What to do if my horse gets “The Thumps”?

The Thumps, more technically known as Synchronous Diaphragmatic Flutter is the excitation of the diaphragm. It’s similar to hiccups in humans and can be seen as twitching or spasms of one or both flanks. In some cases, a loud thump can be heard coming from the horse’s chest.

What causes it?

The diaphragm is a thin muscle separating the horse’s chest and abdomen. It is controlled by the phrenic nerve, which is important for regulating the horse’s breathing. Electrolyte (salt) disturbances in the body (particularly abnormalities in calcium, chloride, magnesium, and bicarbonate) can make the phrenic nerve become hyper-excited. This causes it to be more sensitive to the activity in the heart which it runs past. If the nerve conductions are not normal due to the nerve being excited, then the diaphragm begins to vibrate. Meaning that unusual noises or contractions are produced. Because the phrenic nerve runs over the heart, the unusual movements, vibrations, or thumps are a result of the heartbeat, not the breathing cycle.

Increased excitation of the phrenic nerve is most commonly associated with intense exercise. Such as endurance rides or racing as the horse usually sweats a lot, resulting in a loss of electrolytes. 

How serious is it?

Because the condition usually occurs when a horse has been sweating a lot, in most cases the signs resolve once the electrolyte level gets back to normal. Which occurs after the horse eats and drinks normally. In more severe cases, the horse may need to be given electrolytes, either via a stomach tube or in a drip (intravenously). This is in order to correct the imbalances. The prognosis is usually good but a rest period of 7-10 days is often recommended after an episode. This is to ensure that the horse has recovered fully before carrying out intense exercise again.