not rely on geometric assumptions and excludes the confluence of the pulmonary veins and LA appendage from analysis []. Absolute and indexed values of mean LA function, volume, and diameter for all ages correlated with previously published echocardiographic and cardiac MRI data [ ] when the exact method of analysis was applied. Our volumetric values were slightly lower compared with those published by Hudsmith et al. [], who used cardiac MRI. Those authors included the LA appendage in the analysis, which probably accounts for the difference. Our LA diameter values are concordant with those previously published [6, 7]. Influence of Age on Left Atrial Volume, Function, and Diameter We found that age did not influence LA volume and function after adjustment for sex and BSA. If LA volume is not adjusted for BSA and sex, the reference range for the specific age group should be used, given the significant difference in LA EDV and ESV between age groups. Our results correlate with those previously published [, 8, 9]. Age influenced LA diameter even after adjustment for sex and BSA [6]. However, the magnitude of change in LA diameter may not be clinically relevant [, 8] because aging is associated with LA dilation and is not associated with impairment of LA volume and function because of preserved LA reservoir and pump function. Effect of Sex on Left Atrial Volume, Function, and Diameter After adjustment for age and BSA, sex significantly influenced LA ESV and EF but not EDV and diameter, indicating the need to use a sex-specific normal reference range. LA EF is higher in women than in men. Our results agreed with those of previous studies [, 6, 8]. Effect of Body Surface Area on Left Atrial Volume, Function, and Diameter LA volume and diameter are significantly influenced by BSA. This finding indicates the need and appropriateness of indexing LA volume and diameter to BSA when reporting these parameters. EF was not significantly influenced by BSA. To our knowledge, our study is the first to evaluate age-, sex-, and BSA-specific reference ranges of LA volume, function, and diameter for MDCT for use of the same method of LA analysis, excluding the LA appendage during analysis. TABLE : Interrater Variability of Left Atrial Volume, Function, and Diameter Reproducibility We found excellent reproducibility of LA volume and function between readers. We used not only the Pearson correlation coefficient which has flaws in evaluation of interrater reproducibility because it only assesses correlation between the means of the two raters but also a Bland-Altman approach to assess interrater variability and calculate the difference of means between the two raters. Our data correlate well with previously published data acquired with the same approach [7,, ]. Importance and Potential Clinical Implications The increasing availability and use of contrast-enhanced retrospectively ECG-gated CT in the care of cardiac patients allows additional volumetric and functional analysis of all cardiac chambers. Impairment of LA function is extremely important in patients with atrial fibrillation because of increased risk of stroke and other embolic events due to atrial thrombi. MDCT is an established imaging method for evaluation of the anatomy of the pulmonary veins in patients with atrial fibrillation who are to undergo radiofrequency ablation therapy. Assessment of LA volume, function, and diameter is important before radiofrequency ablation to adequately evaluate patients eligible for the procedure and after ablation to observe patients for postprocedural complications and thrombus formation in the left atrium []. Therefore, establishing reference normal ranges of LA volume, function, and diameter with MDCT is very important to risk stratify not only patients with atrial fibrillation but also patients with other cardiac and cerebrovascular diseases. Limitations The retrospective approach of identifying healthy subjects to obtain reference ranges for LA volume, function, and diameter with MDCT resulted in a small sample size for each stratum. Stolzmann et al. [7] emphasized ethical concern about the radiation dose and contrast medium risks of contrast- Pearson Correlation of Means of Two Raters (n = 7) Method Comparison Test Using Bland-Altman Procedure (n = 7) Measurement Mean (Rater / Rater SD (Rater / Rater ) r p Mean Difference of Two Raters SD of Mean Difference of Two Raters r p End-diastolic volume (ml) 8/79 /.9 < End-systolic volume (ml) /9 /.9 < Stroke volume (ml) / /.87 < Ejection fraction (%) / 8/8.88 < AJR:97, September

7 ECG-Gated MDCT enhanced MDCT as a reason for the lack of prospectively established CT-based normal range of reference values for the LA. In our study, we faced a similar dilemma and therefore used cardiac CT data on patients who had undergone the test for clinically indicated reasons. Although all subjects underwent coronary CTA as part of an evaluation of atypical chest pain, we rigorously excluded all subjects with cardiac disease and cardiac risk factors. Mahabadi et al. [7] used a similar cohort but included subjects with coronary artery risk factors and therefore were not able to provide normal reference ranges for LA volume and function. Although the sample size per stratum was limited, our results on the influence of age, sex, and BSA on LA function, volume, and diameter are concordant with those in the study by Pritchett et al. [], which had a sample size of subjects. Other previous studies had similar sample sizes for calculating normal reference ranges for right ventricular and LV volume and diameter with cardiac MRI [, ]. We did not perform echocardiography or cardiac MRI on the same subjects to compare the results with our LA volumetric and functional values, but