Equis ISSN 2398-2977

Cardiovascular: ECG (electrocardiography)

Contributor(s): Christopher Brown, Wendy Furness, Lesley Young

Introduction

An electrocardiogram (ECG) is a recording of the changes in the electrical potential difference of the heart, which occur during depolarization and repolarization of the myocardial cells and are plotted against time.
The body itself is a conduction system therefore this activity can be monitored from electrodes placed on the surface.

Print off the Owner factsheet on Diagnostic imaging to give to your clients.

Documentation and analysis of cardiac arrhythmias.
Monitoring, eg heart rate and rhythm during general anesthesia or drug therapy.
Assessing the effect of training and exercise on heart rate and rhythm.
Has been used to assess LV size to predict racing performance, although there is little convincing data to support this practice.

Non-invasive.
Relatively easy to perform.
Can permanently document arrhythmias that may also be difficult to definitively diagnose on auscultation alone.
Can be used for long-term heart rate and rhythm recording to diagnose intermittent dysrhythmia in the investigation of collapse Heart: ventricular septal defect .
Can be used to assess the exercising horse.

Many potential sources of artifacts, eg:
- Electrical interference, eg poor electrode contact, improper grounding, other electrical equipment, fluorescent lighting, patient in contact with damp or metal suface.
- Patient movement, eg muscle tremor, shivering, breathing, moving.
- Interference from holder.
There is limited useful information on cardiac chamber size from measurement of the height and duration of the components of the equine ECG in contrast to companion animal species.