In Praise of Norman J Holter

This dog seems to be wearing a coat. So what? Well, in fact she's wearing a Holter monitor - which is a device which can continuously record the ECG - the electrical signal from the heart - for many hours, even days, whilst the dog goes about her normal life. The device is about the size of a mobile phone, solid state with no moving parts, and quite robust - though if the dog goes swimming - the monitor will drown. The jacket she is wearing keeps the Holter monitor and its electrodes (which are stuck on the chest wall) in place.

Holter monitoring - or ambulatory telemetric electrocardiography - was invented by Normal J ("Jeff") Holter in 1949. Holter was a biophysicist. He donated the rights to his invention to medical science. It is wonderful to be able to record the ECG from a freely behaving animal, or human. The beauty lies in the fact that Holter monitoring can unlock the diagnosis when clinical examination or other tests cannot. Disturbances of cardiac rhythm can cause fainting or lightheadedness, they are frequently serious and often the first warning that the heart, or its control mechanisms, are diseased. Because rhythm disturbances are often very infrequent they evade detection. To give you some idea of the problem; a dog will often have 100,000 - 150,000 heartbeats in 24 hours but a run of only 30 abnormal beats can cause death.

Norman Holter realised that this problem was in essence a simple one, but when he began work on it modern electronics had hardly begun. The first Holter monitor was almost as big as, and certainly heavier than, the patients on which it was used. The dog in this picture is wearing a modern Holter which is so small the dog will hardly be aware she has it on.

In a few days I hope to know why she is fainting.