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

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.

Possible development and resolution of dilated cardiomyopathy phenotype secondary to atypical hypoadrenocorticism in a dog

OBJECTIVE

To report the possible occurrence of dilated cardiomyopathy phenotype associated with atypical hypoadrenocorticism and subsequent marked improvement with treatment in a mixed breed dog.

CASE SUMMARY

A 4.5-year-old, neutered male mixed breed dog was evaluated for a history and clinicopathological changes consistent with atypical hypoadrenocorticism. The dog was being fed a grain-free diet. While hospitalized for supportive care and diagnostics, the patient developed and was diagnosed with biventricular congestive heart failure secondary to dilated cardiomyopathy phenotype and IV fluid administration. The left-sided congestive heart failure resolved with discontinuation of IV fluid therapy and short-term administration of diuretics. After treatment of atypical hypoadrenocorticism with glucocorticoid supplementation, and while continuing to be fed varying grain-free diets, the patient's dilated cardiomyopathy phenotype largely resolved. The patient fully recovered and did not require any long-term cardiac medications.

NEW OR UNIQUE INFORMATION PROVIDED

Development of dilated cardiomyopathy phenotype has not been described in dogs as a sequela of untreated hypoadrenocorticism but has been reported in human literature. Given the fact that standard management of hypoadrenocorticism typically involves aggressive fluid resuscitation, awareness of this potential sequela is important for patients that fail to respond or develop signs consistent with volume overload.

Use of regression models for development of a simple and effective biogas decision-support tool

Anaerobic digestion (AD) is an alternative way to treat manure while producing biogas as a renewable fuel. To increase the efficiency of AD performance, accurate prediction of biogas yield in different working conditions is necessary. In this study, regression models were developed to estimate biogas production from co-digesting swine manure (SM) and waste kitchen oil (WKO) at mesophilic temperatures. A dataset was collected from the semi-continuous AD studies across nine treatments of SM and WKO, evaluated at 30, 35 and 40 °C. Application of polynomial regression models and variable interactions with the selected data resulted in an adjusted R² value of 0.9656, much higher than the simple linear regression model (R² = 0.7167). The significance of the model was observed with the mean absolute percentage error score of 4.16%. Biogas estimation using the final model resulted in a difference between predicted and actual values from 0.2 to 6.7%, except for one treatment which was 9.8% different than observed. A spreadsheet was created to estimate biogas production and other operational factors using substrate loading rates and temperature settings. This user-friendly program could be used as a decision-support tool to provide recommendations for some working conditions and estimation of the biogas yield under different scenarios.

QT interval instability and variability in dogs with naturally-occurring hypercortisolism

Hypercortisolism is one of the most common endocrine diseases in dogs. In humans, it is clearly associated with a higher risk of cardiovascular events, but studies in dogs are scarce. To investigate the arrhythmogenic risk of dogs with naturally-occurring hypercortisolism (NOHC), indices of variability and instability of the QT interval were retrospectively studied in 38 dogs with NOHC and prospectively studied in 12 healthy dogs: variance (QTv), total instability (TI), short-term (STI) and long-term (LTI), and mean (QTm). Except for QTm, all parameters studied were higher in the NOHC group than in the control group. In addition, STI and QTv showed moderate positive correlation with left ventricle wall thickness. The NOHC group was subdivided according to cortisol suppression pattern in the low-dose dexamethasone suppression test. All electrocardiographic indices of partial and absent suppression patterns were numerically higher than healthy dogs. QTv and TI were lower in the control group than in both NOHC subgroups. LTI and STI were lower in the CG than in the group with the partial suppression pattern. There was no statistical difference between sex groups in any of the electrocardiographic parameters studied. This result might indicate that the etiology of NOHC, and its consequent influence on hypothalamus-pituitary-adrenal axis could interfere on the heterogeneity of ventricular repolarization parameters in different ways, especially in the short-term and the long-term stability; however further studies are necessary to understand the role of cortisol on electrical instability in dogs.

