advances in diagnostics: detecting cardiac disease
Different veterinarians perform physical exams on pets differently. I generally start at the top of the pet and work my way back, but some prefer a different approach. One thing that every veterinarian has in common when it comes to physical exams is the use of their stethoscope. At some point during the exam, your veterinarian always employs his or her stethoscope to listen to your pet’s heart and lungs. Not only are we listening to make sure that the lungs sound nice and clear, we are also listening for the presence of arrhythmias or murmurs in your pet’s heart.
We’ve discussed both arrhythmias and heart murmurs before, and we’ve had several discussions about cardiac disease in dogs and cats. Some cases are congenital, meaning they are present at birth, and some are acquired sometime in the span of a pet’s life. Some cardiac conditions are inherited from your pet’s parents (like hypertrophic cardiomyopathy in Maine Coon cats or dilated cardiomyopathy in Dobermans, and some are the result of illness, as is the case with advanced heartworm disease.
Whatever the cause of cardiac disease, early detection is key. Your veterinarian listens for changes to your pet’s heart sounds every time your pet is in for a check-up. But the presence of a heart murmur doesn’t always mean that there is trouble in the heart. Many times, heart murmurs are completely benign. But a heart murmur in addition to clinical signs of heart disease does raise our suspicion.
Dogs aren’t shy about letting their heart disease be known – typically they have clinical signs of cardiac conditions to guide your veterinarian towards a diagnosis. Coughing, panting, increased respiratory rates, exercise intolerance, and fainting are all signs we see in dogs with cardiac disease.
Cats can prove to be tricky for us. Up to 15% of the general cat population has heart disease, but often it is undetected. That’s because not all cats with heart disease have murmurs to warn us of impending disease. Sometimes, heart disease in cats only becomes evident after an emergency situation arises, such as a saddle thrombus or decompensated congestive heart failure following IV fluid administration or anesthesia. And sadly, sometimes sudden death occurs from heart disease before we even know it was present.
So, how do we find heart disease in patients who are so good at hiding it? The answer may be found in a blood test that measures the amount of NT-proBNP found in your pet’s blood. NT-proBNP is a biomarker of cardiac disease. It is found in the ventricles of the heart and when there is stress or stretch in the ventricles, the amount of NT-proBNP increases. Therefore, if your pet’s NT-proBNP level is elevated, there is a good chance that there is stress on the heart. This may tell us that your cat, who appears perfectly healthy and doesn’t have a murmur, actually does have underlying heart disease.
NT-proBNP tests do have their limits, though. For instance, patients with kidney disease may also have elevated levels, so it’s not completely specific for heart disease 100% of the time. But for patients like cats, who like to hide their disease, this simple blood test may unmask a deadly disease.
Routine testing of clinically normal dogs isn’t recommended at this time, as dogs with heart disease often have clinical signs. If elevated NT-proBNP levels are found in dogs or cats with suspected heart disease, further evaluations should be performed to further classify disease. While this blood test is a simple test to run, it doesn’t replace the valuable information that an x-ray of the chest and an ultrasound of the heart (echocardiogram) gives us.
Still, if you have a cat, especially a breed of cat who is prone to heart disease, you may want to ask your vet about this potentially life-saving detection test!