Distinguishing Cardiac and Noncardiac Dyspnea in 48 Dogs Using Plasma Atrial Natriuretic Factor, B-Type Natriuretic Factor, Endothelin, and Cardiac Troponin-I

N-terminal brain natriuretic peptide, cardiac troponin-I, and point-of-care ultrasound in dogs with cardiac and noncardiac causes of nonhemorrhagic ascites

BACKGROUND

Nonhemorrhagic ascites (NHA) can be caused by cardiac diseases (cNHA) and noncardiac diseases (ncNHA). N-terminal brain natriuretic peptide (NT-proBNP), cardiac troponin-I (cTnI), and point-of-care ultrasound (POCUS) may differentiate between cNHA and ncNHA.

HYPOTHESIS/OBJECTIVES

We compared NT-proBNP and cTnI concentrations as well as POCUS findings in dogs presented with cNHA and ncNHA.

ANIMALS

Dogs (n = 60) were enrolled based on identification of NHA with an effusion packed cell volume < 10%.

METHODS

Blood samples were collected and POCUS was performed on all dogs. Dogs were diagnosed with cNHA (n = 28) or ncNHA (n = 32) based on echocardiography. The cNHA group was subdivided into cardiac non-pericardial disease (n = 17) and pericardial disease (n = 11).

RESULTS

The NT-proBNP concentration (median; range pmol/L) was significantly higher in the cNHA group (4510; 250-10 000) compared to the ncNHA group (739.5; 250-10 000; P = .01), with a sensitivity of 53.8% and specificity of 85.7% using a cut-off of 4092 pmol/L. The NT-proBNP concentrations were significantly higher in the cardiac non-pericardial disease group (8339; 282-10 000) compared with the pericardial disease group (692.5; 250-4928; P = .002). A significant difference in cTnI concentration (median; range ng/L) between the cNHA group (300; 23-112 612) and ncNHA group (181; 17-37 549) was not detected (P = .41). A significantly higher number of dogs had hepatic venous and caudal vena cava distension in the cNHA group compared to the ncNHA group, respectively (18/28 vs 3/29, P < .0001 and 13/27 vs 2/29, P < .001). Gall bladder wall edema was not significantly different between groups (4/28 vs 3/29, P = .74).

CONCLUSIONS AND CLINICAL IMPORTANCE

NT-proBNP concentration and POCUS help distinguish between cNHA and ncNHA.

Evaluation of blood pressure and NT-proBNP in pugs with and without clinical signs of Brachycephalic Obstructive Airway Syndrome

Brachycephalic Obstructive Airway Syndrome (BOAS) is a pathologic condition of the upper airways, frequently occurring in dogs of brachycephalic breeds including pugs. It has been suspected that BOAS may be associated with cardiovascular changes and an increased risk for hypertension. The cardiac biomarker NT-proBNP can help to differentiate cardiac from non-cardiac respiratory distress. A possible influence of BOAS on NT-proBNP values has not been investigated, however. The aim of the current study was to examine blood pressure and NT-proBNP levels in pugs with and without clinical signs of BOAS and compare them to values of mesocephalic dogs. For this purpose, NT-proBNP values of 42 pugs and six mesocephalic dogs and blood pressure measurements of 34 pugs and four mesocephalic dogs were explored in the present study. Pugs were examined for clinical signs of BOAS at rest and after a submaximal fitness test, and a functional BOAS grading was applied. Blood pressure (BP) was measured at the beginning and end of the study day and NT-proBNP values were obtained before and after exercise. Measured values of pugs with different degrees of clinical impairment due to BOAS were compared among each other as well as to the CG. In terms of systolic, mean, diastolic BP, and NT-pro BNP, there were no relevant differences between pugs and the CG and no obvious connection between the severity of BOAS symptoms and measured values. BP values of all groups were lower at the second measurement at the end of the study day. NT-proBNP measurements were higher after exercise. BP and NT-proBNP values in all groups were in agreement with commonly used reference ranges. In conclusion, the study adds evidence, that BP and NT-proBNP values did not differ between mesocephalic dogs and pugs with different levels of severity of BOAS but between the measurement times. Thus, in the present study, excitement and exercise seemed to have a greater influence on BP and NT-proBNP values than presence of BOAS symptoms or breed. Discovered values show that the commonly used reference ranges for BP and NT-proBNP are applicable in pugs. This indicates that NT-proBNP can be used to differentiate between cardiac and non-cardiac respiratory distress even in pugs with clinical symptoms of BOAS.

Evaluation of plasma N-terminal pro-B-type natriuretic peptide levels in healthy North American Salukis with normal echocardiographic measurements

Measurement of N‐terminal pro‐B‐type natriuretic peptide (NT-proBNP) levels has been shown to have clinical significance for diagnosis and management of heart disease in dogs. Evaluation of current reference limits for specific breeds is necessary to ensure the test can accurately distinguish between healthy and diseased animals. The objective of this study is to evaluate the adequacy of currently established NT-proBNP reference limits for clinical use in healthy Salukis. Cardiac health of 33 clinically healthy Salukis was evaluated via echocardiography using available breed standards. Plasma concentrations of NT-proBNP were measured using a commercially available assay. A one-sided 97.5% upper reference limit for the NT-proBNP concentrations was calculated using non-parametric percentile method. The 97.5% upper reference limit was 769 pmol/L (90% CI, 547–1214 pmol/L) for the study dogs. This upper reference limit was within the currently established non-breed specific NT-proBNP upper reference limit of 900 pmol/L. No relationship between sex, age, or body weight on plasma levels of NT-proBNP was noted. Results of this study supports the use of currently available non-breed specific NT-proBNP cut-off values for clinical evaluation of healthy Salukis.

