Cardiac troponin (I, high-sensitivity I, T) in cats and dogs
Cardiac troponins are proteins of the contraction machinery inside heart muscle cells. When these cells are damaged, troponin leaks into the blood, so a raised value shows that heart muscle is being injured. It does not say why: the cause is looked for with an echocardiogram, an ECG and other tests.
What it shows
Troponin I, troponin T and troponin C form one complex attached to the muscle fibres. Because cardiac troponin sits in heart cells, a rise is fairly specific for damage to heart muscle, and in animals troponin is the marker used for cardiac injury. Like ALT for the liver, it shows that cells are damaged, not which disease damaged them.
A form can show it in three rows:
- Cardiac troponin I (cTnI) — the standard test. Together with NT-proBNP it is one of only two heart biomarkers in dogs and cats studied enough for recommendations.
- High-sensitivity troponin I (hs-cTnI) — the same protein measured by a method with a lower detection limit, so it picks up smaller amounts. It has its own reference range.
- Cardiac troponin T (cTnT) — another protein of the same complex; Merck notes that in dogs and cats troponin I is the one most commonly measured.
Higher than reference — what it may be a sign of
- Heart disease — in dogs troponin I rises with the severity of mitral valve disease; it is also raised in cardiomyopathies, narrowed heart valves, heartworm, pericardial effusion and heart tumours. In cats it can rise in moderate to severe hypertrophic cardiomyopathy, but values overlap with healthy cats.
- Inflammation of the heart muscle (myocarditis) — from infections or parasites.
- Diseases outside the heart — in dogs pancreatitis, pyometra and sepsis, parvovirus, leptospirosis, babesiosis, ehrlichiosis, leishmaniasis and gastric dilatation-volvulus have been linked to raised troponin.
- Reduced kidney function — troponin is partly cleared by the kidneys, so kidney disease can raise the value.
- Age and breed — some troponin is released with age; Greyhounds and Boxers may have higher values.
Lower than reference
A low or undetectable troponin is the expected result: active injury of the heart muscle is unlikely at the time of the test. It does not rule out heart disease. Troponin and NT-proBNP are not 100% accurate and are never read in isolation; the heart itself is assessed by ultrasound.
Look at together with
- NT-proBNP — shows stretch and strain of the heart wall, while troponin shows cell damage. In dogs with mitral valve disease the two together predicted survival better than either alone. In cats NT-proBNP is the more useful screen; troponin values overlap too much for screening.
- Creatinine — kidney function affects troponin.
- CK — a muscle enzyme; for heart injury in animals troponin is used instead.
Units and conversion
Standard troponin I and troponin T are reported in ng/mL; µg/L is the same number (1 ng/mL = 1 µg/L). High-sensitivity troponin I is usually reported in ng/L or pg/mL, which are also the same number. Between the two groups there is a factor of a thousand: 1 ng/mL equals 1000 ng/L. In the app each row keeps the unit printed on the form; the chart converts within each row.
Reference range
The reference range is on your lab’s form. Standard and high-sensitivity tests have different ranges, and they are not compared with each other. As an example, a Texas A&M veterinary laboratory describes its high-sensitivity troponin I in dogs like this: below 50 pg/mL active injury is unlikely; from 50 to 168 pg/mL the result is in the upper part of its range, can be normal in older dogs, and injury is possible; from 169 pg/mL active injury is likely. These values belong to one lab and one test. A value that falls on repeat suggests a single insult; one that stays high suggests ongoing damage — so the trend matters.
Cats and dogs
In cats troponin I tends to be higher in heart muscle disease than in healthy cats, but the overlap is large, so it is not a good screening test for cardiomyopathy, and overlap also limits its use in telling heart from other causes of breathing trouble. The same laboratory notes that the diagnostic accuracy of its high-sensitivity test in cats is not fully characterised and found no link with age in healthy cats.
In dogs troponin I has been studied more. In healthy dogs it rises with age, and Greyhounds and Boxers may have higher values. According to the same laboratory, results of healthy and injured dogs overlap, so false positives and false negatives happen. One laboratory guide lists troponin I with NT-proBNP among screening tests for dilated cardiomyopathy in dogs, naming Dobermans.
Add a lab form — Pet Tracker Space recognises the lines, keeps the form’s units and draws each indicator over time with your lab’s reference band.
Sources
- Merck Veterinary Manual — Heart Failure in Dogs and Cats
- Texas A&M Gastrointestinal Laboratory — High-Sensitivity Cardiac Troponin I
- Gavazza A et al. Canine Traditional Laboratory Tests and Cardiac Biomarkers. Frontiers in Veterinary Science, 2020
- Aona B, Adin D. Advances in Feline Cardiac Diagnostics. Today’s Veterinary Practice, 2017 (updated 2022)
- Saunders AB. Cutting Edge Cardiology: Five State-of-the-Art Developments. Today’s Veterinary Practice, 2014
- IDEXX — Hidden Heartbreak: Diagnosing Early Cardiac Disease
- eClinPath (Cornell University) — Creatine kinase
This page explains what a lab value means. It is not a diagnosis and not a substitute for your veterinarian — only they can interpret results for your pet.