VERTEBRAL HEART SIZE IN RETIRED RACING GREYHOUNDS

The vertebral heart size (VHS) is used to objectively assess cardiac dimensions on thoracic radiographs. A high VHS suggest the presence of cardiac pathology, such as dilated cardiomyopathy, degenerative atrioventricular valvular disease, pericardial effusion, pericardioperitoneal diaphragmatic hernia, tricuspid dysplasia, ventricular septal defect, or patent ductus arteriosus, among others. However, breed or body conformation can influence the VHS. Because Greyhounds have a high prevalence of physiologic systolic murmurs associated with high aortic velocity, and large cardiac dimensions when compared with dogs of similar size, they are frequently suspected of having heart disease. The purpose of this study was to compare the VHS in normal Greyhounds with those in Rottweilers, and a group of dogs from various other breeds using both analog and digital radiology. The VHS was significantly higher in Greyhounds (P< 0.0001), when compared with Rottweilers and to other dog breeds. The mean VHS on lateral radiographs for Greyhounds was 10.5 +/- 0.1, for Rottweilers it was 9.8 +/- 0.1, and for mixed breed dogs it was 10.1 +/- 0.2. This study confirms that the relative cardiomegaly reported in necropsy and echocardiographic studies in Greyhounds is easily detected using plain radiography and the VHS.     

Prediction of clinically important acquired cardiac disease without an echocardiogram in large breed dogs using a combination of clinical,radiographic and electrocardiographic variables

IntroductionLarge breed (LB) dogs develop dilated cardiomyopathy (DCM) and myxomatous mitral valve disease (MMVD). Echocardiography is required for a definitive diagnosis but is not always available. Our objective was to assess the clinical utility of thoracic radiographs alone and in combination with physical examination and electrocardiography findings for the prediction of clinically important DCM or MMVD in LB dogs.AnimalsFour hundred fifty-five client-owned dogs ≥20 kg with concurrent thoracic radiographs and echocardiogram.Materials and methodsMedical records were reviewed and stored thoracic radiographs and echocardiographic images were measured to classify dogs as normal heart size (NHS), preclinical DCM, clinical DCM, preclinical MMVD (with cardiomegaly), clinical MMVD, or equivocal. Dogs with preclinical MMVD, without cardiomegaly, were classified as NHS. Vertebral heart size (VHS) and vertebral left atrial size (VLAS) were measured. Receiver operating characteristic curves and prediction models were derived.ResultsPrevalence of MMVD (39.3%) was higher than the prevalence of DCM (24.8%), though most MMVD dogs (67.0%) lacked cardiomegaly and were classified as NHS for analysis. The area under the curve for VHS to discriminate between NHS and clinical DCM/MMVD or preclinical DCM/MMVD was 0.861 and 0.712, respectively, while for VLAS, it was 0.891 and 0.722, respectively. Predictive models incorporating physical examination and electrocardiography findings in addition to VHS/VLAS increased area under the curve to 0.978 (NHS vs. clinical DCM/MMVD) and 0.829 (NHS vs. preclinical DCM/MMVD).ConclusionsThoracic radiographs were useful for predicting clinically important DCM or MMVD in LB dogs, with improved discriminatory ability when physical examination abnormalities and arrhythmias were accounted for.     

Comparison of different radiographic scores with associated echocardiographic measurements and prediction of heart enlargement in dogs with and without myxomatous mitral valve disease

IntroductionStaging of myxomatous mitral valve disease (MMVD) requires an echocardiographic examination along with thoracic radiographs. The aims of this study were to calculate mean values for radiographic scores vertebral heart size (VHS), left atrial width (LA_Width), radiographic left atrial dimension (RLAD), and vertebral left atrial size (VLAS) in conventional and grayscale inverted images in healthy dogs and dogs with different stages of MMVD, and to find cutoff values for a stage assignment.AnimalsOne hundred fifty dogs in different stages of MMVD and 50 unaffected dogs were evaluated.MethodsRadiographic scores, echocardiographic left atrium-to-aorta ratio and normalized left ventricular internal dimension at end-diastole, and results of a clinical examination were obtained. Analyses were performed to evaluate the correlation between radiographic scores and echocardiographic values, to determine cutoff values for a radiographic stage assignment, and to compare measurements in conventional and inverted radiographs.ResultsAfter excluding breed-specific higher VHS, the means of VHS, LA_Width, RLAD, and VLAS were similar in the control group and stage B1. All radiographic scores increased in stages B2 and C. The cutoff values identifying heart enlargement, and therefore differentiating stages B1 and B2, were 11.0 for VHS, 1.8 for LA_Width, 2.0 for RLAD, and 2.3 for VLAS. Besides RLAD, scores were similar in conventional and inverted radiographs.ConclusionCutoff values for the different radiographic scores for stage assignment were calculated. Radiographic cardiac scores using either conventional or inverted grayscale could be a tool to differentiate between different stages of MMVD when echocardiography is unavailable.     

