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Copyright of Canadian Veterinary Journal / Revue Vétérinaire Canadienne is the property of Canadian Veterinary Medical Association and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective Plasma atrial/A-type natriuretic peptide concentration (Cp ANP ) was measured in horses presenting with various heart diseases to assess its potential diagnostic value. Animals Fifteen healthy horses ( Group 1 ) and 60 horses with various heart diseases associated with normal chamber size and function ( Group 2, n = 24 ), associated with abnormal left atrial (LA) size and/or function but normal left ventricle (LV) ( Group 3, n = 19 ), or associated with both abnormal LA and LV size and/or function ( Group 4, n = 17 ). Methods Cp ANP was measured by a commercially available radioimmunoassay. Echocardiographic measurements were compared between groups by one-way ANOVA and Holm-Sidak post-hoc test. Receiver operating characteristics (ROC) analyses were performed to identify the best cut-offs to distinguish between groups. Relations between echocardiographic measurements and biomarker concentrations were assessed with backward stepwise multiple linear regression. Results Cp ANP increased from Group 1 to 4 and was significantly higher in horses with heart disease than in controls. Cp ANP was associated with maximum LA area and LV fractional area change. The ROC analyses showed good specificity but poor sensitivity to distinguish between healthy horses and horses with heart disease overall, and between healthy horses and horses with altered left-sided chamber dimensions and/or function. Conclusion Cp ANP is increased in horses with heart disease associated with altered left-sided chamber dimensions and/or function. However, its diagnostic value is compromised by poor sensitivity. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Atrial natriuretic peptide (ANP) and cardiac troponin I (cTnI) serve as biomarkers for increased cardiac pressure/volume loading and for myocardial stress or damage. The objective was to describe the time course of plasma ANP concentrations (CpANP) and plasma cTnI concentrations (CpcTnI) in horses with mitral regurgitation (MR) compared to healthy horses at rest and after exercise, and to describe the relationship of CpANP with cardiac dimensions and intracardiac pressures. Animals: 15 healthy Warmblood horses and 7 Warmblood horses with MR. Methods: Cardiac dimensions at rest were measured using echocardiography. All horses underwent standardized treadmill exercise. Biomarker concentrations and intracardiac pressures were measured at rest and after exercise. Hypotheses were tested using statistical methods. The level of significance was P < 0.05. Results: Horses with MR showed increased left atrial (LA) and left ventricular (LV) dimensions but similar exercise capacity compared to healthy horses. Pulmonary capillary wedge pressures (PCWP) and CpANP increased with exercise. Horses with MR had higher PCWP and higher CpANP at rest and after exercise compared to healthy horses, with the maximum difference in CpANP reached 10 min after exercise. CpANP was significantly related to PCWP and – although inconsistently and only in healthy horses – to echocardiographic indices of LA and LV size and function. CpcTnI was low throughout the study in both groups. Conclusions: CpANP is increased in horses with MR and is related to LA pressures and to left heart dimensions. MR is not necessarily associated with exercise intolerance and exercise-induced myocardial stress or damage. [Copyright &y& Elsevier]

Abstract: Objectives: To investigate the relationship of heart rate (HR) and ECG time intervals to body weight (BWT) in healthy horses and ponies. We hypothesized that HR and ECG time intervals are related to BWT. Animals: 250 healthy horses of >30 breeds; 5.5 (1–30) y [median (range)]; 479 (46–1018) kg. Methods: Prospective study. Standard base-apex ECGs were recorded while the horses were standing quietly in a box stall. Mean HR over 15 s was calculated and RR interval, PQ interval, QRS duration, and QT interval were measured by a single observer.QT was corrected for differences in heart rate using Fridericia''s formula (QTcf = QT/3√RR). The relationship between ECG variables and BWT, age, sex, and RR interval was assessed using multivariate backward stepwise regression analyses. Goodness of fit of the model was improved when using log(BWT) compared to BWT. Body weight was overall the strongest predictor of HR and ECG time intervals. Therefore, only log(BWT) was included as an independent variable in the final model. The level of significance was p = 0.05. Results: HR (R 2 = 0.21) showed a significant negative relationship and PQ (R 2 = 0.53), QRS (R 2 = 0.23), QT (R 2 = 0.14), and QTcf (R 2 = 0.02) showed significant positive relationships to log(BWT). Conclusions: Small equine breeds undergoing routine ECG recordings have slightly faster heart rates and shorter ECG time intervals compared to larger equine breeds. Although the magnitude of absolute differences may be small, body weight needs to be considered among other factors when comparing HR and ECG time intervals to normal ranges in horses. [Copyright &y& Elsevier]

Abstract: Objective: To study the applicability of anatomical M-mode (AMM) for assessment of left ventricular (LV) size and function in horses, evaluate agreement with conventional M-mode (CMM), determine reliability, and establish reference intervals for AMM measurements. Animals: 98 horses; 13.1 ± 5.6 years; 538 ± 78 kg. Methods: Two-dimensional and M-mode recordings were analyzed retrospectively. Standard LV dimensions and indices of LV function, including time intervals, were measured in CMM and compared with AMM studies in long-axis (lx) and short-axis (sx) views. Results: The percentages of measureable cycles were 99%, 97%, and 90% for routine LV studies in CMMsx, AMMsx, and AMMlx mode. For time intervals, ≥ 93% of cycles could be measured using AMM compared to a maximum of 77% using CMM. AMMsx measurements agreed well with CMMsx measurements for LV studies; the agreement of AMMlx with CMMsx was markedly lower. The LV ejection time and the duration of electromechanical systole, but not the LV pre-ejection period and the index of myocardial performance, showed fair agreement between methods. Intraobserver and interobserver measurement variabilities were low for most variables. Conclusions: AMM can replace CMM for assessment of LV dimensions in horses, but is not recommended for measurement of time intervals. [ABSTRACT FROM AUTHOR]