Quantification of left atrial function by the area-length method overestimates left atrial emptying fraction.

PURPOSE: The biplane area-length method is commonly used in cardiac magnetic resonance (CMR) to assess left atrial (LA) volume (LAV) and function. Associations between left atrial emptying fraction (LAEF) and clinical outcomes have been reported. However, only limited data are available on the calculation of LAEF using the biplane method compared to 3D assessment. This study aimed to compare volumetric and functional LA parameters obtained from the biplane method with 3D assessment in a large, multiethnic cohort. METHOD: 158 participants of MESA (Multi-Ethnic Study of Atherosclerosis) underwent CMR that included standard two- and four-chamber steady-state free precession (SSFP) cine imaging for the biplane method. For 3D-based assessment, short-axis SSFP cine series covering the entire LA were obtained, followed by manual delineation of LA contours to create a time-resolved 3D LAV dataset. Paired t-tests and Bland-Altman plots were used to analyze the data. RESULTS: Standard volumetric assessment showed that LAVmin (bias: -8.35 mL, p < 0.001), LAVmax (bias: -9.38 mL, p < 0.001) and LAVpreA (bias: -10.27 mL, p < 0.001) were significantly smaller using the biplane method compared to 3D assessment. Additionally, the biplane method reported significantly higher LAEFtotal (bias: 7.22 %, p < 0.001), LAEFactive (bias: 6.08 %, p < 0.001), and LAEFpassive (bias: 4.51 %, p < 0.001) with wide limits of agreement. CONCLUSIONS: LA volumes were underestimated using the biplane method compared to 3D assessment, while LAEF parameters were overestimated. These findings demonstrate a lack of precision using the biplane method for LAEF assessment. Our results support the usage of 3D assessment in specific settings when LA volumetric and functional parameters are in focus.

Evaluation of left atrial reservoir function and sphericity index in patients with mitral valve disease: a cardiac magnetic resonance imaging study.

To assess the performance of biplane area-length method in measuring left atrial (LA) volume and sphericity index and to investigate the correlation of LA reservoir function and sphericity index with atrial fibrosis on cardiac magnetic resonance imaging (MRI) in patients with mitral valve disease (MVD). Forty-eight patients with MVD undergoing cardiac MRI scan were enrolled in this retrospective study. LA reservoir function, measured as maximum volume (LAVmax), minimum volume (LAVmin) and ejection fraction (LAEF), and sphericity index were quantified using the biplane area-length method and standard short-axis approach, respectively. Comparisons of LA reservoir function and sphericity index between the two different methods were performed, as well as between positive (n = 17, 35%) and negative atrial wall fibrosis groups (n = 31, 65%). There was no difference in the values of LAVmax index and sphericity index between the two different methods. The biplane area-length method had poor performance in assessing LAVmin index and LAEF compared to standard short-axis approach, with an underestimation of 13.5% for LAVmin index and an overestimation of 27% for LAEF. Patients with positive atrial fibrosis had larger LAVmax index, LAVmin index and sphericity index, and lower LAEF levels in comparison to the negative atrial fibrosis group. The biplane area-length method has good performance in assessing LA sphericity index for patients with MVD, not in LA reservoir function. Patients with positive atrial fibrosis tend to suffer from more adverse LA remodelling.

A geometrical pitfall of Area-Length method; -Is left ventricle volume evaluation of repaired Tetralogy of Fallot by angiocardiography accurate?

