What is an electrocardiogram?
An electrocardiogram (ECG) is a test that is commonly used to assess the heart. When your cat’s heart beats, an electrical impulse is generated within a region of the heart known as the pacemaker. This impulse passes through the heart in a predictable manner that can be traced on an ECG recording.
"An electrocardiogram (ECG) is a test that is commonly used to assess the heart."
By analyzing the electrical impulses produced as the heart beats, abnormalities within the heart can be found. These abnormalities may include issues such as arrhythmias (irregular heartbeats), abnormalities in the size and structure of the various heart chambers, abnormal conduction, and other defects of the heart.
How is an electrocardiogram performed?
In most cases, an ECG can be performed in your veterinarian’s office as an outpatient visit. No special preparation is typically required for this procedure.
Your cat will be required to remain still for this test, either standing or laying down on an examination table. The ECG electrodes are applied to your cat’s skin, at the base of each of her four legs. Rubbing alcohol or a special conduction gel may also be applied to help the electrical impulses travel more easily from your cat’s body into the ECG electrodes.
"No special preparation is typically required for this procedure."
Once the electrodes are applied, your cat will be kept still for a brief period of time, in order to allow the ECG to record the electrical impulses passing through the heart. Your cat’s electrical conduction may be traced for less than a minute or for several minutes, depending on what abnormality your veterinarian suspects and how effectively your cat is able to remain still for a high-quality ECG recording.
After the test is run, it may be interpreted in-house by your veterinarian or it may be sent out to a veterinary cardiologist for interpretation.
In some cases, the ECG machine may be attached to your cat and left in place for 24 hours or more. This test, called a Holter Monitor, can help your veterinarian detect arrhythmias that are occurring occasionally. See handout "Holter Monitor in Cats" for more information.
Why would my veterinarian want to perform an electrocardiogram?
An ECG is often a component of the workup for any cat suspected of having heart disease.
Clinical signs of heart disease that you may see at home, which might indicate a need for an ECG, can include any of the following:
- exercise intolerance
- shortness of breath
Even if your cat is not showing signs of heart disease at home, your veterinarian may also recommend an ECG of your cat if physical exam findings are suggestive of heart disease. These findings may include:
- an irregular heartbeat
- a heart murmur (which indicates turbulent blood flow over a valve within the heart)
- irregular pulses
- abnormal lung sounds
An ECG may also be performed as a screening test in geriatric cats or cats that are undergoing anesthesia. Additionally, ECG monitoring is common in cats of any age when they are under general anesthesia.
What information can be gained from an electrocardiogram?
An ECG can provide your veterinarian with a variety of information about your cat’s heart function.
- Is the heart rate normal? An ECG allows an accurate determination of your cat’s heart rate. This can reveal whether her heart is beating at a normal pace, or whether it is beating too quickly or too slowly. An elevated or decreased heart rate can suggest specific medical issues that may warrant investigation.
- Is the heart rhythm normal? An ECG provides a very accurate way for your veterinarian to assess your cat’s heart rhythm. If her heart rhythm is abnormal, analysis of the ECG results can diagnose the exact arrhythmia that is present and suggest likely underlying causes for this arrhythmia.
- Does the cat’s heart size appear to be normal? An ECG measures electrical conduction through the heart. Enlarged heart tissue conducts electricity differently than normal heart tissue; therefore, an ECG can sometimes suggest abnormalities in the size of specific heart chambers. While this determination is not completely accurate or reliable, it can suggest the need for further investigation via radiographs (X-rays) or echocardiography (an ultrasound of the heart).