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

Comparative evaluation of left atrial size in healthy cats measured by two-dimensional echocardiography and cardiovascular MRI

OBJECTIVES

This study aimed to assess left atrial (LA) size in healthy cats using cardiovascular MRI (cMRI) and to compare this with LA size assessed by two-dimensional echocardiography. The hypothesis was that cMRI would accurately determine LA size in domestic cats.

METHODS

A prospective comparative study was performed. Six healthy cats were selected for the study. Standard two-dimensional echocardiography was performed with and without general anaesthesia. cMRI was conducted under general anaesthesia. A comprehensive analysis of LA mass and function measurements was performed to determine the consistency and correlation of LA size and function indicators between two-dimensional echocardiography and cMRI.

RESULTS

Our study found that intraobserver variability for cMRI measurements was lower than that for two-dimensional echocardiography. Compared with cMRI, echocardiography under anaesthesia significantly overestimated maximal LA volume (LAVmax_2D, P <0.01) and significantly underestimated minimal LA volume (LAVmin_2D, P <0.01). The LAVmin measured by two-dimensional echocardiography exhibited the highest consistency (intraclass correlation coefficient = 0.857) and correlation (R = 0.75, P <0.01) with LAVmin measured by cMRI. The linear regression equation was LAVmin_ cMRI = 0.891 × LAVmin_2D + 0.304.

CONCLUSIONS AND RELEVANCE

cMRI represents a reproducible method for assessing LA mass in domestic cats. This study underscored the importance of echocardiography in veterinary cardiology, and the LAVmin measured by two-dimensional echocardiography may reflect the true LAVmin.

ECG-Gated Cardiac Multidetector CT Evaluation of the Normal Pulmonary Valve and Right Ventricular Outflow Tract in Dogs

With the advancement in imaging technology, ECG-gated cardiac multidetector computed tomography (MDCT) has emerged as a tool for the anatomic evaluation of the pulmonary valve and right ventricular outflow tract (RVOT) in human medicine. Currently, the evaluation of the pulmonary valve relies primarily on echocardiographic examination. However, the bi-dimensional nature of this technique and the location/orientation of the pulmonary valve in the thoracic cavity can pose challenges. In human medicine, ECG-gated MDCT distinguishes four main anatomic components of the pulmonary valve and RVOT: the pulmonary valve leaflets, the sinotubular junction, the anatomic ventriculo-arterial junction and the hemodynamic ventriculo-arterial junction. Hence, this study aimed to describe the computed tomographic findings of the normal RVOT and pulmonary cusps in a population of dogs. This is an anatomic prospective descriptive study. A total of 24 dogs underwent a complete echocardiographic examination and an ECG-gated MDCT to rule out pulmonary valve abnormalities. Multiplanar reconstruction of the pulmonary valve was obtained. Additionally, hearts from three dogs euthanized for reasons unrelated to the study were collected and their gross and histological findings were compared with the CT images. The ECG-gated MDCT provided good visualization of the pulmonary valve leaflets, the sinotubular junction, the anatomic ventriculo-arterial junction and the hemodynamic ventriculo-arterial junction. Notably, the short-axis view of the pulmonary valve anatomy resembled the 'Mercedes-Benz sign' characteristic of the aortic valve in all dogs. In conclusion, this study provides the first description of the CT anatomy of the RVOT in dogs without pulmonary valve and RVOT abnormalities.

Effect of additional dimensions and views in the echocardiographic determination of 3-dimensional left ventricular volume in myxomatous mitral valve disease in dogs

BACKGROUND

Left ventricular (LV) volumes can be calculated from various linear, monoplane, and multiplane echocardiographic methods, and the same method can be applied to different imaging views. However, these methods and their variations have not been comprehensively evaluated against real-time 3-dimensional echocardiography (RT3D).

HYPOTHESIS/OBJECTIVES

To identify the LV volumetric approaches that produce the least bias and the best agreement with RT3D, and to assess interoperator reproducibility between an experienced and an inexperienced operator.

ANIMALS

Fifty-nine client-owned dogs with myxomatous mitral valve disease (38 Stage B1, 13 Stage B2, 8 Stages C/D) received echocardiograms, with a subset of 28 dogs (14 Stage B1, 10 Stage B2, 4 Stages C/D) imaged by 2 operators.

