Echocardiographic parameters and indices in the normal beagle dog

Echocardiographic findings in apparently healthy Czechoslovakian wolfdogs

INTRODUCTION

To echocardiographically evaluate a large number of apparently healthy Czechoslovakian wolfdogs (CWDs) to identify possible subclinical cardiac abnormalities and to generate reference intervals.

ANIMALS

One-hundred and seventeen apparently healthy client-owned CWDs.

MATERIALS AND METHODS

Standard two-dimensional, M-mode, and Doppler echocardiographic measurements were obtained on non-sedated, manually restrained standing dogs. Animals with no relevant echocardiographic abnormalities were used to generate reference intervals. Echocardiographic variables were compared between males and females and between dogs with and without mitral regurgitation (MR).

RESULTS AND DISCUSSION

Among the 117 CWDs, 103 dogs were used to generate reference intervals. The 14 dogs with abnormalities had more than trivial MR (12 dogs), subaortic stenosis (one dog), and equivocal subaortic stenosis (one dog). The 44 males were heavier than 59 females (P<0.001) and had a larger maximum left atrial dimension (P=0.015), left ventricular internal dimension at end-diastole (P<0.001) and systole (P<0.001), and thicker interventricular septum thickness at end-diastole (P=0.016). A positive linear correlation was identified between bodyweight and aortic root and left atrial diameters and left ventricular dimensions and between age and aortic root and left atrial diameter and peak late transmitral flow velocity. A negative linear correlation was identified between age and peak early transmitral flow velocity and the ratio between peak early and late transmitral flow velocities. No differences in echocardiographic-derived cardiac dimensions were detected between healthy dogs and dogs with more than trivial MR.

CONCLUSIONS

In this population of CWDs, subclinical cardiac abnormalities were uncommon, and they were mainly classified as MR.

M-Mode Echocardiography in Canine Veterinary Practice: A Comprehensive Review of Left Ventricular Measurements in 44 Different Dog Breeds

This review article focuses on the use of canine M-mode in veterinary medicine, specifically in assessing the left ventricle measurements in several breeds. It traces the historical development of echocardiography techniques, including A-mode, B-mode, and motion mode (M-mode), which provide accurate unidimensional records of cardiac structures. This article highlights the significance of M-mode measurements in diagnosing stage B2 of MMVD, where left ventricular end-diastolic internal diameter corrected with body weight (LVIDdN) is essential for identifying cardiac enlargement. It also explains the role of M-mode in diagnosing DCM, outlining criteria such as left ventricular dilatation. The authors emphasize the importance of breed-specific reference values for echocardiographic measurements due to variations in somatotype among dogs. This review provides a comprehensive table summarizing M-mode measurements of the left ventricle for 44 different dog breeds, including interventricular septum thickness, left ventricular internal diameter, and left ventricular posterior wall thickness during systole and diastole. This review's methodology involves compiling data from various scientific literature sources, providing an extensive tabular representation of M-mode measurements for different breeds, ages, and sexes. Overall, this review highlights the critical role of M-mode echocardiography in diagnosing and managing cardiac diseases in dogs, underscores the importance of breed-specific reference values, and presents a comprehensive summary of M-mode measurements for various dog breeds, aiding both clinicians and researchers.

Morphogeometric Evaluation of the Left Ventricle and Left Atrioventricular Ring in Dogs: A Computerized Anatomical Study

In veterinary, there is scarce availability of morphogeometric studies in normal and remodeled hearts; furthermore, ventricular geometry acts as an indicator of cardiac function. It is a highly necessary field of knowledge for the development of therapeutic protocols, especially surgical ones. The objectives of this study were: to obtain measurements of the left atrioventricular valve ring and left ventricle, to analyze the proportionality between the segments of the left cardiac chamber of normal hearts and to describe reference values for morphogeometric analysis of the left ventricle. For this, 50 hearts from small (Group 1-G1) and medium to large (Group 2-G2) dogs were laminated in the apical, basal and equatorial segments, and submitted to computer analysis to identify the perimeter of each segment and the left atrioventricular ring, wall thickness and distance from the atrioventricular sulcus to the apex. The largest internal perimeter was that of the equatorial. The basal segment had the highest mean for ventral parietal wall thickness, suggesting greater contractile reserve at that location. Considering the proportionality relationships, there was no statistical difference between the intersegmental perimeter indices for the two groups. This suggests that despite the animals' weight variations, the proportions between the left ventricular segments are maintained. Therefore, it is concluded that the data can be used as a standard of comparison for cardiac geometric assessments, as well as a basis for the development of therapeutic measures in the context of adverse cardiac remodeling.

Use of proposed systolic and myocardial performance indices derived from simultaneous ECG and PCG recordings to assess cardiac function in healthy Beagles

Background and Aim:

Cardiac time intervals (CTIs) can provide important information on the electrical and mechanical properties of the heart. We hypothesized that cardiac function can be described using the combined power of electrocardiography (ECG) and phonocardiography (PCG) signals. This study aimed to (1) validate a novel custom device in measuring CTI parameters; (2) compare CTI parameters with a commercially available device and standard transthoracic echocardiography (STE); and (3) compare calculated systolic performance index (SPI) and myocardial performance index (MPI) with Tei index from the STE.

Materials and Methods:

This study determined CTIs based on simultaneous ECG and PCG recordings in 14 healthy Beagle dogs using the custom-built device. These CTI parameters were compared with a commercially available device (Eko DUO ECG + Digital Stethoscope; Eko DUO) and the STE. Agreement of CTI parameters between the custom device and the commercially available device or STE was evaluated. Calculated SPI and MPI based on Wigger’s diagram were proposed, compared with SPI and Tei index, and correlated with STE parameters.

Results:

We found that the ECG and PCG parameters measured from the custom-built device did not differ from the commercially available device and the STE. By combining ECG and PCG signals, we established CTI parameters in healthy dogs including indices for systolic function (SPI: QS1/S1S2) and global cardiac function {F1 ([QS1+S2]/S1S2), F2 ([RS1+S2]/S1S2), and F3 (RS1 + [QS2-QT]/S1S2)}. The SPI, F2, and F3 were comparable with echocardiographic parameters describing systolic (Pre-ejection period/left ventricular ejection time [LVET]) and Tei index ([MCOdur-LVET]/LVET), respectively. Only SPI and F3 were correlated significantly with MCOdur and heart rate, respectively.

Conclusion:

We have validated the use of the custom-built device to describe CTIs that are comparable to the commercially available device and STE in healthy Beagles. The proposed SPI and MPI derived from CTI parameters can be useful in clinical practice to describe the cardiac function, especially in areas where access to STE is constrained.

