Primary hyperthyroidism is a rarely diagnosed endocrinopathy in equids and there have been no previous reports of structural and functional cardiac changes associated with hyperthyroidism in these species. This case report investigates a 20-year-old mule gelding that presented for a three-month history of thin body condition despite polyphagia, with a heart murmur and elevated free and total thyroid hormone concentrations. On presentation, physical exam revealed a body condition score of two out of nine, persistent tachycardia, pansystolic heart murmur and firm bilateral ventral proximal cervical masses. Bloodwork confirmed markedly elevated free T4, total T4 and T3 concentrations. Echocardiogram demonstrated left ventricular concentric hypertrophy with increased ventricular and atrial systolic function. Bilateral thyroidectomy was performed under standing sedation without complications. Histopathology demonstrated adenocarcinoma of the left thyroid gland and multiple adenomas with osseous metaplasia within the right thyroid. The mule was supplemented with levothyroxine sodium two weeks post-op after a thyroid panel demonstrated undetectable concentrations. Polyphagia resolved following surgery and the mule began gaining weight. Echocardiographic changes improved but did not resolve at two years post-operative. Continued bi-annual follow up and monitoring of thyroid levels was recommended. This case represents the first documentation of hemodynamically relevant cardiac remodeling in an equid associated with primary hyperthyroidism.

Gastric ulceration can be induced by athletic training and is a significant welfare concern. The objective of this study was to evaluate the effect of gastric ulcer induction on heart rate variability (HRV) in the horse. We hypothesized that induction of gastric ulcers would decrease HRV and increase low frequency fluctuations, consistent with increased sympathetic tone. A convenience sample of 8 horses in a larger study were enrolled. Horses were randomly assigned to receive water or 2 mg/kg omeprazole orally once daily for 28 days. Gastric ulcers were induced through intermittent feed withholding on days 21 to 28. Gastroscopy was performed and gastric ulcers were graded (0-IV) by three blinded reviewers on days 21 and 28. Continuous electrocardiograms were obtained for one hour at the start and end of ulcer induction. HRV was assessed in 1-hour recordings for time domain variables and 5 minute sections for frequency domain analysis. HRV and ulcer grade across treatments were compared by a mixed effect model, with treatment and time as fixed effects and horse as a random effect. Gastric ulcer grade increased with induction protocol (P < .0001) and decreased with omeprazole treatment (P = .0007). Omeprazole treatment increased R-R intervals (P = .01) and decreased ratio of low frequency/high frequency signal (P = .008) as compared to horses receiving water. This was attributable to decreasing low frequency fluctuations (P = .05). While limited by the small sample size (four horses/treatment), this study suggests that omeprazole treatment decreases heart rate, and LF/HF ratio during ulcer induction, consistent with a decrease in sympathetic tone.

Background: Omega-3 fatty acid and alpha-tocopherol supplementation reduces gastric ulcer formation in humans and rodents; however, efficacy of prevention in horses is unknown. Equine Omega Complete (EOC) is an oral supplement containing omega-3 fatty acids and alpha-tocopherol. Hypothesis/Objective: Determine if EOC supplementation prevents gastric ulcers and increases serum alpha-tocopherol concentrations in healthy horses. Animals: Nine thoroughbred geldings; 5-13 years old. Methods: Prospective randomized block design, repeated in crossover model. Horses were administered EOC, omeprazole, or water PO for 28 days. Horses underwent an established gastric ulcer induction protocol from days 21-28 via intermittent feed deprivation. Gastroscopies were performed on days 0, 21, and 28. Serum alpha-tocopherol concentrations were measured on days 0 and 28. The effects of treatment and time on ulcer grades were assessed with ordinal logistic regression, with significance at P-value <.05. Results: Ulcer grades increased during ulcer induction in control and EOC but not omeprazole groups (P = .02). Grades increased in EOC-treated horses after ulcer induction from a median of 1 [95% confidence interval 0-2.5] (day 0) to 2.5 [1.5-3.5] (day 28) and were similar to the control group (P = .54). Serum alpha-tocopherol increased in EOC-treated horses from day 0 to day 28 (mean 2.2 ± 0.43 μg/mL to 2.96 ± 0.89 μg/mL; P < .001) with high individual variation; this increase was not different from omeprazole or control groups. Conclusion and Clinical Importance: Supplementation with EOC for 28 days did not prevent gastric ulcer formation nor increase alpha-tocopherol concentrations relative to the control group.

