In addition to abnormalities found on physical examinations, X-rays, electrocardiograms, echocardiograms, and other diagnostic tests, heart disease also can cause changes in the blood. Recent studies have identified several natural substances (for example, cardiac Troponin I and NT-proBNP) whose levels increase in many types of heart disease. Blood tests measuring the amount of these substances (cardiac biomarkers) help to diagnose certain heart diseases (even when the animal is not showing any of the signs listed earlier), measure the severity of disease, and allow the veterinarian to evaluate the effectiveness of treatment.
Other blood tests may be used to monitor your pet's treatment. For example, electrolyte levels such as potassium, sodium, or magnesium can become abnormal in animals with heart disease. In additional testing of kidney function—blood urea nitrogen (BUN) and creatinine—is often done in order to ensure that medication doses are at optimal levels.