Effects of inter- and intra-observer variability on echocardiographic measurements in awake cats

The objective of this study was to determine intra- and inter-observer variability of echocardiographic measurements in awake cats. Four observers with different levels of experience in echocardiography performed 96 echocardiographic examinations in four cats on four different days over a 3-week period. The examinations were randomized and blinded. The maximum within-day and between-day CV values were 17.4 and 18.5% for inter-ventricular septal thickness in diastole, 18.7 and 22.6% for left ventricular free-wall thickness in diastole, 9.8 and 14.9% for left ventricular end-diastolic diameter, 20.8 and 15.2% for left ventricular end-systolic diameter, and 21.2 and 18.4% for left ventricular shortening fraction. The maximum within-day CV values were most often associated with the least competent observer (i.e. the graduate student) and, the minimum CV values with the most competent observer (i.e. the associate professor in cardiology). A significant interaction between cat and observer was also evidenced. Thus, the most competent observer could not be replaced by any of the other observers.     

Methods and reliability of echocardiographic assessment of left atrial size and mechanical function in horses

OBJECTIVE: To assess the feasibility, describe the techniques, and determine the reliability of transthoracic echocardiography for characterization of left atrial (LA) size and LA mechanical function in horses. ANIMALS: 6 healthy adult horses. PROCEDURES: Repeated echocardiographic examinations were performed independently by 2 observers in standing, unsedated horses by use of 2-dimensional echocardiography, pulsed-wave flow Doppler, and tissue Doppler imaging (TDI) techniques. Test reliability was determined by estimating measurement variability, within-day interobserver variability, and between-day inter- and intraobserver variability of all echocardiographic variables. Variability was expressed as the coefficient of variation (CV) and the absolute value below which the difference between 2 measurements will lie with 95% probability. RESULTS: Most echocardiographic variables of LA size had low overall variability (CV, < 15%). Among the 2-dimensional indices of LA mechanical function, area-based and volume-based ejection phase indices had moderate between-day variability (CV usually < 25%). Transmitral Doppler flow indices were characterized by low to high between-day variability (CV, 6% to 35%). The TDI wall motion velocities had high between-day variability (CV, > 25%), whereas most TDI-derived time intervals had low variability (CV, < 15%). CONCLUSIONS AND CLINICAL RELEVANCE: LA size and mechanical function can be reliably assessed in standing, unsedated horses by use of 2-dimensional echocardiography, transmitral blood flow velocity profiles, and analyses of LA wall motion by use of TDI. These results may provide useful recommendations for echocardiographic assessment of LA size and function in horses.     

ASSESSMENT OF CARDIAC CHAMBER SIZE USING ANATOMIC M-MODE

Anatomic M-mode (AMM) is an echocardiographic technique that is capable of generating M-mode studies from two-dimensional (2D) cine loops. Unlike conventional M-mode (CMM) whose scan line must lie along the axis of the ultrasound signal, AMM produces M-mode studies independent of the orientation of the ultrasound beam. We sought to determine the ability of AMM to measure cardiac dimensions in normal dogs and to assess the accuracy and variability of AMM and CMM vs. 2D measurements. Thirty-eight healthy dogs underwent physical exam and 2D, CMM, and AMM echocardiographic studies. The end-diastolic and end-systolic dimension of the left ventricle and the diameter of the left atrium (LAD) and aortic root were evaluated from the right parasternal short- and long-axis views. Results of the AMM and CMM study were compared with the 2D study via linear regression and calculation of a coefficient of correlation. AMM increased the level of correlation with both the left ventricular dimensions and LAD. Bland-Altman analysis revealed that AMM increased the level of agreement with 2D measurements and CMM greatly underestimated LAD vs. AMM. In healthy dogs, cardiac AMM measurements are associated with greater accuracy and less variability than CMM. AMM has the potential to improve quantification of cardiac dimensions.     