Effect of a Weight Loss Program on Biochemical and Immunological Profile, Serum Leptin Levels, and Cardiovascular Parameters in Obese Dogs

This study aimed to investigate the effects of a weight loss program (WLP) on biochemical and immunological profile, and cardiovascular parameters in a cohort of dogs with naturally occurring obesity. Eleven obese dogs [body condition scoring (BCS), ≥7/9] were enrolled into the study and underwent clinical and cardiovascular examination, and blood testing before (T0) and after 6 months (T1) of WLP. Eleven normal weight (BCS, 4/5) healthy dogs were used as a control (CTR) group. Compared to the CTR group, at T0 obese dogs expressed higher serum leptin concentrations (p < 0.0005) that significantly decreased after weight loss (p < 0.005) but remained higher than the CTR group. Furthermore, obese dogs showed considerably lower levels (p < 0.0005) of regulatory T cell (Treg) compared to the CTR group, but they did not change after weight loss at T1. In obese dogs, tumor necrosis factor (TNF)-α and interleukin (IL)-6 concentrations were substantially reduced at T1 (p < 0.0001 and p < 0.005). Regarding the cardiovascular parameters, only one obese dog was hypertensive at T0, and systolic blood pressure values showed no significant differences at the end of the WLP. The ratio of interventricular septal thickness in diastole to left ventricle internal diameter in diastole (IVSd/LVIDd) was significantly greater in obese dogs at T0 than in the CTR group (p < 0.005). It decreased after weight loss (p < 0.05). In obese dogs, troponin I level significantly reduced with weight loss (p < 0.05), while endothelin-1 level did not differ statistically. The results suggest that the immune dysregulation in the presence of high leptin levels and reduced number of Treg could affect obese dogs as well as humans. Based on our findings, we may speculate that a more complete immune-regulation restore could be obtained by a greater reduction in fat mass and a longer-term WLP. Finally, left ventricular remodeling may occur in some obese dogs. However, in canine species, further studies are needed to investigate the impact of obesity and related WLP on cardiovascular system.

Review of canine dilated cardiomyopathy in the wake of diet-associated concerns

Dilated cardiomyopathy (DCM) has been in the literature and news because of the recent opinion-based journal articles and public releases by regulatory agencies. DCM is commonly associated with a genetic predisposition in certain dog breeds and can also occur secondary to other diseases and nutritional deficiencies. Recent communications in veterinary journals have discussed a potential relationship between grain-free and/or novel protein diets to DCM, citing a subjective increase in DCM in dog breeds that are not known to have a genetic predisposition for the disease. This literature review describes clinical presentations of DCM, common sequelae, treatment and preventative measures, histopathologic features, and a discussion of the varied etiological origins of the disease. In addition, current literature limitations are addressed, in order to ascertain multiple variables leading to the development of DCM. Future studies are needed to evaluate one variable at a time and to minimize confounding variables and speculation. Furthermore, to prevent sampling bias with the current FDA reports, the veterinary community should be asked to provide information for all cases of DCM in dogs. This should include cases during the same time period, regardless of the practitioner's proposed etiology, due to no definitive association between diets with specific characteristics, such as, but not limited to, grain-free diets and those containing legumes, novel protein diets, and those produced by small manufacturers to DCM in dogs. In summary, in order to determine if certain ingredients, categories of diets, or manufacturing processes are related to an increased risk of DCM, further studies investigating these variables are necessary.

Long-term biological variability and the generation of a new reference interval for plasma N-terminal pro-B-type natriuretic peptide in Labrador retrievers

OBJECTIVES

First, to investigate the biological variability of N-terminal pro-B-type natriuretic peptide (NT-proBNP) in healthy Labrador retrievers and compare this with current laboratory recommendations for dilated cardiomyopathy screening. Second, to calculate a breed-specific reference interval and validate it in a retrospective cohort.

MATERIALS AND METHODS

Plasma NT-proBNP was measured in 51 clinically healthy Labrador retrievers at 0, 2, 4, 6 and 8 weeks. Coefficient of variation for individual dogs over time, the coefficient of variation for the group at each time point and the index of individuality were calculated. A reference interval was derived and tested on a clinical dataset available from four UK cardiology referral centres.

RESULTS

Median NT-proBNP was 865 pmol/L (315 to 2064 pmol/L). Mean individual coefficient of variation was 19% (95% CI: 16 to 21%) and group coefficient of variation was 43% (95% CI: 41 to 46%), with index of individuality at 0.44. The breed-specific reference interval was 275 to 2100 pmol/L. In the validation group, 93% of NT-proBNP measurements from healthy dogs were within the reference interval. NT-proBNP measurements exceeded the reference interval in 82% of dogs with dilated cardiomyopathy. The upper bound of the reference interval (2100 pmol/L) had a positive predictive value of 90% and a negative predictive value of 87% for identification of dilated cardiomyopathy in this population.

CLINICAL SIGNIFICANCE

Breed-specific reference intervals might improve the diagnostic accuracy of NT-proBNP measurement. Applying the currently recommended general cut-off value to Labradors is likely to result in frequent false positives and diagnosis would be improved by application of the new breed-specific reference interval calculated here.

Correlation between NT-proBNP and lipase levels according to the severity of chronic mitral valve disease in dogs

Chronic mitral valve disease (CMVD) is the most common cardiovascular disease in dogs, causing decreased cardiac output that results in poor tissue perfusion and tissue damage to kidneys, pancreas, and other organs. The purpose of this study was to evaluate the relationships between heart disease severity and N-terminal pro B-type natriuretic peptide (NT-proBNP) and lipase in dogs with CMVD, as well as to evaluate longitudinal changes in these values. A total of 84 dogs participated in this 2015 to 2017 study. Serum values of NT-proBNP and lipase were analyzed; radiography was used to measure the vertebral heart score and assess various echocardiographic values. NT-proBNP showed a strong positive correlation with increasing stage of heart disease; lipase showed a mild positive correlation with heart disease stage. When the three values (NT-proBNP, lipase and month) were continuously measured at 6-month intervals, all showed a correlation with the increasing length of the disease.

Cardiovascular biomarkers in dogs with systemic inflammatory response syndrome

OBJECTIVE

To measure plasma N-terminal fragments of pro-B-type natriuretic peptides (NT-proBNP) and cardiac troponin T (cTnT) concentration in hospitalized dogs and relate these markers to underlying conditions and evaluate their potential as prognostic markers in dogs with systemic inflammatory response syndrome (SIRS).

DESIGN

Prospective, observational, clinical study.

SETTING

Emergency department of a university teaching hospital.

