Thoracic Aortic Rupture and Aortopulmonary Fistulation in the Friesian Horse

Abstract

Aortic rupture in horses is a rare condition. Although it is relatively common in the Friesian breed, only limited histopathologic information is available. Twenty Friesian horses (1-10 years old) were diagnosed with aortic rupture by postmortem examination. Ruptured aortic walls were analyzed with histology and immunohistochemistry. Based on the histologic and immunohistochemical findings, these cases were divided into 3 groups: acute (n = 4, 20%), subacute (n = 8, 40%), and chronic (n = 8, 40%). Features common to samples from horses in all groups included accumulation of mucoid material; disorganization and fragmentation of the elastic laminae; aortic medial smooth muscle hypertrophy; and medial necrosis of varying degrees, ranging from mild and patchy in the acute cases to severe midzonal necrosis in the chronic cases. Inflammation, most likely secondary to medial necrosis, varied from predominantly neutrophilic infiltrates in the media and periadventitial tissue in the acute group to the presence of mainly hemosiderophages in the periadventitial tissue in the chronic group. Medial fibrosis with aberrant collagen morphology was seen in the subacute group and, more commonly, in the chronic group. Only minimal changes were seen in the aortic vasa vasorum. Smooth muscle hypertrophy and accumulation of mucoid material were not related to the age of the lesions. The findings of this study suggest that a connective tissue disorder affecting elastin or collagen in the aortic media is potentially the underlying cause of aortic rupture in Friesian horses.

Morphometric changes in the aortic arch with advancing age in fetal to mature thoroughbred horses

“…MPS deposition is generally reported to occur in cystic medial necrosis lesions. Cystic medial necrosis has been suggested to be an underlying cause of aortic rupturing [9, 14, 19]; however, other studies have indicated that it is related to physiological activity [13, 18]. In our study, cystic medial necrosis was first found in a 234-day-old (embryonic) horse.…”

“…It mainly affects elderly horses [1, 9] and can lead to sudden death [3]. Histopathologically, aortic lesions, including cystic medial necrosis, elastin fragmentation and medionecrosis of the aortic tunica media, might contribute to aortic rupturing [1, 9].…”

“…It mainly affects elderly horses [1, 9] and can lead to sudden death [3]. Histopathologically, aortic lesions, including cystic medial necrosis, elastin fragmentation and medionecrosis of the aortic tunica media, might contribute to aortic rupturing [1, 9]. While such lesions have been evaluated using medial grading systems based on their extent and localization [5, 18, 23], the relationship between these lesions and aortic rupturing remains unclear [14, 19, 21].…”

Pulmonary artery dissection in eight dogs with patent ductus arteriosus

“…Aortic rupture and dissection with extension to the pulmonary artery has been described in several horses, particularly of Friesian ancestry. 29,30 Pulmonary artery dissection and rupture has also been reported in cattle with fibrillin deficiency and a syndrome comparable to the human Marfan syndrome. 31 The authors are aware of 4 cases reported in the literature describing pulmonary artery dissections in dogs.…”

Differences in ultrasound‐derived arterial wall stiffness parameters and noninvasive blood pressure between Friesian horses and Warmblood horses

“…However, valvular abnormalities, which would be expected with an embryological disorder, are not described in affected Friesians . In human medicine, aortic rupture usually is preceded by aortic aneurysm formation, which is not the case in Friesians . In human patients, elastin and especially collagen have been shown to be important factors contributing to aortic aneurysm formation .…”