Reproducibility and repeatability of M-mode echocardiographic measurements collected from 25 normal horses

Three different operators with varying levels of experience made repeated echocardiographic measurements of the aortic root diameter, interventricular septal thickness, left ventricular internal diameter, and left ventricular free wall thickness of 25 horses using a 3.5 MHz transducer. Each operator followed specific guidelines in order to determine the reproducibility (inter-operator variation) and repeatability (intra-operator variation) of their measurements. Variations due to horse differences, operator differences, and horse by operator interactions were determined. The largest variation was due to differences between horses. Inter-operator-based variability was only significant with respect to interventricular septal and aortic root measurements. All other measurements were reproducible and repeatable when obtained by well-trained operators. The experience of operators affects reproducibility and repeatability, however. It was concluded that different operators could apply equine M-mode echocardiography to obtain measurements of ventricular chamber and free wall dimensions that can be legitimately compared to measurements obtained by others if operators are adequately trained and landmarks are clearly standardized.     

Echocardiography and conventional Doppler examination in clinically healthy adult Cavalier King Charles Spaniels: Effect of body weight,age, and gender,and establishment of reference intervals

ObjectivesThe objectives of this study were (1) to assess the potential effect of body weight (BW), age, and gender on the most commonly used echocardiographic and conventional Doppler variables in a large population of healthy Cavalier King Charles Spaniels (CKCS), and (2) to establish the corresponding reference intervals (RI).Animals134 healthy adult CKCS.MethodsUltrasound examinations were performed by trained observers in awake dogs. M-mode variables included left ventricular (LV) end-diastolic and end-systolic diameters, LV free wall and interventricular septal thicknesses at end-diastole and end-systole, and LV fractional shortening (FS%). The left atrium (LA) and aortic (Ao) diameters were measured using a 2D method, and the LA/Ao was calculated. Pulsed-wave Doppler variables included peak systolic aortic and pulmonary flow velocities, mitral E and A waves, and E/A ratio. Effects of BW, age, and gender on these 15 variables were tested using a general linear model, and RIs were determined by applying the statistical procedures recommended by the Clinical and Laboratory Standards Institute.ResultsA significant BW effect was observed for all variables, except LA/Ao, FS%, and mitral E/A ratio. A significant but negligible effect of gender and age was also observed for 5/15 and 4/15 of the tested variables, respectively. Only the BW effect on M-mode variables was considered as clinically relevant and the corresponding regression-based RIs were calculated.ConclusionsBody weight should be taken into account when interpreting echocardiographic values in CKCS, except for LA/Ao, FS%, and mitral E/A ratio.     

Methods and Reliability of Tissue Doppler Imaging for Assessment of Left Ventricular Radial Wall Motion in Horses

Background: Noninvasive assessment of left ventricular (LV) function is incompletely studied in horses.
Objectives: The goals of this study were to investigate the feasibility, techniques, and reliability of tissue Doppler imaging (TDI) for characterization of LV radial wall motion in healthy horses.
Animals: Three Standardbreds, 3 Thoroughbreds; age 8–14 years; body weight 517–606 kg.
Methods: Repeated echocardiographic examinations were performed by 2 observers in unsedated horses using TDI. Test reliability was determined by estimating measurement variability, within-day interobserver variability, and between-day interobserver and intraobserver variability of all echocardiographic variables. Variability was expressed as coefficient of variation (CV) and the absolute value below which the difference between 2 measurements will lie with 95% probability.
Results: Assessment of LV radial wall motion by TDI was feasible in all horses. Measurement variabilities were very low (CV < 5%) to low (CV 5–15%) for most variables. Within-day interobserver variability as well as between-day interobserver and intraobserver variabilities were low to moderate (CV 16–25%) for most variables. All pulsed-wave TDI variables of systolic LV function showed very low to low variability, whereas some of the variables of LV diastolic and LA function showed moderate to high (CV > 25%) variability. Pulsed-wave TDI variables appeared more reliable than color TDI variables.
Conclusions and Clinical Importance: Measurement of TDI indices of LV function is feasible and reliable in adult Standardbred and Thoroughbred horses. The clinical relevance of LV function assessment by TDI remains to be determined.     