ANIMALS

Sixty-nine dogs with SIRS examined in the emergency department were prospectively studied. Patient age ranged from 5 months to 15 years, and weight ranged from 5.5 to 75 kg.

MEASUREMENTS AND MAIN RESULTS

Blood samples were obtained at presentation, during hospitalization until discharge or death, and at a "control" visit (T1m) at least 1 month after hospital discharge. NT-proBNP was assayed with a commercially available canine ELISA, while cTnT was measured with an automated immunoassay previously used in dogs. A correlation procedure, mixed procedure on a linear model, and a logistic procedure were performed. Forty-four patients survived, 19 of which had control visits. cTnT concentrations were significantly higher than T0 and T1m at T12, T24, and T72. In 28 dogs, cTnT was detected during hospitalization, but cTnT was not detected in any dog at the control visits. Higher concentrations of cTnT were negatively associated with survival, irrespective of disease category. NT-proBNP concentrations were significantly higher than T0, T6, T12, and T1m at T24, T72, and T120, but were not associated with survival.

CONCLUSIONS

NT-proBNP and cTnT increased significantly in dogs with SIRS, regardless of the underlying disease process. Nonsurvivors displayed significantly higher cTnT concentrations during hospitalization.

Plasma NT-proBNP and Cell-Free DNA Concentrations after Prolonged Strenuous Exercise in Working Farm Dogs

BACKGROUND

Plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentration is increased in dogs with myocardial dysfunction, and cell-free DNA (cfDNA) increases in numerous disease states. In humans, both of these biomarkers can be altered after endurance exercise.

OBJECTIVE

To investigate the effect of prolonged strenuous exercise on circulating NT-proBNP and cfDNA concentrations in working farm dogs.

ANIMALS

Six healthy, privately owned working farm dogs (4 Huntaways and 2 heading dogs) from the same hill country farm in New Zealand.

METHODS

Prospective, nonrandomised cohort study. Venous blood samples were collected before and after the dogs worked over 4 days. Plasma NT-proBNP concentrations were measured by a commercially available ELISA assay and cfDNA concentrations were determined by fluorometry without prior DNA extraction.

RESULTS

The baseline (before work, Day 1) median plasma NT-proBNP concentration was 664 pmol/L. A linear mixed-effects model showed that work increased plasma NT-proBNP concentrations by 101 ± 9% (P < 0.001), but with each consecutive day of work, NT-proBNP concentrations declined by 16 ± 4% (P < 0.001). The baseline median plasma cfDNA concentration was 653 ng/mL, and plasma cfDNA concentrations increased by 138 ± 45 ng/mL after work (P = 0.004).

CONCLUSIONS AND CLINICAL IMPORTANCE

The plasma concentration of NT-proBNP in healthy Huntaways and heading dogs after work can exceed the upper limit of the reference range. Results in dogs sampled on the day of prolonged strenuous exercise should be interpreted with caution. Plasma concentrations of cfDNA also increase with exercise, but further studies are needed to establish reference ranges in healthy dogs.

Plasma N-terminal pro-brain natriuretic peptide concentrations before and after pericardiocentesis in dogs with cardiac tamponade secondary to spontaneous pericardial effusion

OBJECTIVE

To determine if concentrations of plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) are increased in dogs with cardiac tamponade and if there is a significant increase in plasma NT-proBNP after pericardiocentesis.

ANIMALS

Ten client-owned dogs with spontaneous cardiac tamponade.

METHODS

Prospective clinical study. Cardiac tamponade was suspected from physical examination and confirmed with echocardiography. Blood was collected and plasma NT-proBNP concentrations were measured before and 30-60 min following pericardiocentesis and resolution of cardiac tamponade. Within-subject changes in plasma NT-proBNP were compared by the Wilcoxon signed-rank test.

RESULTS

The plasma NT-proBNP concentrations measured within the reference interval in seven of 10 dogs before pericardiocentesis and in six of 10 dogs following pericardiocentesis. Following pericardiocentesis, there was a statistically significant increase in median NT-proBNP concentration (733 pmol/L, range 250-3,297) compared with the values measured before (643 pmol/L, range 250-3,210, P = 0.004). The NT-proBNP concentration increased in 90% of the dogs following pericardiocentesis.

CONCLUSIONS

An upper reference limit of 900 pmol/L for plasma NT-proBNP is insensitive for the diagnosis of pericardial effusion and cardiac tamponade in dogs. Plasma NT-proBNP concentration commonly increases following pericardiocentesis, perhaps related to improved ventricular filling and stretch.

Using Cardiac Biomarkers in Veterinary Practice

Blood-based assays for various cardiac biomarkers can assist in the diagnosis of heart disease in dogs and cats. The two most common markers are cardiac troponin-I and N-terminal pro-B-type natriuretic peptide. Biomarker assays can assist in differentiating cardiac from noncardiac causes of respiratory signs and detection of preclinical cardiomyopathy. Increasingly, studies indicate that cardiac biomarker testing can help assess the risk of morbidity and mortality in animals with heart disease. Usage of cardiac biomarker testing in clinical practice relies on proper patient selection, correct interpretation of test results, and incorporation of biomarker testing into existing diagnostic methods.

Effect of Breed on Plasma Endothelin-1 Concentration, Plasma Renin Activity, and Serum Cortisol Concentration in Healthy Dogs

BACKGROUND

There are breed differences in several blood variables in healthy dogs.

OBJECTIVE

Investigate breed variation in plasma endothelin-1 (ET-1) concentration, plasma renin activity, and serum cortisol concentration.

ANIMALS

Five-hundred and thirty-one healthy dogs of 9 breeds examined at 5 centers (2-4 breeds/center).

METHODS

Prospective observational study. Circulating concentrations of ET-1 and cortisol, and renin activity, were measured using commercially available assays. Absence of organ-related or systemic disease was ensured by thorough clinical investigations, including blood pressure measurement, echocardiography, ECG, blood and urine analysis.