METHODS

Prospective method comparison study. Body weight-indexed end-diastolic and end-systolic LV volumes using linear methods in long- and short-axis views (Teichholz, cube, modified cube), monoplane methods in right parasternal and left apical views (area-length and Simpson's method of discs), biplane Simpson's method of discs, and real-time triplane (RT3P) were compared against RT3D.

RESULTS

The RT3P method exhibited no bias and demonstrated the highest agreement with RT3D. The linear methods showed significant bias and lower agreements for end-diastolic volumes, end-systolic volumes, or both. Volumes derived from different imaging views using the same method showed poor agreement. Both RT3P and RT3D methods demonstrated poor interoperator reproducibility.

CONCLUSIONS AND CLINICAL IMPORTANCE

Incorporating additional dimensions improves bias and agreement in LV volume quantification, but comprehensive clinical experience with RT3P and RT3D is needed to improve consistency across all operators.

Evaluation of right ventricular function using conventional and real-time three-dimensional echocardiography in healthy dogs and dogs with myxomatous mitral valve disease

INTRODUCTION/OBJECTIVES

To compare conventional and three-dimensional (3D) echocardiographic indices of right ventricular (RV) systolic function in dogs with various stages of myxomatous mitral valve disease (MMVD), classified according to the 2009 guidelines of the American College of Veterinary Internal Medicine (ACVIM), with those from normal dogs.

ANIMALS

Seventy-eight unsedated dogs (22 healthy controls, 23 ACVIM stage B1 MMVD, 20 ACVIM stage B2 MMVD, and 13 ACVIM stage C MMVD) were included in the study.

MATERIALS AND METHODS

All dogs underwent conventional and 3D echocardiography. Three-dimensional RV end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and ejection fraction (EF) were recorded. Right ventricular EDV, ESV, and SV were indexed to bodyweight. Echocardiographic variables were compared across groups using a Kruskal-Wallis test with subsequent post hoc analysis using Dunn's method for multiple comparisons between groups. A P-value of <0.05 was considered significant.

RESULTS

Right ventricular EDV was smaller in stage B1 (P=0.012), stage B2 (P=0.035), and stage C (P=0.004) dogs than in controls. Stage B2 (P=0.003) and stage C (P<0.001) dogs had smaller RV ESV than controls. Stage B1 dogs had smaller RV SV than controls (P=0.012). Right ventricular EF was greater in stage C dogs than in controls (P=0.003) and in stage B1 (P=0.017) dogs.

CONCLUSIONS

Several 3D echocardiographic indices of RV systolic function differ between dogs with advanced MMVD when compared with normal dogs. Further investigation is required to determine if these differences have clinical implications.

Predictive value of left atrial volumes assessed using real-time three-dimensional echocardiography for pulmonary hypertension in dogs with myxomatous mitral valve disease

Introduction

Left atrial volume (LAV) obtained using real-time three-dimensional echocardiography (RT3DE) is an independent predictor of post-capillary pulmonary hypertension (PH) in humans; however, no studies have investigated LAV obtained using RT3DE as a predictor of post-capillary PH in dogs with myxomatous mitral valve disease (MMVD). Therefore, we aimed to evaluate the clinical applicability of LAV obtained using RT3DE compared to that obtained using two-dimensional echocardiography (2DE) in dogs with MMVD, with or without PH.

Methods

Medical records and echocardiographic images of 237 privately owned dogs with naturally occurring MMVD with or without PH were retrospectively reviewed. A total of 49 privately owned dogs with naturally occurring MMVD, with or without PH, were finally included (35 MMVD without PH, 14 MMVD with PH). The LAV and left ventricular volumes were obtained using 2DE and RT3DE. Echocardiographic parameters were analyzed to identify independent predictors of post-capillary PH.

Results

We found that the left atrial and left ventricular volumes obtained using 2DE and RT3DE indexed to body weight and several 2DE-derived variables were univariately associated with post-capillary PH. Furthermore, multivariable logistic regression analysis revealed that the RT3DE minimum LAV indexed to body weight (LAVi min) was the only significant independent predictor of post-capillary PH (odds ratio, 12.86; 95% confidence interval [CI], 2.40-68.99; p = 0.003), with the highest area under the curve value of 0.86 (95% CI, 0.75-0.96; p < 0.001).