VERTEBRAL HEART SCORES IN EIGHT DOG BREEDS

The vertebral heart score (VHS) measurement is commonly used to provide a more objective measurement of cardiomegaly in canines. However, several studies have shown significant breed variations from the value previously established by Buchanan and Bücheler (9.7 ± 0.5). This study describes VHS measurements in Pug, Pomeranian, Yorkshire Terrier, Dachshund, Bulldog, Shih Tzu, Lhasa Apso, and Boston Terrier dog breeds. Dogs with two or three view thoracic radiographs, no subjective radiographic evidence of cardiomegaly, and no physical examination findings of heart murmurs or gallop rhythms were included in the study. The Pug, Pomeranian, Bulldog, and Boston Terrier groups were found to have a VHS significantly greater than 9.7 ± 0.5 (P < 0.00001, P = 0.0014, P < 0.0001, P < 0.00001, respectively). Body condition score (BCS) was found to have a significant effect on the VHS of Lhasa Apso group. Anomalous vertebrae in the thoracic column were associated with a significant increase in VHS of the Bulldog (P = 0.028) and Boston Terrier (P = 0.0004) groups. Thoracic depth to width ratio did not have a significant effect on VHS.     

Normal electrocardiographic and echocardiographic (M-mode and two-dimensional) values in Polish Landrace pigs

Background

Swine are recognized animal models of human cardiovascular diseases. Normal values of cardiac morphology and function have been published for swine but for smaller number of pigs and not for swine whose weights ranged up 100 kg. In order to improve the value of results of an investigation on cardiac morphology and function in swine when such data are extrapolated to humans, the aim of this study was to document electrocardiographic and echocardiographic measures of cardiac morphology and function in swine. The study comprised 170 single and repeated measurements that were made in 132 healthy domestic swine (Sus domesticus) whose weights ranged between 20-160 kg and were used as controls in three different experiments. All electrocardiographic and echocardiographic measurements in all swine were done under general anaesthesia.

Results

Statistically significant correlations were found between body weight and heart rate (HR), the duration of the P-wave, the duration of the QRS interval, the duration of the QT interval, and the corrected QT ratio (QTc). Since body weight was positively correlated with age, statistically significant correlations were also found between age and HR, the duration of the P-wave, the duration of the QRS interval, the duration of the QT interval, and the QTc. We found that the thickness of the left ventricular wall and the internal diameter of the left ventricle increased with age and body weight. We also found positive trends between body weight and ejection fraction and body weight and fractional shortening. We also found a positive relationship between age, body weight, and the ratio of the left ventricular internal diameter to its wall thickness, as well as the relative left atrial size.

Conclusion

Many electro- and echocardiographic measures of cardiac morphology and function of healthy swine are related to their body weight. When the electro- and echocardiographic measures of domestic swine and humans are compared, the most comparable electrocardiographic values are those that were determined in swine whose body weights are not greater than 70 kg. In contrast, the most comparable echocardiographic measures are those that were determined in swine with a body weight of 40–110 kg.     

