Aborted sudden death.

This is a short extract from a 24hr ECG recoding (known as a Holter recording) from a dog who has been suddenly collapsing.

It can be very difficult to identify why a dog (or a cat, horse, pig, or child) is collapsing because these events occur randomly usually without warning. So, if you want to discover what is happening you have to stake out the system(s) which you believe is responsible and then wait…

The recording shows the heart beat which falters in this recording in the middle of the night (03:16 am). The record runs from the upper left to the lower right and is continuous. The heart stops (asystole), there is a pause, then the atria start trying to revive the body - you can see this as tiny electrical signals - wobbles of the line, which are "P waves" - atrial events. Usually these should be followed a few milliseconds later by QRS waves, which are the electrical signals associated with the contraction of the ventricles (the principal pumping chambers) of the heart.

Towards the end of this recording you can see some large deflections which appear a bit odd compared with the normal beats. These are "idioventricular beats," sometimes called "rescue beats," which are ventricular events pushing blood around the body. Finally, normal heart rhythm is restored during this recording. The abnormal rhythm lasted for around 40 seconds, which is long enough to cause fainting, but not long enough to cause death. Fortunately.

The dog lived. My job is now to find a way to solve this problem on a longer term.