Noninvasive assessment of systolic left ventricular torsion by 2-dimensional speckle tracking imaging in the awake dog: repeatability, reproducibility, and comparison with tissue Doppler imaging variables

BACKGROUND: Left ventricular (LV) torsional deformation plays an important role in myocardial function. However, it has never been assessed in the awake dog, because magnetic resonance imaging and sonomicrometry have been the only methods available so far. HYPOTHESIS: Two dimensional speckle tracking echocardiography (STE), a new ultrasound imaging technique, provides a repeatable and reproducible noninvasive assessment of systolic LV wringing motion in the awake dog. ANIMALS: Six healthy dogs were used to determine the repeatability and reproducibility of STE variables (study 1). These variables also were prospectively assessed in a population of 35 healthy dogs (study 2). METHODS: Peak LV basal and apical systolic rotations were measured by STE from right parasternal short-axis views using automatic frame-to-frame tracking of gray-scale speckle patterns. Systolic LV torsion (LVtor, degrees ) was defined as apical rotation relative to the base. RESULTS: All within-day and between-day coefficients of variation were <20% (6.8-18.0%). Amplitude of apical systolic rotation was significantly higher (P < .001) than the basal value (5.4 +/- 3.2 degrees and -3.1 +/- 1.3 degrees , respectively). Global LVtor was significantly correlated with systolic longitudinal LV myocardial velocity gradient assessed by tissue Doppler (P < .05), but not with either systolic radial LV myocardial velocity gradient or the ratio of early mitral inflow velocity to early mitral annular velocity (Em/Ea). CONCLUSIONS AND CLINICAL IMPORTANCE: Speckle tracking echocardiography is a repeatable and reproducible method for assessing systolic LV torsional deformation. The combination of these new STE indices with tissue Doppler variables could provide a new approach for quantifying canine LV systolic function.     

Quantification of mitral valve regurgitation in dogs with degenerative mitral valve disease by use of the proximal isovelocity surface area method

OBJECTIVE: To determine the within-day and between-day variability of regurgitant fraction (RF) assessed by use of the proximal isovelocity surface area (PISA) method in awake dogs with degenerative mitral valve disease (MVD), measure RF in dogs with MVD, and assess the correlation between RF and several clinical and Doppler echocardiographic variables. DESIGN: Prospective study. ANIMALS: 6 MVD-affected dogs with no clinical signs and 67 dogs with MVD of differing severity (International Small Animal Cardiac Health Council [ISACHC] classification). PROCEDURES: The 6 dogs were used to determine the repeatability and reproducibility of the PISA method, and RF was then assessed in 67 dogs of various ISACHC classes. Mitral valve regurgitation was also assessed from the maximum area of regurgitant jet signal-to-left atrium area (ARJ/LAA) ratio determined via color Doppler echocardiographic mapping. RESULTS: Within- and between-day coefficients of variation of RF were 8% and 11%, respectively. Regurgitation fraction was significantly correlated with ISACHC classification and heart murmur grade and was higher in ISACHC class III dogs (mean +/- SD, 72.8 +/- 9.5%) than class II (57.9 +/- 20.1%) or I (40.7 +/- 19.2%) dogs. Regurgitation fraction and left atriumto-aorta ratio, fractional shortening, systolic pulmonary arterial pressure, and ARJ/LAA ratio were significantly correlated. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that RF is a repeatable and reproducible variable for noninvasive quantitative evaluation of mitral valve regurgitation in awake dogs. Regurgitation fraction also correlated well with disease severity. It appears that this Doppler echocardiographic index may be useful in longitudinal studies of MVD in dogs.     

Observer-dependent variability of quantitative clinical endpoints: the example of canine echocardiography

The objective of this study was to determine the intra- and inter-observer variability of echocardiographic measurements in dogs. Four observers with different levels of experience in echocardiography performed 192 echocardiographic examinations of six dogs on four different days. The lowest within- and between-day coefficients of variation (CV) (%) were 13.8 and 5.2 for the right ventricle in diastole, 8.9 and 4.5 for the interventricular septal thickness in diastole (6.3 and 7.0 in systole), 7.7 and 9.4 for the left ventricular free-wall thickness in diastole (8.1 and 5.2 in systole), 3.1 and 5.0 for the left ventricular end-diastolic diameter (6.2 and 7.0 for end-systolic diameter), 10.2 and 10.8 for the left ventricular shortening fraction, and 8.2 and 9.8 for the left atrium/aorta ratio, respectively. Most of these lowest CVs were observed by the two most experienced observers. Conversely, all maximum values were obtained with the two less experienced observers. These differences in observer-dependent variability may considerably influence the minimum number of animals required to detect a treatment-associated change in echocardiographic variables.     