Biplane Area-Length (AL) method by left ventriculography (LVG) has been widely adopted as a standard method to estimate left ventricular volume. However, we have experienced difficulties in adopting the value by AL method for the children with Tetralogy of Fallot (TOF) due to the discrepancy among volumetric modalities. This study validated some limitations of AL method, considering the basic principles of its formulation. A single center retrospective cohort study was conducted for 1 year. The confirmed 22 cases with repaired TOF at our hospital were enrolled. The clinical characteristics, some cardiac MRI analyses, and all the cardiac catheterization studies were collected. Angiographic data were compared with historic cohorts of Kawasaki disease without any coronary artery lesions by using AL method. Cardiac MRI analyses of ten TOF patients were additionally available. LVG studies showed that the length of the long axis on anteroposterior view (AP) was not equal to that on lateral view (LT) due to anatomically apical elevation in TOF, followed by a significant difference found in the sagittal lengths of the LV long axis between AP and LT (P = 0.003). Because the difference critically affected the formula depending on biplane AL method, the calculated LVEDV of TOF group appeared overestimated, compared with the control group (TOF vs control group: 119.5% ± 6.3% vs 96.4 ± 3.5% of Normal, P = 0.006). Available cardiac MRI analyses of some patients in TOF group revealed 55% increase of LVEDV by AL method (angiocardiography 116 ± 7.0 vs CMR 75 ± 3.7 ml/m2, P = 0.0025). A pitfall exists when applying biplane AL method to measure LV volume especially for TOF patients, because the long axis on AP view is not always identical to that on LT view.

Prognostic value of selected one-, two- and three-dimensional and Doppler echocardiographic methods to assess severity in dogs with myxomatous mitral valve disease.

INTRODUCTION: Although challenging, predicting outcomes in dogs with myxomatous mitral valve disease (MMVD) is of importance to owners and veterinarians. Our aim was to compare the prognostic value of selected one-, two-, and three-dimensional and Doppler echocardiographic methods to predict cardiac-related and all-cause mortality in MMVD dogs. We hypothesize that three-dimensional methods would better predict prognosis than one- and two-dimensional methods. ANIMALS: One-hundred thirty-eight privately-owned dogs with MMVD. MATERIALS AND METHODS: Cox proportional Hazard analyses and Kaplan-Meier curves were used to investigate the predictive value of 14 variables; left atrial (LA) volume indexed to body weight (BW) measured by real-time three-dimensional echocardiography (RT3DE) and calculated using Simpson's modified method of discs (SMOD) and the area-length method; LA diameter in short-axis and long-axis to aortic in short-axis ratio, effective regurgitant orifice area indexed to body surface area measured in RT3DE en face view and calculated using four-chamber (4Ch) and two-chamber views alone or in combination; percentage increase in left ventricular end-diastolic and systolic internal diameters; fractional shortening; E wave velocity; regurgitant jet area/LA area. RESULTS: All 14 variables were significantly predictive of cardiac-related mortality, and 11 were predictive of all-cause mortality. The prognosis was best predicted by LA volume/BW estimated by SMOD or RT3DE, consistently showing the highest predictive value in all analyses. CONCLUSIONS: Left atrial volume calculated by SMOD showed a similar predictive value compared to RT3DE. Performing SMOD from apical 4Ch images should be considered an alternative to RT3DE for echocardiographic examinations where prognostication of disease outcome is sought.

Left atrial-left ventricular angle, a new measure of left atrial and left ventricular remodeling.

We assessed the left atrial-left ventricular (LA-LV) long axis angulation value as a new measure of LA remodeling, and studied its predictors, its effect on two-dimensional LA volume (2D LAVol) estimation, and optimization techniques for 2D LAVol values. Retrospective electrocardiogram-gated coronary computed tomographic angiograms of 164 consecutive patients were reviewed. The LA-LV angle was measured in reconstructed 3-chamber views, and its predictors were determined. The LAVol measured by the area-length method after image optimization along the LV long axis (AL) and the LA long axis (AC-AL), was compared with that measured by the three-dimensional (3D)-volumetric method. LAVol calculation was modified to minimize differences from the 3D values. LA-LV angles ranged from 0° to 63°. In the univariate analysis, decreasing angulation was significantly associated with increasing LV end-diastolic volume (LVEDV), mitral regurgitation grade, LV and LA anteroposterior dimensions, and decreasing LV ejection fraction (LVEF). On multivariate analysis, increasing LVEDV, MR, and LA anteroposterior dimension inversely correlated with angulation; LVEF was positively correlated. The AL and 3D methods significantly differed only for patients with angles ≤ 29.9°. Conversely, LAVol was overestimated for all angules by AC-AL. Modification of AL LAVol using a regression equation, or by substituting the shortest with the longest and average LA lengths in patients with angles ≤ 29.9° and 30-39.9°, respectively neutralized the difference. The LA-LV angle is a new measure of LA and LV remodeling predicted by LV size and function, MR, and LA-anteroposterior dimension. AL formula modifications based on angulation in LV-optimized views better correlate with the 3D method than LA-view modification.

