Differentiation of Cardiac from Noncardiac Pleural Effusions in Cats using Second-Generation Quantitative and Point-of-Care NT-proBNP Measurements

Hypertrophic Cardiomyopathy-Advances in Imaging and Diagnostic Strategies

Hypertrophic cardiomyopathy (HCM) is the most important and prevalent cardiac disease in cats. Due to the highly variable nature of HCM, a multimodal approach including physical examination, genetic evaluation, cardiac biomarkers, and imaging are all essential elements to appropriate and timely diagnosis. These foundational elements are advancing rapidly in veterinary medicine. Newer biomarkers such as galectin-3 are currently being researched and advances in tissue speckle-tracking and contrast-enhanced echocardiography are readily available. Advanced imaging techniques, such as cardiac MRI, are providing previously unavailable information about myocardial fibrosis and paving the way for enhanced diagnostic capabilities and risk-stratification in cats with HCM.

Clinical findings associated with N-terminal pro-B-type natriuretic peptide measurement in dogs and cats attending first opinion veterinary practices

BACKGROUND

Clinical findings associated with N-terminal pro-B-type natriuretic peptide (NT-proBNP) measurement in dogs and cats in primary practice, and their relevance to published measurement indications, have not been described.

METHODS

Using electronic health record data collected by the Small Animal Veterinary Surveillance Network, appointments in which NT-proBNP was measured were identified using keyword-based text filtering. For these appointments, clinical findings were manually identified from each patient's clinical narrative (CN) and their frequencies described.

RESULTS

CNs of 3510 appointments (357 dogs and 257 cats) from 99practices were evaluated. The most frequently recorded clinical findings in dogs were: heart murmur (n = 147, 41.2% (95% confidence interval (CI) = 36.1%-46.3%), coughing (n = 83, 23.2% (95% CI = 18.8%-27.6%)) and panting (n = 58, 16.2% (95% CI = 12.4%-20.0%)) and in cats: heart murmur (n = 143, 55.6% (95% CI = 49.5%-61.7%)), suspected thromboembolism (n = 88, 34.2% (95% CI = 28.4%-40.0%)) and weight loss (n = 53, 20.6% (95% CI = 15.7%-25.5%)). Dyspnoea and tachypnoea were infrequently reported in dogs (n = 29, 8.1% (95% CI = 5.3%-10.9%) and n = 21, 5.9% (95% CI = 3.5%-8.3%), respectively) and cats (n = 26, 10.1% (95% CI = 6.4%-13.8%) and n = 36, 14.0% (95% CI = 9.8%-18.2%), respectively).

CONCLUSION

Clinical findings referable to cardiac disease were recorded contemporaneously with NT-proBNP measurement and suggested both published and other indications (coughing (in dogs and cats), and serial measurements and thromboembolism (in cats)) for testing.

Updates on Laboratory Evaluation of Feline Cardiac Diseases

Laboratory tests can be altered in cardiovascular diseases and the investigation of specific tests or biomarkers may provide additional information about myocardial damage. Traditional laboratory tests, such as cell blood count, serum biochemistry, and coagulation, can be useful in investigating patients, but are not specific. However, markers like Troponin and Natriuretic Peptides may possibly furnish further data on myocardium damage and can be used in both studying and monitoring cats with cardiac disease. Moreover, the evaluation of the thyroid profile is very important as hyperthyroid cats concomitant cardiovascular diseases are very common and they can also be a direct consequence of endocrinopathy. The purpose of this manuscript is to provide the widest possible overview of what is present in the literature about the feline clinical pathology of heart diseases through a rational division of the main alterations of traditional tests and biomarkers.

Predictors of inflammatory lower airway disease in cats presented to the emergency room in respiratory distress: a case-control study

OBJECTIVES

The objective of the study was to identify whether venous blood gas (VBG) variables may serve as a predictor of inflammatory lower airway disease (ILAD) in cats presenting with respiratory distress. A secondary objective of this study was to compare the diagnostic utility of patient signalment, history and physical examination findings, as compared with VBG variables.