RESULTS

Median ET-1 concentration was 1.29 (interquartile range [IQR], 0.97-1.82) pg/mL, median cortisol concentration 46.0 (IQR, 29.0-80.8) nmol/L, and median renin activity 0.73 (IQR, 0.48-1.10) ng/mL/h in all dogs. Overall, breed differences were found in ET-1 and cortisol concentrations, and renin activity (P < .0001 for all). Pair-wise comparisons between breeds differed in 67% of comparisons for ET-1, 22% for cortisol, and 19% for renin activity, respectively. Within centers, breed differences were found at 5/5 centers for ET-1, 4/5 centers for cortisol, and 2/5 centers for renin activity. Newfoundlands had highest median ET-1 concentration, 3 times higher than Cavalier King Charles Spaniels, Doberman Pinschers, and Dachshunds. Median renin activity was highest in Dachshunds, twice the median value in Newfoundlands and Boxers. Median cortisol concentration was highest in Finnish Lapphunds, almost 3 times higher than in Boxers.

CONCLUSIONS AND CLINICAL IMPORTANCE

Breed variation might be important to take into consideration when interpreting test results in clinical studies.

Cardiac Troponins in Dogs and Cats

Cardiac troponins are sensitive and specific markers of myocardial injury. The troponin concentration can be thought of as a quantitative measure of the degree of injury sustained by the heart, however, it provides no information on the cause of injury or the mechanism of troponin release. Conventionally, the cardiac troponins have been used for diagnosis of acute myocardial infarction in humans and have become the gold standard biomarkers for this indication. They have become increasingly recognized as an objective measure of cardiomyocyte status in both cardiac and noncardiac disease, supplying additional information to that provided by echocardiography and ECG. Injury to cardiomyocytes can occur through a variety of mechanisms with subsequent release of troponins. Independent of the underlying disease or the mechanism of troponin release, the presence of myocardial injury is associated with an increased risk of death. As increasingly sensitive assays are introduced, the frequent occurrence of myocardial injury is becoming apparent, and our understanding of its causes and importance is constantly evolving. Presently troponins are valuable for detecting a subgroup of patients with higher risk of death. Future research is needed to clarify whether troponins can serve as monitoring tools guiding treatment, whether administering more aggressive treatment to patients with evidence of myocardial injury is beneficial, and whether normalizing of troponin concentrations in patients presenting with evidence of myocardial injury is associated with reduced risk of death.

Biologic variability in NT-proBNP and cardiac troponin-I in healthy dogs and dogs with mitral valve degeneration

BACKGROUND

The N-terminal fragment of the prohormone B-type natriuretic peptide (NT-proBNP) and cardiac troponin-I are candidate biomarkers for cardiac disease in dogs. The degree of biologic variation in these biomarkers has not previously been reported in healthy dogs or dogs with mitral regurgitation.

OBJECTIVES

The purpose of the study was to derive estimates of intrinsic biologic variability and reference change values for NT-proBNP and cardiac troponin-I in healthy dogs and dogs with mitral regurgitation grade IB and II according to the International Small Animal Cardiac Health Council (ISACHC) grading system.

METHODS

Plasma and sera were collected weekly for up to 7 weeks from 12 control dogs and 9 dogs with mitral regurgitation. NT-proBNP and troponin-I (C-TnI) concentrations were determined. Indices of biologic variation such as reciprocal index of individuality (r-IoI) and reference change values (RCV) were calculated in both the groups.

RESULTS

Individuality was high in control dogs and dogs with grade IB and II mitral valve regurgitation for both C-TnI (r-IoI 1.6 and 2) and NT-proBNP (1.5 and 2.7), while the 2-sided RCV for NT-proBNP was significantly lower in dogs with mitral regurgitation (52.5% vs 99.4%, P<0.01.).

CONCLUSIONS

High individuality of these cardiac biomarkers suggests that, following diagnosis, these assays are best interpreted by serial determination in individual canine patients rather than by comparison to a population-based reference interval. The smaller RCV values for dogs with mitral regurgitation suggest that smaller relative changes in NT-proBNP are clinically meaningful in these patients.

The effects of storage conditions on measurements of canine N-terminal pro-B-type natriuretic peptide

OBJECTIVES

The study aims were to assess the temporal stability following storage at room temperature, the effect of up to 4 freeze-thaw cycles and the effect of simulated freezer failure on measurements of canine N-terminal pro-B-type natriuretic peptide (NT-proBNP) in serum and protease-inhibited (PI) plasma.

ANIMALS

Twenty-five blood samples were collected from 16 dogs with myxomatous mitral valve disease.

METHODS

Aliquots of canine serum and PI plasma were stored at room temperature (17-26 °C) for 30 min, 6, 24, 48 and 72 h, respectively. Further aliquots were subjected to between 1 and 4 freeze-thaw cycles. A further aliquot was transferred to storage at 4 °C for 24 h while a paired aliquot remained at -80 °C. All samples were returned to storage at -80 °C until subsequent analysis. N-terminal pro-B-type natriuretic peptide was measured in serum and PI plasma samples using first- and second-generation versions of a commercially-available ELISA. Repeated measures models were used to assess change in NT-proBNP measurements. Wilcoxon signed ranks were used to compare paired measurements.

RESULTS

N-terminal pro-B-type natriuretic peptide concentrations declined over time in all samples stored at room temperature. Of the four situations tested, the rate of decrease was lowest for PI plasma samples measured using the second-generation assay. N-terminal pro-B-type natriuretic peptide is stable in samples subjected to up to 4 freeze-thaw cycles and in previously-frozen samples stored at 4 °C for 24 h.

CONCLUSIONS

Use of the second-generation assay, compared with the first-generation, resulted in significantly higher recovery of NT-proBNP measured in PI plasma stored at room temperature. Transport of serum at room temperature for NT-proBNP measurement is not recommended.

Relationship of plasma N-terminal pro-brain natriuretic peptide concentrations to heart failure classification and cause of respiratory distress in dogs using a 2nd generation ELISA assay

Background

Cardiac biomarkers provide objective data that augments clinical assessment of heart disease (HD).

Hypothesis/Objectives

Determine the utility of plasma N‐terminal pro‐brain natriuretic peptide concentration [NT‐proBNP] measured by a 2nd generation canine ELISA assay to discriminate cardiac from noncardiac respiratory distress and evaluate HD severity.

Animals

Client‐owned dogs (n = 291).