our results correlate with previously published LA volumetric and functional values for MRI and echocardiography [, ] obtained with a similar method of analysis. The use of anteroposterior LA diameter may be a limitation of this study. Other investigators [, ] have proposed that enlargement of the LA is not symmetric and that the anteroposterior LA linear dimension measurement, although a simple and convenient method, may not be the most accurate and should not be used for risk stratification. Unlike LA diameter measurement, LA volume measurement is a more accurate and reproducible estimate of LA enlargement and may serve as a predictor of cardiovascular outcome []. Conclusion We obtained normal 6-MDCT reference values of LA volume, function, and diameter normalized by age, sex, and BSA. We also found significant differences in LA volume, function, and diameter with respect to sex and BSA. We therefore emphasize the importance of using values indexed to BSA and sex. However, if absolute values are used, reference ranges for specific age decades should be reported. Given the importance of LA volume and function in risk stratifying patients with cardiac and cardiovascular diseases, LA volume and function should be measured and the results reported., especially because of the availability of automated functional analysis tools that do not significantly increase postprocessing time but add important information that can be used in clinical care. References. Leung DY, Boyd A, Ng AA, Chi C, Thomas L. Echocardiographic evaluation of left atrial size and function: current understanding, pathophysiologic correlates, and prognostic implications. Am Heart J 8; 6:6 6. Rossi A, Vassanelli C. Left atrium: no longer neglected. Ital Heart J ; 6: Pritchett AM, Jacobsen SJ, Mahoney DW, Rodeheffer RJ, Bailey KR, Redfield MM. Left atrial volume as an index of left atrial size: a population-based study. J Am Coll Cardiol ; : 6. Christiaens L, Lequeux B, Adilouze P, et al. A new method for measurement of left atrial volumes using 6-slice spiral computed tomography: comparison with two-dimensional echocardiographic techniques. Int J Cardiol 9; :7. Grothues F, Smith GC, Moon JC, et al. Comparison of interstudy reproducibility of cardiovascular magnetic resonance with two-dimensional echocardiography in normal subjects and in patients with heart failure or left ventricular hypertrophy. Am J Cardiol ; 9:9 6. Martinez MW. Onward and upward! From ventricle to atria, volumetric measurements for chamber quantification. J Cardiovasc Comput Tomogr 9; : Mahabadi AA, Samy B, Seneviratne SK, et al. Quantitative assessment of left atrial volume by electrocardiographic-gated contrast-enhanced multidetector computed tomography. J Cardiovasc Comput Tomogr 9; : Alfakih K, Thiele H, Plein S, Bainbridge GJ, Ridgway JP, Sivananthan MU. Comparison of right ventricular volume measurement between segmented k-space gradient-echo and steady-state free precession magnetic resonance imaging. J Magn Reson Imaging ; 6: 8 9. Wilson PW, D Agostino RB, Levy D, Belanger AM, Silbershatz H, Kannel WB. Prediction of coronary heart disease using risk factor categories. Circulation 998; 97: Mosteller RD. Simplified calculation of body surface area. N Engl J Med 987; 7:98. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 986; :7. Lang RM, Bierig M, Devereux RB, et al. Recommendations for chamber quantifications: a report from the American Society of Echocardiography s Guidelines and Standards Committee and the Chamber Quantifications Writing Group, Developed in Conjunction with the European Association of Echocardiography, a branch of the European Society of Cardiology. J Am Soc Echocardiogr ; 8: 6. Hudsmith LE, Cheng AS, Tyler DJ, et al. Assessment of left atrial volumes at. Tesla and Tesla using FLASH and SSFP cine imaging. J Cardiovasc Magn Reson 7; 9: Thomas L, Thomas SP, Hoy M, Boyd A, Schiller NB, Ross DL. Comparison of left atrial volume and function after linear ablation and after cardioversion for chronic atrial fibrillation. Am J Cardiol ; 9:6 7. Ujino K, Barnes ME, Cha SS, et al. Two-dimensional echocardiographic methods for assessment of left atrial volume. Am J Cardiol 6; 98: Sievers B, Kirchberg S, Franken U, et al. Determination of normal gender specific left atrial dimensions by cardiovascular magnetic resonance imaging. J Cardiovasc Magn Reson ; 7: Stolzmann P, Scheffel H, Leschka S, et al. Reference values for quantitative left ventricular and left atrial measurements in cardiac computed tomography. Eur Radiol 8; 8: Abhayaratna WP, Seward JB, Appleton CP, et al. Left atrial size. J Am Coll Cardiol 6; 7: Nikitin NP, Witte KK, Thackray SD, Goodge LJ, Clark AL, Cleland JG. Effect of age and sex on left atrial morphology and function. Eur J Echocardiogr ; :6. Hudsmith LE, Petersen SE, Francis JM, Robson MD, Neubauer S. Normal human left and right ventricular and left atrial dimensions using steady state free precession magnetic resonance imaging. J Cardiovasc Magn Reson ; 7: Stojanovska J, Cronin P. Computed tomography imaging of left atrium and pulmonary veins for radiofrequency ablation of atrial fibrillation. Semin Roentgenol 8; : 66. Maceira AM, Prasad SK, Khan M, Pennell DJ. Normalized left ventricular systolic and diastolic function by steady state free precession cardiovascular magnetic resonance. J Cardiovasc Magn Reson 6; 8:7 6. Maceira AM, Prasad SK, Khan M, Pennell DJ. Reference right ventricular systolic and diastolic function normalized to age, gender and body surface area from steady-state free precession cardiovascular magnetic resonance. Eur Heart J 6; 7: Tsang TS, Abhayaratna WP, Barnes ME, et al. Prediction of cardiovascular outcomes with left atrial size. J Am Coll Cardiol 6; 7:8 AJR:97, September 67