Atri-U: assisted image analysis in routine cardiovascular magnetic resonance volumetry of the left atrium.

BACKGROUND: Artificial intelligence can assist in cardiac image interpretation. Here, we achieved a substantial reduction in time required to read a cardiovascular magnetic resonance (CMR) study to estimate left atrial volume without compromising accuracy or reliability. Rather than deploying a fully automatic black-box, we propose to incorporate the automated LA volumetry into a human-centric interactive image-analysis process. METHODS AND RESULTS: Atri-U, an automated data analysis pipeline for long-axis cardiac cine images, computes the atrial volume by: (i) detecting the end-systolic frame, (ii) outlining the endocardial borders of the LA, (iii) localizing the mitral annular hinge points and constructing the longitudinal atrial diameters, equivalent to the usual workup done by clinicians. In every step human interaction is possible, such that the results provided by the algorithm can be accepted, corrected, or re-done from scratch. Atri-U was trained and evaluated retrospectively on a sample of 300 patients and then applied to a consecutive clinical sample of 150 patients with various heart conditions. The agreement of the indexed LA volume between Atri-U and two experts was similar to the inter-rater agreement between clinicians (average overestimation of 0.8 mL/m2 with upper and lower limits of agreement of - 7.5 and 5.8 mL/m2, respectively). An expert cardiologist blinded to the origin of the annotations rated the outputs produced by Atri-U as acceptable in 97% of cases for step (i), 94% for step (ii) and 95% for step (iii), which was slightly lower than the acceptance rate of the outputs produced by a human expert radiologist in the same cases (92%, 100% and 100%, respectively). The assistance of Atri-U lead to an expected reduction in reading time of 66%-from 105 to 34 s, in our in-house clinical setting. CONCLUSIONS: Our proposal enables automated calculation of the maximum LA volume approaching human accuracy and precision. The optional user interaction is possible at each processing step. As such, the assisted process sped up the routine CMR workflow by providing accurate, precise, and validated measurement results.

Assessment of left atrial volume in dogs: comparisons of two-dimensional and real-time three-dimensional echocardiography with ECG-gated multidetector computed tomography angiography.

INTRODUCTION: We hypothesized that real-time three-dimensional echocardiography (RT-3DE) was superior to two-dimensional echocardiography for the estimation of left atrial volume (LAV), using electrocardiographic (ECG)-gated multidetector computed tomography angiography (MDCTA) as a volumetric gold standard. The aim was to compare maximum LAV (LAVmax) and minimum LAV (LAVmin) measured by biplane area-length method (ALM), biplane method of disk (MOD) and RT-3DE with 64-slice ECG-gated MDCTA in dogs ANIMALS: The study included twenty dogs, anaesthetized for various diagnostic purposes and without evidence of cardiovascular disease. METHODS: Left atrial volume was estimated by ALM, MOD and RT-3DE following ECG-gated MDCTA. The results were compared with LAV from MDCTA and correlations were performed. The limits of agreement (LoA) between methods were evaluated using Bland-Altman analysis and intraclass correlations. Coefficients of variation were calculated. RESULTS: Area-length method (r = 0.79 and 0.72), MOD (r = 0.81 and 0.70) and RT-3DE (r = 0.94 and 0.82) correlated with MDCTA for LAVmax and LAVmin, respectively (all p < 0.05). Biases for LAVmax (-0.96 mL, 95% LoA: -5.6 to 3.7) and LAVmin (-0.67 mL, 95% LoA: -5.4 - 4.1) were minimal with RT-3DE, reflecting a slight underestimation. Conversely, MOD (LAVmaxbias = 3.19 mL, 95% LoA: -5.7 - 12.1; LAVminbias = 1.96 mL, 95% LoA: -4.6 - 8.5) and ALM (LAVmaxbias = 4.05, 95% LoA: -5.7 - 13.8; LAVminbias = 2.80 mL, 95% LoA: -3.9 - 9.5) suggested LAV overestimation. Intraobserver and interobserver variability were adequate. CONCLUSIONS: Real-time three-dimensional echocardiography is a non-invasive, accurate and feasible method with superior accuracy to two-dimensional methods.

