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Thursday, January 26, 2012
Horse with heaves....not so fast!
A middle-aged draft gelding presented for a complaint of difficulty breathing for several months duration. The increased respiratory rate began during the late summer months and was presumed to be likely Heaves/COPD. As the ambient temperature cooled during the fall and winter months, the gelding's respiratory efforts remained elevated. He was referred to PHD Veterinary services to confirm the diagnosis of Heaves/COPD. At presentation, the gelding displayed a significant abdominal component during inspiration and expiration. However his lung sounds were relatively normal. The typical crackles and wheezes that are common in horses with Heaves/COPD were not present. The gelding was slightly under weight and the rest of the physical exam was normal. A bronchio-alveolar lavage (BAL) was performed through a bronchoscope. Upon inspection of the larynx, it was noted that there was minimal if any movement of either arytenoid cartilage (Figure 1). The image below was taken during inspiration when the airway should be at its maximum diameter. Due to the apparent bilateral paralysis, the gelding's airway consisted of a small slit which would be similar to trying to breath through a straw. The BAL procedure was performed and the cytology results were normal which completely ruled Heaves/COPD.
The figure below is that of a normal larynx during inspiration with functioning arytenoid cartilages. Note the size of the airway compared to the above image.
The image below is that of a "roarer" in which the left arytenoid cartilage is completely paralyzed and not moving. This type of condition and varying degrees of paralysis are most common in horses. Bilateral paralysis is rare and carries a worse prognosis. The cause of the paralysis is unknown and management of horses with bilateral arytenoid paralysis is limited. Permanent tracheostomy is a recommended procedure and will allow the horse to return to a normal respiratory rate and comfortable life in the pasture.
There are many horses with increased respiratory effort during the warm summer months in the Southeastern USA that suffer from Heaves/COPD. A large percentage of these horses are treated empirically with medications and management practices. However, this case highlights the importance of diagnostic imaging of the airway to help confirm the diagnosis, especially in those horses that are not responding as expected to medical treatment.
Posted by Michael Porter DVM at 8:33 PM