An electrocardiogram (ECG, sometimes EKG) for a dog or cat costs roughly $75 to $250 in-clinic. A 24-hour Holter monitor — an ambulatory recorder your pet wears at home — costs $300 to $500 including analysis.
An ECG records the heart's electrical activity. That single word is the key to everything else on this page.
ECG versus echocardiogram — the distinction that saves you money
Owners are frequently quoted both and assume they are the same test billed twice. They are not, and declining the wrong one causes real harm.
An ECG measures rhythm. It shows how fast the heart is beating, whether the beats are regular, and where in the heart each beat originates. It is a tracing, not a picture.
An [echocardiogram](/procedures/echocardiogram/) measures structure. It is an ultrasound of the heart, showing chamber sizes, wall thickness, valve function and blood flow.
A dog can have a structurally perfect heart with a lethal arrhythmia, and a dog can have severe valve disease with a completely normal rhythm. Neither test detects the other's territory. Which one you need depends on the question:
- Fainting, collapse, an irregular or very fast or very slow pulse → ECG
- A murmur, a cough, breathlessness, suspected valve or muscle disease → echocardiogram
- Many cardiology cases → both, and a cardiologist will explain why.
When a normal ECG is not reassurance
This is the most useful thing on the page for anyone whose dog has collapsed.
An in-clinic ECG records two to five minutes. If your dog's arrhythmia occurs a few times a day — or a few times a week — the odds of catching it in that window are poor. A normal trace in a pet with a convincing history of collapse does not rule out an arrhythmia; it means you did not catch it.
The correct next step is a Holter monitor: a small recorder in a vest, worn at home for 24 hours (sometimes longer), recording every beat while your pet does normal things. The analysis counts abnormal beats, characterises them, and correlates them with an activity diary you keep.
This matters especially for:
- Dogs that faint or collapse, particularly during or just after excitement or exercise.
- Boxers and Dobermanns, which have breed-specific screening pathways for arrhythmogenic cardiomyopathy and dilated cardiomyopathy. Annual Holter screening is standard practice in these breeds, and the count of abnormal beats over 24 hours is what drives the decision to treat.
- Monitoring a dog already on anti-arrhythmic medication, to confirm the dose is working.
If your dog has collapsed and you have been sent home with a normal ECG and no further plan, ask about a Holter by name.
What an ECG detects
- Atrial fibrillation — a fast, chaotic, irregular rhythm, common in giant breeds and in advanced heart disease.
- Ventricular arrhythmias — abnormal beats from the ventricles, which can degenerate into something fatal.
- Bradyarrhythmias — a heart too slow, from sick sinus syndrome or heart block, and the reason a dog might need a [pacemaker](/procedures/pacemaker-implantation/).
- Supraventricular tachycardia — a heart running much too fast.
- Electrolyte emergencies. A blocked male cat has dangerously high potassium, and the ECG changes are what tell the emergency team how close to cardiac arrest that cat is. This is one of the fastest and most valuable uses of the test.
Before anaesthesia
A pre-anaesthetic ECG in an older patient, a breed at risk, or a pet with an irregular pulse is a legitimate cost rather than padding. Finding a bradyarrhythmia or frequent ventricular beats before induction changes the drug protocol, the monitoring, and sometimes the decision to proceed at all. It costs a fraction of what managing an arrhythmia under anaesthesia costs.
What happens during the test
Nothing uncomfortable. Your pet lies on its side, small clips or adhesive patches go on the skin near the elbows and knees, contact gel or alcohol is applied, and a trace is recorded for a few minutes. No sedation is needed and nothing is injected. Most pets find lying still the hardest part.
For a Holter, electrodes are stuck to a clipped patch of chest and held under a vest. Your pet goes home, and you keep a diary of activity and any events.
The urgent signs
Do not wait for an appointment if you see any of these:
- Collapse or fainting, especially during or just after exertion or excitement.
- A resting breathing rate persistently above 30–35 breaths per minute in a pet with known heart disease — count it while your pet is asleep. This is the single most useful home measurement in veterinary cardiology.
- A pulse that is very fast at rest, very slow, or obviously irregular, with weakness or laboured breathing.
- Sudden hind-limb paralysis in a cat, with cold, painful legs and crying — an arterial thromboembolism from underlying heart disease. This is an emergency.
Who isn't a candidate
- Other: An ECG shows electrical activity only — it does not show heart structure, valves or muscle thickness, so it cannot replace an echocardiogram and a normal trace does not rule out heart disease.
- Other: An intermittent arrhythmia may not appear during a two-minute recording; a normal in-clinic ECG in a pet that faints at home is an argument for a Holter monitor, not reassurance.
Common questions
How much does an ECG cost for a dog?
Roughly $75 to $250 for an in-clinic recording, which usually includes interpretation. A 24-hour Holter monitor, worn at home, costs $300 to $500 including analysis. Both are considerably cheaper than an echocardiogram, which typically runs $400 to $900 with a cardiologist.
What is the difference between an ECG and an echocardiogram for pets?
An ECG records electrical activity and answers questions about rhythm. An echocardiogram is an ultrasound showing structure — chamber size, wall thickness, valves and blood flow. A heart can be structurally normal with a dangerous arrhythmia, or structurally diseased with a normal rhythm, so neither test substitutes for the other.
What is a Holter monitor for dogs?
A small recorder worn in a vest at home for 24 hours or more, capturing every heartbeat during normal activity. It exists because an in-clinic ECG records only a few minutes and intermittent arrhythmias rarely oblige. It is the correct next step for a dog that collapses with a normal in-clinic trace, and is standard annual screening in Boxers and Dobermanns.
Does my dog need to be sedated for an ECG?
No. Clips or adhesive patches are placed on the skin near the elbows and knees, contact gel applied, and a trace recorded over a few minutes while your pet lies on its side. Nothing is injected and nothing hurts. Sedation is generally avoided because many sedatives alter heart rate and rhythm, which would distort the result.
Why does my dog need an ECG before surgery?
Because finding an arrhythmia before induction changes the anaesthetic protocol, the monitoring plan, and occasionally the decision to proceed. It is most valuable in older patients, breeds predisposed to cardiac disease, and any pet with an irregular pulse or a history of collapse. The cost is a fraction of managing an unexpected arrhythmia under anaesthesia.
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