Dear Christopher Cat: Henry, my 2-year-old cat, was breathing fast during his annual exam. The veterinarian said his rapid breathing could be due to stress, heart disease or a respiratory condition such as asthma.

She did a blood test called NT-proBNP which indicated he may have heart disease, and she referred me to a cardiologist who confirmed that Henry has cardiomyopathy.

Now Henry takes medicine to improve his heart function and prolong his life.

I’m grateful my vet recognized the problem and did the NT-proBNP test. How does this blood test reveal heart disease?

Christopher Responds: Heart muscle cells produce small amounts of a hormone called BNP and its inactive precursor, NT-proBNP.

Heart disease causes the heart to enlarge and the heart muscle cells to stretch, which induces them to secrete more of these chemicals.

NT-proBNP is more stable than BNP, and the magnitude of the NT-proBNP elevation reflects the severity of heart disease.

So veterinarians use it as a marker for heart enlargement, heart disease and congestive heart failure.

Henry and other cats with cardiomyopathy, the most common type of feline heart disease, may display no clinical signs or have abnormal breathing, a heart murmur or an erratic heart rhythm. Untreated patients can die suddenly, so your veterinarian likely saved Henry’s life during what started out as just a routine annual exam.