Background Aortic regurgitation (AR) may lead to left ventricular (LV) dilatation, cardiac arrhythmias and heart failure. Close follow-up of horses with AR is therefore paramount to detect onset of cardiac decompensation. The aim of this study was to examine whether two-dimensional speckle tracking (2DST) can be used to detect altered myocardial function in horses with chronic AR compared to control horses. