A veterinarian often diagnoses cardiovascular disease by reviewing the medical history and signs, conducting a physical examination, and interpreting the results of specific tests or imaging procedures. The physical examination includes using a stethoscope to listen to the heart and lungs. A veterinarian may hear an abnormal heart rate (for example, a rate that is too slow, fast, or irregular), an abnormal breathing rate (fast or labored breathing), additional heart sounds (called a "gallop" rhythm), a murmur (an abnormal sound caused by abnormal blood flow or vibrations in the heart), decreased or muffled heart sounds, or abnormal sounds in the lungs that suggest the fluid accumulation. Veterinarians also feel a cat's pulse, which may feel rapid, weak, or irregular. In addition, veterinarians feel the body with their hands and fingers to detect abnormal fluid accumulation in the abdomen. A cat's gums are also examined to look for evidence of blue, purple, or grey color, a sign that oxygen is not reaching the body's tissues adequately.
Your cat's age and breed may help your veterinarian diagnose its heart disease. For example, a middle-aged cat with labored breathing and reluctance to lie down may have heart muscle disease (most commonly hypertrophic cardiomyopathy), whereas an older cat with weight loss and behavioral changes is more likely to have hyperthyroidism, which can cause high blood pressure and worsen heart disease. In addition, certain heart diseases are more common in some breeds.
Imaging techniques include x-rays, electrocardiography (recording electrical activity of the heart), and echocardiography (a type of ultrasonography). Many cardiovascular diseases can be diagnosed by physical examination and x-rays. X-rays are also used to diagnose and monitor congestive heart failure. Electrocardiography is used to diagnose heart rhythm disturbances (arrhythmias). Echocardiography is excellent for confirming tentative diagnoses, assessing the severity of leaky heart valves or narrowed vessels, evaluating chamber sizes and heart muscle function, identifying types of cardiomyopathy, diagnosing high blood pressure in the lungs, identifying birth defects in the heart, detecting heart tumors, or identifying disease of the membrane that surrounds the heart (the pericardium). Your veterinarian may also recommend a specific blood test that measures proteins that increase in certain types of heart disease and failure. Occasionally, more specialized tests such as cardiac catheterization (using a thin flexible tube inserted and threaded through an artery into the heart) or nuclear studies (x-ray tests that include injection of radioactive isotopes) are necessary. In cats, diagnosis of heartworm disease may include blood tests, x-rays, and echocardiography.
Also see professional content regarding diagnosis of cardiovascular disease.