Posted on April 30, 2017
NT-proBNP Testing for Canine Heart Disease
Should your dog ever develop coughing or labored breathing, your veterinarian may recommend an NT-proBNP blood test. This stands for N-terminal pro-B-type natriuretic peptide. Now, how’s that for a mouthful?
What the heck is NT-proBNP?
B-type natriuretic peptide is a hormone that is manufactured and stored within the heart. When stretching of the heart muscle occurs in association with certain types of heart disease, proBNP divides into two smaller protein molecules that are released into the bloodstream. These two smaller molecules are called C-BNP and NT-proBNP.
How BNP testing is used
The amounts of C-BNP and NT-proBNP within the bloodstream increase in people, dogs, and cats with various types of heart disease. In human medicine, BNP testing is commonly used in patients that present with difficulty breathing. The beauty of the BNP test is that it helps determine whether or not heart disease is the cause of this symptom. In fact C-BNP measurement is a more accurate way of diagnosing congestive human heart failure than either chest x-rays or an ECG.
In the world of veterinary medicine, we rely on NT-proBNP measurements. While an increased NT-proBNP result points to heart disease, in no way does it differentiate the type of heart disease at play. For this reason, assessing the amount of BNP in the bloodstream is typically used as a screening test when heart disease is suspected. If the result is consistent with a heart abnormality, other diagnostic testing such as chest x-rays, an ECG, and an echocardiogram (ultrasound of the heart) are often indicated to gather more specific information.
Coughing and labored breathing are commonly reported symptoms in dogs. And, in some cases, it can be difficult to know whether heart or respiratory tract disease is at the root of the problem. The NT-proBNP test can be of tremendous help in terms of pointing the diagnostic workup more towards one direction than the other.
An imperfect test
As is true for many diagnostic tests, NT-proBNP assays are imperfect in that the results can be influenced by a variety of factors, from improper sample handling to non-heart disease abnormalities such as dehydration, kidney disease, and hypertension (high blood pressure). Additionally, there can be overlap of blood NT-proBNP concentrations between healthy animals and those with significant heart disease.
Mitral valve disease
The most common type of heart disease in dogs is myxomatous mitral valve disease . This results in a leaky mitral valve that can ultimately lead to heart failure. The presence of a characteristic heart murmur (left sided and systolic) in an adult small breed dog reliably diagnoses this disease.
Some dogs with mitral valve degeneration live their entire lives without ever developing any problems referable to this disease. For others, heart failure develops as a consequence, but the “if and when” are unpredictable. Unfortunately, there is no documented benefit to treatment of any sort prior to the onset of heart failure. The NT-proBNP assay makes all of this less of a guessing game. It is recommended for dogs with known mitral valve disease who are symptom-free. The test is used as a way of predicting whether or not the onset of heart failure will be imminent (within the next three to six months). For dogs identified as being at high risk, careful at home monitoring is recommended looking for the earliest symptoms of heart failure such as an increased respiratory rate during rest or sleep, exercise intolerance, weakness, and coughing. Should one or more such symptoms arise, immediate veterinary intervention will likely prevent a heart failure crisis and the need for hospitalization for emergency care.
A pretty darned awful heart disease referred to idiopathic dilated cardiomyopathy occurs mostly in larger breed dogs. For reasons that are unknown, the heart muscle becomes weak and flabby and its normal dynamic pumping action fails. Dogs with dilated cardiomyopathy often show no evidence of their disease until something dramatic happens such as fulminant heart failure or a severe heart rhythm abnormality resulting in sudden weakness, collapse, or even death.
Doberman Pinschers, Irish Wolfhounds, Great Danes, Newfoundlands, Portuguese Water Dogs, Saint Bernards, and Airedale Terriers are particularly predisposed to dilated cardiomyopathy. Boxers have their own unique version of this disease referred to as arrhythmogenic right ventricular cardiomyopathy .
As a screening test for high-risk breed groups, NT-proBNP results can help identify dogs who have an increased probability of having occult (asymptomatic) dilated cardiomyopathy. If this screening test is positive, more involved testing such as an ultrasound of the heart and/or Holter monitoring (a device worn by the dog to record a 24-hour ECG) is warranted.
Do you have experience with a dog with heart disease? Was NT-proBNP testing part of the diagnostics used by your veterinarian?
Nancy Kay, DVM
Diplomate, American College of Veterinary Internal Medicine
Author of Speaking for Spot: Be the Advocate Your Dog Needs to Live a Happy, Healthy, Longer Life
Author of Your Dog’s Best Health: A Dozen Reasonable Things to Expect From Your Vet
Recipient, Leo K. Bustad Companion Animal Veterinarian of the Year Award
Recipient, American Animal Hospital Association Animal Welfare and Humane Ethics Award
Recipient, Dog Writers Association of America Award for Best Blog
Recipient, Eukanuba Canine Health Award
Recipient, AKC Club Publication Excellence Award
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Please visit http://www.speakingforspot.com to read excerpts from Speaking for Spot and Your Dog’s Best Health. There you will also find “Advocacy Aids”- helpful health forms you can download and use for your own dog, and a collection of published articles on advocating for your pet’s health. Speaking for Spot and Your Dog’s Best Health are available at http://www.speakingforspot.com, Amazon.com, local bookstores, and your favorite online book seller.