Echocardiographic evaluation of the bottlenose dolphin (Tursiops truncatus).

Safe and effective echocardiography would represent a valuable tool for marine mammal veterinarians and physiologists evaluating the dolphin heart. Unfortunately, conventional ultrasound technology (transthoracic echocardiography) has been limited by logistic, anatomic, and behavioral challenges. Five mature male Atlantic bottlenose dolphins (Tursiops truncatus) were trained for echocardiographic imaging (four for both transthoracic and transesophageal imaging, and one for only transthoracic imaging). It was noted that transesophageal image quality transiently improved when the dolphins spontaneously exhaled. Subsequently, dolphins were conditioned to hold their breath following forced exhalation, and imaging proceeded during such behavioral breath holds. Over 25 transthoracic and 100 transesophageal echocardiographic studies were performed, including both two-dimensional imaging and color flow mapping. Transthoracic imaging yielded poor-quality images of only small portions of the heart. In contrast, transesophageal imaging, which improved dramatically with behavioral breath holding following exhalation, yielded consistently high-quality images of the entire heart (mitral, tricuspid, aortic, and pulmonary valves, atrial and ventricular septa, left and right atria, left and right ventricles, and ascending aorta and main pulmonary artery). Color flow mapping demonstrated mild tricuspid regurgitation in all dolphins, and mild aortic regurgitation in one dolphin found to have a pedunculated mass arising from the sinutubular junction just above the aortic valve. There were no complications in nonsedated dolphins. The heart of the bottlenose dolphin can be safely, effectively, and reproducibly evaluated with the use of transesophageal echocardiography in conjunction with behavioral breath holding following forced exhalation. This approach, and the normative echocardiographic data generated from this work, lays the foundation for future echocardiographic studies of cetaceans.     

Quantification, repeatability, and reproducibility of feline radial and longitudinal left ventricular velocities by tissue Doppler imaging

OBJECTIVE: To measure the radial and longitudinal velocities of several myocardial segments of the left ventricular wall by use of tissue Doppler imaging (TDI) in healthy cats and determine the repeatability and reproducibility of the technique. ANIMALS: 6 healthy cats. PROCEDURE: 72 TDI examinations were performed on 4 days by the same trained observer. Radial parameters included left endocardial and epicardial myocardial velocities. Longitudinal parameters included left basal, middle, and apical myocardial velocities. RESULTS: All velocity profiles had 1 positive systolic wave (S) and 2 negative diastolic waves (E and A). Myocardial velocities were higher in the endocardial than epicardial segments during the entire cardiac cycle (systolic wave S, 4.4 +/- 0.82 and 1.9 +/- 0.55; diastolic wave E, 9.7 +/- 1.70 and 2.2 +/- 0.74; and diastolic wave A, 5.1 +/- 1.56 and 1.4 +/- 0.76, respectively). Velocities were also higher in the basal than in the apical segments (systolic wave S, 4.7 +/- 0.76 and 0.2 +/- 0.11; diastolic wave E, 9.7 +/- 1.36 and 0.5 +/- 0.17; and diastolic wave A, 3.7 +/- 1.51 and 0.2 +/- 0.13, respectively). The lowest within-day and between-day coefficients of variation were observed in endocardial segments (8.2% and 6.5% for systolic wave S and diastolic wave E, respectively) and in the basal segment in protodiastole (5.5%). CONCLUSIONS AND CLINICAL RELEVANCE: Repeatability and reproducibility of TDI were adequate for measurement of longitudinal and radial left ventricular motion in healthy awake cats. Validation of TDI is a prerequisite before this new technique can be recommended for clinical use.     

Spectrum of M-mode echocardiographic abnormalities in 75 cats with systemic hypertension

A retrospective study was performed in 75 hypertensive cats to determine the spectrum and frequency of M-mode echocardiographic abnormalities. Results indicated that 21.3% of the cats had M-mode measurements within normal reference ranges. For cats with echocardiographic abnormalities, changes were variable. Thirty-nine percent of hypertensive cats had hypertrophy of the interventricular septum in diastole, and 41.3% had hypertrophy of the left ventricular (LV) posterior wall in diastole. One cat in five had a dilated left atrium, while fractional shortening and LV internal dimension in diastole were normal in 82.7% and 86.7% of the cats, respectively. The marked variability of echocardiographic findings in hypertensive cats made echocardiography an unreliable screening test for hypertension.     

