If your dog or cat is experiencing an illness or injury that is causing irregularities in their heart rate then your vet may order an ECG. In this post, our St. Louis vets talk about what an ECG is and how this diagnostic test can help our veterinary team diagnose your cat or dog.
What is an ECG?
An ECG, or as it is sometimes called an EKG, stands for electrocardiogram. This is a test that is used to monitor the heart. Little sensors are attached to the skin and they monitor electrical activity to give a representation of what the heart is doing. This is a non-invasive way of observing the heart in pets and people.
What Does an ECG Tell Your Veterinarian About Your Pet?
An ECG tells your vet several things about your pet's heart. It gives the rate and the rhythm of the heartbeat along with an understanding of the electrical impulses that are going through each section of the heart.
A typical ECG will consist of a pattern where it will be a small bump that rises up that is called the P wave, then A large spike upward called the QRS complex and then another small bump called the T wave.
The P wave represents the atria contracting. The QRS complex is where the ventricles depolarize (The large contraction of the heart that is the typical heartbeat). And The T wave in the ventricles is repolarizing.
The important data your vet will be looking for is that the shape of the wave is correct and the distance between the various parts of the wave. Often the concerns are the information provided by the PR interval and the QRS complex interval. These tell how fast the heart is taking in blood and how fast it is pumping it.
The next major information is to look at the peaks of the QRS complex (the big spike) and measure the distance between them. If they are a constant distance between the spikes you have a regular heartbeat if they vary in distance you have an irregular heartbeat.
Last but not least you can read how many QRS complexes there are and calculate how many there are over a time interval and you will have the heart rate.
The rate and rhythm of cats and dogs can vary. Please consult your veterinarian about what are the expected values for your breed of pet.
Are ECG Safe
Yes, ECG tests are safe. ECG is a non-invasive diagnostic test that passively monitors the heart.
When Would a Vet Use an ECG
Some examples of when a vet may order an ECG test are:
Abnormal Cardiovascular Physical Exam
Cardiac murmurs, gallop sounds and arrhythmias are some obvious physical exam abnormalities that are clear indications for an echocardiogram. This can often be an indication of diastolic dysfunction and an echocardiogram is always warranted when this occurs in dogs and cats. Arrhythmias can be caused by intracardiac or extracardiac disease. An echocardiogram helps rule out primary cardiomyopathy and/or infiltrative cardiac disease that may explain the arrhythmia. The echocardiogram also helps to determine appropriate anti-arrhythmic therapy for the individual patient.
Many breeds of dogs and cats have a heritable predisposition for heart disease. In some cases, auscultation by a board-certified cardiologist is indicated to rule out the presence of a murmur. If a murmur is auscultated, then an echo is indicated for a complete evaluation. In some breeds, however, an echo is always indicated to screen for heart disease.
Thoracic Radiographic Changes
Cardiomegaly noted on radiographs can be due to cardiac enlargement, pericardial fat accumulation, and/or patient variability. An echocardiogram is the most specific tool for determining the size of each cardiac chamber and is a very useful tool in delineating a cause for radiographic cardiomegaly. The echocardiogram is highly specific and sensitive for congestive heart failure and pulmonary hypertension.
Cats can be particularly challenging cardiology patients because they can have severe cardiomyopathy despite the absence of physical exam abnormalities, radiographic changes, and/or clinical signs. An echocardiogram is often the only appropriate diagnostic test that is both specific and sensitive for heart disease in cats. Purebred cats have a higher incidence of heart disease, and therefore echocardiographic evaluation is often high yield in these patients. If this test results in suspected heart disease, an echocardiogram is recommended in these patients to confirm the presence of heart disease and determine the therapeutic needs of the patient.
Before placing a dog or cat under anesthesia, it can be helpful to obtain a complete understanding of the patient’s cardiovascular status.
Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.