An ECG is a measurement or trace of the electrical activity from the heart measured at the surface (skin ) of the animal. (I think that it’s quite clever that we can measure this activity of the heart at the skin surface!!).
As our heart beats it generates a voltage which can be measured using an ECG recorder. The heart conducts the electrical impulse through the muscle cells and it is this electrical stimulus that causes the heart muscle cells to contract and cause the heart to beat. An ecg measures this electrical activity in millivolts (mv) and produces a characteristic trace. The diagram shows a typical trace.
HOW IS AN ELECTROCARDIOGRAM (ECG) PERFORMED IN DOGS AND CATS?
An ECG is performed with your dog or cat awake, not sedated as most sedatives will slow the heart and can even cause irregularities of rhythm. Your pet will have sticky electrodes or clips attached to their skin and an ecg trace will be taken. We have recently started to use more comfortable clips that do not pinch the skin too much and our patients seem to tolerate these much better.
WHAT INFORMATION CAN WE OBTAIN FROM AN ELECTROCARDIOGRAM (ECG) TEST IN YOUR DOG OR CAT?
ECGs are primarily used for assessment of heart rhythm, irregular rhythms known as arrhythmias are broken down into tachyarrhythmias (too fast) or bradyarrhythmias (too slow). Further distinctions can be made depending on whether the arrhythmias originate in the atria or ventricles.
ECGs can also give an indication of heart chamber size although chamber size is more accurately measured using echocardiography.