Effects of animal position and number of repeated measurements on selected two-dimensional and M-mode echocardiographic variables in healthy dogs

OBJECTIVE: To evaluate the effects of positioning and number of repeated measurements on intra- and interobserver variability of echocardiographic measurements in dogs. DESIGN: Prospective study. ANIMALS: 4 healthy dogs. PROCEDURE: Each observer performed 24 examinations, separately assessing each dog 6 nonconsecutive times (3 times with the dog in lateral recumbency and 3 with the dog in a standing position). Variables evaluated included M-mode measurements of left ventricular end-diastolic and left ventricular end-systolic diameters, left ventricular free-wall thickness in diastole and systole, interventricular septal thickness in diastole and systole, left ventricular shortening fraction, and 2-dimensional measurements of the left atrial diameter-to-aortic diameter ratio. RESULTS: All coefficients of variation (range, 3.4% to 26.6%) were similar between operators and positions and were < 15% for 27 of 32 values. For both operators, repeatability of the measurements was better for left ventricular end-systolic diameter, left ventricular free-wall thickness in diastole, left ventricular free-wall thickness in systole, and the left atrial diameter-to-aortic diameter in the standing position, and similar for both positions for shortening fraction and left ventricular end-diastolic diameter. No effect of cardiac cycle was observed. CONCLUSIONS AND CLINICAL RELEVANCE: Within-day variability of conventional echocardiography performed with the dog in the standing position was at least as good as that obtained with the dog in lateral recumbency for most measured variables. Single measurements of each variable may be sufficient for trained observers examining dogs that do not have an arrhythmia. The standing position should be used, particularly for stressed or dyspneic dogs.     

Quantitative assessment of two- and three-dimensional transthoracic and two-dimensional transesophageal echocardiography,computed tomography,and magnetic resonance imaging in normal canine hearts

IntroductionThe objective of the study was to evaluate the accuracy of two- and three-dimensional (2D, 3D) transthoracic echocardiography (TTE), 2D transesophageal echocardiography, and computed tomography angiography (CTA) compared with cardiac magnetic resonance imaging (CMR) in normal dogs and to assess repeatability of 2D and 3D TTE for the assessment of left ventricular (LV) and left atrial (LA) dimensions.AnimalsThe study was performed on six healthy dogs.Materials and MethodsTransthoracic echocardiography, transesophageal echocardiography, CTA, and CMR were performed on each dog. Right ventricular (RV) and LV volumes (in systole and diastole), ejection fraction (EF), and LA and right atrial (RA) volumes were assessed. Repeatability and intrarater and interrater measurements of variability were quantified by average coefficient of variation (CV) for 2D and 3D TTE.ResultsNo clinically relevant differences in LV volume were detected between CMR and all modalities. Importantly, 3D TTE had the lowest CV (6.45%), correlated with (r_s = 0.62, p = 0.01), and had the highest overlap in distribution with CMR (OVL >80%). Left ventricular EF and LA size via CTA compared best with CMR and RV and RA volumes were best estimated by 3D TTE. Assessment of LV and LA volumes via 3D TTE had moderate repeatability (15–21%) compared with LV M-mode measurements and 2D LA-to-aortic ratio (<10%), respectively. For LV size, interrater CV for 3D TTE (19.4%) was lower than 2D TTE (23.1%).ConclusionsMeasurements of LV, RV, and RA volumes via 3D TTE and LA volume and LV EF assessed by CTA compared best with CMR. Three-dimensional echocardiography had lower interrater and intrarater CV compared with 2D TTE.     