Discussion

In conclusion, LAV indexed to body weight obtained using 2DE and RT3DE, can be a useful predictor of post-capillary PH in dogs with MMVD. In particular, the RT3DE LAVi min was observed to be the strongest predictor of post-capillary PH.

Reference intervals for various measurements of canine left atrial size and function obtained using two-dimensional and three-dimensional echocardiography

BACKGROUND

Many canine cardiac diseases are associated with left atrial (LA) remodeling and decreased function. For accurate assessment of LA indices, large-scale and prospectively determined reference intervals are necessary.

OBJECTIVES

To generate reference intervals of LA size and function using two-dimensional and three-dimensional echocardiography.

ANIMALS

Two hundred and one healthy adult dogs.

METHODS

Left atrial volume was assessed in right parasternal long-axis, left apical 4-chamber and 2-chamber views using monoplane Simpson's method, two-dimensional and three-dimensional speckle tracking. Additionally, LA diameter was measured in right parasternal short-axis and long-axis views. Furthermore, LA function was determined by measuring strain and calculating LA fractional shortening and ejection fraction. All variables were tested for correlation to heart rate, age, and body weight. For LA diameter and volume, scaling exponents and prediction intervals were generated using allometric scaling. Reference intervals for LA function parameters were calculated using nonparametric methods.

RESULTS

Left atrial diameter and volume showed a strong correlation with body weight. The scaling exponent for LA diameter was approximately 1/3 (0.34-0.40) and approximately 1 for volume measurements (0.97-1.26). Parameters of LA function showed no clinically relevant correlation with body weight, except for two variables, which showed a mild negative correlation. No clinically relevant correlations with age or heart rate were found.

CONCLUSIONS

Reference intervals for linear, two-dimensional and three-dimensional measurements of LA size and function were established. The wide range of measurement methods offers the opportunity to select the appropriate reference values for LA evaluation depending on the available technical possibilities.

The Depiction of Hypertension in Heart Imaging Examinations: An Up-to-Date Review of the Evidence

Hypertension is one of the main preventable cardiovascular (CV) risk factors all over the years, closely related to CV morbidity and mortality. One of the most common hypertensive target organ damages is hypertensive heart disease (HHD), including left ventricular hypertrophy, which progresses gradually and leads to systolic or diastolic dysfunction of the left ventricular, and finally to end-stage heart failure. Regarding its prevalence and the need for early diagnosis, assessment of heart imaging examination is of major importance. Echocardiography has been used as the standard imaging technique to evaluate HHD for years, providing an accurate evaluation of the left ventricular geometry, along with the systolic and diastolic function. However, nowadays there is a growing interest in cardiovascular magnetic resonance (CMR). Despite the importance of the use of echocardiography in everyday clinical practice, numerous studies have shown the superiority of CMR as an imaging technique for clinical and research purposes, mainly due to its strength to provide an unlimited area of view, as well as the identification and quantification of the type and extent of myocardial fibrosis. Hence, this review aims to analyze the importance of heart imaging in the hypertensive population, with a special interest in CMR imaging.

Current use of real-time three-dimensional transthoracic echocardiography in animals

This review includes 36 studies of transthoracic real-time three-dimensional echocardiography (RT3DE) in animals. Most of these studies concern cardiac chamber quantification of the left atrium and left ventricle, in dogs. Comparisons of RT3DE and different two-dimensional echocardiographic (2DE) methods have been reported in dogs with myxomatous mitral valve disease (MMVD), dilated cardiomyopathy, and in healthy control dogs. Comparisons of RT3DE and standard reference methods have been reported in healthy control dogs. In dogs with MMVD, volumetric RT3DE measurements of left atrium do not appear to provide superior prognostic value compared with 2DE methods using Simpson's method of discs in dogs with MMVD. The major advantages of RT3DE compared to 2DE include improvements in visualization of the complex morphology of the mitral valve, the estimation of mitral valve regurgitation, and improved visualization of complex congenital cardiac abnormalities.

