HEART AND CIRCULATION
Electrocardiogram (ECG)
A recording of the heart’s electrical activity used to evaluate heart rhythm, rate and selected conduction problems.
THE SHORT VERSION
Testing helps answer a clinical question.
An electrocardiogram records electrical signals produced by the heart. It is primarily a rhythm test—not a complete picture of chamber size, valve structure or pumping function.
What is this test?
An electrocardiogram records electrical signals produced by the heart. It is primarily a rhythm test—not a complete picture of chamber size, valve structure or pumping function.
An ECG records the heart's electrical activity during the recording period. It helps assess rate, rhythm, and conduction, rather than showing the full structure of the heart. A normal short recording may not capture an intermittent rhythm problem, so longer monitoring may be considered when the history suggests episodes. ECG, radiographs, and echocardiography answer different questions. Ask whether the concern is a rhythm disturbance, whether the recorded abnormality explains the signs, and whether monitoring needs to occur during ordinary activity at home.
What information can it provide?
- Heart rate and rhythm can be assessed for abnormal electrical patterns.
- Timing between electrical events can suggest conduction changes.
- Some abnormal rhythms are intermittent and may require extended monitoring.
- Results are interpreted together with history, examination, blood pressure and other cardiac tests.
Heart disease describes a problem with the heart, but it does not always mean that the animal is in heart failure. The examination and tests help identify the affected structure, the stage of disease, and whether circulation or breathing is compromised. Different diseases can produce similar outward signs, and some animals have substantial disease before an owner notices a change. Treatment and monitoring therefore depend on the diagnosed problem, not simply on the presence of a murmur or the animal's age.
A recheck is not simply a repeat of the first appointment. It assesses whether the original problem is improving, whether complications are appearing, and whether the treatment remains appropriate. The useful measures may include comfort, function, intake, body weight, examination findings, or selected tests. Ask which changes are expected before the visit and which should trigger an earlier call. Improvement in one sign does not always mean that every part of the disease has resolved.
When might your veterinarian recommend it?
- Investigate fainting, collapse, irregular heartbeat, weakness or anesthesia concerns.
- Assess suspected arrhythmias or electrolyte-related rhythm changes.
- Monitor a known cardiac condition or a patient receiving certain treatments.
What can owners do before the visit?
- The test usually uses small skin electrodes and gentle positioning.
- Tell the team about fainting episodes, exercise intolerance and medications.
- Ask whether a longer monitoring period is needed for intermittent events.
Ask the team whether the planned study requires fasting, sedation, anesthesia, contrast material, or changes to the usual medication schedule. Requirements depend on the patient, species, and procedure; do not withhold food or medication by copying instructions from another visit. Bring previous results and the current treatment list so that findings can be compared. After a sedated or anesthetized study, obtain written recovery and feeding instructions and a contact plan for unexpected problems.
What can this test not tell you by itself?
- An electrocardiogram does not directly show heart-valve structure or chamber dimensions.
- A brief recording can miss an intermittent arrhythmia.
- An abnormal rhythm requires interpretation in the context of symptoms and overall patient stability.
Do not change medication, interpret an abnormal number as a diagnosis or delay urgent treatment without direction from your veterinary team.
Useful questions for your appointment
- Is the concern a heart rhythm problem, structural disease or both?
- Would echocardiography, blood pressure or longer monitoring be helpful?
- Do fainting or collapse signs require emergency action?