Reference ranges for standard-echocardiography in pugs and impact of clinical severity of Brachycephalic Obstructive Airway Syndrome (BOAS) on echocardiographic parameters

BACKGROUND

Echocardiographic measurements may be influenced by breed-specific characteristics. Therefore, this study aims to establish reference values for standard echocardiographic measurements in pugs by investigating the influence of age, sex, heart rate, body weight and Brachycephalic Obstructive Airway Syndrome (BOAS). Sixty-two privately owned pugs underwent physical examination, blood sample collection, non-invasive blood pressure measurements and echocardiography. Influences of independent variables on echocardiographic measurements were examined using a multiple linear regression analysis model. For the entire study population, 95% prediction intervals were generated. Further, reference ranges for subcategories of clinical severities of BOAS were provided. Selected echocardiographic measurements of pugs were compared to reference values of previous studies generated from various breeds.

RESULTS

In the study, a total of fifty-one privately owned pugs aged between two and 10 years were included for establishing reference ranges. Mainly body weight, but also age, sex and heart rate had influence on several echocardiographic parameters. The clinical grading of BOAS was conducted in 42 pugs. Except for pulmonic peak velocity (Pvel), which declined with increasing severity of BOAS, clinical symptoms of upper airway disease did not have significant impact on echocardiographic measurement results. Significant deviations, however, of left ventricular (LV) internal dimension (LVID), interventricular septum (IVS), LV posterior wall (LVPW), and tricuspid annular plane systolic motion excursion (TAPSE) compared to interbreed reference values were observed.

CONCLUSIONS

Breed-specific reference ranges for echocardiographic values with special regard to BOAS are provided to enable a more accurate assessment of cardiac health in pugs.

Echocardiographic assessment of dilated cardiomyopathy in dogs

Dilated cardiomyopathy (DCM) is a frequent cause of cardiac disability, congestive heart failure (CHF), and arrhythmic death in dogs. The etiology of DCM is usually idiopathic/genetic, but some causes of a DCM phenotype are reversible. The disease is classified into preclinical (occult) and clinical (overt) stages; the latter stems from heart failure with reduced ejection fraction. DCM is further characterized by clinical, electrocardiographic, circulating biomarker, and imaging abnormalities. The diagnosis of clinical DCM with CHF is straightforward; however, identification of the preclinical stage can be challenging. Echocardiography is central to the diagnosis of both stages and characterized by left ventricular (LV) systolic dysfunction with progressive chamber dilation and variable enlargements of the left atrium and right-sided chambers. Left ventricular dilation is defined by increased LV end-diastolic volumes, areas, and internal dimensions normalized to body size or indexed to the aorta. Systolic dysfunction is characterized by decreased LV ejection fraction, increased end-systolic volume, and reduced shortening across minor and longitudinal LV axes. Dyssynchrony can confound the interpretation of linear indices of systolic function. A comprehensive echocardiogram in DCM includes two-dimensional and M-mode studies, spectral and tissue Doppler imaging, and potentially three-dimensional echocardiography and myocardial strain imaging. Echocardiographic findings should be interpreted within the context of identifiable risks and comorbidities, physical diagnosis, complementary diagnostic testing, and limitations of current reference intervals. Ambiguous examinations should be repeated. Specific echocardiographic criteria for the diagnosis of DCM are proposed to encourage discussion and additional outcome and breed-specific echocardiographic studies of canine DCM.

Interpretation of cardiac chamber size on canine thoracic radiographs is limited and may result in the false identification of right-sided cardiomegaly in the presence of severe left-sided cardiomegaly