Current use of cardiac MRI in animals

Cardiovascular magnetic resonance (CMR) imaging has evolved to become an indispensable tool in human cardiology. It is a non-invasive technique that enables objective assessment of myocardial function, size, and tissue composition. Recent innovations in magnetic resonance imaging scanner technology and parallel imaging techniques have facilitated the generation of parametric mapping to explore tissue characteristics, and the emergence of strain imaging has enabled cardiologists to evaluate cardiac function beyond conventional metrics. As veterinary cardiology continues to utilize CMR beyond the reference standard, clinical application of CMR will further expand our capabilities. This article describes the current use of CMR and adoption of more recent advances such as T1/T2 mapping in veterinary cardiology.

Cardiac Magnetic Resonance Imaging Detects Myocardial Abnormalities in Naturally Infected Dogs with Chronic Asymptomatic Chagas Disease

Trypanosoma cruzi infection causes inflammation and fibrosis, resulting in cardiac damage in dogs. The objectives of this study were to describe cardiac magnetic resonance imaging (CMR) in naturally infected dogs with chronic Chagas disease and the frequency of abnormalities for CMR and cardiac diagnostic tests. Ten asymptomatic, client-owned dogs seropositive for T. cruzi were prospectively enrolled in an observational study evaluating echocardiography, ECG (standard and ambulatory), cardiac troponin I (cTnI), and CMR. Standard ECG measurements (3/10) and cTnI concentration (1/10) outside the reference range were uncommon. Ambulatory ECG abnormalities were documented more frequently (6/10 dogs) than with standard ECG and included ventricular arrhythmias (4), supraventricular premature beats (3), second-degree atrioventricular block (2), and sinus arrest (1). Echocardiographic abnormalities were documented in 6/10 dogs including mildly increased left ventricular internal dimension in diastole (1) and decreased right ventricular (RV) systolic function based on reductions in tricuspid annular plane systolic excursion (3) and RV S' (4). Abnormalities were detected with CMR in 7/10 dogs including delayed myocardial enhancement in 5 of which 2 also had increased extracellular volume, abnormal wall motion in 5, and loss of apical compact myocardium in 1. In conclusion, CMR abnormalities were common, and the results of this study suggest CMR can provide useful information in dogs with T. cruzi infection and may support naturally infected dogs for future clinical investigation as an animal model for Chagas disease.

Clinicopathologic features, comorbid diseases, and prevalence of pulmonary hypertension in dogs with bronchomalacia

Background

Reports of clinicopathologic features of bronchomalacia (BM) differ because of inconsistent definitions and frequent prevalence of comorbid cardiopulmonary disease. Pulmonary hypertension (PH) secondary to BM is poorly described.

Objectives

Dogs with BM will be older but of any somatotype, and increased expiratory effort, ≥1 comorbid disease, and PH will be more common than in dogs without BM.

Animals

Client‐owned dogs (n = 210) evaluated for respiratory signs.

Methods

Medical records of dogs with paired inspiratory: expiratory‐breath‐hold computed tomography, tracheobronchoscopy, or both between January 2016 and December 2019 were retrospectively reviewed. Comparisons between dogs with and without BM using Mann‐Whitney rank sum or χ² tests (P < .05 significant were made). Because of high numbers of variables, criteria with high prevalence (>25%) were identified (n = 10) for univariate analysis (P < .005 significant). Significant variables were submitted for multivariate analysis.

Results

Bronchomalacia was identified in 41% of dogs of all sizes/somatotypes; 38% were >10 kg. All dogs with BM had ≥1 comorbid cardiopulmonary disorder. Dogs with BM were significantly older (P < .001), smaller (P < .001), and were more likely diagnosed with tracheal or mainstem bronchial collapse (P < .001) or bronchiectasis (P < .001). Multivariate analysis confirmed associations with age, tracheal or mainstem bronchial collapse, and bronchiectasis. In dogs with BM, PH was more prevalent.

Conclusions and Clinical Importance

Although significantly more common in older, smaller dogs, BM occurs in dogs of all sizes and in all instances with comorbidities. Echocardiography should be considered in dogs with BM to identify PH.

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.

Echocardiographic reference intervals for right ventricular indices, including 3-dimensional volume and 2-dimensional strain measurements in healthy dogs

BACKGROUND

There is currently a lack of reference intervals (RIs) for the novel measures like 3-dimensional (3D) echocardiography or speckle-tracking strain for assessment of right ventricular (RV) structure and function.

