The electrocardiogram or ECG is a valuable component of the medical evaluation of many dogs and cats. It can also be a useful
tool for monitoring patients during hospitalization. It is imperative that a rapid and accurate rhythm diagnosis can be made
so appropriate therapeutic intervention can be made.
The ECG is most valuable when used in combination with a complete medical history and physical examination. It is also often
used in combination with a diagnostic data base which may vary dependent on the clinical setting and the suspected differential
diagnoses. It is important to remember that abnormalities detected on the ECG may be due to cardiovascular disease or diseases
affecting systems other than the cardiovascular system.
How to perform the ECG
Patients should be placed in right lateral recumbency. If using a metallic table top a blanket or cushion should be used
to prevent artifact. There are generally 4 leads to attach to the patient. There are several techniques for attaching leads
but the easiest for recording is to use alligator clip leads. These can be used in conjunction with alcohol or water soluble
gel to help conduction. The leads should be placed behind the elbows on the forelimbs and over the stifles on the hindlimbs.
The leads of the electrocardiograph are color coded, red, green, black and white. These colors correspond to placement on
There are several pneumonics that can be used to remember which colors go to which limbs. One is if you think of yourself
driving your car on a sunny day, your left arm is out the window and getting tan (black) while your right arm remains in the
car (white). Your right foot uses the brake to stop (red) and the gas to go is on the left (green).
Your patient should be as calm as possible when recording the ECG, as motion such as struggling and tremors will cause artifact.
When ready to record the ECG the settings on the electrocardiograph should be checked. It is considered standard to record
leads I, II, III, AVR, AVL and AVF at a sensitivity of 1.0 cm = 1.0 mv and a paper speed of 50 mm/sec. An additional lead
II recording can be made at 25 mm/sec and is referred to as a rhythm strip. Each lead should be recorded for a couple of
seconds and the rhythm strip for longer.
Once the recordings are made they should be labeled with the patient name and or number, time and date.