Qualitative assessment of individual cardiac chamber enlargement on thoracic radiographs was assessed using echocardiography as the gold standard in dogs. Using this method, the presence of severe left-sided cardiomegaly was hypothesized to contribute to the false identification of right-sided cardiomegaly on radiographs. 175 dogs with three-view thoracic radiographs were retrospectively included in this diagnostic accuracy study if echocardiography was done within 24 h, and no rescue therapy was provided in the interim. All radiographic studies were reviewed by two groups of five board-certified veterinary radiologists with greater and less than 10 years of experience for grading of cardiac chamber enlargement as normal or mildly, moderately, or severely enlarged. The agreement, sensitivity, and specificity of the radiologists' interpretation of cardiac chamber size on thoracic radiographs to measured echocardiographic grades were evaluated. A total of 147 cases had complete echocardiographic data available for analysis. Intragroup agreement was moderate for the evaluation of left atrial enlargement and slight to fair for all other cardiac chambers. Between the mode of the radiologists' responses in the two groups and the echocardiographic grades, there was slight agreement for all cardiac chambers with higher severity grades reported using echocardiography. When moderate to severe left-sided cardiomegaly was identified on echocardiography, the sensitivity, specificity, and accuracy of radiographs were low, identifying dogs with radiographic evidence of right-sided cardiomegaly in the absence of corresponding right-sided cardiomegaly on echocardiography. Therefore, thoracic radiographs should be used with caution for the evaluation of cardiac chamber enlargement, particularly in the presence of severe left-sided cardiomegaly.

Echocardiographic parameters in 50 healthy English bulldogs: preliminary reference intervals

INTRODUCTION/OBJECTIVES

The objective of the study was to provide echocardiographic reference intervals for English bulldogs (EBs) and to assess if age, sex, body weight (BW), and heart rate have an influence on echocardiographic variables.

ANIMALS

We prospectively enrolled client-owned EBs that were considered healthy based on unremarkable history, normal physical examination, six-lead electrocardiography, and transthoracic echocardiography.

MATERIALS AND METHODS

Breed-related reference intervals were provided, and associations between age, sex, BW, and heart rate and echocardiographic variables were tested using a multivariate analysis. Allometric scales were generated for echocardiographic variables showing correlation with BW. Moreover, echocardiographic variables obtained in our population of EBs and previous published reference ranges were compared.

RESULTS

Echocardiographic reference intervals were generated from 50 healthy adult EBs. As per the multivariate analysis, left atrial diameter (p = 0.015), left ventricular internal end diastolic diameter (p = 0.002), aortic valve annulus (p = 0.032), and pulmonary valve annulus (p = 0.017) resulted influenced by BW, and reference intervals were generated using allometric scales. Our study suggests that EBs tend to have a smaller aortic root and sphericity index than other breeds. In addition, EBs seem to have smaller indexed left ventricular volumes and higher left ventricular ejection fraction than boxers and Doberman.

CONCLUSION

Preliminary reference intervals in the EBs are reported, which might be helpful for accurate echocardiographic interpretation and screening purposes in this breed.

Resolution of caval syndrome during initial hemodynamic stabilization in dogs with heartworm disease

OBJECTIVE

To report on the spontaneous resolution of caval syndrome in 5 dogs selected for their response to medical stabilization prior to scheduled heartworm extraction.

SERIES SUMMARY

Five dogs with heartworm caval syndrome were treated with sildenafil, fluid, and supplemental oxygen therapy. Moreover, 4 of 5 dogs were also administered pimobendan to achieve hemodynamic stabilization in preparation for percutaneous heartworm extraction. Spontaneous heartworm migration back into the pulmonary arteries was detected from 2 h to 5 days after treatment initiation.

UNIQUE INFORMATION PROVIDED

Unanticipated spontaneous resolution of caval syndrome was documented in a low number of dogs after initiation of a patient stabilization protocol aiming at improving right ventricular hemodynamics and reducing pulmonary artery pressure prior to scheduled heartworm extraction. At this time, it is unknown if intervention to improve the hemodynamic status of the animal prior to heartworm extraction improves procedure outcome, and which factors contributed to the migration of the heartworms back into the pulmonary arteries in these selected cases. Therefore, this approach cannot be recommended in place of current recommendations for treatment of caval syndrome.

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.