OBJECTIVES

To generate RIs and to determine the influence of age, heart rate, and body weight (BW) on various RV function indices using a dedicated RV software for 3D RV end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), global and free wall RV longitudinal strain (RVLS), end-diastolic area (RVEDA), end-systolic area (RVESA), fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE), and tissue Doppler imaging (TVI)-derived systolic myocardial velocity of the lateral tricuspid annulus (S').

ANIMALS

Healthy adult client-owned dogs (n = 211) of various breeds and ages.

METHODS

Prospective study. Reference intervals were estimated as statistical prediction intervals using allometric scaling for BW-dependent variables. Right-sided (upper limit) or left-sided (lower limit) 95% RIs were calculated for every variable. Inter- and intraobserver variability was determined.

RESULTS

Most variables showed clinically acceptable repeatability with coefficient of variation less than 10. Upper or respectively lower RI after allometric scaling to normalize for different BWs were: EDVn ≤ 2.5 mL/kg^0.942 , ESVn ≤ 1.2 mL/kg^0.962 , TAPSEn ≥ 4.5 mm^0.285 , RVEDAn ≤ 1.4 cm² /kg^0.665 , RVESAn ≤ 0.8 cm² /kg^0.695 , and TVI S'n ≥ 5.6 cm/s/kg^0.186 . The calculated limits for indices without allometric normalization were: EF > 42.1%, FAC > 30.0%, free wall RVLS < -20.8%, and global RVLS < -18.3%.

CONCLUSIONS

Echocardiographic RIs for RV structure and function are provided.

Formula to estimate left atrial volume using antero-posterior diameter in patients with catheter ablation of atrial fibrillation

In patients undergoing atrial fibrillation (AF) ablation, an enlarged left atrium (LA) is a predictor of procedural failure as well as AF recurrence on long term. The most used method to assess LA size is echocardiography-measured diameter, but the most accurate remains computed tomography (CT).The aim of our study was to determine whether there is an association between left atrial diameters measured in echocardiography and the left atrial volume determined by CT in patients who underwent AF ablation.The study included 93 patients, of whom 60 (64.5%) were men and 64 (68.8%) had paroxysmal AF, who underwent AF catheter ablation between January 2018 and June 2019. Left atrial diameters in echocardiography were measured from the long axis parasternal view and the LA volume in CT was measured on reconstructed three-dimensional images.The LA in echocardiography had an antero-posterior (AP) diameter of 45.0 ± 6 mm (median 45; Inter Quartile Range [IQR] 41-49, range 25-73 mm), longitudinal diameter of 67.5 ± 9.4 (median 66; IQR 56-88, range 52-100 mm), and transversal diameter of 42 ± 8.9 mm (IQR 30-59, range 23-64.5 mm). The volume in CT was 123 ± 29.4 mL (median 118; IQR 103-160; range 86-194 mL). We found a significant correlation (r = 0.702; P < .05) between the AP diameter and the LA volume. The formula according to which the AP diameter of the LA can predict the volume was: LA volume = AP diam3 + 45 mL.There is a clear association between the left atrial AP diameter measured on echocardiography and the volume measured on CT. The AP diameter might be sufficient to determine the increase in the volume of the atrium and predict cardiovascular outcomes.

Echocardiographic assessment of right ventricular systolic function in healthy Beagle dogs compared to high field cardiac magnetic resonance imaging

Ten healthy Beagle dogs were used to compare selected echocardiographic parameters of right ventricular (RV) systolic function with high field cardiac magnetic resonance imaging (MRI). All dogs underwent complete transthoracic echocardiography before and during anesthesia, as well as cardiac MRI with determination of morphology-based ejection fraction, and phase contrast angiography-derived stroke volume. A correlation analysis was carried out between echocardiographic and MRI parameters. The values of fractional area change, tricuspid annular plane systolic excursion, tissue Doppler imaging derived peak velocity of the isovolumic contraction wave and systolic wave of the lateral tricuspid valve annulus showed lower values under general anesthesia. Of all echocardiographic parameters of RV systolic function, only fractional area change (r = 0.671, P = 0.034) and tissue Doppler imaging derived peak velocity of the systolic wave of the lateral tricuspid valve annulus (r = 0.768; P = 0.01), showed a significant correlation with MRI derived stroke volume. None of the echocardiographic parameters correlated with MRI derived ejection fraction. When evaluating the RV echocardiographically, fractional area change and peak velocity of the systolic wave of the lateral tricuspid valve annulus appear to be the most reliable predictors of RV systolic function when compared to MRI under anesthesia.

