Sudden deaths of horses in multiple equestrian disciplines have been attributed to acute and chronic respiratory and cardiovascular diseases. The aim of this study was to perform a review of aortic rupture in horses analyzing, case studies and assessing risk factors. The literature has reported a total of 137 cases of aortic rupture in horses for 28 years (1986-2014), with approximately five horses dying of aortic rupture per year. Histopathologically, there are observed discrete macroscopic degenerative changes in the intima layer only in the aorta. The histological evaluation in the beginning portion of the aorta of the heart evidenced degenerative changes with loss of continuity and distribution of elastic fibers. Risk factors for the rupture of the aorta are: spontaneous rupture associated with hypertension, preexisting vascular injury (aneurysm), dilated or hypertrophic cardiomyopathy, copper levels in the endothelium, genetic factors such as inbreeding, toxicology or pharmacological factors. Aortic rupture shows similarity with pulmonary hemorrhage induced by exercise especially under the locomotors induced trauma theory of exercise that can induce pulmonary hemorrhage. In conclusion, degenerative changes to discrete elastic fiber of the intima of the aorta in the emergence of the heart seem to predispose the aorta wall rupture at the time of maximum blood pressure during exercise and the consequent collapse and athletic horse’s death.

OBJECTIVE To determine the scan delay for use in performing cardiac CT angiography in dogs. ANIMALS 4 clinically normal adult Beagles. PROCEDURES In a crossover study, 12 formulations of iohexol solutions differing in iodine dose (300, 400, and 800 mg/kg) and concentration (undiluted and diluted 1:1, 1:2, and 1:3 with saline [0.9% NaCl] solution) were administered IV to each dog. Dynamic CT angiography was performed to evaluate enhancement characteristics of each formulation, with the region of interest set over the aorta. Time-attenuation curves (TACs) were obtained and analyzed. RESULTS Peak arc–type TACs were obtained after administration of all undiluted formulations. Curve shape changed from peak arc type to plateau type as the total volume of the contrast solution (ie, dilution) increased. Prolonged peaks characteristic of plateau-type TACs suggested that a sufficient period of homogeneous attenuation could be achieved for CT scanning with administration of higher iohexol dilutions (1:2 or 1:3) containing higher iodine doses (400 or 800 mg/kg). In particular, attenuation values for plateau-type TACs remained between 200 and 300 Hounsfield units for > 16 seconds after the plateau endpoint was reached for 1:2 and 1:3 dilutions containing an iodine dose of 800 mg/kg. Scan delays of 13 to 17 seconds were computed for those 2 formulations. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that for clinically normal dogs, a scan delay of 13 to 17 seconds could be used to perform cardiac CT angiography with iohexol solutions containing an iodine dose of 800 mg/kg at dilutions of 1:2 or 1:3.