Association of left atrial volume index and all-cause mortality in patients referred for routine cardiovascular magnetic resonance: a multicenter study.

BACKGROUND: Routine cine cardiovascular magnetic resonance (CMR) allows for the measurement of left atrial (LA) volumes. Normal reference values for LA volumes have been published based on a group of European individuals without known cardiovascular disease (CVD) but not on one of similar United States (US) based volunteers. Furthermore, the association between grades of LA dilatation by CMR and outcomes has not been established. We aimed to assess the relationship between grades of LA dilatation measured on CMR based on US volunteers without known CVD and all-cause mortality in a large, multicenter cohort of patients referred for a clinically indicated CMR scan. METHOD: We identified 85 healthy US subjects to determine normal reference LA volumes using the biplane area-length method and indexed for body surface area (LAVi). Clinical CMR reports of patients with LA volume measures (n = 11,613) were obtained. Data analysis was performed on a cloud-based system for consecutive CMR exams performed at three geographically distinct US medical centers from August 2008 through August 2017. We identified 10,890 eligible cases. We categorized patients into 4 groups based on LAVi partitions derived from US normal reference values: Normal (21-52 ml/m2), Mild (52-62 ml/m2), Moderate (63-73 ml/m2) and Severe (> 73 ml/m2). Mortality data were ascertained for the patient group using electronic health records and social security death index. Cox proportional hazard risk models were used to derive hazard ratios for measuring association of LA enlargement and all-cause mortality. RESULTS: The distribution of LAVi from healthy subjects without known CVD was 36.3 ± 7.8 mL/m2. In clinical patients, enlarged LA was associated with older age, atrial fibrillation, hypertension, heart failure, inpatient status and biventricular dilatation. The median follow-up duration was 48.9 (IQR 32.1-71.2) months. On univariate analyses, mild [Hazard Ratio (HR) 1.35 (95% Confidence Interval [CI] 1.11 to 1.65], moderate [HR 1.51 (95% CI 1.22 to 1.88)] and severe LA enlargement [HR 2.14 (95% CI 1.81 to 2.53)] were significant predictors of death. After adjustment for significant covariates, moderate [HR 1.45 (95% CI 1.1 to 1.89)] and severe LA enlargement [HR 1.64 (95% CI 1.29 to 2.08)] remained independent predictors of death. CONCLUSION: LAVi determined on routine cine-CMR is independently associated with all-cause mortality in patients undergoing a clinically indicated CMR.

Comparison between real-time 3-dimensional and 2-dimensional biplane echocardiographic assessment of left atrial volumes in dogs with myxomatous mitral valve disease.

BACKGROUND: Assessment of left atrial (LA) size is important in medical decision making and prognostication in dogs with myxomatous mitral valve disease (MMVD). Real-time 3-dimensional (RT3DE) and 2-dimensional echocardiographic (2DE) methods may be used to assess LA size. OBJECTIVES: To compare measured LA volumes obtained by RT3DE with those calculated by biplane Simpson's modified method of discs (SMOD) and the area-length method (ALM) using the same RT3DE acquisition with the same timing. ANIMALS: One hundred twenty-one privately owned dogs with naturally occurring MMVD. METHODS: Prospective observational study comparing LA volumes indexed to body weight using RT3DE and 2DE-based biplane SMOD and ALM. Agreement between methods was evaluated using Bland-Altman plots and linear regression analyses. RESULTS: Estimations of LA volume using SMOD or ALM did not show good agreement with RT3DE-derived measurements. Absolute differences between methods increased with increasing LA volume, but SMOD underestimated whereas ALM overestimated calculated volumes compared to RT3DE-derived measurements. The difference in LA volume between RT3DE and the biplane methods showed a systematic underestimation of 7% for SMOD and a systematic overestimation of 24% for ALM. Comparison of LA volumes obtained by SMOD and ALM did not show good agreement. The ALM yielded 30% larger LA volumes compared to SMOD. CONCLUSION AND CLINICAL IMPORTANCE: In comparison with RT3DE, SMOD systematically underestimated whereas ALM systematically overestimated LA volumes in dogs with MMVD. Because the systematic difference between RT3DE and SMOD was only 7%, SMOD might be considered the method of choice.

