NT-proBNP as a diagnostic marker in dogs with dyspnea and in asymptomatic dogs with heart murmur

Objective: The cardiac biomarker NT-proBNP indicates cardiac load in terms of myocardial wall stress. The objective of the study was to compare the results of NT-proBNP measurements in healthy dogs and dogs with dyspnea as well as asymptomatic dogs with heart murmur with the literature. Material and methods: Between April 2007 and December 2007 dogs with dyspnea of non-cardiac origin (n = 11), dogs with dyspnea of cardiac origin (n = 18) and asymptomatic dogs with heart murmur (n = 22) were included. Twelve clinically healthy dogs served as a control group. All animals underwent cardiologic examination including echocardiography and measurement of serum NT-proBNP concentration. Serum was centrifuged and frozen within 30 minutes and was stored frozen until analysis was performed. Results: Median NT-proBNP concentration in healthy dogs was 240 pmol/l (range 131-546 pmol/l). Dogs with dyspnea and primary respiratory disease displayed a median NT-proBNP concentration of 876 pmol/l (range 97-2614 pmol/l). In patients with dyspnea of non-cardiac origin, there was a difference in the values of NT-proBNP of dogs with and without pulmonary hypertension diagnosed by echocardiography. Dogs with dyspnea of cardiac origin displayed a median NT-proBNP concentration of 2000 pmol/l (range 137-2614 pmol/l). Low normal NT-proBNP values were only found in patients with pericardial effusion. Median NT-proBNP concentration in asymptomatic dogs with heart murmur was 698.5 pmol/l (range 121-2614 pmol/l). Considerably increased values were particularly measured in asymptomatic patients with severe congenital heart disease. Conclusion and clinical relevance: NT-proBNP represents a useful additional diagnostic parameter in veterinary clinical cardiology to assess the severity of cardiac disease. Interpretation must take into consideration the clinical picture of the patient, as dogs with severe arrhythmias, sepsis and pulmonary thromboembolism may display high NT-proBNP levels without congestive heart failure. Our results indicate the following cut-off values: < 500 pmol/l: no relevant cardiac load; 500-900 pmol/l: moderate cardiac load; > 900 pmol/l: severe cardiac load.