Very common procedure in Veterinary Practices Electrocardiographyis one of the most commonly used pieces of monitoring equipment in veterinary practices. The ECG can determine the rate, rhythm and nature of cardiac depolarisation and repolarisation. It can also indicate changes in myocardial mass, conductivity between the heart and skin and the presence of metabolic abnormalitiesthat affect the heart. The ECG detects the electrical activity of the heart through 3 electrodes. In small animals these electrodes are most commonly placed on the 2 forelimbs and the left hindlimb. An additional electrode may be placed on the right hindlimb. Resting ECGs in the horse are recorded using a base-apex lead - with negative (red) electrode placed over the jugular groove, the positive electrode (yellow) placed just behind the left elbow over the apex beat of the heart (B) and the earth electrode attached at a site remote to the heart. This produces an ECG with large complexes that are not significantly affected by movement artifact. The electrodes are attached to the patient via ECG pads, crocodile clips (more common in horses) and transcutaneous needles (rare). Hair should be clipped to improve contact between the ECG pad and the skin. Pads should be secured with tape and additional electrode gel or alcohol should be used to improve contact between the patient and electrodes. The electrodes are connected to the ECG machine by colour-coded cables.