TWO-DIMENSIONAL ECHOCARDIOGRAPHY IN THE NORMAL CAT

Two-dimensional echocardiography (2DE) and M-mode echocardiography were used to image the heart of 13 clinically healthy cats. Seven awake cats and six cats tranquilized with a combination of acetylpromazine and ketamine were studied. Six cats were studied by 2DE on 3 consecutive days to assess repeatability of the study. Long-axis and short-axis echocardiographic tomograms were obtained from the right parasternal location, and these images were used to determine internal cardiac dimensions, ventricular and septal wall thicknesses, repeatability of the study, and interobserver variability. Some but not all parameters were significantly (P < 0.05) related to body weight. Significant correlations (P <0.05) were found between measurements obtained by long-axis and by short-axis image planes. Comparison of parameters measured by 2DE and M-mode echocardiography demonstrated minimal differences between mean values. Repeatability of the 2DE study was good with 14 of 16 parameters having a mean percent error less than 10%. Interobserver variability was acceptable for some but not all parameters. The study indicates that repeatable 2DE tomograms can be obtained in the cat and that quantitation of cardiac anatomy is possible with this imaging technique.     

Echocardiographic ratio indices in overtly healthy Boxer dogs screened for heart disease

BACKGROUND: Boxer dogs are routinely screened by echocardiography to exclude congenital and acquired heart disease. Individuals of a given breed may span a large range of body sizes, potentially invalidating linear regression of M-mode measurements against body weight. Echocardiographic ratio indices (ERIs) provide a novel method of characterizing echocardiographic differences between Boxers and other dog breeds. HYPOTHESIS: ERIs obtained from overtly healthy Boxer dogs presented for cardiac screening will be different from ERIs established for normal non-Boxer dogs, and those differences will be unrelated to aortic velocity or systolic blood pressure. ANIMALS: Eighty-one Boxers with no outward clinical signs of heart disease were studied. METHODS: All dogs were examined by 2-dimensional, M-mode, and Doppler echocardiography. M-mode measurements were used to perform ERI calculations, and the indices in Boxers were compared between Boxers with varying severity of arrhythmia and those of normal non-Boxer dogs. RESULTS: Differences in weight-based ERIs, which reflect increased thickness of the left ventricular free wall (LVW) and interventricular septum (IVS) and smaller aortic size, were found in overtly healthy Boxer dogs compared with normal non-Boxer dogs. ERIs of left atrial and LV cavity size in overtly healthy Boxers were not significantly different from those of non-Boxer dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: Boxer dogs may have an increased relative thickness of the LVW and IVS that is independent of aortic size, aortic velocity, or arterial blood pressure, and this morphology should be taken into consideration when screening Boxers by echocardiography.     

Left Ventricular Radial and Circumferential Wall Motion Analysis in Horses Using Strain, Strain Rate, and Displacement by 2D Speckle Tracking

Background: Noninvasive assessment of left-ventricular (LV) function is clinically relevant, but is incompletely studied in horses.
Objectives: To document the feasibility, describe the techniques, and determine the reliability of 2D speckle tracking (2DST) for characterization of LV radial and circumferential wall motion in horses.
Animals: Three Standardbreds, 3 Thoroughbreds; age 8–14 years; body weight 517–606 kg.
Methods: Observational study. Repeated 2-dimensional echocardiographic examinations were performed in unsedated horses by 2 observers and subsequently analyzed by 2DST. Test reliability was determined for segmental and for averaged 2DST indices (including strain, strain rate, displacement, and rotation) by estimating measurement variability, within-day interobserver variability, between-day interobserver variability, and between-day intraobserver variability. Variability was expressed as coefficient of variation (percent) and the absolute value below which the difference between 2 measurements will lie with 95% probability.
Results: 2DST analyses were feasible in 16 of 18 echocardiographic studies. The automated tracking was accurate during systole but inaccurate during diastole. Reliability was higher for radial compared to circumferential measurements. For radial strain, radial systolic strain rate, and radial systolic displacement, the test-retest variabilities ranged between 2.4 and 33.1% for segmental and between 4.1 and 16.1% for averaged measurements.
Conclusions and Clinical Importance: Systolic radial motion of the LV at the chordal level could be reliably characterized in horses by 2DST. Circumferential measurements were less reliable. Diastolic measurements were invalid because of inaccurate tracking. The clinical value of LV wall motion analysis by 2DST in horses requires further investigation.     