Validation of 3D echocardiographic volume detection of left atrium by human cadaveric casts.

BACKGROUND: Left atrial volume is a prognostic factor in cardiac pathologies. We aimed to validate left atrial volume detection with 3D and 2D echocardiography (3DE and 2DE) by human cadaveric casts. 3DE facilitates measurement of atrial volume without geometrical assumptions or dependence on imaging angle in contrast to 2DE methods. METHODS: For method validation, six water-filled balloons were submerged in a 20-l water tank and their volumes were measured with 3DE. Seven human cadaveric left atrial casts were prepared of silicone and were transformed into ultrasound-permeable casts. Casts were imaged in the same setting, so that 3DE and 2DE of casts represented transthoracic apical view. Left ventricle analysis softwares GE 4D Auto LVQ and TomTec 4D LV-Function were used for 3DE volumetry. RESULTS: Balloon volumes ranged 37 to 255 ml (mean 126 ml). 3DE resulted in an excellent volumetric agreement with balloon volumes, absolute bias was - 3.7 ml (95% CI -5.9 to - 1.4). Atrial cast volumes were 38 to 94 ml (mean 56.6 ml). 3DE and 2DE volumes were excellently correlated with cast volumes (r = 0.96 to 0.99). Biases were for GE 4D LVQ -0.7 ml (95% CI -6.1 to 4.6), TomTec 4D LV-Function 3.3 ml (- 1.9 to 8.5) and 2DE 2.9 ml (- 4.0 to 9.9). 3DE resulted in lower limits of agreement and showed no volume-related bias in contrast to area-length method. CONCLUSIONS: We conclude that measurement of human cadaveric left atrial cast volumes by 3DE is in excellent agreement with true cast volumes.

Left atrial volume index: Can it provide additional prognostic information in ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention?

INTRODUCTION: We sought to assess the prognostic impact of left atrial (LA) size on long-term outcomes of ST-segment elevation myocardial infarction (STEMI). METHODS: We studied 200 consecutive patients admitted to a single center between January 2010 and December 2014 with non-fatal STEMI treated with primary percutaneous coronary intervention (pPCI) who underwent a comprehensive echocardiographic examination at discharge. LA volume was estimated by the area-length method. The left atrium was classified as normal, mildly, moderately or severely enlarged by LA volume index (LAVI). The endpoints were defined as all-cause mortality, a cardiac composite endpoint (all-cause mortality, reinfarction, unplanned revascularization and hospitalization for heart failure) and a cardiovascular composite endpoint (cardiac endpoint plus atrial fibrillation and ischemic stroke) during follow-up. RESULTS: In this STEMI population, 58% had normal LA size, 22.5% had mild LA enlargement, 10% had moderate LA enlargement and 9.5% had severe LA enlargement. During a median follow-up of 28 (IQR 21-38) months, 14 (7.0%) patients died, 53 (26.5%) had the cardiac and 58 (29%) the cardiovascular composite endpoints. There was a stepwise increase in the incidence of all-cause mortality (p=0.020) and both cardiac (p<0.001) and cardiovascular (p<0.001) endpoints with each increment of LAVI class. In multivariate analysis, severe LA enlargement by LAVI was an independent predictor of all-cause mortality (HR: 11.153; 95% CI: 1.924-64.642, p=0.007) and the cardiac (HR: 4.351; 95% CI: 1.919-9.862, p<0.001) and cardiovascular (HR: 4.351; 95% CI: 1.919-9.862, p<0.001) endpoints during follow-up. CONCLUSIONS: This contemporary study confirms the prognostic effect of LA size at discharge, applying the most recent reference values in STEMI patients treated with pPCI.

Quantification of left atrial volume and phasic function using cardiovascular magnetic resonance imaging-comparison of biplane area-length method and Simpson's method.