Echocardiographic evaluation of working dogs of the Military Police of Rio de Janeiro: effects of the breed and body weight

The Military Police of Rio de Janeiro state use dogs as a decisive tool for patrol and detection of drugs, weapons, and explosives. Complementary tests, such as echocardiography, are essential to maintain the integrity of these animals. This study aimed to evaluate the echocardiographic parameters of the working dogs belonging to the Military Police of Rio de Janeiro and compare them with the available data. Echocardiographic evaluation was performed on 48 healthy adult dogs from the Canine Action Battalion of the Military Police of Rio de Janeiro, Brazil. The sample consisted of 13 Labrador Retrievers, 12 Malinois Belgian Shepherds, 10 German Shepherds, 8 Dobermann Pinschers, and 5 Dutch Shepherds. Echocardiographic variables were correlated with body weight (BW). A positive correlation (P=0.0142, r=0.6837) between BW and the diameter of the left atrium was found in Malinois Belgian Shepherds. In German Shepherds, a positive correlation between BW and the internal diameter of the right ventricle during diastole (P=0.0320, r=0.6757) was observed; in addition, a positive correlation between BW and left ventricular internal diameter (P=0.0344, r=0.6689) during diastole was also found. Echocardiographic evaluations of these working dogs differed slightly from those previously established for similar-sized dog breeds.

Echocardiographic parameters and indices in 23 healthy Maltese dogs

BACKGROUND

Echocardiography is a primary tool used by veterinarians to evaluate heart diseases. In recent years, various studies have targeted standard echocardiographic values for different breeds. Reference data are currently lacking in Maltese dogs and it is important to fill this gap as this breed is predisposed to myxomatous mitral valve disease, which is a volume overload disease.

OBJECTIVES

To establish the normal echocardiographic parameters for Maltese dogs.

METHODS

In total, 23 healthy Maltese dogs were involved in this study. Blood pressure measurements, thoracic radiography, and complete transthoracic echocardiography were performed. The effects of body weight, age and sex were evaluated, and the correlations between weight and linear and volumetric dimensions were calculated by regression analysis.

RESULTS

The mean vertebral heart size was 9.1 ± 0.4. Aside from the ejection fraction, fractional shortening, and the left atrial to aorta root ratio, all the other echocardiographic parameters were significantly correlated with weight.

CONCLUSION

This study describes normal echocardiographic parameters that may be useful in the echocardiographic evaluation of Maltese dogs.

Echocardiographic reference intervals for volumetric measurements of the left ventricle using the Simpson's method of discs in 1331 dogs

Background

Echocardiographic measurements play an important role in detecting cardiac enlargement and assessing cardiac function. In human cardiology, M‐mode measurements have been widely replaced by volumetric measurements of the left ventricle (LV) using Simpson's method of disc (SMOD). In veterinary cardiology, more large‐scale studies are necessary to generate reference intervals (RIs) for SMOD LV volume measurements.

Objective

To generate body size independent RIs for LV volume measurements in dogs.

Animals

Healthy adult dogs (n = 1331) of variable size and somatotype.

Methods

Prospective study. The SMOD was measured from the right parasternal long axis and the left apical 4‐chamber view in clinically healthy dogs. The SMOD measurements were normalized to various allometric scales (kg, kg^2/3, or kg^1/3). RIs for LV end‐diastolic volume (LVEDV) and LV end‐systolic volume (LVESV) using SMOD were estimated as prediction intervals of both a linear and an additive regression model. Additionally, after normalization to body weight, 95% RIs were determined using nonparametric methods with 2.5 and 97.5 percentiles serving as the lower and upper limits. Separate analyses were performed for 120 sighthound breeds and 1211 other breeds.

Results

Echocardiographic LV volumes correlated best with weight in kilograms. The additive model proved to be more flexible and accurate than the other 2 methods to generate RIs. Separate RIs for sighthound and all other breeds are provided.

Conclusions and Clinical Importance

Body size and breed‐independent RIs for LV volume measurements using SMOD were generated prospectively from a large and diverse population of dogs and are available for clinical use.

Reference intervals for transthoracic echocardiography in the American Staffordshire Terrier

This study reports the echocardiographic reference intervals in the American Staffordshire Terrier (AST). The echocardiographic variables obtained in 57 healthy adult AST were compared with published data from the general canine population and other breeds. In the AST, the left ventricular volumes were lower than values reported in Boxers and Dobermans (P<0.0001), but higher than in small breeds (P<0.0001). The left ventricular ejection fraction was higher than Boxers and Dobermans (P<0.0001), but lower than small breed dogs (P=0.027). The aortic peak velocity values were similar to Boxers (P=0.55) but higher than the general canine population (P<0.0001). The reference intervals presented in this study are clinically useful for an accurate echocardiographic interpretation and screening in the AST.

Left ventricular M-mode prediction intervals in 7651 dogs: Population-wide and selected breed-specific values

BACKGROUND

Echocardiography is a common method to measure heart size in dogs. The heart dimensions are influenced by body weight (BW) and potentially by breed.

OBJECTIVES

To establish BW-dependent prediction intervals (PIs) of the left ventricular (LV) linear dimensions in a population of dogs of many breeds in multicenter environment, and to identify breeds deviating from these intervals. DOGS: Seven thousand six hundred and fifty-one dogs.

METHODS

Retrospectively, data from heart screens conducted between 2009 and 2016 were included. Cardiac dimensional PIs were generated using allometric scaling including all nonsighthound dogs and values were compared to previously published PIs. The values measured in dogs of respective breeds, including sighthounds, were then compared to the overall nonsighthound PIs to identify deviant breeds. The interobserver-variability of the measurements was determined using the explained residual variance.

RESULTS

Prediction intervals for the nonsighthound dogs were in agreement with previously published cardiac PIs, although the upper limits of the generated PIs of our study were slightly below those currently applied (except the interventricular septum in systole and the left ventricular free wall in diastole below 10.0 kg and 15.0 kg, respectively). Values measured in the nonsighthound breed Newfoundland deviated for most dimensions. Most of the sighthound breeds analyzed had greater cardiac dimensions, with the exception of the Irish Wolfhound.

CONCLUSION AND IMPORTANCE

Findings of our study reinforces the value of BW-dependent PIs for cardiac dimensions in dogs and suggest that these PIs are valid for most nonsighthound breeds, but not the sighthound breeds.

