The most common tools used by a cardiologist to investigate heart disease in pets are the echocardiogram, electrocardiogram (ECG), Holter monitors, and chest X-rays. Your primary veterinarian may use some of these tools prior to referring your pet to a cardiologist, as well as some other diagnostics including simple blood tests.

Echocardiogram

An echocardiogram is an ultrasound of the heart. Ultrasound uses high frequency sound waves to generate a real-time image of a structure within the body. This is a non-invasive way to evaluate the heart’s structure and function. It is the best test available to specifically evaluate the heart. Chest X-rays can also be used to assess the size of the heart, though small changes may not be visible and normal variations can sometimes be exaggerated.

An echocardiogram is typically recommended for most animals during their first visit to a cardiologist. The test requires laying your pet gently on their side. Some animals may require mild sedation. Additionally, the person performing the echocardiogram will sometimes have to shave a small amount of hair from your pet’s chest over the heart. A small amount of alcohol and gel is applied to the area to allow for the ultrasound to work properly. A number of images are then recorded and the heart’s size and function are measured

Chest X-rays

Chest X-rays are often used by your primary veterinarian to see if there are hints that the heart has changed in size prior to referring your pet to a cardiologist. Additionally, chest X-rays are the best test to look for evidence of left sided congestive heart failure. In some animals with advanced heart disease, fluid will begin to build up as the heart becomes unable to pump effectively. When this happens on the left side of the heart (the side that takes blood from the lungs and sends it to the rest of the body), fluid will begin to back up in the lungs. This may lead to clinical signs such as exercise intolerance or trouble breathing. This fluid can sometimes be seen on X-rays.

Electrocardiogram (ECG) and Holter Monitors

An electrocardiogram (ECG) is a test to look for any abnormalities in your pet’s heart rate or rhythm (arrhythmias). Arrhythmias are often first noted when your vet notes an irregularity while listening to your pet’s heart and feeling their pulses. However, there are many kinds of arrhythmias, and many of them sound the same. The best way to investigate this further is by visualizing the rhythm with an ECG. Like an echocardiogram, your pet will be laid on their side. Small clips will be attached to each leg. These clips will record the electrical energy of the heart on a screen for the cardiologist to review. Characterization of the arrhythmia is important when determining when and how to treat them.

A Holter monitor is essentially a wearable ECG. This device will record and store information about your pet’s heart rate and rhythm over a number of days. This information is then reviewed to look at things like how frequently the arrhythmia occurs or if the arrhythmia is associated with clinical signs at home such as intermittent weakness or collapse. The placement of the monitor is simple: an area is shaved on each side of the chest. Sticky electrode patches are placed in the shaved areas, and the wires of the Holter monitor are attached to the patches. The device and the wires are then secured to the patient with a vest that they will wear for the duration of the Holter monitor. While most animals only need to wear the monitor for one or two days, they can often stay on for a week or more if clinical signs are infrequent. The monitor is then removed and returned to the doctor for further analysis.

While additional testing is sometimes required in the long-term management of a patient, such as monitoring blood pressure or other lab work, these are the most common tests used by veterinary cardiologists.