METHODS

The medical records of cats presenting with respiratory distress secondary to ILAD (54 cases) and non-ILAD (121 controls) were retrospectively reviewed.

RESULTS

No admission VBG variables were predictive of a final diagnosis of ILAD. Comparatively, multivariable analysis identified a history of a cough (P <0.001), increased respiratory rate (P = 0.001), the presence of an abdominal component to respiration (P = 0.007) and the absence of pleural effusion (P <0.01) to be independently associated with a final diagnosis of ILAD. Cats with a history of a cough and an abdominal component to respiration had 7.86 and 5.81 greater odds of being diagnosed with ILAD, respectively. Cats with pleural effusion had 7.43 lower odds of having this final diagnosis. For every 10 breaths/min increase in respiratory rate, cats had 1.48 greater odds of being diagnosed with ILAD. Cats diagnosed with ILAD had a survival rate of 94% (95% CI 84-99%) vs 61% (95% CI 51-70%) for non-ILAD controls (P <0.001).

CONCLUSIONS AND RELEVANCE

The results of this study found patient history and physical examination findings to be more useful predictors of a final diagnosis of ILAD in comparison with VBG variables at presentation. A history of a cough, an abdominal component to respiration and a lack of pleural effusion were found to be significant predictors of this diagnosis. Further investigation into the role of respiratory rate in ILAD is warranted.

Biomarker changes with systolic anterior motion of the mitral valve in cats with hypertrophic cardiomyopathy

BACKGROUND

N-terminal pro B-type natriuretic peptide (NT-proBNP) and cardiac troponin-I (cTnI) are biomarkers commonly evaluated in cats with suspected heart disease. Many cats with hypertrophic cardiomyopathy (HCM) have systolic anterior motion of the mitral valve (SAM), but its influence on circulating NT-proBNP or cTnI concentrations is currently unknown.

HYPOTHESIS/OBJECTIVES

Cats with HCM and SAM (HCM^SAM+ ) have higher NT-proBNP and cTnI concentrations than do cats with HCM but without SAM (HCM^SAM- ).

ANIMALS

One hundred forty cats with HCM: 70 with SAM and 70 without SAM.

METHODS

Retrospective case-to-case study. Cats were recruited if diagnosed with HCM by echocardiography and results were available for NT-proBNP or cTnI concentrations or both. Cats with SAM were matched to those without SAM for clinical presentation, left atrial (LA) size and left ventricular (LV) fractional shortening.

RESULTS

A total of 119 NT-proBNP and 123 cTnI results were available. The HCM^SAM+ cats had higher median concentrations than did HCM^SAM- cats for NT-proBNP (729 pmoL/L; interquartile range [IQR], 275-1467 versus 65 pmoL/L; IQR, 25-271; P < .001) and cTnI (0.27 ng/mL; IQR, 0.10-0.81 versus 0.07 ng/mL; IQR, 0.01-0.43; P = .002). In general linear models for both NT-proBNP and cTnI, the independent explanatory variables were SAM, congestive heart failure, maximal LV wall thickness, and LA size.

CONCLUSIONS AND CLINICAL IMPORTANCE

For cats with HCM and equivalent LA size and LV systolic function, those with SAM had higher NT-proBNP and cTnI concentrations than did those without SAM. Presence of SAM should be considered when interpreting biomarker concentrations in cats with HCM.

Focused cardiac ultrasound and point-of-care NT-proBNP assay in the emergency room for differentiation of cardiac and noncardiac causes of respiratory distress in cats

OBJECTIVE

To assess the accuracy of focused cardiac ultrasound (FOCUS) and point-of-care N-terminal proBNP assay in the emergency setting for differentiation of cardiac from noncardiac causes of respiratory distress in cats.

DESIGN

Prospective diagnostic accuracy study between 2014 and 2016.

SETTING

Emergency room at an urban university teaching hospital.