Surgery for partial atrioventricular septal defect with pulmonary hypertension in an adult dog

A 4-year-old, 5.9-kg female Japanese Spitz presented with syncope and exercise intolerance. Echocardiography revealed an ostium primum atrial septal defect (ASD), a cleft mitral valve, mitral valve regurgitation (MR), and tricuspid regurgitation (TR) (velocity: 3.6 m/sec, pressure gradient: 52 mmHg), leading to a diagnosis of partial atrioventricular septal defect (AVSD) with moderate pulmonary hypertension (PH). Open-heart surgery using cardiopulmonary bypass was performed through right atriotomy. The cleft of the mitral valve was sutured with polypropylene and the AVSD was closed using an autologous pericardial patch fixed with glutaraldehyde. No postoperative pulmonary hypertensive crisis occurred. Shunting flow through the ASD, TR and PH had completely disappeared 2 months postoperatively; however, moderate MR persisted. The dog is still alive 5 years postoperatively without clinical signs.

Utility of Tissue Doppler Imaging in the Echocardiographic Evaluation of Left and Right Ventricular Function in Dogs with Myxomatous Mitral Valve Disease with or without Pulmonary Hypertension

Background

In human medicine, right ventricular (RV) functional parameters represent a tool for risk stratification in patients with congestive heart failure caused by left heart disease. Little is known about RV alterations in dogs with left‐sided cardiac disorders.

Objectives

To assess RV and left ventricular (LV) function in dogs with myxomatous mitral valve disease (MMVD) with or without pulmonary hypertension (PH).

Animals

One‐hundred and fourteen dogs: 28 healthy controls and 86 dogs with MMVD at different stages.

Methods

Prospective observational study. Animals were classified as healthy or having MMVD at different stages of severity and according to presence or absence of PH. Twenty‐eight morphological, echo‐Doppler, and tissue Doppler imaging (TDI) variables were measured and comparison among groups and correlations between LV and RV parameters were studied.

Results

No differences were found among groups regarding RV echo‐Doppler and TDI variables. Sixteen significant correlations were found between RV TDI and left heart echocardiographic variables. Dogs with PH had significantly higher transmitral E wave peak velocity and higher E/eʹ ratio of septal (sMV) and lateral (pMV) mitral annulus. These 2 variables were found to predict presence of PH with a sensitivity of 84 and 72%, and a specificity of 71 and 80% at cut‐off values of 10 and 9.33 for sMV E/eʹ and pMV E/eʹ, respectively.

Conclusions and clinical importance

No association between variables of RV function and different MMVD stage and severity of PH could be detected. Some relationships were found between echocardiographic variables of right and left ventricular function.

Review of Diagnostic and Therapeutic Approach to Canine Myxomatous Mitral Valve Disease

The most common heart disease that affects dogs is myxomatous mitral valve disease. In this article, we review the current diagnostic and therapeutic approaches to this disease, and we also present some of the latest technological advancements in this field.

Short-term effect of granulocyte colony-stimulating factor in dogs with severe myxomatous mitral valve disease

BACKGROUND

Use of granulocyte colony-stimulating factor (G-CSF) to treat damaged myocardium is a relatively new concept. Clinical beneficial and safety outcomes are still controversial.

OBJECTIVE

The aim of this study was to evaluate recruitment of hematopoietic stem cells and therapeutic efficacy of G-CSF in the treatment of myxomatous mitral valve disease (MMVD) of dogs.

ANIMALS AND METHODS

Thirty client-owned MMVD dogs with clinical signs of heart failure were enrolled in a prospective double-blind, randomized, placebo-controlled study to compare the short-term effect of G-CSF (n = 17) with control group (n = 13) for identical periods. Clinical, hematological, and cardiovascular assessments were performed on days 0, 1, 3, and 7. Follow-up examination was conducted four weeks after the study.

RESULTS

Dogs treated with G-CSF had a significantly elevated white blood cell (WBC) (×10(3)/μL) count at day 3 compared with baseline (from 10.23 ± 4.42 to 42.84 ± 11.84; P = .000). The WBC population was also changed (elevated neutrophils and decreased lymphocytes) and the numbers of CD34+ cells in the peripheral blood were also increased at day 3. However, the results of clinical, laboratory, and echocardiographic assessments did not differ significantly between the G-CSF treatment and control groups after four weeks.

