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This article provides an overview on the principles of transthoracic echocardiography in horses. Indications for echocardiography, equipment, and technical considerations are discussed and a systematic approach for a complete echocardiographic examination in horses is described. Methods for assessment of chamber dimensions, allometric scaling of measurements, assessment of systolic and diastolic ventricular function, assessment of atrial function, hemodynamic assessment, and evaluation of valvular regurgitation are explained, focusing on traditional 2-dimensional (2D), motion-mode, and Doppler echocardiographic methods. Selected applications of newer echocardiographic methods, such as tissue Doppler imaging and 2D speckle tracking are also described., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Assessment of left ventricular (LV) systolic function can be achieved by conventional echocardiographic methods, but quantification of contractility, regional myocardial function, and ventricular synchrony is challenging. The goal of this study was to investigate the applicability of two-dimensional speckle tracking (2DST) to characterize segmental and global wall motion for assessment of LV function and LV synchrony in healthy goats. We aimed to describe the techniques, report normal values of a variety of 2DST indices, and determine the influence of general anesthesia., Methods: Prospective study on 22 healthy female Saanen goats (3.7 ± 1.1 y, 60.2 ± 10.5 kg [mean ± SD]). All goats underwent two transthoracic echocardiographic examinations, the first standing and unsedated and the second 7.4 ± 3.5 days later during isoflurane anesthesia and positioned in sternal recumbency. Data analyses were performed offline, blinded, and in random order. Left ventricular longitudinal, radial and circumferential strain and strain rate as well as longitudinal and radial displacement were measured using 2DST methods. Summary statistics were generated and differences of 2DST variables between myocardial segments and treatments (i.e., awake vs. anesthetized) were assessed statistically (alpha level=0.05)., Results: Echocardiographic analyses by 2DST were feasible in all goats and at both time points. Longitudinal systolic strain, strain rate and displacement followed a gradient from apex to base. Absolute systolic strain was generally lower and strain rate was higher in awake goats compared to anesthetized goats. Circumferential and radial indices did not consistently follow a segmental pattern. Generally, peak strain occurred later in anesthetized goats compared to awake goats. General anesthesia did not significantly influence LV synchrony., Conclusions: 2SDT is a valid method for non-invasive characterization of LV wall motion in awake and anesthetized goats. The results of this study add to the understanding of LV mechanical function, aid in the diagnosis of global and segmental LV systolic dysfunction, and will be useful for future cardiovascular studies in this species. However, effects of anesthesia and species-specific characteristics should be considered when goats are used as animal models for human disease.

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 CMM(sx), AMM(sx), and AMM(lx) mode. For time intervals, >or= 93% of cycles could be measured using AMM compared to a maximum of 77% using CMM. AMM(sx) measurements agreed well with CMM(sx) measurements for LV studies; the agreement of AMM(lx) with CMM(sx) 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., (Copyright (c) 2010 Elsevier B.V. All rights reserved.)

Objective: To assess the feasibility, describe the techniques, and determine the reliability of transthoracic echocardiography for characterization of left atrial (LA) size and LA mechanical function in horses., Animals: 6 healthy adult horses., Procedures: Repeated echocardiographic examinations were performed independently by 2 observers in standing, unsedated horses by use of 2-dimensional echocardiography, pulsed-wave flow Doppler, and tissue Doppler imaging (TDI) techniques. Test reliability was determined by estimating measurement variability, within-day interobserver variability, and between-day inter- and intraobserver variability of all echocardiographic variables. Variability was expressed as the coefficient of variation (CV) and the absolute value below which the difference between 2 measurements will lie with 95% probability., Results: Most echocardiographic variables of LA size had low overall variability (CV, < 15%). Among the 2-dimensional indices of LA mechanical function, area-based and volume-based ejection phase indices had moderate between-day variability (CV usually < 25%). Transmitral Doppler flow indices were characterized by low to high between-day variability (CV, 6% to 35%). The TDI wall motion velocities had high between-day variability (CV, > 25%), whereas most TDI-derived time intervals had low variability (CV, < 15%)., Conclusions and Clinical Relevance: LA size and mechanical function can be reliably assessed in standing, unsedated horses by use of 2-dimensional echocardiography, transmitral blood flow velocity profiles, and analyses of LA wall motion by use of TDI. These results may provide useful recommendations for echocardiographic assessment of LA size and function in horses.

Background: Atrial contractile dysfunction occurs in some species after conversion of atrial fibrillation (AF) to normal sinus rhythm (NSR) but has not been reported in horses with naturally occurring AF., Hypothesis: Transthoracic echocardiography allows detection of left atrial (LA) mechanical dysfunction in horses after conversion of AF to NSR., Animals: Five Standardbreds with AF and 6 healthy Standardbreds of similar age, weight, and athletic condition were included in this study., Methods: Four horses were treated pharmacologically (quinidine), and 1 horse was treated by means of transvenous electrical cardioversion. Echocardiographic examinations were performed in normal horses (once) and in AF horses (24 hours and 72 hours after conversion to NSR) by means of 2-dimensional echocardiography (2DE), transmitral flow Doppler, and tissue Doppler imaging (TDI) techniques. Echocardiographic indices of LA mechanical function were compared between normal horses and AF horses., Results: Two-dimensional echocardiography and TDI indices of LA mechanical function revealed significant decreases in LA contractile function and LA reservoir function 24 hours after cardioversion. This decrease was no longer statistically significant 72 hours after cardioversion, but changes in echocardiographic variables between 24 and 72 hours varied among horses., Conclusions and Clinical Importance: LA contractile dysfunction can be evaluated in horses by use of 2DE, transmitral Doppler flow velocity profiles, and analyses of LA wall motion by TDI. The results of this study are consistent with AF-induced atrial remodeling, although residual treatment effects or influence of underlying primary myopathy cannot be excluded.

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]