ANIMALS

Forty-one client-owned cats presenting for evaluation of respiratory distress.

INTERVENTIONS

Emergency clinicians made an initial diagnosis of noncardiac or cardiac cause of respiratory distress based on physical examination (PE) findings and history. The diagnoses were updated after performing FOCUS and point-of-care N-terminal B-type natriuretic peptide (POC-BNP). Reference standard diagnosis was determined by agreement of a board-certified cardiologist and critical care specialist with access to subsequent radiographs and echocardiograms.

MEASUREMENTS AND MAIN RESULTS

Forty-one cats were enrolled. Three cats with incomplete data and 1 cat with an uncertain reference standard diagnosis were excluded. The remaining 37 cats were used for analysis: 21 cardiac and 16 noncardiac cases. The ratio of left atrial to aortic root diameter (LA:Ao) measured by FOCUS was significantly correlated with LA:Ao measured by echocardiography (R = 0.646, P < 0.0001). Emergency clinicians correctly diagnosed 27 of 37 (73.0%), yielding a PE positive percent agreement = 76.2% (95% CI, 52.8-91.8%) and negative percent agreement = 68.8% (95% CI, 41.3-89.0%). Five noncardiac and 5 cardiac cats were misdiagnosed. Post FOCUS, overall percent agreement improved to 34 of 37 (91.9%), with positive percent agreement = 95.2% (95% CI, 76.2-99.9%) and negative percent agreement = 87.5% (95% CI, 61.7-98.5%). The POC-BNP yielded an overall percent agreement = 32/34 (94.1%), positive percent agreement = 100% (95% CI, 82.4-100.0%), and negative percent agreement = 86.7% (95% CI, 59.5-98.3%) in differentiating cardiac versus noncardiac cases.

CONCLUSIONS

FOCUS evaluation of basic cardiac structure and LA:Ao by trained emergency clinicians improved accuracy of diagnosis compared to PE in cats with respiratory distress. FOCUS and POC-BNP are useful diagnostics in the emergent setting.

ACVIM consensus statement guidelines for the classification, diagnosis, and management of cardiomyopathies in cats

Cardiomyopathies are a heterogeneous group of myocardial disorders of mostly unknown etiology, and they occur commonly in cats. In some cats, they are well‐tolerated and are associated with normal life expectancy, but in other cats they can result in congestive heart failure, arterial thromboembolism or sudden death. Cardiomyopathy classification in cats can be challenging, and in this consensus statement we outline a classification system based on cardiac structure and function (phenotype). We also introduce a staging system for cardiomyopathy that includes subdivision of cats with subclinical cardiomyopathy into those at low risk of life‐threatening complications and those at higher risk. Based on the available literature, we offer recommendations for the approach to diagnosis and staging of cardiomyopathies, as well as for management at each stage.

Evaluation of point-of-care thoracic ultrasound and NT-proBNP for the diagnosis of congestive heart failure in cats with respiratory distress

BACKGROUND

The diagnosis of congestive heart failure (CHF) in cats is challenging. Point-of-care (POC) thoracic ultrasound and NT-proBNP testing are emerging tools that may aid in diagnosis.

HYPOTHESIS/OBJECTIVES

To assess the diagnostic accuracy of POC lung ultrasound (LUS), focused cardiac ultrasound (FCU), and NT-proBNP in predicting a final diagnosis of CHF.

ANIMALS

Fifty-one cats in respiratory distress.

METHODS

Blood NT-proBNP, LUS, and FCU evaluating left atrial (LA) size and presence of pericardial effusion (PCEFF) were performed in all cats. Lung ultrasound findings including pleural effusion (PLEFF), number of B-lines, and sub-pleural abnormalities were noted. Medical records were evaluated for final diagnosis.

