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The long QT syndrome (LQTS) is a channelopathy that can lead to severe arrhythmia and sudden cardiac death. Pharmacologically induced LQTS is caused by interaction between drugs and potassium channels, especially the Kv11.1 channel. Due to such interactions, numerous drugs have been withdrawn from the market or are administered with precautions in human medicine. However, some compounds, such as trimethoprim–sulfonamide combinations are still widely used in veterinarian medicine. Therefore, we investigate the effect of trimethoprim–sulfadiazine (TMS), trimethoprim, sulfadiazine, and detomidine on equine‐specific Kv11.1 channels. Kv11.1 channels cloned from equine hearts were heterologously expressed in Xenopus laevis oocytes, and whole cell currents were measured by two‐electrode voltage‐clamp before and after drug application. TMS blocked equine Kv11.1 current with an IC50 of 3.74 m m (95% CI: 2.95–4.73 m m) and affected the kinetics of activation and inactivation. Similar was found for trimethoprim but not for sulfadiazine, suggesting the effect is due to trimethoprim. Detomidine did not affect equine Kv11.1 current. Thus, equine Kv11.1 channels are also susceptible to pharmacological block, indicating that some drugs may have the potential to affect repolarization in horse. However, in vivo studies are needed to assess the potential risk of these drugs to induce equine LQTS. [ABSTRACT FROM AUTHOR]

Measurement of atrial/A-type natriuretic peptide (ANP) concentrations may be of use for assessment of cardiac disease, and reliable data on the analytic performance of available assays are needed. To assess the suitability for clinical use of commercially available ANP assays, intra-assay and inter-assay coefficient of variation and dilution parallelism were calculated for three immunoassays (RIAPen, RIAPhoen, and an ELISAPen) using blood samples from healthy and diseased horses to cover a wide range of ANP concentrations. Further, agreement between assays was assessed using linear regression and Bland-Altman analyses. For all assays, precision was moderate but acceptable and dilution parallelism was good. All assays showed analytic performance similar to other immunoassays used in veterinary medicine. However, the results from the three assays were poorly comparable. Our study highlights the need for an optimised species-specific assay for equine samples. [ABSTRACT FROM AUTHOR]

Atrial natriuretic peptide (ANP) is a cardiovascular biomarker that might be useful in assessing the severity, of cardiac disease in horses. Plasma ANP concentrations (CpANP) were compared between horses with heart disease but normal chamber size and function (Group A; n = 6), horses with heart disease associated with left atrial (LA) enlargement, LA dysfunction, and/or left ventricular (LV) enlargement (Group B; n = 5), and horses with no clinically apparent cardiovascular disease (Group C; n = 13). The median (min-max) for CpANP was significantly higher in Group B (53.5 (36.0-70.7) pg/mL), compared to Group A (12.5 (6.3-19.8) pg/mL) and Group C (13.4 (7.2-34.0) pg/mL). Backwards stepwise multiple linear regression showed that CpANP in horses with heart disease was related to LA dimensions, but not to LV size, LA function, and LV function. The results indicated that CpANP in horses might be useful in detecting LA enlargement and that CpANP could be related to the severity of cardiac disease. Larger prospective studies are necessary to confirm these results. [ABSTRACT FROM AUTHOR]

Objectives: Quantitative measurements of cardiac repolarization, defined as the electrocardiographic QT interval, have important diagnostic implications in humans, as irregularities can trigger potentially fatal ventricular tachyarrhythmia. In both humans and horses, cardiac repolarization is influenced to some extent by heart rate, age, body weight (BW), sex, autonomic tone, and environment. In horses, there is substantial inter-breed variation in size and training, and the aims of this study were therefore to determine the best model describing the QT to RR relationship in breeds of various athletic horses and to test for differences in the QT interval., Animals: Ten Icelandic horses, 10 Arabian horses, 10 Thoroughbreds, 10 Standardbreds, six Coldblood trotters, 10 Warmbloods (dressage) and 10 Warmbloods (show jumping). All horses were geldings., Methods: QT intervals were measured from resting to peak exercise level and plotted against RR intervals. Data points were fitted with relevant regression models, and the effect of breed, BW, and estimated exercise intensity was examined., Results: For all breeds in this study, the QT interval was best described as a function of RR by the piecewise linear regression model. The breed of horse had a significant effect on the model. There was no systematic effect of BW or estimated exercise intensity, but a high inter-horse variability was observed., Conclusions: The equine QT interval should preferably be corrected for heart rate according to breed. In addition, the results indicate that equine studies of the QT interval must be designed to eliminate the influence of a large inter-horse variation., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The present retrospective study describes the diagnostic workup and collected findings in 7 horses with chronic inflammatory bowel disease over the years 2000-2006. The diagnosis could be confirmed histologically with biopsies taken during laparoscopy or laparotomy or during post mortem examination. Weight loss and chronic diarrhoea were the most commonly reported clinical findings. Among ancillary examinations (fecal analysis, gastroscopy, abdominal ultrasonography, rectal mucosal biopsy) the D-xylose absorption test provided the most useful information. Although clinical signs and laboratory findings are helpful diagnostic tools, a definitive diagnosis is only possible by histological analysis of the intestinal segment.