Methods

Multicenter, cross‐sectional, prospective investigation. Medical history, physical examination, echocardiography, and thoracic radiography classified 113 asymptomatic dogs (group 1, n = 39 without HD; group 2, n = 74 with HD), and 178 with respiratory distress (group 3, n = 104 respiratory disease, either with or without concurrent HD; group 4, n = 74 with congestive heart failure [CHF]). HD severity was graded using International Small Animal Cardiac Health Council (ISACHC) and ACVIM Consensus (ACVIM‐HD) schemes without knowledge of [NT‐proBNP] results. Receiver‐operating characteristic curve analysis assessed the capacity of [NT‐proBNP] to discriminate between dogs with cardiac and noncardiac respiratory distress. Multivariate general linear models containing key clinical variables tested associations between [NT‐proBNP] and HD severity.

Results

Plasma [NT‐proBNP] (median; IQR) was higher in CHF dogs (5,110; 2,769–8,466 pmol/L) compared to those with noncardiac respiratory distress (1,287; 672–2,704 pmol/L; P < .0001). A cut‐off >2,447 pmol/L discriminated CHF from noncardiac respiratory distress (81.1% sensitivity; 73.1% specificity; area under curve, 0.84). A multivariate model comprising left atrial to aortic ratio, heart rate, left ventricular diameter, end‐systole, and ACVIM‐HD scheme most accurately associated average plasma [NT‐proBNP] with HD severity.

Conclusions and Clinical Importance

Plasma [NT‐proBNP] was useful for discriminating CHF from noncardiac respiratory distress. Average plasma [NT‐BNP] increased significantly as a function of HD severity using the ACVIM‐HD classification scheme.

Breed differences in natriuretic peptides in healthy dogs

BACKGROUND

Measurement of plasma concentration of natriuretic peptides (NPs) is suggested to be of value in diagnosis of cardiac disease in dogs, but many factors other than cardiac status may influence their concentrations. Dog breed potentially is 1 such factor.

OBJECTIVE

To investigate breed variation in plasma concentrations of pro-atrial natriuretic peptide 31-67 (proANP 31-67) and N-terminal B-type natriuretic peptide (NT-proBNP) in healthy dogs.

ANIMALS

535 healthy, privately owned dogs of 9 breeds were examined at 5 centers as part of the European Union (EU) LUPA project.

METHODS

Absence of cardiovascular disease or other clinically relevant organ-related or systemic disease was ensured by thorough clinical investigation. Plasma concentrations of proANP 31-67 and NT-proBNP were measured by commercially available ELISA assays.

RESULTS

Overall significant breed differences were found in proANP 31-67 (P < .0001) and NT-proBNP (P < .0001) concentrations. Pair-wise comparisons between breeds differed in approximately 50% of comparisons for proANP 31-67 as well as NT-proBNP concentrations, both when including all centers and within each center. Interquartile range was large for many breeds, especially for NT-proBNP. Among included breeds, Labrador Retrievers and Newfoundlands had highest median NT-proBNP concentrations with concentrations 3 times as high as those of Dachshunds. German Shepherds and Cavalier King Charles Spaniels had the highest median proANP 31-67 concentrations, twice the median concentration in Doberman Pinschers.

CONCLUSIONS AND CLINICAL IMPORTANCE

Considerable interbreed variation in plasma NP concentrations was found in healthy dogs. Intrabreed variation was large in several breeds, especially for NT-proBNP. Additional studies are needed to establish breed-specific reference ranges.

Management of respiratory emergencies in small animals

Management of respiratory distress involves careful consideration of the history, physical examination, and diagnostic testing. Supplemental oxygen is useful. Urgent procedures, such as intubation, thoracococentesis, or tracheostomy, may be required. The prognosis is dependent on the underlying disease, but is often favorable. This article reviews the approach, differential diagnoses, and the approach to management for dogs and cats with respiratory distress.

Circulating natriuretic peptide concentrations in hyperthyroid cats

OBJECTIVES

To assess the influence of thyroid function on natriuretic peptide concentration in hyperthyroid cats before and after treatment.

METHODS

Serum natriuretic peptide concentration was measured in 61 hyperthyroid cats recruited from first-opinion clinics before and after treatment.

RESULTS

Following successful treatment, total thyroxine, heart rate, systolic blood pressure and packed cell volume all decreased and bodyweight and creatinine concentrations increased. Furthermore, a significant (P < 0·001) decline in NT-proBNP concentration but not NT-proANP was identified.

CLINICAL SIGNIFICANCE

Thyroid function has a modest but significant effect on NT-proBNP concentration. Thyroid status should be taken into account when interpreting NT-proBNP concentrations in cats.

Diagnostic utility of NT-proBNP and ANP in a canine model of chronic embolic pulmonary hypertension

The information needed to diagnose pulmonary arterial hypertension (PAH) in dogs based on N-terminal pro B-type natriuretic peptide (NT-proBNP) and atrial natriuretic peptide (ANP) levels is unclear. In this study, serial changes in plasma NT-proBNP and ANP concentrations were evaluated in association with the development of chronic embolic pulmonary hypertension (CEPH). Six Beagle dogs underwent percutaneous pulmonary artery catheterization. CEPH was induced by the repeated injection of 300 μm microspheres into the pulmonary artery via the catheter. Measured peak systolic pulmonary arterial pressure (PAPs) was elevated up to 80 mm Hg at 90 days by repeated injection of microspheres. Echocardiographic examination showed significant increase in the main pulmonary artery enlargement, right ventricular dilation, transtricuspid late diastolic flow, and ventricular late diastolic myocardial velocity. Plasma concentrations of NT-proBNP and ANP were significantly increased by microsphere-induced severe CEPH, but not by mild CEPH. Measured PAPs correlated weakly with plasma NT-proBNP and ANP concentrations (r=0.63 and 0.69, respectively) and with several echocardiographic variables. Our results indicated that plasma ANP and NT-proBNP responded to severe PAH, but that they were not sensitive for mild PAH.