INTEROBSERVER VARIABILITY OF VERTEBRAL HEART SIZE MEASUREMENTS IN DOGS WITH NORMAL AND ENLARGED HEARTS

The vertebral heart size (VHS) method by Buchanan is based on anatomic landmarks. A potential source of variation among observers is differences in the selection of measurement points. The objective was to test variability between observers with different levels of training in thoracic radiology and small animal clinical practice. Fifty sets of thoracic radiographs of cavalier King Charles spaniels, were divided into five groups; (Normal) normal cardiopulmonary structures, (I) slight cardiomegaly, (II) moderate cardiomegaly, (II +) moderate cardiomegaly with congestive heart failure, and (III +) severe cardiomegaly with congestive heart failure. Cardiomegaly was confirmed by echocardiography to be caused by mitral regurgitation because of myxomatous mitral valve disease. Sixteen observers representing four levels of experience (four observers/level) evaluated the radiographs; (1) European Diplomates in Veterinary Diagnostic Imaging, (2) Experienced small animal clinicians, (3) Trainees in small animal clinical practice (4) Veterinary students. Almost identical mean VHS values were found among the four experience levels for each of the five groups of radiographs with a low coefficient of variation, range 1.5-3.2%. Mean difference among the 16 observers was 1.05 +/- 0.32 vertebrae (v). Mean difference among individuals in each observer group was approximately 0.5 v for all but the groups of trainees were the difference was 0.6-0.9 v. The conclusion is that VHS method for heart size is independent of observer experience but dependent of individual observers selection of reference points and transformation of long and short axis dimensions into VHS units.     

Vertebral heart size in healthy Australian cattle dog

The vertebral heart score or size (VHS) measurement is routinely used to provide a more objective measurement of cardiomegaly in dogs. However, breed or body conformation can influence the VHS. To assess the specific VHS for the Australian Cattle Dog, left‐to‐right lateral, right‐to‐left lateral, dorsoventral and ventrodorsal thoracic radiographs from 20 individuals free from cardiac and pulmonary disease were obtained. The mean VHS was significantly higher in Australian Cattle Dog (10.5 ± 0.4 vertebrae), when compared with the average VHS for 100 normal dogs of different breeds that had been initially published (9.7 ± 0.5 vertebrae). This emphasizes the importance of breed‐specific VHS ranges. In our study group of normal Australian Cattle Dogs, the mean VHS was 10.5 ± 0.5 vertebrae (mean ±SD) on right lateral and 10.3 ± 0.5 vertebrae on left lateral radiographs. The VHS on right lateral views was significantly larger than on left lateral views. The VHS was 10.5 ± 0.6 vertebrae on dorsoventral and 11.1 ± 0.6 vertebrae on ventrodorsal radiographs. The VHS on ventrodorsal views was significantly larger than on dorsoventral views.     

Echocardiography, electrocardiography, and radiography of cats with dilatation cardiomyopathy, hypertrophic cardiomyopathy, and hyperthyroidism

The echocardiographic, ECG, and radiographic findings of sequentially examined cats with dilatation cardiomyopathy (DCM, n = 7), hypertrophic cardiomyopathy (HCM, n = 8), and hyperthyroidism (HT, n = 20) were compared with those of healthy control cats (n = 11). Cats with DCM were easily differentiated from healthy cats by echocardiography and from cats with HCM and HT by a dilated left ventricle at end-diastole with a mean +/- SD of 2.20 +/- 0.36 cm, reduced fractional shortening (2.9% +/- 3.7%), reduced aortic amplitude (0.07 +/- 0.05 cm), reduced left ventricular wall amplitude (0.09 +/- 0.09 cm), and increased E-point septal separation (0.83 +/- 0.29 cm). The cats with HCM were most consistently recognized echocardiographically by increased left ventricular wall thickness at end-diastole (0.75 +/- 0.12 cm). Some cats with HT had abnormal echocardiograms with left ventricular wall hypertrophy. These cats could usually be differentiated from the cats with HCM because of normal or increased ventricular wall amplitude, aortic amplitude, or percentage of thickening of the left ventricular wall and interventricular septum. Left atrial enlargement (left atrial diameter greater than 1.57 cm or left atrium/aorta greater than 1.75) was commonly detected by the echocardiogram in cats with DCM, HCM, or HT. The echocardiogram was helpful in differentiating the type of cardiomyopathy (DCM, HCM, or HT) when plain thoracic radiographs indicated that cardiomegaly existed. The ECG may have indicated incorrectly that there was left ventricular enlargement in some cats with HT, and it did not indicate consistently that left ventricular enlargement existed when present in cats with DCM or HCM. The ECG was a poor indicator of left atrial enlargement in all cats.     