CONCLUSIONS

G-CSF administration elevated the peripheral WBC count, especially neutrophils, and recruited hematopoietic stem cells. However, positive effects of G-CSF on cardiac function were not detected during short-term monitoring.

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

OBJECTIVES

The objectives of this study were (1) to assess the potential effect of body weight (BW), age, and gender on the most commonly used echocardiographic and conventional Doppler variables in a large population of healthy Cavalier King Charles Spaniels (CKCS), and (2) to establish the corresponding reference intervals (RI).

ANIMALS

134 healthy adult CKCS.

METHODS

Ultrasound examinations were performed by trained observers in awake dogs. M-mode variables included left ventricular (LV) end-diastolic and end-systolic diameters, LV free wall and interventricular septal thicknesses at end-diastole and end-systole, and LV fractional shortening (FS%). The left atrium (LA) and aortic (Ao) diameters were measured using a 2D method, and the LA/Ao was calculated. Pulsed-wave Doppler variables included peak systolic aortic and pulmonary flow velocities, mitral E and A waves, and E/A ratio. Effects of BW, age, and gender on these 15 variables were tested using a general linear model, and RIs were determined by applying the statistical procedures recommended by the Clinical and Laboratory Standards Institute.

RESULTS

A significant BW effect was observed for all variables, except LA/Ao, FS%, and mitral E/A ratio. A significant but negligible effect of gender and age was also observed for 5/15 and 4/15 of the tested variables, respectively. Only the BW effect on M-mode variables was considered as clinically relevant and the corresponding regression-based RIs were calculated.

CONCLUSIONS

Body weight should be taken into account when interpreting echocardiographic values in CKCS, except for LA/Ao, FS%, and mitral E/A ratio.

Evaluation of adverse reactions in dogs following intravenous mesenchymal stem cell transplantation

Background

Recent studies have assessed the therapeutic potential and drawbacks of mesenchymal stem cells (MSCs). The adverse reactions of intravenous transplantation of bone marrow (BM)-derived MSCs were examined at varying doses and frequencies of administration.

Nine healthy beagle dogs were purchased from a commercial laboratory. The dogs were distributed equally (n = 3 per group) and randomly into three groups. All dogs received allogeneic BM-derived MSCs: 2 × 10⁶ once (group A), 2 × 10⁷ once (group B), and 2 × 10⁶ for three consecutive days (group C). Various laboratory examinations, multi-detector computed tomography features and histopathology were evaluated to clarify the clinical and diagnostic features of adverse reactions of MSCs administration, prior to receiving MSCs (pre procedure) and on days 1, 3, and 7 post transplantation.

Results

Only one dog had clinical signs during and after MSCs transplantation. Dogs receiving 2 × 10⁶ MSCs showed increased numbers of lymphocytes but the total white blood cell counts were not elevated (P < 0.01). Multi-detector computed tomography (MDCT) revealed pulmonary parenchymal changes in one dog and histopathologic examination revealed pulmonary parenchymal edema and hemorrhage in four dogs. The presence of pulmonary thromboembolism was not detected in either examination.

Conclusions

We considered the presence of pulmonary edema and hemorrhage as possible adverse reactions after intravenous MSCs transplantation; however these results should be cautiously interpreted.

Evaluation of autologous blood clot subsegmental pulmonary thromboembolism in minimally invasive experimental canine model

The incidence and significance of subsegmental pulmonary (SSP) thromboembolism is currently under investigation. We aimed to evaluate the clinical and diagnostic features of SSP thromboembolism in an experimental canine model. Obstruction of pulmonary arterial branches was induced in three beagle dogs by intravenous injection of a barium-coated autologous blood clot (size, approximately 1.7 × 5 mm). The clinical signs, haemodynamic changes (blood pressure, electrocardiogram, echocardiography), coagulation (aPTT, PT, FDPs and D-dimer test) and cytokine variations (TNF-a, IL-4, IL-6, and IL-10) were evaluated over a 24-hour period. Multidetector computed tomography (MDCT) with contrast was conducted to evaluate the pulmonary obstruction, and histopathological confirmation was performed. Pulmonary artery pressure gradient (PAPG) was increased 12 h after the autologous blood clot injection (14.2 ± 2.8 mmHg to 23.6 ± 1.7 mmHg, P = 0.003) and normalized 24 h later (P < 0.01). Infused radiopaque clots were confirmed with MDCT and histopathological examination. Pulmonary parenchymal changes such as arterial dilation and inflammatory reactions were also confirmed in histopathological examinations and were barely observable in MDCT. Usually small emboli are not easily detected through CT imaging, and the clinical relevance of these emboli is controversial. In this experimental study, we made radiopaque small emboli and induced SSP thromboembolism. Thus, we infer that obstruction of the small segmental and subsegmental pulmonary arteries does result in a pulmonary thromboembolism (PTE) and PTE-related pulmonary parenchymal changes which could be clinically significant.