Mitochondrial PCK2 Missense Variant in Shetland Sheepdogs with Paroxysmal Exercise-Induced Dyskinesia (PED)

Four female Shetland Sheepdogs with hypertonic paroxysmal dyskinesia, mainly triggered by exercise and stress, were investigated in a retrospective multi-center investigation aiming to characterize the clinical phenotype and its underlying molecular etiology. Three dogs were closely related and their pedigree suggested autosomal dominant inheritance. Laboratory diagnostic findings included mild lactic acidosis and lactaturia, mild intermittent serum creatine kinase (CK) elevation and hypoglycemia. Electrophysiological tests and magnetic resonance imaging of the brain were unremarkable. A muscle/nerve biopsy revealed a mild type II fiber predominant muscle atrophy. While treatment with phenobarbital, diazepam or levetiracetam did not alter the clinical course, treatment with a gluten-free, home-made fresh meat diet in three dogs or a tryptophan-rich, gluten-free, seafood-based diet, stress-reduction, and acetazolamide or zonisamide in the fourth dog correlated with a partial reduction in, or even a complete absence of, dystonic episodes. The genomes of two cases were sequenced and compared to 654 control genomes. The analysis revealed a case-specific missense variant, c.1658G>A or p.Arg553Gln, in the PCK2 gene encoding the mitochondrial phosphoenolpyruvate carboxykinase 2. Sanger sequencing confirmed that all four cases carried the mutant allele in a heterozygous state. The mutant allele was not found in 117 Shetland Sheepdog controls and more than 500 additionally genotyped dogs from various other breeds. The p.Arg553Gln substitution affects a highly conserved residue in close proximity to the GTP-binding site of PCK2. Taken together, we describe a new form of paroxysmal exercise-induced dyskinesia (PED) in dogs. The genetic findings suggest that PCK2:p.Arg553Gln should be further investigated as putative candidate causal variant.

Reference intervals and echocardiographic findings in Leonberger dogs

INTRODUCTION

Leonbergers are large-breed dogs believed to be predisposed to dilated cardiomyopathy, yet the normal echocardiographic measurements of these dogs are unknown. The aim of this study was to describe echocardiographic findings and propose breed-specific reference intervals (RIs) for Leonbergers.

ANIMALS

A total of 42 clinically healthy dogs were involved in this study.

MATERIALS AND METHODS

This study was designed as a cross-sectional study of 42 Leonberger dogs undergoing complete transthoracic echocardiographic studies at a national show. Reference intervals were determined using robust method with bootstrapping. The effects of age, sex, and body weight (BW) on linear and volumetric dimensions were evaluated by regression analysis. Intra- and interobserver variability were evaluated by coefficient of variation from 10 of the studies.

RESULTS

There were significant linear correlations with BW for many of the cardiac variables evaluated. However, despite the statistical significance, most regression equations had small slopes, necessitating large changes in BW for small changes in two-dimensional echocardiographic variables. As such, this study resulted in breed-specific RIs irrespective of BW. Trace mitral insufficiency (n = 18), trace aortic insufficiency (n = 15), or both (n = 1) was identified in 81% of dogs in this population. Coefficients of variation were <9% for all two-dimensional, volumetric, and motion mode measurements.

CONCLUSIONS

This study describes echocardiographic findings and provides RIs, which may be useful in echocardiographic evaluations of Leonbergers and may aid in early identification of heart disease within the breed.

Reference Values and Repeatability of B-Mode and M-Mode Echocardiographic Parameters in Healthy Donkey (Equus asinus)-The Guide to Assess Healthy Heart

Donkey (Equus asinus), the cheapest form of agricultural power in Egypt, is used principally as draught or pack animals and may also be ridden, or used for threshing, raising water, milling, and other work. The aim of the present study was to provide B-mode and M-mode echocardiographic reference ranges from a sample of population of donkeys (E. asinus) based on the probability theory and statistics. In the present study, B-mode and 2-dimensional guided M-mode echocardiography were performed on 44 clinically healthy donkeys (E. asinus) (22 males and 22 females), without any neither clinical nor echocardiographic evidence of cardiovascular diseases, aged 2-25 year old, and weighed 150-350 kg. The echocardiographic dimensions, including interventricular septum thickness at end diastole, interventricular septum thickness at end systole, left ventricular internal diameter at end diastole, left ventricular internal diameter at end systole, left ventricular posterior wall thickness at end diastole, and left ventricular posterior wall thickness at end systole were assessed. The cardiac function indices, including end diastolic volume, end systolic volume, stroke volume, ejection fraction, and fractional shortening were also measured. B-mode and guided M-mode echocardiographic examination of healthy donkeys revealed that both the interventricular septum thickness and the left ventricular posterior free wall were greater during systole than diastole. However, the left ventricular dimension during diastole was greater than systole. Furthermore, the recorded data of cardiac function indices, including end diastolic volume, end systolic volume, stroke volume, ejection fraction, and fractional shortening using B-mode echocardiography were closer to those recorded by guided M-mode echocardiography. To our knowledge, this is the first Egyptian study to report the echocardiographic reference ranges of donkeys (E. asinus) based on the probability theory and statistics, the coefficient of variation. The results of the present study can be used as standard and reference values for further echocardiographic studies in donkeys and represent a step in the identification, interpretation, and evaluation of cardiovascular disorders in such animals.

Echocardiographic study of healthy Indian Spitz dogs with normal reference ranges for the breed

Aim:

The present study was aimed to determine the normal reference values of M-mode echocardiographic measurements in healthy Indian Spitz dogs and evaluate the influence of gender and body weight on these measurements.

Materials and Methods:

M-mode echocardiography was performed in twenty-four clinically healthy conscious Indian Spitz dogs, aged 3-5 years and weighing 7-18 kg. Measurements were made from the right parasternal long axis left ventricular outflow tract view of the heart. The parameters recorded were: Left ventricular internal dimension, interventricular septal thickness and left ventricular posterior wall thickness during diastole and systole, left atrial diameter, aortic root diameter, left ventricular systolic functional parameters, and indices and mitral valve parameters.

Results:

M-mode echocardiographic measurements in healthy Indian Spitz dogs were standardized. Gender had no influence on echocardiographic measurements except mitral valve excursion amplitude and time interval between onset and end of mitral valve closure, which were significantly (p<0.05) higher in females than males. Left ventricular internal dimension at end-diastole, left ventricular internal dimension at end-systole, left ventricular posterior wall dimension at end-systole, end-diastolic volume, end-systolic volume, stroke volume, cardiac output, left ventricular ejection time, and mitral valve excursion amplitude correlated significantly (p<0.05) with body weight in Indian Spitz dogs.