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

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

A radiographic study of breed‐specific vertebral heart score and vertebral left atrial size in Chihuahuas

Although echocardiography is the gold standard for the diagnosis of cardio‐structural disease, thoracic radiography is a rapid, cost‐effective, and widely accessible method for evaluating cardiac size in dogs. The vertebral heart score (VHS) and the vertebral left atrial size (VLAS) are established as objective measures of cardiomegaly on thoracic radiographs. However, several studies have shown significant variations in the VHS among different breeds. The Chihuahua is predisposed to both congenital and acquired cardiac diseases. The aim of this prospective, single‐center, cross sectional study was thus to evaluate the VHS and the VLAS in healthy adult Chihuahua dogs. A total of 30 Chihuahuas were included. The VHS values in our sample population of Chihuahuas were 10.0 ± 0.6 (95% range, 8.9‐11.0). This was significantly greater than the canine reference value of 9.7 ± 0.5 established by Buchanan and Bücheler (P = .002). The VLAS of Chihuahuas in our study was 1.8 ± 0.2 (95% range, 1.3‐2.1). This was significantly lower than the values previously reported by Malcolm et al (2.07 ± 0.25; P = .0004). The VHS and the VLAS were not influenced by sex, body weight, short or long hair, and body condition score in normal Chihuahuas. Our results indicated that breed‐specific reference values for radiographic VHS and VLAS are needed. In Chihuahuas, the values found in this study can be used as a normal reference in order to help avoid overinterpretation of cardiomegaly in these dogs.     

RADIOGRAPHIC AND ECHOCARDIOGRAPHIC ASSESSMENT OF LEFT ATRIAL SIZE IN 100 CATS WITH ACUTE LEFT‐SIDED CONGESTIVE HEART FAILURE

The aims of this study were to evaluate left atrial size in cats with acute left‐sided congestive heart failure. We hypothesized that left atrial size as determined by thoracic radiography can be normal in cats with acute left‐sided congestive heart failure. One hundred cats with acute left‐sided congestive heart failure in which thoracic radiography and echocardiography were performed within 12 h were identified. Left atrial size was evaluated using right lateral and ventrodorsal radiographs. Measurements were compared to two‐dimensional echocardiographic variables of left atrial size and left ventricular size. On echocardiography, left atrial enlargement was observed in 96% cats (subjective assessment) whereas maximum left atrial dimension was increased (>15.7 mm) in 93% cats. On radiographs left atrial enlargement (subjective assessment) was found in 48% (lateral view), 53% (ventrodorsal view), and 64% (any view) of cats whereas left atrial enlargement was absent in 36% of cats in both views. Agreement between both methods of left atrial size estimation was poor (Cohen's kappa 0.17). Receiver operating characteristic curve analysis identified a maximum echocardiographic left atrial dimension of approximately 20 mm as the best compromise (Youden index) between sensitivity and specificity in the prediction of radiographic left atrial enlargement. Left atrial enlargement as assessed by thoracic radiography may be absent in a clinically relevant number of cats with congestive heart failure. Therefore, normal left atrial size on thoracic radiographs does not rule out presence of left‐sided congestive heart failure in cats with clinical signs of respiratory distress.     

Heart rate variability in relation to severity of mitral regurgitation in Cavalier King Charles spaniels

Heart rate variability was measured in 81 Cavalier King Charles spaniels to investigate if it could be used to evaluate the severity of mitral regurgitation and to predict decompensation. Heart rate variability was assessed by the natural logarithm of the variance of the R-R intervals for 20 consecutive beats obtained from electrocardiographic recordings. Twenty-two of the dogs were clinically normal and 59 had mitral regurgitation caused by chronic valvular disease. The severity of mitral regurgitation was evaluated by echocardiography and thoracic radiography. Heart rate variability was found to be reduced (P < 0.001) among dogs with severe left atrial and ventricular dilatation and clinical signs of congestion. No significant differences in heart rate variability were found among normal dogs, dogs with only cardiac murmur, and dogs with echocardiographic evidence of slight to moderate left atrial and ventricular dilatation. Overall, an association was found between heart rate variability and left atrial to aortic root ratio and left ventricular end diastolic diameters (r = 0.72 and 0.64, respectively, P < 0.001), as well as heart and respiratory rate (r = 0.80 and 0.69, respectively, P < 0.001). Multiregression analysis showed that, in order of importance, heart rate, left atrial diameter and respiratory rate had significant effects on heart rate variability. Among these parameters, heart rate variability and left atrial diameter were found to be most efficient in separating decompensated dogs from compensated. It is concluded that heart rate variability may provide the clinician with valuable information when assessing the severity of mitral regurgitation caused by chronic valvular disease.     