Basal plasma concentrations of N-terminal pro-B-type natriuretic peptide in clinically healthy adult small size dogs: effect of body weight, age, gender and breed, and reference intervals

Plasma NT-proBNP has previously been evaluated in dogs with degenerative mitral valve disease (DMVD). However, reference intervals (RI) established according to the Clinical Laboratory and Standards Institute (CLSI) recommendations have never been provided. The objectives of this prospective study were to assess effects of breed, body weight, age, and sex on plasma NT-proBNP, and to establish RI according to CLSI for this biomarker in a large population of dogs predisposed to DMVD. 183 Healthy small-sized dogs from 7 breeds were included. Assays were performed by ELISA. Effects of covariates were tested using a general linear model. Although a sex effect was demonstrated (P=0.01), no significant effect of breed, body weight or age was shown. The proposed RI was 157-2842 pmol/L. 7% of dogs had plasma NT-proBNP >2617 pmol/L, and were considered as outliers despite normal cardiovascular examination. In conclusion, plasma NT-proBNP may be high in a few healthy small-sized dogs.

Lowered N-terminal pro-B-type natriuretic peptide levels in response to treatment predict survival in dogs with symptomatic mitral valve disease

OBJECTIVES

In humans with congestive heart failure (CHF), better outcome is correlated with lower natriuretic peptide (NP) levels after starting treatment and greater percentage reduction of NP levels. Therefore, the aim of this study was to determine the relationship between absolute and relative changes in N-terminal pro-B-type natriuretic peptide (NT-proBNP) and pro-atrial natriuretic peptide 31-67 (proANP 31-67) and overall cardiac survival in patients with symptomatic myxomatous mitral valve disease (MMVD). Furthermore, we sought to compare clinical and echocardiographic status of 12-month survivors and non-survivors.

ANIMALS, MATERIALS AND METHODS

26 dogs with CHF due to MMVD. Initial NP levels, as well as absolute and percentage changes of follow-up NP levels (between 7 and 30 days after treatment start) and heart failure (HF) class were tested as potential predictors of overall cardiac survivorship. Additionally, various echocardiographic parameters, creatinine concentrations and furosemide doses were compared between 12-month survivors and non-survivors.

RESULTS

Dogs with follow-up NT-proBNP level <965 pmol/l had a significantly longer overall cardiac survival than patients with NT-proBNP level >965 pmol/l (P = 0.03). Dogs in a higher HF class had a significantly (P = 0.03) higher probability of shorter survival independent of their NP levels. When dogs were grouped by 12-month survival, only follow-up NT-proBNP levels were significantly different between groups.

CONCLUSIONS

HF class at presentation and NT-proBNP levels after initiating treatment are predictive of mortality in patients with symptomatic MMVD. ProANP 31-67 levels, percentage reduction in NPs levels, creatinine or urea concentration, echocardiographic parameters and furosemide dose did not predict outcome.

Echocardiographic and tissue Doppler imaging alterations associated with spontaneous canine systemic hypertension

BACKGROUND

Feline systemic arterial hypertension (SHT) is associated with a wide spectrum of left ventricular (LV) geometric patterns as well as diastolic, and to a lesser extent, systolic myocardial dysfunction. However, little is known about SHT-related cardiac changes in dogs.