Conclusion:

Data obtained in the present study can be used as breed-specific reference values for cardiac disease diagnosis as well as for future studies in Indian Spitz dogs.

ACVIM consensus guidelines for the diagnosis and treatment of myxomatous mitral valve disease in dogs

This report, issued by the ACVIM Specialty of Cardiology consensus panel, revises guidelines for the diagnosis and treatment of myxomatous mitral valve disease (MMVD, also known as endocardiosis and degenerative or chronic valvular heart disease) in dogs, originally published in 2009. Updates were made to diagnostic, as well as medical, surgical, and dietary treatment recommendations. The strength of these recommendations was based on both the quantity and quality of available evidence supporting diagnostic and therapeutic decisions. Management of MMVD before the onset of clinical signs of heart failure has changed substantially compared with the 2009 guidelines, and new strategies to diagnose and treat advanced heart failure and pulmonary hypertension are reviewed.

MORPHOMETRIC ASSESSMENT OF CANINE HEART WITHOUT MACROSCOPICALLY VISIBLE CHANGES CAUSED BY CARDIAC DISEASE

Abstract The purpose of this study was to collect data on the cardiac morphometry of thirty adult male and female dogs without macroscopic changes indicative of heart disease, regardless of animal's body weight and score. The dogs were weighed, grouped according to their body weight, and necropsied for a macroscopic evaluation of their cardiac measurements. The data obtained were included in a database. The following cardiac measures were evaluated: vertical and horizontal axes, weight, volume, thickness of the right and left atria and ventricles, and horizontal and vertical axes of the atrial and ventricular chambers. The heart weight was found to represent 0.6 to 1.1% of the animal's body weight. No differences were found in cardiac size and weight as a function of sex. The ratio between the vertical and horizontal cardiac axes was 1.11. The left ventricle was found to be 1.6 to threefold thicker than the right ventricle. The results were considered standard for dogs and can be used for macroscopic evaluations of cardiac hypertrophy or dilation.

Dose-dependent effects of isoflurane and dobutamine on cardiovascular function in dogs with experimental mitral regurgitation

OBJECTIVE

To investigate the dose-dependent effects of isoflurane and dobutamine on haemodynamics in dogs with experimentally induced mitral valve insufficiency (MI).

STUDY DESIGN

Experimental, dose-response study.

ANIMALS

Six healthy Beagle dogs.

METHODS

Dogs with surgically induced MI were anaesthetized once. First, anaesthesia was maintained at an end-tidal isoflurane concentration (Fe'Iso) 1.0% (ISO1.0) for 20 minutes. Then, dobutamine was infused successively at 2, 4, 8 and 12 μg kg^-1 minute^-1 (DOB2-12) for 10 minutes at each dose rate. Measurements were recorded at each stage. Dobutamine was discontinued and Fe'Iso was increased to 1.5% (ISO1.5) for 20 minutes. Dobutamine was administered similarly to ISO1.0, and cardiovascular variables were recorded. The same sequence was repeated for Fe'Iso 2.0% (ISO2.0). Aortic pressure (AoP) and left atrial pressure (LAP) were recorded by radiotelemetry. The combination method of the pressure-volume loop analysis and transoesophageal echocardiography was used to measure cardiovascular variables: end-systolic elastance (Ees), effective arterial elastance (Ea), Ea/Ees, forward stroke volume (FSV), heart rate (HR), and cardiac output (CO).

RESULTS

High isoflurane concentration resulted in reduced Ees and increased Ea/Ees, which indicated low arterial pressure. High-dose dobutamine administration resulted in increased Ees and FSV at all isoflurane concentrations. In ISO1.5 and ISO2.0, HR was lower at DOB4 than baseline (BL) but increased at DOB12 compared with DOB4. CO increased at ≥ DOB8 compared with BL. In ISO1.5 and ISO2.0, systolic and mean AoP increased at ≥ DOB4 and ≥ DOB8, respectively. LAP did not change under all conditions.

CONCLUSIONS AND CLINICAL RELEVANCE

The dose-dependent hypotensive effect of isoflurane in MI dogs was mainly derived from the decrease in contractility. Dobutamine increased AoP without increasing LAP by increasing the contractility attenuated by isoflurane. Our findings may improve the cardiovascular management of dogs with MI undergoing general anaesthesia with isoflurane.

Effects of systemic multiexon skipping with peptide-conjugated morpholinos in the heart of a dog model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a lethal genetic disorder caused by an absence of the dystrophin protein in bodywide muscles, including the heart. Cardiomyopathy is a leading cause of death in DMD. Exon skipping via synthetic phosphorodiamidate morpholino oligomers (PMOs) represents one of the most promising therapeutic options, yet PMOs have shown very little efficacy in cardiac muscle. To increase therapeutic potency in cardiac muscle, we tested a next-generation morpholino: arginine-rich, cell-penetrating peptide-conjugated PMOs (PPMOs) in the canine X-linked muscular dystrophy in Japan (CXMD_J) dog model of DMD. A PPMO cocktail designed to skip dystrophin exons 6 and 8 was injected intramuscularly, intracoronarily, or intravenously into CXMD_J dogs. Intravenous injections with PPMOs restored dystrophin expression in the myocardium and cardiac Purkinje fibers, as well as skeletal muscles. Vacuole degeneration of cardiac Purkinje fibers, as seen in DMD patients, was ameliorated in PPMO-treated dogs. Although symptoms and functions in skeletal muscle were not ameliorated by i.v. treatment, electrocardiogram abnormalities (increased Q-amplitude and Q/R ratio) were improved in CXMD_J dogs after intracoronary or i.v. administration. No obvious evidence of toxicity was found in blood tests throughout the monitoring period of one or four systemic treatments with the PPMO cocktail (12 mg/kg/injection). The present study reports the rescue of dystrophin expression and recovery of the conduction system in the heart of dystrophic dogs by PPMO-mediated multiexon skipping. We demonstrate that rescued dystrophin expression in the Purkinje fibers leads to the improvement/prevention of cardiac conduction abnormalities in the dystrophic heart.

Two-dimensional left atrium-to-aorta ratios and left ventricular M-mode transthoracic echocardiographic measurements in clinically normal adult Dachshunds

OBJECTIVE

To estimate the left atrium-to-aorta ratio (LA:Ao) and establish 95% prediction intervals for left ventricular M-mode transthoracic echocardiographic measurements in clinically normal adult Dachshunds.

ANIMALS

40 healthy Dachshunds.

