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Aims

Aortic rupture and aortopulmonary fistulation are reported with increased incidence in the Friesian breed. In contrast to Warmblood horses, the aorta in Friesian horses typically ruptures at the level of the ligamentum arteriosum (Ploeg et al. 2013). This remote location often creates difficulties in identifying the rupture with transthoracic ultrasound. The aim of this study was to evaluate the usefulness of transoesophageal visualisation of the aortopulmonary region with a linear probe in both standing unsedated horses and horses suffering from aortic rupture.

Methods

Five Friesian horses, 2 healthy and 3 affected, were subjected to transthoracic ultrasound (2.5 MHz sectorial probe GE) followed by transoesophageal ultrasound (7.5 or 10 MHz linear probe). Correct oesophageal introduction of the probe was guided by means of endoscopy. After visualisation of the aortopulmonary region, horses were anaesthetised, and the transoesophageal ultrasound was repeated. In 4 horses, simultaneous carotid artery catheterisation was performed, to visualise the catheter at the zone of interest. After obtaining a diagnosis, all affected horses were subjected to euthanasia and autopsies were performed.

Results

The aortopulmonary region could be visualised in all horses. In the affected horses presence or absence of a periaortic blood cuff, aortic rupture and or aortopulmonary fistulation could be clearly identified. In one horse during carotid catheterisation, the catheter could be guided into the fistulation site, which was clearly visualised by means of transoesophageal ultrasound.

Conclusions and practical significance

Transoesophageal ultrasound by means of a 7.5 or 10 MHz linear probe allows for good visualisation of the aortopulmonary region and for diagnosing aortic rupture in Friesian horses. The technique will be further developed as an elegant noninvasive way to screen Friesian horses for this pathology, even in the standing nonsedated horse.

Ethical animal research

Owner informed consent was obtained for all horses. Sources of funding: This study was funded by the Dutch Royal Friesian Studbook and Scil Animal Care. Competing interests: None.