Quantitative assessment of left ventricular volume and function by transthoracic and transesophageal echocardiography, ultrasound velocity dilution, and gated magnetic resonance imaging in healthy foals

OBJECTIVE

To compare measurements of left ventricular volume and function derived from 2-D transthoracic echocardiography (2DE), transesophageal echocardiography (TEE), and the ultrasound velocity dilution cardiac output method (UDCO) with those derived from cardiac MRI (cMRI) in healthy neonatal foals.

ANIMALS

6 healthy 1-week-old Standardbred foals.

PROCEDURES

Foals were anesthetized and underwent 2DE, TEE, and cMRI; UDCO was performed simultaneously with 2DE. Images acquired by 2DE included the right parasternal 4-chamber (R4CH), left apical 4- and 2-chamber (biplane), and right parasternal short-axis M-mode (M-mode) views. The longitudinal 4-chamber view was obtained by TEE. Measurements assessed included left ventricular end-diastolic volume (LVEDV), end-systolic volume (LVESV), ejection fraction, stroke volume (LVSV), cardiac output (CO), and cardiac index (CI). Bland-Altman analyses were used to compare measurements derived from biplane, R4CH, and M-mode images and UDCO with cMRI-derived measurements. Repeatability of measurements calculated by 3 independent reviewers was assessed by the intraclass correlation coefficient.

RESULTS

Compared with cMRI, all 2DE and TEE modalities underestimated LVEDV and LVESV and overestimated ejection fraction, CO, and CI. The LVSV was underestimated by the biplane, R4CH, and TEE modalities and overestimated by UDCO and M-mode methods. However, the R4CH-derived LVSV, CO, and CI were clinically comparable to cMRI-derived measures. Repeatability was good to excellent for measures derived from the biplane, R4CH, M-mode, UDCO, and cMRI methods and poor for TEE-derived measures.

CONCLUSIONS AND CLINICAL RELEVANCE

All assessed modalities yielded clinically acceptable measurements of LVEDV, LVESV, and function, but those measurements should not be used interchangeably when monitoring patient progress.

Recommendations for standardized plane definition in canine cardiac MRI

With the growing interest in cardiac magnetic resonance imaging (cMRI), veterinary radiologists will increasingly be asked to use this modality to answer complex cardiological questions. Plane alignment is crucial for reproducible assessment of the heart. Anesthesia time is a limiting factor in cMRI. Aims of this prospective experimental study were to introduce a flow chart for standardized cMRI-examination in dogs, to test it for reproducibility using a cardiac CT simulation and to estimate time requirements needed to complete the examination accurately. Six operators (3 radiologists, 1 cardiologist, 1 imaging-resident, 1 technician) simulated a cMRI examination on CT-scans of 6 healthy Beagle dogs twice within two to four weeks. Assessment included qualitative and quantitative scoring of plane quality and time requirements. The quality of planes was high for the left and moderate for the right side of the heart. The intraclass correlation coefficient (ICC) of linear measurements of structures on the left was good to excellent (ICC-range: 0.789-0.948) but dropped to moderate to poor levels for the right side (ICC-range: 0.429-0.738). The median time required to complete a full examination was 30 (range: 13-103) min in the first and 24 (range: 15-62) min in the second evaluation. It differed significantly between operators and was consistently shorter for the left than for the right side. In conclusion, a new standardized scheme for cMRI can be quickly adopted by radiologists with some expertise in cross sectional imaging. Qualitative and quantitative results were highly reproducible for the left but less for the right side.

Reproducibility of echocardiographic indices of left atrial size in dogs with subclinical myxomatous mitral valve disease

Background

Reliability of echocardiographic measurements of left atrial (LA) size, an important marker of disease severity, has not been reported in dogs with myxomatous mitral valve disease (MMVD).