HYPOTHESIS

SHT in dogs is responsible for morphological and functional cardiac alterations.

ANIMALS

Thirty dogs with spontaneous untreated SHT and 28 age- and body weight-matched healthy dogs as controls.

METHODS

Prospective observational study. Conventional echocardiography and 2-dimensional color tissue Doppler imaging were performed in SHT dogs by trained observers and compared with controls.

RESULTS

Forty-seven percent of SHT dogs (14/30) had diffuse concentric hypertrophy. None had left atrial dilatation and 10/30 (33%) had aortic insufficiency (AoI) associated with proximal aortic dilatation. Longitudinal diastolic left ventricular free wall (LVFW) motion was altered in all SHT dogs at the base (early to late diastolic wave ratio, E/A = 0.5 ± 0.1 versus 1.3 ± 0.3 for controls, P < .0001) and the apex (E/A = 1.6 ± 1.7 versus 3.9 ± 3.1, P < .05). Longitudinal motion of the interventricular septum at the base (E/A = 0.7 ± 0.4 versus 1.1 ± 0.1, P < .01) and radial LVFW motion in the subendocardium (E/A = 0.9 ± 0.5 versus 1.6 ± 0.3, P < .01) were also altered in dogs with SHT. Longitudinal LVFW systolic velocities and gradients were also significantly decreased (P < .05) in SHT dogs.

CONCLUSION AND CLINICAL IMPORTANCE

As in SHT in cats, SHT in dogs is associated with myocardial dysfunction independently of the presence of myocardial hypertrophy. However, unlike feline SHT, it results in a homogeneous LV geometric pattern with a relatively high prevalence of AoI.

Echocardiographic assessment of interventricular and intraventricular mechanical synchrony in normal dogs

OBJECTIVES

The aims of this prospective study are to (1) generate normal ranges for interventricular and intraventricular mechanical synchrony in dogs, and (2) generate normal ranges for tissue Doppler imaging (TDI) velocity imaging and speckle tracking strain imaging assessment of segmental intraventricular mechanical synchrony in dogs.

ANIMALS

10 prospectively recruited healthy dogs.

METHODS

Dogs were excluded if they had abnormal historical, physical examination, echocardiographic, ECG or systolic blood pressure findings. Interventricular mechanical synchrony was assessed using time difference between left and right ventricular pre-ejection periods. Intraventricular mechanical synchrony was assessed using both M-mode and color M-mode septal to posterior wall mechanical delay (SPWMD). Intraventricular segmental mechanical synchrony was assessed using both color TDI and speckle tracking strain analysis of segmental myocardial motion during systole and diastole.

RESULTS

All synchrony measures were found to be independent of age or body weight. Normal range for mechanical interventricular synchrony was found to be -10.2 to 12.6 ms. Assessment of mechanical intraventricular synchrony using either M-mode or color M-mode SPWMD was found to be associated with an extremely wide normal range, limiting clinical applicability. Normal ranges for segmental intraventricular mechanical synchrony assessed using either color TDI or speckle tracking were found to be comparable to those published for human subjects.

CONCLUSIONS

Interventricular and intraventricular mechanical synchrony in dogs is independent of age and body weight. The normal ranges identified in this study form a basis for assessment of normal versus abnormal mechanical synchrony in canine cardiovascular disease patients.

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.

ECHOCARDIOGRAPHIC REFERENCE VALUES IN WHIPPETS

The aim of the study was to establish reference echocardiographic values for whippets, to compare these values with previously published reference values for the general dog population, and to determine whether there is an influence of gender and breeding lines on echocardiographic measurements. Echocardiographic parameters from 105 apparently healthy whippets without cardiac symptoms were used to establish reference values for the breed and to compare these values with two previously reported reference ranges. The coefficients of the allometric equation Y= aM(b), useful to reconstruct normal M-mode and two-dimensional average values for whippets of varying weights, were calculated, as well as the lower and upper limits of the 95% prediction interval. First, we found that whippets have a significantly larger left ventricular diameter, increased left ventricular wall, and interventricular septum thickness than expected, in diastole as well as in systole. Fractional shortening was significantly lower than the reference value. Second, comparing males and females, taking body weight differences into account, females had a significantly larger left ventricular diameter in diastole and systole. Minor differences were found between racing and show pedigree dogs. In conclusion, the results of this study confirm that breed-specific reference values are needed in echocardiography. In whippets, the values found in this study can be used as references in order to avoid overinterpretation of cardiac dilation, hypertrophy, and/or decreased contractility in these dogs.