PROCEDURES

For each dog, 3 standard 2-D echocardiographic methods (diameter, circumference, and cross-sectional area) were used to measure the left atrium and aorta and calculate the LA:Ao from right parasternal short axis (RPSA) images obtained at the level of the aortic valve cusps. Left ventricular M-mode measurements were acquired from RPSA images obtained at the chordal level immediately below the mitral valve. Descriptive data were generated, and the 95% prediction intervals were calculated by use of an allometric scaling equation and linear regression and compared with those calculated on the basis of data obtained from dogs of multiple breeds in a previous study.

RESULTS

The mean (SD) LA:Ao was 1.40 (0.13), 2.09 (0.17), and 2.85 (0.48) for the diameter, circumference, and cross-sectional area methods, respectively. The 95% prediction intervals for the left ventricular M-mode measurements determined by an allometric scaling equation on the basis of Dachshund-specific data were narrower than those determined on the basis of data obtained from dogs of multiple breeds. For that allometric equation, scaling exponents on the basis of Dachshund-specific data ranged from 0.129 to 0.397 and did not absolutely conform to the presumed index for linear measurements (ie, body weight(0.333)).

CONCLUSIONS AND CLINICAL RELEVANCE

The LA:Aos and 95% prediction intervals calculated in this study can be used as preliminary guidelines for echocardiographic measurements of clinically normal Dachshunds.

Simpson's method of discs in Salukis and Whippets: Echocardiographic reference intervals for end-diastolic and end-systolic left ventricular volumes

BACKGROUND

Sighthound breeds are known to have different cardiac sizes and dimensions from other breeds; therefore, breed-specific references are required to avoid misinterpretation of echocardiographic findings. End-diastolic volume (EDV) and end-systolic volume (ESV) reference intervals derived from Simpson's method of discs (SMOD) do not exist for Salukis or Whippets.

OBJECTIVES

To establish EDV and ESV reference intervals for SMOD in Salukis and Whippets.

ANIMALS

110 Salukis and 119 Whippets.

METHODS

Reference intervals for SMOD with and without normalization to body surface area (BSA) were established using the right parasternal and left apical views in 93 healthy Salukis and 82 healthy Whippets. Volumes were compared between both echocardiographic views, genders, and racing and show pedigree dogs. The 90% reference intervals were calculated using the robust method.

RESULTS

Agreement between right-sided and left-sided echocardiographic views was good. Reference intervals indexed to body surface area (BSA) for Whippets were 59-109 mL/m² for end-diastolic volume index and 18-53 mL/m² for end-systolic volume index. Corresponding values for Salukis were 68-126 mL/m² for end-diastolic volume index and 27-64 mL/m² for end-systolic volume index. There were no indexed volume differences between male and female or racing and show pedigree dogs in both breeds. The non-normalized volumes significantly differed between genders.

CONCLUSIONS AND CLINICAL IMPORTANCE

Whippets and Salukis had larger systolic and diastolic left ventricular volumes compared with other breeds. This study provided echocardiographic reference intervals for SMOD-derived left ventricular volumes for these athletic breeds.

Short-term obesity results in detrimental metabolic and cardiovascular changes that may not be reversed with weight loss in an obese dog model

The time course of metabolic and cardiovascular changes with weight gain and subsequent weight loss has not been elucidated. The goal of the present study was to determine how weight gain, weight loss and altered body fat distribution affected metabolic and cardiovascular changes in an obese dog model. Testing was performed when the dogs were lean (scores 4-5 on a nine-point scale), after ad libitum feeding for 12 and 32 weeks to promote obesity (>5 score), and after weight loss. Measurements included serum glucose and insulin, plasma leptin, adiponectin and C-reactive protein, echocardiography, flow-mediated dilation and blood pressure. Body fat distribution was assessed by computed tomography. Fasting serum glucose concentrations increased significantly with obesity (P< 0·05). Heart rate increased by 22 (SE 5) bpm after 12 weeks of obesity (P= 0·003). Systolic left ventricular free wall thickness increased after 12 weeks of obesity (P= 0·002), but decreased after weight loss compared with that observed in the lean phase (P= 0·03). Ventricular free wall thickness was more strongly correlated with visceral fat (r 0·6, P= 0·001) than with total body fat (r 0·4, P= 0·03) and was not significantly correlated with subcutaneous body fat (r 0·3, P= 0·1). The present study provides evidence that metabolic and cardiovascular alterations occur within only 12 weeks of obesity in an obese dog model and are strongly predicted by visceral fat. These results emphasise the importance of obesity prevention, as weight loss did not result in the return of all metabolic indicators to their normal levels. Moreover, systolic cardiac muscle thickness was reduced after weight loss compared with the pre-obesity levels, suggesting possible acute adverse cardiovascular effects.

Ecocardiografia de cães da raça Yorkshire Terrier clinicamente normais

Determinaram-se os parâmetros ecocardiográficos em modo-M normais de cães da raça Yorkshire Terrier. Foram utilizados 30 cães clinicamente sadios, com peso médio de 2,42±0,64kg e idades entre um e seis anos. O diâmetro do átrio esquerdo e da aorta, a dimensão interna do ventrículo esquerdo na diástole e na sístole, a espessura do septo interventricular na diástole e na sístole, e a espessura da parede posterior do ventrículo esquerdo na diástole e na sístole correlacionaram-se com o peso corporal. As demais variáveis do modo-M não se correlacionaram com peso corporal, sexo ou idade. Os valores ecocardiográficos obtidos neste estudo podem ser utilizados como referência para cães dessa raça.

Echocardiographic values in clinically healthy adult dogue de Bordeaux dogs

OBJECTIVES

To assess the influence of body surface area, age and gender on echocardiographic parameters and to establish echocardiographic reference values for dogue de Bordeaux dogs.

METHODS

Thirty-nine healthy dogue de Bordeaux dogs of both sexes, older than one year, were recruited and 31 of these were included in the study. The classic linear regression model proved to be the best way to analyse the data. The reference limits of the echocardiographic measurements were calculated using the regression equations. The difference between the mean values of body surface area in both gender groups was evaluated by using one-way ANOVA.

RESULTS

A significant correlation was seen between several echocardiographic parameters and body surface area or body surface area and age, and high coefficients of determination (R2) were found. No effect of gender was detected on echocardiographic variables, except for the thickness of the left ventricular posterior wall at end diastole.

CLINICAL SIGNIFICANCE

The echocardiographic parameters related to body surface area, in the absence of correlation with other independent variables (gender and age) should be interpreted with caution because their variation could be significant for the presence of heart disease. The proposed statistical model allows estimation of echocardiographic parameters in dogue de Bordeaux dogs with different body surface areas and ages.

Age-matched comparison reveals early electrocardiography and echocardiography changes in dystrophin-deficient dogs

The absence of dystrophin in the heart leads to Duchenne cardiomyopathy. Dystrophin-deficient dogs represent a critical model to translate novel therapies developed in mice to humans. Unfortunately, little is known about cardiophysiology changes in these dogs. We performed prospective electrocardiographic and echocardiographic examinations at 3, 6 and 12 months of age in four normal and three affected dogs obtained from the same litter. Affected dogs showed growth retardation and serum creatine kinase elevation. Necropsy confirmed cardiac dystrophin deficiency and histopathology. Q/R ratio elevation and diastolic left ventricular (LV) internal diameter reduction were the most consistent findings in affected dogs at all ages. At 6 and 12 months, dystrophic dogs also showed significant reduction of PR intervals, LV end diastolic/systolic volumes and systolic LV internal diameters. Epicardial and endocardial slope times were significantly reduced in affected dogs at 12 months. These results establish the baseline for evaluating experimental therapies in the future.

M-mode and two-dimensional echocardiographic reference values for three Hungarian dog breeds: Hungarian Vizsla, Mudi and Hungarian Greyhound

The aim of the study was to establish normal reference echocardiographic values for three Hungarian dog breeds, and to determine the potential dependence of intracardiac parameters on body weight, age and gender. M-mode and two-dimensional echocardiography were performed on 95 clinically healthy dogs including 45 Hungarian Vizslas, 28 Mudis and 22 Hungarian Greyhounds. Linear intracardiac measurements included interventricular septal thickness (IVS), left ventricular internal diameter (LVID), left ventricular posterior wall thickness (LVPW) both in systole and diastole, as well as left atrial internal diameter (LAD), and aortic diameter (AOD) in early diastole. Fractional shortening (FS), end-diastolic and end-systolic left ventricular volumes (EDV and ESV), as well as LAD:AOD ratio were calculated from the linear parameters. Mean, range and standard deviation of measurements were calculated for each breed. Body weight positively correlated in all three breeds with all left ventricular dimensions, such as IVS d , IVS s , LVID d , LVIDD s , LVPW d and LVPW s parameters. LA values showed positive correlations to body weight in all three breeds. AOD and LA demonstrated a positive correlation with body weight in Hungarian Vizslas and Mudis, whilst the LAD:AOD ratio was related to body weight only in Mudis. Gender did not correlate with any of the measured echocardiographic parameters in any breeds. In Mudis, a positive correlation was found between the LAD: AOD ratio and age, as well as between the LAD: AOD ratio and E point to septal separation (EPSS).

Efeitos de diferentes FiO2 sobre variáveis ecocardiográficas em cães submetidos à infusão contínua de propofol

Avaliaram-se os efeitos do fornecimento de diferentes frações inspiradas de oxigênio (FiO2) em cães anestesiados com infusão contínua de propofol e mantidos em ventilação espontânea sobre os parâmetros ecocardiográficos, obtidos em modo M. Oito cães adultos foram submetidos a cinco protocolos anestésicos diferenciando um do outro pela FiO2 fornecida ao paciente. Formaram-se cinco grupos denominados G100 (FiO2=1), G80 (FiO2=0,8), G60 (FiO2=0,6), G40 (FiO2=0,4) e G20 (FiO2=0,21). Os animais foram induzidos à anestesia com propofol na dose necessária para intubação e, ato contínuo, iniciou-se a infusão do fármaco. Os cães receberam oxigênio conforme a FiO2 determinada para cada grupo. As primeiras mensurações foram efetuadas antes da administração do fármaco (M0), aos 30 minutos (M30) após o início da infusão do anestésico e a cada 15 minutos (M45, M60, M75 e M90) durante 60 minutos. Para espessura do septo interventricular ao final da sístole (ESIVs) registrada em M60, a média de G100 foi maior do que as obtidas de G60 e G20. Em M30, o espessamento fracional da parede livre do ventrículo esquerdo (ELPVE) de G100 foi menor que de G80, e, em M75, G80 foi maior que G40. Em relação ao índice de volume ventricular esquerdo ao final da sístole (IVVEFs), em M45, G40 foi maior que G80. Conclui-se que as variáveis ecocardiográficas estudadas não são afetadas pelo emprego de diferentes FiO2.

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.

Cardiovascular toxicity of minoxidil in the marmoset

The aim of the experiments was to assess the toxicity of minoxidil, a potent vasodilator, in marmosets. The animals were treated either at escalating doses from 2 to 40 mg/kg, escalating doses from 40 to 200 mg/kg or single doses of 150 mg/kg or 200 mg/kg. ECG recording and echocardiographic examination were conducted before and 1h after treatment. Necropsy and histopathology were performed 24h after the last dose. The treatment with minoxidil induced myocardial necrosis, coronary arteriopathy and degeneration of renal tubules in animals treated with 150 mg/kg or 200 mg/kg. Myocardial necrosis associated with fibrosis in some animals was located mainly in the left and right ventricles (including papillary muscles), but also in the right atrium, left atrium and/or interventricular septum. Arteriopathy was observed in small coronary arteries of the right or left atrium. ECG and echocardiographic examinations showed that in animals treated with 150 mg/kg or 200 mg/kg, there were positive chronotropic and inotropic effects that compensated for the hypotensive effect of the drug and were considered to have played a key role in the pathogenesis of the cardiovascular lesions. The cardiotoxicity of minoxidil in marmosets was similar to that described in dogs, but occurred at much higher doses. In conclusion minoxidil produced cardiovascular toxicity in the marmoset, which was probably due to the marked changes in the cardiac function associated with exaggerated pharmacological effects of the compound. The marmosets were found to be less sensitive than dogs to the cardiotoxicity of minoxidil.

