Synchronous Diaphragmatic Flutter

Also known as: SDF — Thumps — Exhausted Horse syndrome

Introduction

Synchronous diaphragmatic flutter is a condition characterised by unilateral or bilateral contraction of the horse's diaphragm. It results from electrolyte losses that occur during physical exertion or from hypocalcaemic tetany or hypocalcaemia secondary to blister beetle toxicosis.

This syndrome is often seen in horses participating in competitive trail and endurance races or on long-distance rides.

A decrease in the plasma calcium, chloride and/or potassium concentration, or a body deficit of these electrolytes, sensitises the phrenic nerve to the depolarising electrical activity of the adjacent myocardium. Therefore the involuntary diaphragmatic contraction and "thump" are synchronous with the heartbeat and not with the breathing cycle.

This can occur during or following physical exertion, severe diarrhoea or colic, or following prolonged surgery and anaesthesia.

Clinical Signs

Pathognomonic clinical signs include: sudden bilateral or unilateral movement of the horse's flanks (and sometimes hindlimbs) each time the heart beats. The "thump" can usually be heard or palpated over the thorax or flanks.

Diagnosis

The clinical signs are very suggestive.

Typical biochemical abnormalities include: hypoglycaemia, increased fatty acid concentrations, hyponatraemia, hypochloraemia, hypokalaemia, hypocalcaemia, hypomagnesaemia and hyperphosphataemia.

Blood lactate and creatine kinase might be moderately elevated.

Dehydration might also be observed.

Treatment

Prevention and treatment include the replacement of the depleted electrolytes.

If the condition is severe, 20 to 100 litres of isotonic or slightly hypertonic fluids supplemented in calcium, potassium and glucose should be given intravenously over 24 hours.

In less severe cases, electrolytes and glucose can be given orally, possibly via nasogastric intubation.

The response to treatment is usually rapid and thus supports the diagnosis.

Prognosis is favourable although horses should be rested for 7-10 days.

In endurance horses, prevention of the condition includes supplementation of electrolytes in the feed or water.

Synchronous Diaphragmatic Flutter Learning Resources
Flashcards Test your knowledge using flashcard type questions	Equine Internal Medicine Q&A 08

References

McGorum, B. (2007) Equine respiratory medicine and surgery Elsevier Health Sciences

Stashak, T. (2002) Adams' Lameness in Horses Wiley-Blackwell

WikiVet® Introduction - Help WikiVet - Report a Problem