Left atrial (LA) enlargement and dysfunction are markers of chronic diastolic dysfunction and an important predictor of adverse cardiovascular and cerebrovascular outcomes. Accordingly, accurate quantification of left atrial volume (LAV) and function is needed. In routine clinical cardiovascular magnetic resonance (CMR) imaging the biplane area-length method (Bi-ALM) is frequently applied due to time-saving image acquisition and analysis. However, given the varying anatomy of the LA we hypothesized that the diagnostic accuracy of the Bi-ALM is not sufficient and that results would be different from a precise volumetric assessment of transversal multi-slice cine images using Simpson's method. Thirty one patients of the FIND-AFRANDOMISED-study with status post acute cerebral ischemia (mean age 70.5 ± 6.2 years) received CMR imaging at 3T. The study protocol included cine SSFP sequences in standard 2- and 4 CV and a stack of contiguous slices in transversal orientation. Total, passive and active LA emptying fractions were calculated from LA maximal volume, minimal volume and volume prior to atrial contraction. Intra- and inter-observer variability was assessed in ten patients. Significant differences were found for LA volume and phasic function. The Bi-ALM significantly underestimated LA volume and overestimated LA function in comparison to Simpson's method (Bi-ALM vs. Simpson's method: LAVmax: 80.18 vs. 98.80 ml; LAVpre-ac: 61.09 vs. 80.41 ml; LAVmin: 36.85 vs. 52.66 ml; LAEFTotal: 55.17 vs. 47.85%; LAEFPassive: 23.96 vs. 19.15%; LAEFBooster: 40.87 vs. 35.64%). LA volumetric and functional parameters were reproducible on an intra- and inter-observer levels for both methods. Intra-observer agreement for LA function was better for Simpson's method (Bi-ALM vs. Simpson's method; ICC LAEFTotal: 0.84 vs. 0.96; ICC LAEFPassive: 0.74 vs. 0.92; ICC LAEFBooster: 0.86 vs. 0.89). The Bi-ALM is based on geometric assumptions that do not reflect the complex individual LA geometry. The assessment of transversal slices covering the left atrium with Simpson's method is feasible and might be more suitable for an accurate quantification of LA volume and phasic function.

Left atrial volume and function in dogs with naturally occurring myxomatous mitral valve disease.

OBJECTIVE: Myxomatous mitral valve disease (MMVD) induces progressive left atrial (LA) enlargement. The LA modulates left ventricular filling and performance through its reservoir, conduit, and contractile function. Assessment of LA size and function may provide valuable information on the level of cardiac compensation. Left atrial function in dogs with naturally occurring MMVD remains largely unexplored. The objective of this study was to evaluate LA volume and function in dogs with naturally occurring MMVD. ANIMALS: This prospective study included 205 client-owned dogs of different breeds, 114 healthy dogs, and 91 dogs with MMVD of different disease severities. METHODS: Using two-dimensional echocardiography, the biplane area-length method was applied to assess LA volume and calculate volumetric indices of LA reservoir, conduit, and contractile function. RESULTS: Left atrial volume and LA stroke volume increased, whereas LA reservoir and contractile function decreased with increasing disease severity. A maximal LA volume <2.25mL/kg was the optimal cut off identified for excluding congestive heart failure in dogs with chronic MMVD with a sensitivity of 96% and a specificity of 100%. An active LA emptying fraction <24% and/or a LA expansion index <126% were suggestive of congestive heart failure in dogs with chronic MMVD with a sensitivity of 77% and a specificity of 89% and a sensitivity of 82% and a specificity of 82%, respectively. CONCLUSION: Dogs with MMVD appear to have larger LA volumes with poorer LA function. Deteriorating LA function, characterized by a decreasing reservoir and active contractile function, was evident in dogs with MMVD with increasing disease severity.

Comparison of four echocardiographic methods to determine left atrial size in dogs.