Preclinical cardiac safety assessment of drugs

The heart is a frequent site of toxicity of pharmaceutical compounds in humans, and when developing a new drug it is critical to conduct a thorough preclinical evaluation of its possible adverse effects on cardiac structure and function. Changes in cardiac morphology such as myocardial necrosis, hypertrophy or valvulopathy are assessed in regulatory toxicity studies in laboratory animals, although specific models may be needed for a more accurate detection of the risk. The potential proarrhythmic risk of new drugs is a major subject of concern and needs to be fully addressed before treatment of volunteers or patients takes place. In vitro assays are conducted to determine the effects on cardiac ion channels, in particular I(Kr) potassium channel antagonism. Prolongation of the QT interval is assessed in vivo, generally in telemetered dogs. Together, these two tests are considered to detect most arrhythmic drugs. The results of this core battery can be refined by additional studies, in particular assays on isolated cardiac tissues determining changes in cardiac action potential duration, shape and variability over time. Triggering of arrhythmia is assessed in hypokalaemic dogs with artificially created bradycardia, or in vitro in isolated whole hearts. The proarrhythmic risk of the new compound is then evaluated by integrating the results of these different tests. Drug adverse effects on cardiac electrophysiological function, in particular impulse formation and conduction, are evaluated through changes in ECG, generally recorded in dogs, pigs or monkeys. Changes in cardiac contractility occurring either as a primary effect of the drug on cardiac function or as a consequence of cardiac lesions should also be carefully assessed. In telemetered or anaesthetised animals, cardiac contractility is evaluated by measurement of left ventricular pressure and its first derivative over time. Echocardiography allows non-invasive measurement of drug-induced changes in ventricular wall movements and cardiac haemodynamics indicative of effects on contractility. In conclusion, a reliable and accurate evaluation of the cardiac safety of a new pharmaceutical agent is based on the results of in vitro tests, with overall moderate to high throughput, and in vivo experiments assessing the effects of the drug on the heart in its physiological environment. The specific sensitivities of the animals used in these assays to cardiac adverse effects should also be considered. The final evaluation of the cardiac risk is therefore based on an integrated analysis of the results from a battery of tests.

Transthoracic echocardiography in Estrela Mountain dogs: reference values for the breed

Of 100 Estrela Mountain dogs, 74 were examined to obtain echocardiographic reference values for the breed. The influence of bodyweight, age and sex on different echocardiographic parameters was studied using either analysis of variance or regression analysis. Statistically significant differences were found between sex and heart rate as well as interventricular septal thickness at end-systole and left ventricular internal dimension at end-diastole. A statistically significant linear correlation was also found between several parameters and (1) age (mean arterial pressure, left ventricular internal dimension at end-systole, fractional shortening, circularity index in systole, aortic valve velocity time integral, pulmonic valve velocity time integral and mitral valve E wave peak velocity), (2) weight (left ventricular posterior wall thickness at end-diastole and end-systole, end-diastolic volume index, left atrium diameter, aortic valve peak velocity and mitral valve E wave deceleration time), (3) sex and age (left ventricle end-diastolic volume), and (4) sex and weight (aortic root diameter and pulmonic valve peak velocity). Reference values for the breed are presented, as well as dispersion graphics for selected parameters, based on a regression equation.

Cardiac involvement in Beagle-based canine X-linked muscular dystrophy in Japan (CXMDJ): electrocardiographic, echocardiographic, and morphologic studies

Background

Cardiac mortality in Duchenne muscular dystrophy (DMD) has recently become important, because risk of respiratory failure has been reduced due to widespread use of the respirator. The cardiac involvement is characterized by distinctive electrocardiographic abnormalities or dilated cardiomyopathy, but the pathogenesis has remained obscure. In research on DMD, Golden retriever-based muscular dystrophy (GRMD) has attracted much attention as an animal model because it resembles DMD, but GRMD is very difficult to maintain because of their severe phenotypes. We therefore established a line of dogs with Beagle-based canine X-linked muscular dystrophy in Japan (CXMD_J) and examined the cardiac involvement.

Methods

The cardiac phenotypes of eight CXMD_J and four normal male dogs 2 to 21 months of age were evaluated using electrocardiography, echocardiography, and histopathological examinations.

Results

Increases in the heart rate and decreases in PQ interval compared to a normal littermate were detected in two littermate CXMD_J dogs at 15 months of age or older. Distinct deep Q-waves and increase in Q/R ratios in leads II, III, and aVF were detected by 6–7 months of age in all CXMD_J dogs. In the echocardiogram, one of eight of CXMD_J dogs showed a hyperechoic lesion in the left ventricular posterior wall at 5 months of age, but the rest had not by 6–7 months of age. The left ventricular function in the echocardiogram indicated no abnormality in all CXMD_J dogs by 6–7 months of age. Histopathology revealed myocardial fibrosis, especially in the left ventricular posterobasal wall, in three of eight CXMD_J dogs by 21 months of age.

Conclusion

Cardiac involvement in CXMD_J dogs is milder and has slower progression than that described in GRMD dogs. The distinct deep Q-waves have been ascribed to myocardial fibrosis in the posterobasal region of the left ventricle, but our data showed that they precede the lesion on echocardiogram and histopathology. These findings imply that studies of CXMD_J may reveal not only another causative mechanism of the deep Q-waves but also more information on the pathogenesis in the dystrophin-deficient heart.

M-mode and Doppler echocardiographic reference values for male New Zealand white rabbits

OBJECTIVE

To determine M-mode and Doppler echocardiographic reference values in healthy New Zealand white rabbits.

ANIMALS

52 healthy male rabbits.

PROCEDURES

The rabbits were anesthetized and M-mode measurements of the left ventricle, left atrium, and aorta and Doppler measurements of pulmonary and aortic outflow and mitral inflow were recorded.

RESULTS

Mean +/- SD heart rate during echocardiographic examination was 155 +/- 29 beats/min. Mean +/- SD measurements in diastole and systole for the interventricular septum thickness, left ventricular internal diameter, and left ventricular free wall thickness were 2.03 +/- 0.37 mm and 3.05 +/- 0.45 mm; 14.37 +/- 1.49 mm and 10.25 +/- 1.22 mm; and 2.16 +/- 0.25 and 3.48 +/- 0.55 mm, respectively. Mean +/- SD left atrial-to-aortic diameter ratio was 1.17 +/- 0.14, and mean +/- SD mitral valve E-point-to-septal separation interval was 1.71 +/- 0.29 mm. Mean +/- SD for fractional shortening and ejection fraction were 30.13 +/- 2.98% and 61.29 +/- 4.66%, respectively. Mean +/- SD maximal aortic and pulmonary artery outflow velocities were 0.85 +/- 0.11 m/s and 0.59 +/- 0.10 m/s, respectively, and the peak E-to-peak A wave velocity ratio of the mitral valve was 2.19 +/- 0.46.

CONCLUSIONS AND CLINICAL RELEVANCE

Results provide echocardiographic reference values for young adult male New Zealand white rabbits anesthetized with ketamine and medetomidine. Values obtained from unanesthetized rabbits, rabbits sedated with other agents, or rabbits of different size may differ from those reported here.