RESULTS

Thirty-three of 51 (65%) cats were diagnosed with CHF. Lung ultrasound and blood NT-proBNP were significant predictors of CHF in a multivariate model. The LUS criterion that maximized accuracy for CHF diagnosis was presence of >1 site strongly positive for B-lines (>3 B-lines per site), resulting in sensitivity of 78.8%, specificity of 83.3%, and area under the curve (AUC) of 0.833. Subjective LA enlargement was 97.0% sensitive and 100% specific for CHF (AUC 0.985). Presence of PCEFF also was 100% specific, but only 60.6% sensitive, for CHF (AUC 0.803). A positive blood NT-proBNP test was 93.9% sensitive and 72.2% specific for the diagnosis of CHF (AUC 0.831).

CONCLUSIONS AND CLINICAL IMPORTANCE

Point-of-care diagnostic techniques of LUS, FCU, and NT-proBNP are useful to diagnose CHF in cats with respiratory distress.

Assessment of a bedside test for N-terminal pro B-type natriuretic peptide (NT-proBNP) to differentiate cardiac from non-cardiac causes of pleural effusion in cats

Background

Cats with pleural effusion represent common emergencies in small animal practice. The aim of this prospective study was to investigate the diagnostic ability of a point-of-care ELISA (POC-ELISA) for the measurement of N-terminal pro B-type natriuretic peptide (NT-proBNP) to differentiate cardiac from non-cardiac disease in cats with pleural effusion. The sample material for use of this rapid test was either plasma or diluted pleural effusion.

Twenty cats with moderate to severe pleural effusion were prospectively recruited. The cats were grouped into two groups, with or without congestive heart failure (CHF; N-CHF), after complete work-up. Blood and effusion were collected in EDTA tubes. Plasma and pleural effusion supernatants were transferred into stabilizer tubes and frozen. POC-ELISA for NT-proBNP was performed with plasma and diluted effusion (1:1). Quantitative NT-proBNP measurement was performed in plasma and diluted and undiluted effusions.

Results

Six cats were assigned to the CHF group. Of the 14 cats in the N-CHF group, 6 had concurrent cardiac abnormalities that were not responsible for the effusion. For the detection of CHF, the test displayed respective sensitivities and specificities of 100% and 79% in plasma and 100% and 86% in diluted pleural fluid. Receiver operating characteristic (ROC) analysis for quantitative NT-proBNP measurement of plasma and diluted and undiluted pleural effusions displayed areas under the curve of 0.98, sensitivities of 100% and specificities of 86%. The optimum cut-off was calculated at 399 pmol/l in plasma and 229 pmol/l in the diluted effusion and 467 pmol/l in the undiluted effusion.

Conclusions

POC-ELISA for NT-proBNP in both plasma and diluted pleural effusion was suitable to differentiate cardiac from non-cardiac causes of feline pleural effusion. According to our results, use of pleural effusion is feasible, but dilution of the effusion before measurement seems to improve specificity.

Electronic supplementary material

The online version of this article (10.1186/s12917-017-1319-6) contains supplementary material, which is available to authorized users.

Assessment of a bedside test for N-terminal pro B-type natriuretic peptide (NT-proBNP) to differentiate cardiac from non-cardiac causes of pleural effusion in cats

BACKGROUND

Cats with pleural effusion represent common emergencies in small animal practice. The aim of this prospective study was to investigate the diagnostic ability of a point-of-care ELISA (POC-ELISA) for the measurement of N-terminal pro B-type natriuretic peptide (NT-proBNP) to differentiate cardiac from non-cardiac disease in cats with pleural effusion. The sample material for use of this rapid test was either plasma or diluted pleural effusion. Twenty cats with moderate to severe pleural effusion were prospectively recruited. The cats were grouped into two groups, with or without congestive heart failure (CHF; N-CHF), after complete work-up. Blood and effusion were collected in EDTA tubes. Plasma and pleural effusion supernatants were transferred into stabilizer tubes and frozen. POC-ELISA for NT-proBNP was performed with plasma and diluted effusion (1:1). Quantitative NT-proBNP measurement was performed in plasma and diluted and undiluted effusions.

