NT-proBNP

A raised NT-proBNP indicates the heart muscle is under stretch or strain, and the higher it is, the more that suggests significant heart disease. Two settings make it especially useful:

• The breathless patient: in a coughing or breathless dog or cat, NT-proBNP helps answer the pivotal question — is this the heart (congestive heart failure) or the lungs (airway or lung disease)? A high value points towards the heart and heart failure; a low value makes a primary heart cause much less likely, redirecting attention to the respiratory system.
• Screening for hidden disease: in a breed at risk, or where a murmur has been heard, a raised NT-proBNP flags heart disease worth imaging even before symptoms appear.

Because other things (notably kidney disease, which slows its clearance) can nudge NT-proBNP up, and because it reports strain rather than a specific diagnosis, a high value is a prompt to image the heart with an echocardiogram, not an end-point in itself.

A low or normal NT-proBNP is reassuring: it makes significant, clinically-important heart strain unlikely. In a breathless patient, a normal value is particularly valuable for ruling out heart failure and steering the work-up towards the lungs. As a screening result in a well pet, it is a good sign, though it does not replace listening to the heart and a physical exam.

In a pet with known heart disease, NT-proBNP can be tracked over time as one measure of how the heart is coping, alongside imaging and clinical signs. A rising trend can signal disease progression or increasing strain; a value that responds to treatment is a reassuring sign. It complements, rather than replaces, the echocardiogram, which remains the tool that characterises the structural problem.

NT-proBNP is used in both species but with different emphasis. In cats, heart disease (especially hypertrophic cardiomyopathy) is notoriously silent — often no murmur, no symptoms — so NT-proBNP is valued as a screening test to pick out cats that warrant an echocardiogram, and as a rapid triage tool in a cat in respiratory distress, where handling for imaging is risky. In dogs, it is widely used in the work-up of murmurs and breed screening, and to help sort cardiac from respiratory causes of cough. Reference thresholds differ between the species, so the value is always read against the species-appropriate range.

NT-proBNP is measured from a blood sample sent to a reference laboratory (a point-of-care version exists for rapid triage), reported in pmol/L. Sample handling matters, and kidney function is taken into account when interpreting it. It is read against species-specific cut-offs on your report.

A raised NT-proBNP is a reason to look at the heart properly — usually an echocardiogram, often with a blood-pressure check and a look at kidney values — rather than a diagnosis to act on directly. In a breathless pet it can rapidly help separate a heart problem from a lung one, guiding urgent treatment; in a well pet it flags a heart worth imaging before trouble becomes obvious.