Heart Disease Blood Test in Horses: Effective and Useful (AAEP 2010)

If a veterinarian suspects heart disease in a horse, running a cardiac troponin I (cTnI) blood test can expedite a diagnosis, according to a team of Cornell University veterinary researchers.

Cardiac troponin I is an excellent marker for injury to human heart muscle tissue, but "until recently, it was not known if measuring cTnI using the same blood analyzer (the i-STAT1) as in human medicine is either useful or feasible in horses with cardiac disease," relayed Thomas J. Divers, DVM, Dipl. ACVIM, ACVECC, professor and chief of large animal medicine at Cornell, who presented results of research on this testing method at the 2010 American Association of Equine Practitioners Convention, held Dec. 4-8 in Baltimore, Md.

He and colleagues measured cTn1 levels in 83 healthy horses to establish normal ranges for the analyte (a substance or chemical constituent that is determined in an analytical procedure). Subsequently, they tested horses that received the cardiotoxic drug monensin (sometimes pinpointed in cases of horse feed contamination with the cattle drug); those with a history of poor performance and chronic intermittent rhabdomyolysis (the breakdown of muscle fibers resulting in the release of muscle fiber contents into the bloodstream); and horses with primary cardiac diseases such as myocarditis (inflammation of the heart muscle, pericarditis (inflammation of the heart's outer sac), and endocarditis (inflammation of the inside lining of the heart chambers and valves) or other systemic illnesses.

Divers et al. found:

  • Normal ranges for cTnI levels in healthy horses are 0 to 0.06 ng/mL;
  • cTnI levels are elevated in horses with acute monensin toxicity, but normal in horses with chronic intermittent rhabdomyolsis;
  • Horses with colic requiring surgery have elevated blood levels (high levels of cTnI might suggest a poorer outcome); and
  • Blood cTnI levels are elevated in horses with myocarditis (inflammation of the heart muscle) and those with severe hypoxia (oxygen deprivation) or systemic inflammation.

"These data indicate that cTnI is a useful test in a wide variety of cases, not just in horses with suspected heart diseases," said Divers. "Not only are cTnI levels measured at the time of hospital admission, but also the changes in the cTnI levels after treatment can be equally or even more useful."

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.