A retrospective evaluation of transthoracic biphasic electrical cardioversion for atrial fibrillation in dogs

OBJECTIVES

To evaluate safety, efficacy, and clinical usefulness of biphasic transthoracic cardioversion for management of dogs with atrial fibrillation (AF).

BACKGROUND

In dogs AF is usually managed with heart rate control rather than by restoration of sinus rhythm (SR). However, restoration of SR has potential advantages of improving cardiac output and reducing ventricular filling pressures, and biphasic cardioversion provides an improved benefit/risk ratio compared to traditional monophasic cardioversion.

ANIMALS, MATERIALS AND METHODS

Retrospective analysis of data from 39 dogs with spontaneous AF managed with biphasic transthoracic cardioversion was done. Conversion characteristics, adverse effects, and duration of SR were evaluated. Effects of heart disease and pretreatment with amiodarone on success of cardioversion and on duration of SR were also evaluated.

RESULTS

Restoration of SR was achieved in 36 of 39 dogs (92.3%). Presence of heart disease or atrial enlargement had no effect on cardioversion characteristics or ability to restore SR. Median duration of SR following cardioversion and treatment with amiodarone was 120 days. Dogs with lone AF remained in SR longer than those with heart disease.

CONCLUSIONS

Biphasic cardioversion is safe and effective. Although duration of SR varied, a majority of dogs remained in SR long enough to benefit.

Advances in echocardiography

Echocardiography is an exceptionally useful technique for diagnosing cardiovascular disease in small animals. It is noninvasive and provides a wealth of data concerning cardiac morphology and function. For many patients, echocardiography is the definitive diagnostic tool. A well-performed study coalesces the findings of the physical examination, electrocardiogram, and radiographs into a clearly defined diagnosis on which treatment decisions can be based. More so than other diagnostic techniques, echocardiography is highly operator dependent and relies on the proper acquisition and interpretation of results by an examiner who is familiar with the principles, capabilities, and limitations of ultrasound imaging. This article reviews the basics of echocardiography, measurement of cardiac dimensions, and assessment of cardiac function. Within these sections, emerging technologies that expand the capabilities of the echocardiographic examination are introduced.

M-Mode Echocardiographic Ratio Indices in Normal Dogs, Cats, and Horses: A Novel Quantitative Method

A novel method for quantitative echocardiographic interpretations is introduced based on the calculation of ratio indices in which each raw M-mode measurement is divided by the aortic root dimension (Ao). "Aorta-based" indices were calculated with the animal's measured aortic root dimension (Ao(m)) as the length standard. Conversely, "weight-based" indices employed an idealized estimate of aortic dimension (Ao(w)) with a weighted least squares linear regression against the cube root of body weight (Ao(w) = kW(1/3)). Use of these indices circumvented undesirable statistical characteristics inherent in linear regression of echocardiographic dimensions against body weight and, to a lesser extent, body surface area. Compared with the regressions, ratio indices resulted in substantial refinement of the predictive range for each M-mode measurement in dogs, particularly with decreasing body size. Weight-based indices outperformed aorta-based indices in this regard. To refine the predictive range, neither type of index was clearly advantageous in cats compared with the simple average method typically employed for that species. Several of the raw M-mode measurements, however, were correlated with body weight in cats and horses, indicating the need for an appropriate correction for body size in these species. The ratio index method was suitable for this purpose. Summary statistics derived from normal dogs (n = 53), cats (n = 32), and horses (n = 17) are presented for each index, including novel clinical indices calculated from area ratios. The latter were designed to represent body size-adjusted lett ventricular stroke area (ie, volume overload) and myocardial wall area (ie, hypertrophy).