RESULTS

Six cats were assigned to the CHF group. Of the 14 cats in the N-CHF group, 6 had concurrent cardiac abnormalities that were not responsible for the effusion. For the detection of CHF, the test displayed respective sensitivities and specificities of 100% and 79% in plasma and 100% and 86% in diluted pleural fluid. Receiver operating characteristic (ROC) analysis for quantitative NT-proBNP measurement of plasma and diluted and undiluted pleural effusions displayed areas under the curve of 0.98, sensitivities of 100% and specificities of 86%. The optimum cut-off was calculated at 399 pmol/l in plasma and 229 pmol/l in the diluted effusion and 467 pmol/l in the undiluted effusion.

CONCLUSIONS

POC-ELISA for NT-proBNP in both plasma and diluted pleural effusion was suitable to differentiate cardiac from non-cardiac causes of feline pleural effusion. According to our results, use of pleural effusion is feasible, but dilution of the effusion before measurement seems to improve specificity.

Pleural lymphocyte-rich transudates in cats

Objectives Non-chylous lymphorrhagic pleural effusions are transudative effusions with a predominance of lymphocytes; however, they do not contain chylomicrons and therefore do not have the classical milky aspect of true chylous effusion. This type of effusion has been anecdotally associated with cardiac diseases in cats, but studies are lacking. The aim of this study was to investigate the association between this type of effusion and the primary disease. Methods In this study, feline non-chylous lymphorrhagic pleural effusions were retrospectively selected from the database of the authors' institutions over a 3 year period. All cases underwent thoracic imaging, including echocardiography. Effusions classified as transudates with a predominance of lymphocytes on cytology were included. Results Thirty-three cases fulfilled the inclusion criteria: 23 (69.7%) had a concurrent cardiac disease, eight (24.2%) cases were associated with the presence of a mediastinal lymphoma or carcinoma or a thoracic mass, one case (3.0%) was a thymoma and one case (3.0%) was a sequela of a pyothorax. Conclusions and relevance Since a clear lymphatic origin of the fluid could not be demonstrated, lymphocyte-rich transudate might be considered a better designation for these kinds of effusions rather than non-chylous lymphorrhagic effusions. Although the number of cases in this preliminary study is low, the presence of a pleural lymphocyte-rich transudate in a cat should prompt the search for cardiac disease or intrathoracic neoplasia.

N-terminal-pro brain natriuretic peptides in dogs and cats: A technical and clinical review

Biomarkers are quantitative indicators of biological processes performed by an organ or system. In recent years, natriuretic peptides (NPs) have emerged as important tools in the diagnosis and therapeutic monitoring of heart diseases. Research has shown that serum and plasma levels of N-terminal pro brain NP (NT-proBNP) in dogs and cats are the only biomarkers that afford to diagnose and monitor congestive processes and, indirectly, the myocardial function of small animals. The present review discusses the peer-reviewed specialized literature about NT-proBNP and presents and compares the potential clinical applications of this NP in veterinary medicine of small animals, considering diagnosis, follow-up, and prognosis of myocardial or systemic diseases. The relevance of NT-proBNP is associated with sample stability, easy determination in laboratory, sensitivity, accuracy, and the possibility to analyze myocardial function. These advantages are specially important when NT-proBNP is compared with other cardiac biomarkers, mostly those that indicate the integrity of the myocardial cell. Fast NT-proBNP assays are marketed today and may be used in association with complementary tests. Together, these methods are an important source of information in differential diagnosis of heart and lung diseases as well in the early diagnosis of cardiopathy in dogs and cats, proving valuable tools in treatment and prognosis.

Biomarkers in Veterinary Medicine

This article summarizes the relevant definitions related to biomarkers; reviews the general processes related to biomarker discovery and ultimate acceptance and use; and finally summarizes and reviews, to the extent possible, examples of the types of biomarkers used in animal species within veterinary clinical practice and human and veterinary drug development. We highlight opportunities for collaboration and coordination of research within the veterinary community and leveraging of resources from human medicine to support biomarker discovery and validation efforts for veterinary medicine.