Reference intervals for echocardiographic measurements in healthy Chihuahua dogs

Chihuahuas are one of the most common small breed dogs in Japan, and this breed is known to be predisposed to myxomatous mitral valve disease (MMVD). Echocardiographic assessment is essential for definitive diagnosis of MMVD in dogs as well as determining the stage. Because the Chihuahua’s body size is the smallest among the dog breeds and the widely used echocardiographic reference range is established on the basis of larger dogs, it is unclear whether the existing reference range can be applied to the Chihuahua breed as well. Therefore, this study aimed to determine an echocardiographic reference range for Chihuahua dogs. The left atrial short-axis diameter (LA), aortic valve short-axis diameter, interventricular septum thickness at end-diastole, left ventricular internal dimension at end-diastole (LVIDd), and left ventricular posterior wall thickness at end-diastole from 47 healthy Chihuahuas were analyzed. These parameters increased logarithmically as body weight increased. Furthermore, LA and LVIDd were within the previously established reference range generated primarily from multiple breeds of moderate to large breed dogs.     

Arrhythmogenic right ventricular cardiomyopathy in a dog

An 8-month-old Labrador retriever bitch was evaluated for sudden-onset, progressive abdominal distension. Physical examination revealed an exaggerated inspiratory effort, severe ascites, bilateral jugular vein distension, and hypokinetic femoral arterial pulses. Thoracic auscultation detected tachycardia with muffled heart sounds, without audible cardiac murmurs. Thoracic radiographs identified severe right ventricular enlargement and pleural effusion. The electrocardiogram was consistent with incomplete right bundle branch block or right ventricular enlargement. Echocardiography demonstrated severe right ventricular and atrial dilation, secondary tricuspid regurgitation, and thinning and hypocontractility of the right ventricular myocardium. Left heart chamber sizes were slightly decreased, with normal left ventricular contractility. A diagnosis of arrhythmogenic right ventricular cardiomyopathy was reached, based on the characteristic clinical, electrocardiographic, radiographic and echocardiographic findings, and the exclusion of other causes of isolated right ventricular failure. Treatment effected good control of clinical signs, until acutely decompensated congestive right heart failure led to euthanasia after 4 months. Arrhythmogenic right ventricular cardiomyopathy is a well-described clinical entity in humans, and has previously been documented in 3 male dogs. The condition is characterised by progressive fibro-adipose replacement of right ventricular myocardium, while the left ventricle usually remains unaffected. It should be considered a differential diagnosis in any young dog presented with isolated right heart failure, syncope, or unexplained ventricular tachyarrhythmias. This article reports the 1st case of arrhythmogenic right ventricular cardiomyopathy in a female dog, and highlights its echocardiographic features.     

M-mode echocardiographic measurements in nonanesthetized healthy cats: effects of body weight, heart rate, and other variables

Body weight, heart rate, and 19 M-mode echocardiographic variables were measured in 41 nonanesthetized healthy cats. Estimated limits were determined for the echocardiographic variables, and each variable was then correlated to body weight, heart rate, and the 18 other variables. A significant (P less than 0.05) positive correlation to body weight was found with aortic diameter, left atrial dimension, septal and left ventricular systolic and left ventricular diastolic wall thicknesses, and left and right ventricular diastolic and right ventricular systolic internal dimensions. Significant inverse correlation (P less than 0.05) to heart rate was found with body weight, left ventricular systolic and diastolic and right ventricular systolic internal dimensions, left atrial dimension, left atrial dimension to aortic ratio, mitral valve E point to ventricular septal separation, and left ventricular ejection time. Left ventricular shortening fraction in the short axis and velocity of circumferential fiber shortening were significantly correlated (P less than 0.05) to heart rate. Significant correlation (P less than 0.05) was also found between many echocardiographic variables.     