Resting and dobutamine stress test induced serum concentrations of brain natriuretic peptide in German Shepherd dogs

Studies of clinical uses of brain natriuretic peptide (BNP) represent one of the most important advances in cardiology since the introduction of echocardiography as a clinical diagnostic procedure. Defining the clinical potential of BNP in canine cardiology has not been completed yet. The aim of this study is to measure BNP concentrations in healthy German Shepherd dogs of different ages as a baseline in resting and when conventional protocol of the dobutamine stress test (DST) is applied to dogs. Concentrations of BNP were measured in blood serum by the radioimmunoassay method. The values of BNP concentrations were compared to cardiac parameters obtained by standard cardiac diagnostic procedures (radiology, electrocardiography and echocardiography). No significant differences in serum BNP concentrations existed in dogs of different ages. A statistically significant increase in BNP concentrations was registered after DST. These changes in BNP concentrations were related to ST/T electrocardiographic changes, and correlated to changes in the left ventricular internal diameter in systole (LVESD). These data suggest that BNP is not increased in aged dogs with normal cardiac systolic function and renal function, and that myocardial ischemia leads to a significant increase in BNP concentrations even in dogs with normal left ventricular function.

Dosagem sérica de troponina I em cães com desnível do segmento ST utilizando quimioluminescência

Com o intuito de verificar algum dano nas células do miocárdio, utilizaram-se 38 cães, 20 com traçado eletrocardiográfico normal, grupo 1, e 18 com desníveis do segmento ST, grupo 2, em registro na derivação II, velocidade de 50mm/s e sensibilidade N (1mV=1cm). No grupo 1, a dosagem sérica da troponina I (cTnI) destinou-se à obtenção dos valores referenciais (ng/mL) que seriam confrontados com os obtidos no grupo 2. A média e o desvio-padrão foram, respectivamente, 0,16ng/mL e 0,11ng/mL e 0,20ng/mL e 0,11ng/mL, nos grupos 1 e 2. A cTnI não apresentou evidências de associação com idade, massa corpórea, creatinafosfoquinase total e potássio nos dois grupos. Não houve diferenças significativas nos valores de cTnI entre os grupos. Conclui-se que é possível a utilização do kit de ensaio imunométrico quimioluminescente humano para a espécie canina e que a hipóxia-isquemia, revelada pelo desnível do segmento ST não acarreta dano miocárdico ou este é mínimo e indetectável.

Evaluation of N-terminal pro-B-type natriuretic peptide as a diagnostic marker of various stages of cardiomyopathy in Doberman Pinschers

OBJECTIVE

To evaluate the diagnostic value of plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations in Doberman Pinschers in various stages of dilated cardiomyopathy (DCM).

ANIMALS

328 Doberman Pinschers.

PROCEDURES

Staging of DCM was determined via analysis of results of physical examinations, 24-hour ambulatory ECG (Holter) recordings, and echocardiographic evaluations. Plasma samples for NT-proBNP assays were obtained at each examination. Concentrations of NT-proBNP were measured in 337 samples obtained from 196 healthy Doberman Pinschers (control dogs) and in 195 samples obtained from 132 Doberman Pinschers in various stages of DCM. These included dogs that had ventricular premature contractions (VPCs; 79 samples), echocardiographic changes (23 samples), or both (51 samples); 16 samples were from dogs with overt DCM, and 26 were from dogs that were considered normal during initial examination but developed DCM within 1.5 years after this assessment. Receiver operating characteristic curves were analyzed to determine sensitivity and specificity of NT-proBNP concentrations for detection of DCM.

RESULTS

NT-proBNP concentrations in dogs that had or developed DCM were significantly higher than those of control dogs. Sensitivity and specificity of NT-proBNP concentrations (cutoff value, > 400 pmol/L) to detect all stages of DCM were 81.1 % and 75.0%, respectively; sensitivity was 90.0% and specificity was 75.0% to predict echocardiographic changes. Specificity to detect echocardiographic changes was 90.4% at a cutoff value of 550 pmol/L.

CONCLUSIONS AND CLINICAL RELEVANCE

Plasma concentrations of NT-proBNP were increased in dogs with DCM and in apparently healthy dogs that developed DCM within 1.5 years after samples were obtained, compared with concentrations in control dogs.

NT-proBNP, NT-proANP and cTnI concentrations in dogs with pre-capillary pulmonary hypertension

OBJECTIVES

To compare [NT-proBNP], [NT-proANP] and [cTnI] between control dogs with respiratory disease without pulmonary hypertension (PH) and dogs with pre-capillary PH, and to assess the accuracy of [NT-proBNP], [NT-proANP], [cTnI] to predict Doppler-derived peak tricuspid regurgitation (TR) gradient.

ANIMALS

20 dogs. 8 control dogs with respiratory disease with no PH and 12 with pre-capillary PH.

METHODS

[NT-proBNP], [NT-proANP] and [cTnI] were compared between the 2 groups and simple linear regression analysis was used to predict peak TR gradients from various blood biomarkers.

RESULTS

Median [NT-proBNP] was higher in the dogs with PH (2011 pmol/L, 274-7713 pmol/L) compared to control dogs (744 pmol/L; 531-2710 pmol/L) (p = 0.0339). [NT-proBNP] was associated with peak TR gradient (R(2) = 0.7851, p = 0.0001). Median [NT-proANP] did not differ between dogs with PH (1747 fmol/L; 894-2884 fmol/L) and control dogs (1209 fmol/L; 976-1389 fmol/L (p = 0.058). [NT-proANP] was not associated with peak TR gradient (R(2) = 0.2780, p = 0.0781). Median [cTnI] did not differ between dogs with PH (0.2850 ng/mL; 0.19-1.13 ng/mL) and control dogs (0.2 ng/mL; 0.19-0.82 ng/mL, p = 0.3051). Median [TnI] was not associated with peak TR gradient (R(2) = 0.024, p = 0.6307).

CONCLUSIONS

[NT-proBNP] concentration is significantly higher in dogs with pre-capillary PH when compared to dogs with respiratory disease without PH, and [NT-proBNP] may be useful to predict the severity of estimated PH. Elevations in [NT-proBNP] due to pre-capillary PH may complicate the interpretation of [NT-proBNP] elevations in patients presenting with cardiorespiratory abnormalities. [NT-proANP] and [cTnI] were not elevated in dogs with pre-capillary PH.