Objectives

To define and compare reliability of left atrial dimension/diameter (LAD), LAD indexed to aortic valve diameter (LAD/AoD), left atrium‐to‐aortic root ratio (LA/Ao), left atrial volume acquired from a right parasternal long‐axis (LAV^RPLx), and left apical view (LAV^LAP) in dogs with subclinical MMVD.

Animals

Nine dogs with subclinical MMVD.

Methods

Prospective reproducibility study. Dogs underwent 12 echocardiographic examinations by 2 operators on the mornings and afternoons of 3 nonconsecutive days within 1 week. Reliability (measurement variability) was quantified using coefficients of variation (CV) and 95% repeatability/reproducibility coefficients (95% RC). A mixed‐model analysis of variance (ANOVA) was used to determine if time of day, day, and operator were significant sources of variability for each index.

Results

Linear measurements (LAD, LAD/AoD, and LA/Ao) exhibited less within‐day, between‐day, and interoperator variability (CVs, 3.9%‐12.5%) than did volume estimate measurements (LAV^RPLx and LAV^LAP; CVs, 11.8%‐17.9%). Of the linear measurements, LA/Ao exhibited greater variability (CVs, 9.9%‐12.5%) compared to LAD and LAD/AoD (CVs, 3.9%‐4.9%). Operator was a significant (P = .005) source of variability for LA/Ao.

Conclusions and Clinical Importance

Compared to other linear measurements, LA/Ao was the least reproducible and most dependent on operator. The 95% RC for each LA size index are provided to help identify clinically relevant changes (beyond intraoperator or interoperator variability) during serial echocardiographic examinations of dogs with subclinical MMVD.

Reproducibility of geometric and flow-based echocardiographic measurements used for quantification of left ventricular total and forward stroke volume in healthy dogs

BACKGROUND

Cardiac structure and function in dogs are commonly assessed using echocardiography. A variety of linear, area, and flow-based measurements can be used to calculate left ventricular (LV) total stroke volume (TSV) and forward stroke volume (FSV), but the reproducibility of many of these measurements has not been fully studied. We hypothesized that survey of echocardiographic variables would identify those with high reproducibility and inform future investigation of different methods to measure LV TSV and FSV.

METHODS

The reproducibility of 25 geometric and flow-based echocardiographic measurements was prospectively evaluated in 23 healthy dogs by two experienced observers. Reproducibility (i.e., interobserver agreement) was described using intraclass correlation coefficients. The reproducibility of various methods to calculate LV TSV and FSV was explored.

RESULTS

Reproducibility was generally good to excellent. Variables of LV width, length, and area and aortic and sinotubular junction diameter and velocity time integral were among measures with the highest reproducibility. Measurements of mitral annular diameter and mitral inflow velocity time integral possessed lower reproducibility. Calculation of LV TSV using measurements involved in the cube and bullet formulas demonstrated higher reproducibility than the Simpson's method of disks or mitral inflow methods. Calculation of LV FSV using LV outflow tract and aortic diameters from the right parasternal view generally demonstrated higher reproducibility compared with the left-sided view.

CONCLUSIONS

The reproducibility of many simple geometric and flow-based echocardiographic measurements is high. Comparison of the reliability of different measurement informs future investigation of echocardiographic methods to determine LV TSV and FSV in dogs.

Effects of the estrous cycle and pregnancy status on cardiovascular variables in healthy bitches

INTRODUCTION

The aim of the study was to characterize changes in maternal cardiovascular variables throughout the reproductive cycle in healthy bitches and determine whether magnitude of pregnancy-induced changes correlates to litter size.

ANIMALS

Eleven client-owned breeding bitches were included in the study.

MATERIALS AND METHODS

Bitches were enrolled prospectively and followed up longitudinally throughout a single reproductive cycle. Physical examination, echocardiography, blood pressure analysis, and plasma volume estimation were performed during proestrus, diestrus (early and late pregnancy), and anestrus. Fetal echocardiography was performed during late pregnancy. Data were compared across visits using a linear mixed-effects model, and correlation between variables was assessed.