M-MODE ECHOCARDIOGRAPHIC PARAMETERS AND INDICES IN THE NORMAL GERMAN SHEPHERD DOG

M-mode echocardiographic measurements were made from 50 healthy German Shepherd dogs (30 males and 20 females). The dogs were awake and unsedated, in right lateral recumbent position. The following parameters were measured on the echocardiographic images: interventricular septal thickness at end-diastole (IVSd), interventricular septal thickness at end-systole (IVSs), left ventricular internal dimension at end-diastole (LVIDd), left ventricular internal dimension at end-systole (LVIDs), left ventricular posterior wall thickness at end-diastole (LVPWd), left ventricular posterior wall thickness at end-systole (LVPWs), left atrial dimension (LAD), aortic root dimension (AOD), left atrial to aortic root ratio (LAD/AOD), right ventricular internal dimension at end-diastole (RVID), amplitude of mitral valve excursion (DE amplitude), velocity of mitral valve opening (D-E slope), and velocity of mitral valve closure (E-F slope). Fractional shortening (FS) was also calculated. The effect of gender and age on each echocardiographic parameter was analyzed and the relationship between body weight (BW) and each parameter was also investigated. There was a significant relationship between gender and LVPW in systole and diastole and FS. Significant association was also found between BW and IVS, LVID, and LVPW in systole and diastole, FS, LAD, AOD, RVID, DE amplitude, and D-E slope of the mitral valve.

Echocardiographic indices in normal German shepherd dogs

Sixty clinically normal German shepherd dogs, 31 males and 29 females, ranging in age from 1 and 5 years and with a body weight ranging from 22 to 37.2 kg, were examined by the two-dimensional mode, M-mode, and Doppler echocardiography. In Doppler mode, the mitral valve flows were obtained, where the aim was to determine the velocity peaks and ratios of the E and A waves and the mitral E wave deceleration time. The velocity peaks were obtained for the tricuspid, pulmonary and aortic valves. On the left ventricular outflow tract flow, the time velocity integral and aortic cross-sectional area was used to calculate the cardiac output. A statistically significant correlation with the body weight was found for the systolic left atrial and diastolic aortic diameter on two-dimensional mode. On M-mode, there was a significant correlation between the body weight and the systolic left atrium and diastolic aortic dimension, systolic and diastolic left ventricular, septal and posterior wall dimensions. Doppler echocardiography showed that there was no significant correlation between the body weight and the mitral, tricuspid, pulmonary and aortic valves flows. These results demonstrate that it is important to know the normal echocardiographic values for German shepherd dogs because there are some characteristics peculiar to this particular breed. The data obtained is expected to be helpful for studies on small animal cardiology.

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.

Linear, logarithmic, and polynomial models of M-mode echocardiographic measurements in dogs

OBJECTIVE

To determine whether logarithmic and polynomial models are superior to simple linear models for predicting reference values for M-mode echocardiographic variables in dogs with a wide range of body weights.

ANIMALS

69 apparently healthy adult male and female dogs of various breeds, ages (range, 1 to 12 years; median, 3.5 years), and body weights (range, 3.9 to 977 kg; median, 25.4 kg).

PROCEDURE

Echocardiographic M-mode measurements of the interventricular septum, left ventricular dimension (LVD), left ventricular wall, aorta, and left atrium were obtained. Simple linear, second-order polynomial, third-order polynomial, and logarithmic regression models were determined by use of the least-squares method to describe the relationship between M-mode measurements and body weight. Differences in adjusted R2 values of logarithmic and polynomial models were tested for significance of contribution, compared with the simple linear model.

RESULTS

Significant differences in adjusted R2 were found when comparing simple linear with logarithmic or polynomial models for LVD-diastole, LVD-systole, aorta, and left atrium. Differences in adjusted R2 between second-order polynomial, third-order polynomial, and logarithmic models were not significant for any M-mode measurement.

CONCLUSIONS AND CLINICAL RELEVANCE

In this study, logarithmic or second-order polynomial models predicted reference values of M-mode measurements for size of the cardiac chambers better than simple linear models for dogs with a wide range of body weights. Logarithmic and polynomial models were not superior to simple linear models for M-mode measurements of cardiac wall thickness.

Comparability of left ventricular M-mode echocardiography in dogs performed in long-axis and short-axis

The purpose of this prospective study was to determine comparability of left ventricular (LV) M-mode echocardiographic indices derived from right parasternal long-axis and short-axis imaging planes. In 104 dogs (37 healthy dogs and 67 dogs with heart disease), LV M-mode echocardiograms were recorded from both long-axis and short-axis views and interventricular septum thickness (IVS), left ventricular internal dimensions (LVD), left ventricular posterior wall thickness (LVPW), and LV shortening fraction (FS) were measured. Statistical analysis included paired t-test and graphical analysis to assess agreement between the two methods of data acquisition. Mean LVD in systole and diastole and mean IVS in systole were significantly (P<0.001) larger when measured from short-axis recordings compared to long-axis measurements. An increased magnitude of measurement resulted in increased differences between the methods for LV dimensions and fractional shortening. Differences between the two methods were small and within clinically acceptable limits in normal dogs. However, in 23 (34%) of the dogs with cardiac abnormality, one or more LV M-mode derived dimension obtained from one imaging plane did not agree sufficiently closely with the same measure from the other plane. Only for measurement of FS was there good agreement between methods in dogs with cardiac disease. Therefore, with the exception of FS, data gained from LV short-axis and long-axis M-mode recordings should not be used interchangeably in dogs with cardiac disease.

Echocardiographic parameters in training compared with non-training greyhounds

Echocardiographic parameters were compared between training and non-training greyhound dogs. When indexed to body weight there was a statistically significant increase (p < 0.05) in the interventricular septal thickness (systole) and when indexed to body surface area there were increased interventricular septal (systole) and left ventricular free wall measurements (systole) in training compared with non-training greyhounds. When each gender was analyzed separately and echocardiographic parameters were indexed to body size, both genders had an increase in the interventricular septal thickness (diastolic in the female, systolic in the male) in the training compared with non-training greyhounds. In male training greyhounds there was additionally an increase in the left ventricular internal dimension (systole) and free wall thickness (systole) when echocardiographic parameters were indexed to body surface area compared with non-training greyhounds (p < 0.05). The results indicate that certain training greyhound echocardiographic parameters are larger than non-training greyhound echocardiographic parameters. The potential effects of training, body size and gender should be considered when interpreting echocardiographic parameters in populations of greyhounds.