Utility of N-terminal pro-brain natriuretic peptide for assessing hemodynamic significance of patent ductus arteriosus in dogs undergoing ductal repair

ObjectiveDetermine if plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) correlates with markers of hemodynamically significant patent ductus arteriosus (PDA) in dogs.AnimalsTen dogs with PDA and 30 healthy dogs of similar ages.MethodsProspective case series with control population. Dogs with PDA were initially evaluated with thoracic radiographs, transthoracic echocardiography, pulmonary capillary wedge pressure (PCWP) and NT-proBNP. Following ductal occlusion, NT-proBNP and echocardiography were repeated within 24 h and at day 90. PCWP was repeated at day 90. Correlation between NT-proBNP and hemodynamic measurements was assessed, and accuracy of NT-proBNP for identifying PDA severity was estimated.ResultsNT-proBNP was significantly higher (median; absolute range) in dogs with PDA (895; 490–7118 pmol/L) than controls (663; 50–1318 pmol/L) (p = 0.025). NT-proBNP decreased significantly 90 days post-ductal closure (597; 154–1858 pmol/L) (p = 0.013). Left atrial and ventricular size decreased significantly within 24 h and at day 90 as did PCWP (day 90 only). NT-proBNP correlated with vertebral heart size (VHS) and indexed left ventricular systolic diameter (iLVIDs); concentrations ≥ 1224 pmol/L distinguished dogs with elevated VHS and iLVIDs.ConclusionsNT-proBNP is elevated in dogs with PDA, decreases following PDA closure and correlates with select radiographic and echocardiographic markers of cardiac remodeling.     

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.     

Assessment of the value of the vertebral heart scale in the radiographic diagnosis of cardiac disease in dogs

In order to assess the influence of the vertebral heart scale (VHS) on the accuracy of the radiographic diagnosis of cardiac disease, thoracic radiographs of 50 dogs with proven cardiac disease, 26 with other thoracic diseases, and 50 with no clinical signs of cardiovascular or respiratory disease were mixed and examined by three independent, blinded observers chosen to represent a range of radiographic abilities. They first examined all the radiographs without making measurements of VHS and made a diagnosis. They then re-examined the radiographs, and measured VHS on both lateral and dorsoventral or ventrodorsal radiographs before again recording a diagnosis without reference to their original diagnoses. For all the observers, the dogs with cardiac disease had a higher mean VHS than the normal dogs. A VHS over 10.7 on the lateral radiograph was a moderately accurate sign of cardiac disease. The observers' accuracy of diagnosis did not change significantly as a result of using VHS as an adjunct to a subjective assessment of the radiographs.     

THORACIC RADIOGRAPHIC FEATURES OF ANTICOAGULANT RODENTICIDE TOXICITY IN FOURTEEN DOGS

Thoracic radiographs and clinical records from 14 dogs with confirmed anticoagulant rodenticide toxicity were reviewed. Twelve of the 14 dogs were presented with a chief complaint of respiratory distress, and 12 had elevated prothrombin and activated partial thromboplastin times consistent with a coagulopathy secondary to a clotting factor deficiency. Thoracic radiographs of the 14 dogs were reviewed and abnomalities included increased mediastinal soft tissue opacity with extra and intrathoracic tracheal narrowing (4/14), increased mediastinal soft tissue opacity without tracheal narrowing (8/14), variable degrees of pleural effusion (13/14) and generalized, patchy interstitial/alveolar pulmonary infiltrates (8/14). Radiographic evidence of cardiomegaly and pulmonary artery abnormalities consistent with concurrent heartworm infestation were detected in one dog. In four dogs, dramatic tracheal narrowing was identified on the lateral thoracic radiograph caused by either mediastinal hemorrhage compressing the trachea or submucosal hemorrhage within the tracheal lumen. The trachea was displaced in a ventral direction in two dogs, and extra and intrathoracic luminal diameter narrowing was evident cranially in all four dogs. Two of these four dogs had soft tissue opacity within the dorsal trachea that extended from the larynx to the intrathoracic trachea. Twelve of the 14 dogs survived with standard treatment protocols utilizing injectable and oral vitamin K₁. One dog died from pancreatitis and disseminated intravascular coagulopathy. The other dog died soon after presentation due to severe, disseminated hemorrhage. Follow-up thoracic radiographs were made in four dogs that survived and showed resolution of the mediastinal, pleural and pulmonary changes within one to five days after the initiation of vitamin K₁ therapy.     

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.