RESULTS

Compared with proestrus, no significant changes were observed at any phase of the cycle in heart rate, blood pressure, echocardiographic measurements of left ventricular size or function, or echocardiographic calculations of stroke volume or cardiac output. Estimated plasma volume increased by 29.6% in early pregnancy (p < 0.001) and 70.7% in late pregnancy (p < 0.001). Fetal echocardiography was feasible in a subset of fetuses for each bitch. There was a significant correlation between estimated total fetal cardiac output and late pregnancy increase in maternal cardiac output (p = 0.0025). The incidence of physiologic heart murmurs ranged from 5 of 11 (45%) bitches in proestrus to 2 of 11 (18%) bitches in late pregnancy, attributed to variations in aortic outflow velocity.

CONCLUSIONS

Hemodynamic alterations in pregnant bitches do not result in consistently detectable echocardiographic changes, suggesting that cardiac screening could be diagnostic at any time during a reproductive cycle. Physiologic heart murmurs were common in this study population and not obviously associated with the reproductive cycle.

Comparison of left and right atrial volumes determined by two- and three-dimensional echocardiography with those determined by multidetector computed tomography for healthy dogs

OBJECTIVE

To compare left atrial volume (LAV) and right atrial volume (RAV) determined by 2-D and 3-D echocardiographic methods with the LAV and RAV determined by ECG-gated multidetector CT (MDCT) for healthy dogs.

ANIMALS

11 healthy purpose-bred young adult hound-type dogs.

PROCEDURES

Each dog was anesthetized and underwent MDCT and a complete echocardiographic examination. Modality-specific software was used to measure the respective atrial volumes at ventricular end systole, and LAV and RAV measurements were subsequently indexed to body weight and compared among imaging modalities.

RESULTS

The LAV determined by echocardiographic methods did not differ significantly from the LAV determined by MDCT. However, the RAV determined by 3-D echocardiography and 2-D echocardiography via the left apical and left cranial windows differed significantly from the RAV determined by MDCT. Bland-Altman analyses indicated that the indexed LAV and RAV determined by echocardiographic methods were systematically underestimated, compared with MDCT measurements, but the bias was much smaller for LAV than for RAV.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that, for dogs, echocardiography might be an acceptable alternative to MDCT for measurement of LAV but not for measurement of RAV. However, the study population was small and homogenous in terms of breed, age, and weight. These findings need to be validated in a larger, more varied population of dogs with and without cardiac disease.

Effect of pimobendan on left atrial function in dogs with preclinical myxomatous mitral valve disease

Background

Left atrial (LA) function is an important determinant of the left ventricular (LV) filling, playing a key role in maintaining optimal cardiac performance. Pimobendan is a phosphodiesterase III inhibitor with positive inotropic and vasodilator effects. The present study aims to investigate the effects of pimobendan on LA function in dogs with stage B2 myxomatous mitral valve disease (MMVD).

Aim

The aim of this investigation was to study the effects of pimobendan on LA function in dogs with preclinical MMVD.

Methods

Twenty-seven dogs with stage B2 MMVD were retrospectively included. LA function was assessed before and 1-6 months following pimobendan initiation. For each dog, two-dimensional (2D) echocardiography was performed to assess LA diameter and volume for each phase of the LA cycle and to assess complete, passive, and active LA function. Pulsed-wave tissue Doppler imaging (TDI) of the left ventricular longitudinal myocardial velocity associated with atrial contraction (A'), both at the level of the interventricular septum and the LV free wall, was also used as an indicator of LA function.

Results

There were no significant differences in any of the left atrial variables pre- and posttreatment.

Conclusion

Echocardiographic estimates of LA function by 2D diameters and volumes and TDI A' in dogs with MMVD do not change after treatment with pimobendan.

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 (LAV_max) and minimum LAV (LAV_min) 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 LAV_max and LAV_min, respectively (all p < 0.05). Biases for LAV_max (-0.96 mL, 95% LoA: -5.6 to 3.7) and LAV_min (-0.67 mL, 95% LoA: -5.4 - 4.1) were minimal with RT-3DE, reflecting a slight underestimation. Conversely, MOD (LAV_maxbias = 3.19 mL, 95% LoA: -5.7 - 12.1; LAV_minbias = 1.96 mL, 95% LoA: -4.6 - 8.5) and ALM (LAV_maxbias = 4.05, 95% LoA: -5.7 - 13.8; LAV_minbias = 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.