Electrocardiography (ECG) can be used to evaluate cardiac anatomical changes, arrhythmias and pericardial and pleural diseases.
The tiger will need to be sedated to carry out an ECG. It should be placed in right lateral recumbency on a surface that is electrically insulated such as a thick blanket. The tiger’s limbs should be positioned so that they are perpendicular to its body.
ECG leads with clips can be applied without removing the fur as they are usually applied to relatively hairless areas of skin. For ECG leads with adhesive electrodes these can be applied directly to the pads of the relevant leg.
The electrodes are colour coded and they are attached to the limbs as follows:
- Red- right forelimb on relatively hairless skin just behind the elbow for a clip/ pad for a self adhesive electrode
- Yellow- left forelimb on relatively hairless skin just behind the elbow for a clip/ pad for a self adhesive electrode
- Green- left hindlimb on skin overlying gastrocnemius tendon for a clip/ pad for a self adhesive electrode
- Black- right forelimb on skin overlying gastrocnemius tendon for a clip/ pad for a self adhesive electrode
- Neutral electrode- this is usually placed in front of the right stifle.
The electrodes are usually attached using crocodile clips. The clips are generally placed on the skin overlying bony protuberances to minimise the effect of muscle interference. The clips should be sprayed with surgical spirit to achieve good electrical conductivity.
Sensitivity control of the ECG allows the operator to vary the number of centimetres of paper equivalent to 1mV. Most traces are recorded at 1cm/mV. Paper speed control is usually set at 25 or 50mm/s. Manual lead selection is preferred and the operator should select the six frontal plane leads (Lead I, II, III, aVR, aVL and aVF) in turn.
ECG traces can always be scanned in/ photographed and sent to experienced feline cardiologists for help with interpretation.