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

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.

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.

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.

Echocardiographic quantitation of left heart size and function in 122 healthy dogs: A prospective study proposing reference intervals and assessing repeatability

Background

Broadly applicable reference intervals (RIs) for measurements of left atrial (LA) and left ventricular (LV) size and function generated prospectively using statistically appropriate methods are limited.

Objectives

To generate body size‐independent RIs for linear, area, and volume measurements of LA size and LV size and function.

Animals

Healthy adult dogs (n = 122) of variable size and somatotype.

Methods

Prospective study. All dogs underwent an echocardiogram performed by the same examiner. Effects of body weight, sex, age, and heart rate were evaluated by regression and correlation analyses. Scaling exponents and prediction intervals were generated for linear measurements using the allometric equation. 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 (each with 90% confidence intervals), respectively.

Results

Linear LA and LV measurements were strongly correlated (R² ≥ 0.79) with body weight. Scaling exponents were close to the expected 1/3 (0.299‐0.392). Prediction intervals for linear measurements of LV chamber size were considerably narrower than previously reported. Weak correlations (r = −0.42 to −0.50) among LV fractional shortening, fractional area change, and ejection fraction and body weight were identified. No other meaningful relationships were identified between the measurements and sex, age, and heart rate.

Conclusions and Clinical Importance

Body size‐independent RIs for several linear, area, and volume measurements of LA and LV size and function were generated prospectively from a large and diverse reference population and are available for clinical use.