Investigation of congestive heart failure in beef cattle in a feedyard at a moderate altitude in western Nebraska

Right-sided congestive heart failure (brisket disease) commonly occurs in cattle raised at elevations >2,500–3,500 m. We investigated clinical cases resembling brisket disease at a western Nebraska feedyard at a moderate altitude (1,369 m). Over a 15-mo period (2009–2010), we examined 17 cases (16 steers and 1 heifer), all purebred Angus. All animals had clinical right-sided heart failure: brisket and ventral abdominal edema, and severe chronic passive congestion of the liver. Gross examination confirmed right ventricular hypertrophy (left ventricle plus septum: right ventricle weight ratio mean: 1.33 vs. 2.8–4.0 reference interval). Microscopically, all 17 cases had interstitial fibrosis (mean score: 2.4 ± 0.8) and 6 had replacement fibrosis of the right ventricle, whereas 14 had interstitial fibrosis (mean score: 1.2 ± 0.2) and 0 had replacement fibrosis of the left ventricle. Lesions of arteriosclerosis were seen in 9 of 16 cases in 51 of 571 (8.9%) right ventricular coronary arteries, and in 10 of 16 cases in 52 of 366 (14.2%) left ventricular coronary arteries. The probability of coronary arteriosclerosis was greater in papillary ventricular muscle (OR = 11.3; p < 0.0001), left ventricle (OR = 4.8; p < 0.0001), and larger arteries (OR = 1.01; p < 0.0001). Pulmonary arteries and arterioles had lesions compatible with hypoxia-induced pulmonary hypertension. We hypothesize that moderate hypobaric conditions significantly contributed to disease in cattle genetically predisposed to hypoxia-induced pulmonary hypertension. Adiposity, coronary arteriosclerosis, and left ventricular fibrosis may have contributed to the condition; however, the cattle died prior to development of advanced obesity.

Cardiac Pathology and Genomics of Sudden Death in Racehorses From New York and Maryland Racetracks

Postmortem evaluation of racehorses has focused primarily on musculoskeletal injuries; however, horses also die suddenly on the track (sudden death [SD]). Although cardiac conditions are frequently suspected as a cause of death, SD racehorses are often autopsy negative; however, previous studies have been limited due to inconsistent or insufficient cardiac sampling and lack of controls. SD in New York (NY) and Maryland (MD) racehorses was evaluated in an observational case vs control study comparing clinical information, postmortem evaluation including cardiac dissection, and cardiac conduction system histopathology. In the study period, there were 40 cases of SD. In NY, SD occurred in 12% (37/316) of submissions, and 36 (11%) cases of SD were exercise associated (EASD); 3 EASD cases occurred in MD. In NY/MD EASD cases with histologic examination of the heart, 11 of 36 (31%) had significant lesions, including mesenteric artery rupture (1), axial trauma (2), systemic inflammation (2), pulmonary hemorrhage (1), and cardiac disease (5). Mild myocardial fibrosis, mild inflammation, coronary arteriosclerosis, and variation in cardiac nodal connective tissue were present in both SD cases and controls and thus were not considered to be causes of SD. While not excluding a genetic basis for SD, analysis of the genotypes (GGP Equine 70 K Array) of cases and controls did not reveal significant differences in allele frequencies at any locus. Most SD racehorses were autopsy negative; further research using standardized protocols and controls is needed to understand the underlying causes of SD, which is crucial to protecting the viability of racing.