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 sounds made by the dog’s internal organs, especially the heart, lungs, and abdominal organs, and examining parts of the body by feeling with hands and fingers to distinguish between solid and fluid-filled swellings and to examine pulses. Imaging techniques include x-rays; electrocardiography (recording electrical activity of the heart); and echocardiography (a type of ultrasonography). Most cardiovascular diseases can be highly suspected by physical examination and x-rays. X-rays are also used to monitor the progression of congestive heart failure. Electrocardiography is specific for diagnosis of arrhythmias. Echocardiography is excellent for confirming tentative diagnoses, for assessing the severity of leaky heart valves or narrowed vessels, for evaluating chamber sizes and heart muscle function, for diagnosing high blood pressure in the lungs, for identifying birth defects in the heart, for detecting heart tumors, or for detecting pericardial disease (problems with the membrane surrounding the heart). 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. Heartworm disease is diagnosed best by performing a blood test to detect the presence of female heartworms.
Many heart disorders are more common in certain breeds. For example, mitral regurgitation is more common in Cavalier King Charles Spaniels, dilated cardiomyopathy is common in middle-aged Doberman Pinschers, and arrhythmogenic right ventricular cardiomyopathy usually affects Boxers. Older Miniature Schnauzers may develop specific types of arrhythmias, and tetralogy of Fallot is more common in young Wirehaired Fox Terriers. Knowledge of these and other breed associations with heart disease can often help your veterinarian make a diagnosis.
Dogs showing signs of heart disease may have a history of exercise intolerance, weakness, coughing, difficulty breathing, increased breathing rate, abdominal swelling (caused by fluid pooling in the abdomen), loss of consciousness due to lack of blood flow to the brain (fainting), a bluish tinge to skin and membranes due to a lack of oxygen in the blood, or loss of appetite and weight. More rarely, swelling of the legs, jaundice (yellowing of the eyes, skin, or membranes), or coughing up blood or bloody mucous may be noted. Your veterinarian may recommend that you count the number of breaths your dog takes per minute when your dog is resting at home. This can be an effective way for you to monitor the development or progression of congestive heart failure in dogs with heart disease.
Also see professional content regarding diagnosis of cardiovascular disease.