Utility of measuring plasma N-terminal pro-brain natriuretic peptide in detecting hypertrophic cardiomyopathy and differentiating grades of severity in cats

BACKGROUND

Cats with hypertrophic cardiomyopathy (HCM) often have no clinical signs or subtle signs. Measurement of N-terminal pro-brain natriuretic peptide (NT-proBNP) has been demonstrated in people to be highly specific for heart disease and also correlates with severity of HCM. NT-proBNP may also be valuable in detecting and grading HCM in cats, but results to date have been equivocal.

OBJECTIVES

The aims of this study were to evaluate NT-proBNP as a screening test for diagnosis of HCM in cats and determine an appropriate cut-off value and to determine if NT-proBNP concentrations correlated with severity of HCM in cats.

METHODS

Plasma NT-proBNP concentrations were measured in 201 cats using an ELISA designed for use in cats. Cats were classified using echocardiography as clinically healthy controls (n=99) or cats with equivocal (n=9), mild (n=15), moderate (n=17), or severe (n=61) HCM.

RESULTS

NT-proBNP concentrations (median; 25th-75th interquartile percentiles) in mildly (216.1; 87.6-392.5 pmol/L), moderately (282.7; 131.9-466.6 pmol/L), and severely (839.5; 655.3-1046.4 pmol/L) affected cats were significantly higher than those in healthy controls (18.9; 3.4-62.4 pmol/L). Concentrations in severely affected cats were significantly higher than in cats from other HCM groups. There was no significant difference between mild and moderate HCM. Cut-off values >49 pmol/L had a sensitivity of 97.8% and specificity of 66.7%; >100 pmol/L had a sensitivity of 92.4% and specificity of 93.9%; and >150 pmol/L had a sensitivity of 88% and a specificity of 100%.

CONCLUSIONS

NT-proBNP with a cut-off value of >100 pmol/L was useful in detecting even mild HCM. Cats with increased NT-proBNP concentrations should be examined by echocardiography.

Comparison of plasma cardiac troponin I concentrations among dogs with cardiac hemangiosarcoma, noncardiac hemangiosarcoma, other neoplasms, and pericardial effusion of nonhemangiosarcoma origin

OBJECTIVE

To determine whether plasma cardiac troponin I (cTnl) concentrations can be used to identify cardiac involvement in dogs with hemangiosarcoma, exclude cardiac hemangiosarcoma in dogs with noncardiac hemangiosarcoma, and identify cardiac hemangiosarcoma in dogs with pericardial effusion.

DESIGN

Cohort study.

ANIMALS

57 dogs (18 with confirmed [5 dogs] or suspected [13] cardiac hemangiosarcoma, 14 with confirmed hemangiosarcoma involving sites other than the heart [noncardiac hemangiosarcoma], 10 with pericardial effusion not caused by hemangiosarcoma, and 15 with noncardiac nonhemangiosarcoma neoplasms).

PROCEDURES

Plasma cTnl concentration was measured, and thoracic radiography, abdominal ultrasonography, and echocardiography were performed in each dog. The cTnl concentration was compared among groups.

RESULTS

Median plasma cTnl concentration in dogs with cardiac hemangiosarcoma was significantly higher than the concentration in each of the other groups. A plasma cTnl concentration > 0.25 ng/mL could be used to identify cardiac involvement in dogs with hemangiosarcoma at any site (sensitivity, 78%; specificity, 71 %). A plasma cTnl concentration > 0.25 ng/mL could be used to identify cardiac hemangiosarcoma in dogs with pericardia effusion (sensitivity, 81%; specificity, 100%).

CONCLUSIONS AND CLINICAL RELEVANCE

The median plasma cTnl concentration was higher in dogs with cardiac hemangiosarcoma, compared with the median concentration in dogs with hemangiosarcoma at other sites, dogs with other neoplasms, and dogs with pericardial effusion not caused by hemangiosarcoma. The plasma cTnl concentration may be used to identify cardiac involvement in dogs with hemangiosarcoma and to identify cardiac hemangiosarcoma in dogs with pericardial effusion.

The use of NT-proBNP assay in the management of canine patients with heart disease

The diagnosis and management of canine heart disease could be facilitated by a highly sensitive and specific laboratory test that predicts risk of morbidity and mortality, is helpful in directing therapy, easy to perform, inexpensive, and widely available. This article details if, how, and when the cardiac biomarker, N-terminal fragment of the prohormone B-type natriuretic peptide (NT-proBNP), helps in the diagnosis and management of canine heart disease. Veterinary cardiac biomarkers, specifically NT-proBNP, hold great promise. The incorporation of NT-proBNP assay into successful clinical practice requires an understanding of the science behind the technology, as well as the clinical data available to date.

Brain-natriuretic peptide and cyclic guanosine monophosphate as biomarkers of myxomatous mitral valve disease in dogs

Elevations in the plasma concentrations of natriuretic peptides correlate with increased severity of myxomatous mitral valve disease (MMVD) in dogs. This study correlates the severity of MMVD with the plasma concentrations of the biomarkers N-terminal fragment of the pro-brain-natriuretic peptide (NT-proBNP) and its second messenger, cyclic guanosine monophosphate (cGMP). Furthermore, the L-arginine:asymmetric dimethylarginine (ADMA) ratio was measured as an index of nitric oxide availability. The study included 75 dogs sub-divided into five groups based on severity of MMVD as assessed by clinical examination and echocardiography. Plasma NT-proBNP and cGMP concentrations increased with increasing valve dysfunction and were significantly elevated in dogs with heart failure. The cGMP:NT-proBNP ratio decreased significantly in dogs with heart failure, suggesting the development of natriuretic peptide resistance. Although the l-arginine:ADMA ratio decreased with increasingly severe MMVD, this was largely due to the older age of the dogs with heart failure.