OBJECTIVES: To compare a linear and three volume-based two-dimensional echocardiographic methods for measuring LA size: left atrium to aorta ratio (LA/Ao ratio), biplane area-length, biplane modified Simpson and monoplane area-length. ANIMALS: One hundred seventy-six client-owned dogs of different breeds, 88 healthy dogs and 88 dogs with myxomatous mitral valve disease of different disease severity. METHODS: The left apical four- and two-chamber views were used to measure LA volumes. The right parasternal short-axis view at the level of the heart base was used to measure the LA/Ao ratio. RESULTS: The biplane area-length method yielded 2.8% larger values than those of the biplane modified Simpson method, consistent across the full range of LA volumes. The monoplane area-length method derived on average 5.8% larger values of LA volume than the biplane area-length method. The difference between these two methods was most pronounced at larger LA volumes. The relation between the LA/Ao ratio and LA volume was curvilinear and with increasing LA size these two methods derived very dissimilar values. CONCLUSIONS: All methods showed good feasibility and reproducibility, with the volume-based methods having the most favourable intra- and inter-observer variabilities. The LA/Ao ratio underestimates at higher values of LA size compared to the biplane area-length method. LA volume methods may be superior to the LA/Ao ratio in quantification of LA size. The biplane area-length method and biplane modified Simpson method can be used interchangeably. The monoplane area-length measurement may be used as a quick and reliable method for assessment of LA size in clinical practice.

Discrepancies in identification of left atrial enlargement using left atrial volume versus left atrial-to-aortic root ratio in dogs.

BACKGROUND: Left atrial size is prognostically important in dogs with myxomatous mitral valve disease (MMVD). HYPOTHESIS/OBJECTIVES: To compare the level of agreement in identification of left atrial enlargement (LAE) between the left atrial-to-aortic root ratio (LA : Ao) and left atrial volume using the biplane area-length method indexed to body weight (LA Vol/BW). ANIMALS: Sixty dogs with MMVD and 22 normal dogs were prospectively studied with 2-dimensional echocardiography. METHODS: The upper limit of normal for LA Vol/BW was defined as 1.1 mL/kg. LA : Ao was deemed normal if ≤1.5. To define overall disease severity, each dog was assigned a mitral regurgitation severity score (MRSS) based on echocardiographic parameters that did not include left atrial size. ACVIM staging also was utilized. RESULTS: Of 60 affected dogs, 20 were ACVIM Stage B1, 25 were Stage B2, and 15 were Stage C. LA Vol/BW identified LAE in 12 cases in which LA : Ao was normal; 7 of these were Stage B1 and 5 were Stage B2. This diagnostic disagreement was significant (P = .00012). Of the 12 cases in which diagnostic discrepancies were identified, 5/5 of the B2 dogs and 3/7 B1 dogs had a moderate MRSS, whereas 4/7 B1 dogs had a mild MRSS. No diagnostic discrepancies between LA : Ao and LA Vol/BW were apparent in dogs with a severe MRSS. CONCLUSIONS AND CLINICAL IMPORTANCE: This study shows evidence of diagnostic disagreement between LA : Ao and LA Vol/BW for assessment of LAE. LA Vol/BW may be superior to LA : Ao for identification of mild LAE.

Left atrial volume and phasic function in clinically healthy dogs of 12 different breeds.

The left atrium (LA) of the heart is a validated marker of clinical and subclinical cardiovascular disease. Since the LA is a three-dimensional structure, volume-based methods of chamber quantification might be more accurate than linear methods. The aims of this study were to establish the feasibility and reproducibility of biplane two-dimensional echocardiographic LA volume measurements and to provide reference ranges for LA volume and phasic function in adult dogs (n=237) without cardiovascular disease. The study also assessed the effects of bodyweight (BW), breed, sex, age and heart rate (HR) on LA volume and function. The biplane area-length method was used to calculate LA volumes from the left apical four- and two-chamber views. LA volume and function were correlated with body size and there were significant breed differences. For dogs of all sizes and breeds, LA maximal volume had a 95th percentile of 0.92 mL/kg. There was no correlation between age or sex and LA volume or LA reservoir function, but conduit function decreased and booster pump function increased with age. LA volume and function varied with HR. LA size was calculated using the biplane area-length method, with good reproducibility and little inter-observer variability. The reference ranges presented for LA volume and function in healthy dogs could be used to refine the diagnostic criteria for the assessment of LA enlargement and altered function by conventional echocardiography.