Two-dimensional echocardiographic assessment of the feline left atrium

Atrial size determined by echocardiography provides a surrogate measure of the hemodynamic burden of cardiac disease. Linear atrial dimensions often are indexed to aortic diameter. Whereas quantitative variables obtained from healthy cats, using 2-dimensional echocardiography (2DE), have been reported, indices from 2DE, have not. Using 2DE and M-mode echocardiography, we calculated indices of left atrial size and a single index of atrial function, left atrial fractional shortening, in 17 healthy cats. Specifically, left atrial dimensions from short- and long-axis 2DE planes were indexed to aortic diameter and also to end-diastolic left ventricular dimension. Additionally, left atrial circumference and area were indexed to aortic circumference and area, respectively. The same variables were obtained from 20 cats with hypertrophic cardiomyopathy (HCM), so that agreement between 2DE indices and indices from M-mode echocardiography could be evaluated over a clinically relevant range of atrial sizes. Atrial dimensions and indices of atrial size from cats with HCM exceeded those of healthy cats. Left atrial dimension from 2D short-axis images indexed to aortic diameter generally was less than the analogous index obtained from M-mode (mean bias, [95% limits of agreement] -0.13, [-0.42, 0.17]). Left atrial dimension from 2D long-axis images indexed to aortic diameter generally was greater than the index obtained from M-mode (0.15, [-0.28, 0.58]). We conclude that ratios of left atrial size and aortic diameter, from 2DE and M-mode echocardiography, are not interchangeable. Normative data that may serve as reference intervals for 2DE assessment of atrial size are presented.     

Comparison of the Repeatability of Echocardiographic Measurements from Different Modes and Views in Horses of Various Breeds and Sizes

The objective of this study was to compare the repeatability of echocardiographic measurements obtained from different echocardiographic modes and views in healthy adult equids of various sizes, breeds, and thorax shapes. Ten equids (body weight: 120–662 kg; age: 1–26 years) from various breeds, free of cardiac disease, were used in this study. Each animal was submitted to a standardized echocardiographic and Doppler protocol 3 times at 1 day interval. This protocol included the measurements of left and right ventricular, aortic, pulmonary, and left atrial parameters obtained from different views using the bidimensional (2D) or the motion (M) modes, and the measurement of several parameters of blood flow obtained from the pulsed wave Doppler mode. Repeatability of each measurement was estimated on the basis of the residual variance using a linear model and the coefficient of variation of repeated measurements. A two by two comparison of the repeatability of measurements performed in different views was performed using the residual variances in a variance ratio F test. Results showed that repeatability of echocardiographic or Doppler measurements in equids of various sizes, breeds, and thorax shapes are comparable to previously reported results in thoroughbred and standardbred horses. Left ventricular morphologic parameters showed a good repeatability in the classic M-mode right parasternal short axis view at the level of the chordae tendineae, but the 2D-mode right parasternal long axis four-chamber view appeared to offer an interesting alternative measurement. This latter view also allowed obtaining the most repeatable measurement of right ventricular internal diameter. The left atrial diameter was maximal and most repeatable in the 2D-mode left parasternal long axis four-chamber angled view, and the repeatability of the aortic diameter was best in the 2D-mode right parasternal long axis five-chamber view. Finally, aortic systolic time intervals were more repeatable when measured from the Doppler mode as compared with the M-mode. In conclusion, repeatability of echocardiographic measurements in horses could be optimized after the following protocol: (1) M-mode right parasternal short axis view at the level of chordae tendineae to measure left ventricular morphologic parameters, and 2D-mode right parasternal long axis four-chamber as an alternative view; (2) 2D-mode right parasternal long axis five-chambers to measure the aortic diameter; (3) 2D-mode left parasternal long axis four-chambers angled view to measure the left atrial diameter.     

Echocardiographic detection of tricuspid atresia in two foals

M-mode, 2-dimensional, and contrast echocardiographic studies were used to detect tricuspid atresia in 2 foals. M-mode echocardiographic findings included a small right ventricle, large left ventricle, large mitral valve excursion, large left atrium (foal 2), dropout of the cranial aspect of the aortic root, and a thick band of echoes in the tricuspid valve region. These findings were confirmed by 2-dimensional echocardiography. In addition, a large right atrium, persistent foramen ovale, ventricular septal defect, and large mitral valve apparatus were imaged. One foal also had a thick right atrial wall. Contrast echocardiography confirmed the intracardiac flow of blood from right to left atrium and then to the left ventricle, followed by simultaneous opacification of the right ventricle and aorta. The use of these echocardiographic techniques enables accurate antemortem diagnosis and prognosis of tricuspid atresia in the foal.