Background: Cardiac arrhythmias are common in horses, but their clinical relevance remains controversial. Objectives: To describe prevalence and identify risk factors for arrhythmias that may warrant additional screening in a sedentary mixed‐breed population of horses. Study Design: Prospective cross‐sectional. Methods: Ninety‐four clinically healthy, university‐owned, sedentary horses underwent 24‐h ambulatory electrocardiograms and echocardiograms. Potential risk factors were recorded for all horses. Affected individuals were defined as those with >1 supraventricular premature complex/h or with any ventricular premature complexes for risk factor analysis. Forward stepwise logistic regression was used to identify factors associated with the presence of arrhythmia. The p value <0.15 was considered significant in univariable screening and p ≤ 0.05 was considered significant overall. Results: During recording, 92.6% (87/94) of horses experienced an arrhythmia. Supraventricular premature complexes were present in 86.2% (81/94) of the horses, and ventricular complexes were present in 24.5% (23/94) of the horses. Of the sample, 38.3% (36/94) were considered affected by arrhythmias. Increased heart girth score was associated with detection of arrhythmias (OR 1.06, 95% CI 1–1.12, p = 0.05) and age was retained in the final model as a confounder. Main Limitations: The study sample included a limited range of body condition scores and number of stallions for risk factor analysis. Conclusion: Arrhythmias occurred with high frequency in this group of horses despite no known history or clinical signs of cardiovascular disease. Increased heart girth is a potential risk factor for arrhythmia in the horse.

Background: Echocardiographic reference intervals for Quarter Horses are infrequently reported. Objectives: To provide standard echocardiographic measurements for sedentary Quarter Horses and evaluate the relationship between physical characteristics (body weight, age, sex) and echocardiographic measurements. Animals: Forty-one sedentary Quarter Horses, free of cardiac disease, from a university research herd. Methods: A cross-sectional study evaluating standardized echocardiograms performed on sedentary Quarter Horses (41) between 2020 and 2022. Reference intervals were calculated for raw and weight-corrected values. Multiple linear regression was performed to evaluate the relationship between the physical characteristics (body weight, age, sex) and echocardiographic variables. Results: Multiple linear regression showed that every 100 kg of body weight was associated with a 3 (95% CI 1–6) mm thicker left ventricular free wall in systole (p = 0.02), an 8 (95% CI 2–13) mm larger left atrial diameter (p < 0.01), and a 4 (95% CI 0–9) mm larger pulmonary artery diameter (p = 0.04). Every year in age was associated with a 0 (95% CI 0–1) mm larger left atrial diameter (p = 0.02), a 0 (95% CI 0–1) mm larger aortic diameter (p = 0.01), and a 0 (95% CI 0–1) mm larger pulmonary artery diameter (p = 0.01). Left atrial to left ventricular ratio was 1 (95% CI −1 to 0) mm smaller in geldings compared to mares (p = 0.03). Conclusions and Clinical Importance: This study provides echocardiographic reference intervals for a cohort of sedentary Quarter Horses and clarifies the association with body weight, age, and sex with these variables.

A 2-day-old Miniature Horse filly presented with severe clinical and clinicopathologic findings consistent with neonatal sepsis, failure of transfer of passive immunity, and aspiration pneumonia. The filly initially was treated with broad spectrum antimicrobials, hemodynamic support, and hyperimmune plasma. Because of a lack of improvement within the first 24 h, extracorporeal blood purification and cytokine removal were implemented. The foal underwent hemoperfusion (HP) using a polymer-based device (VetResQ). Reported notable changes during and after treatment included improved physical examination variables, increased total white blood cell count, and decreased cytokine and chemokine concentrations. However, progressive thrombocytopenia (secondary to sepsis or HP), increased hemolysis index, and hyperbilirubinemia also were observed after the procedure. The treatment was well tolerated. Ultimately, the foal was euthanized approximately 48 h post-procedure because of development of multiple sites of septic polyarthritis and associated financial constraints. Polymer-based HP has not previously been used to treat septic neonatal foals.