Electrocardiogram

The electrocardiogram (ECG) is a non-invasive diagnostic test that allows recording of the heart’s electrical activity through electrodes applied to the skin, which transmit the signal to a device to obtain a graphical trace.

How is it performed?

To be diagnostically useful, the exam should be conducted for at least 5 minutes in a quiet environment, with the patient in right lateral recumbency and limbs perpendicular to the body, unless contraindicated (e.g., dyspneic patient). The patient should not tremble or be in contact with a metal table, as much as possible.

Electrodes are placed on the distal portion of the limbs, regardless of the exact height (placing them lower toward the extremities is recommended in panting animals to reduce artifacts), moistening them with alcohol to enhance contact.Color coding is as follows:

• Red – right forelimb
• Yellow – left forelimb
• Green – left hindlimb
• Black – right hindlimb

Precordial leads are placed as follows:

• V1: right first intercostal space, dorsally
• V2: at the costosternal junction (left sixth intercostal space)
• V4: at the costochondral junction
• V6: at approximately the same level more dorsally
• V3: midway between V2 and V4
• V5: midway between V4 and V6

Once the electrodes are correctly placed, the device settings (sweep speed and amplitude) must be adjusted to minimize artifacts and optimize the test.
Conventionally, a sweep speed of 50 mm/s and amplitude of 10 mm/mV are used; however, adjust amplitude to 5 mm/mV if waves overlap or to 20 mm/mV if complexes are very small.

When is an ECG indicated?

It is essential in cardiologic evaluation and for diagnosing:

• Primary arrhythmias
• Electrical conduction abnormalities (AV blocks, axis deviations)
• Unexplained clinical signs (syncope, weakness, breathing difficulty, exercise intolerance)
• Long-term monitoring of patients with cardiomyopathies

The main canine cardiomyopathies (e.g., occult dilated cardiomyopathy, arrhythmogenic cardiomyopathy) can remain silent for a long time, making ECG a valuable early diagnostic tool. Combined with imaging (thoracic X-ray, echocardiography), it offers a complete overview of cardiac health.

Combined with imaging (thoracic X-ray, echocardiography), it offers a complete overview of cardiac health.

Additional uses:

• Pre-anesthetic screening to identify rhythm abnormalities that could pose a risk
• Respiratory conditions and brachycephalic dogs (vagal tone issues)
• Electrolyte imbalances (especially potassium, calcium, magnesium)
• Metabolic disorders (hypo-/hyperthyroidism, Cushing’s and Addison’s disease, pheochromocytoma)
• Oncology (ventricular complexes in tumor cases)
• Postoperative (e.g., gastric torsion, splenectomy)
• Pancreatitis, Borrelia infections, major trauma, heatstroke, poisoning (especially oleander, methylxanthines)
• Intracranial diseases

Breed-specific conditions include:

• Exercise-induced collapse in Labradors
• Aciduria in Bull Terriers
• Collapse syndrome in Border Collies
• Dogs with spike or cramping syndrome

Advantages of ECG

ECG is quick, painless, and minimally stressful. It can be easily done in a clinic or hospital and often makes a significant difference in the veterinary service provided.

However, interpreting an ECG can be challenging. That’s why Vetconsult offers a reporting service within 24 working hours to support colleagues with advice and discussion on patient management.

How to request an ECG report

1. Register in your personal areaon Vetconsult.

o For first-time access, your registration must be approved by our team.

2. After approval, you can request new cases anytime:

o Log in and click “New Case”
o Fill in all required fields with the patient’s clinical information
o Upload ECG tracings in PDF format, compressed into a ZIP folder

3. Report delivery

o You will receive the report via email within 24 working hours
o A copy will always be available in your personal area, attached to the case, including any notes or considerations by the reporting veterinarian