Routine and specialized laboratory testing for the diagnosis of neuromuscular diseases in dogs and cats

The diagnosis of neuromuscular diseases can be challenging. The first step is recognition that the disease involves the neuromuscular system (muscle, neuromuscular junction, peripheral nerve, and ventral horn cells of the spinal cord). Many neuromuscular diseases share clinical signs and cannot be distinguished based on clinical examination. Routine laboratory screening, including a CBC, biochemical profile, and urinalysis, can identify some of the most common systemic abnormalities that cause muscle weakness and myalgia, such as hypo- and hyperglycemia, electrolyte disorders, or thyroid abnormalities, and may suggest a specific diagnosis, such as diabetes mellitus, hypo- or hyperadrenocorticism, renal failure, or hypothyroidism. Increased creatine kinase activity, increased cardiac troponin I concentration, and myoglobinuria are useful in detecting skeletal and cardiac muscle damage. Identification of acetylcholine receptor antibodies is diagnostic for acquired myasthenia gravis. For primary muscle or peripheral nerve diseases, tissue biopsy is the most direct way to determine specific pathology, correctly classify the disease, and determine the course of additional laboratory testing. For example, inflammatory, necrotizing, dystrophic, metabolic, or congenital myopathies require different laboratory testing procedures for further characterization. Many neuromuscular diseases are inherited or breed-associated, and DNA-based tests may already be established or may be feasible to develop after the disorder has been accurately characterized. This review focuses on both routine and specialized laboratory testing necessary to reach a definitive diagnosis and determine an accurate prognosis for neuromuscular diseases.

Cardiac troponin I in Doberman Pinschers with cardiomyopathy

BACKGROUND

Cardiac troponin I (cTnI) is useful for detection of cardiac myocyte damage, but its efficacy in detecting various stages of dilated cardiomyopathy (DCM) in Doberman Pinschers is unclear.

OBJECTIVES

To evaluate the diagnostic value of cTnI in various stages of DCM in Dobermans.

ANIMALS

Six hundred and fifty-three cTnI measurements of 336 Doberman Pinschers.

METHODS

Using a longitudinal study design, staging of the disease was based upon 24-hour-ambulatory-ECG (Holter) and echocardiography. A total of 447 cTnI measurements were performed in 264 healthy Dobermans, and 206 cTnI measurements in 75 Dobermans with cardiomyopathy. Eighty-eight cTnI samples were from dogs with >100 ventricular premature contractions (VPCs)/24 hour, but without echocardiographic changes ("VPC group"). Additional 19 samples originated from dogs with only echocardiographic changes ("ECHO group"), and 56 samples from dogs with both VPCs and echocardiographic changes ("VPC plus ECHO group"). Twenty samples were from dogs with clinical signs ("clinical group"). The group "incipient" included 23 dogs, that were considered to be normal according to Holter and echocardiography at the time of the exam, but that developed DCM within 1.5 years.

RESULTS

cTnI values of dogs in all disease groups, including the "incipient" (0.30+/-0.20) and "VPC group" (0.36+/-0.34), were significantly (P=.04, P<.001) higher than the control group (0.07+/-0.16). A cut-off value of >0.22 ng/mL had a sensitivity of 79.5% and a specificity of 84.4% to detect all forms of cardiomyopathy.

CONCLUSIONS AND CLINICAL IMPORTANCE

cTnI measurement is a valuable diagnostic test that can detect cardiomyopathy in dogs that are otherwise clinically normal.

Assessment of serum N-terminal pro-B-type natriuretic peptide concentration for differentiation of congestive heart failure from primary respiratory tract disease as the cause of respiratory signs in dogs

OBJECTIVE

To determine whether serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentration is useful in discriminating between cardiac and noncardiac (ie, primary respiratory tract disease) causes of respiratory signs (ie, coughing, stertor, stridor, excessive panting, increased respiratory effort, tachypnea, or overt respiratory distress) in dogs.

DESIGN

Multicenter cross-sectional study.

ANIMALS

P 115 dogs with respiratory signs.

PROCEDURES

Dogs with respiratory signs were solicited for study. Physical examination, thoracic radiography, and echocardiography were used to determine whether respiratory signs were the result of cardiac (ie, congestive heart failure) or noncardiac (ie, primary respiratory tract disease) causes. Serum samples for NT-proBNP assay were obtained at time of admission for each dog. Receiver-operating characteristic curves were constructed to determine the ability of serum NT-proBNP concentration to discriminate between cardiac and noncardiac causes of respiratory signs.

RESULTS

Serum NT-proBNP concentration was significantly higher in dogs with cardiac versus noncardiac causes of respiratory signs. In dogs with primary respiratory tract disease, serum NT-proBNP concentration was significantly higher in those with concurrent pulmonary hypertension than in those without. A serum NT-proBNP cutoff concentration > 1,158 pmol/L discriminated between dogs with congestive heart failure and dogs with primary respiratory tract disease with a sensitivity of 85.5% and a specificity of 81.3%.

CONCLUSIONS AND CLINICAL RELEVANCE

Measuring serum NT-proBNP concentration in dogs with respiratory signs helps to differentiate between congestive heart failure and primary respiratory tract disease as an underlying cause.

N-terminal pro B-type natriuretic peptide and left ventricular diameter independently predict mortality in dogs with mitral valve disease

OBJECTIVES

To determine whether natriuretic peptide concentrations would predict all cause mortality in dogs with degenerative mitral valve disease.

METHODS

One hundred dogs with naturally occurring degenerative mitral valve disease were prospectively recruited for this longitudinal study. Analysis of outcome was undertaken for 73 dogs for which the outcome was known. Dogs underwent physical examination, electrocardiography and echocardiography. Natriuretic peptide concentrations were measured by Enzyme-linked immunosorbent assay. The ability of natriuretic peptide concentrations, clinical, electrocardiographic and echocardiographic data, to predict all cause mortality was determined using univariable and multivariable Cox proportional hazards analyses.

RESULTS

Thirty dogs died during the period of follow-up. Two variables were independently predictive of all cause mortality; these were the normalised left ventricular end-diastolic diameter and the N-terminal pro B-type natriuretic peptide concentration. An increase of the left ventricular end-diastolic diameter by 0.1 increased the hazard of all cause mortality by 20% (95% confidence interval: 4 to 37%, P=0.01) and a 100 pmol/l increase in N-terminal pro B-type natriuretic peptide increased the hazard by 7% (95 confidence interval: 2 to 11%, P=0.003).

CLINICAL SIGNIFICANCE

N-terminal pro B-type natriuretic peptide concentration and left ventricular end-diastolic diameter are significantly and independently predictive of all cause mortality in dogs with degenerative mitral valve disease.