Updated: Mar 13
Synchronous diaphragmatic flutter, also known as "thumps" occurs when the diaphragm contracts in synchrony with the heart. There is often a contraction or twitching in the flank region. Severe cases are associated with a characteristic "thumping" sound. In addition to hypocalcemia, synchronous diaphragmatic flutter has been associated with hypochloremic metabolic alkalosis with hypomagnesemia (most common abnormality). It is postulated that fluid, electrolyte, and acid-base derangements may disrupt the normal membrane potential of the phrenic nerve, resulting in nerve discharges in response to atrial depolarization.
Signs usually abate when the underlying cause no longer exists. Most horses undergo rapid improvement after treatment directed at the electrolyte or acid-base disturbance. Intravenous fluid therapy (23% calcium borogluconate at 250-500 ml/500kg adult horse, diluted 1:4 to 1:20 with 0.9% saline solution) is recommended.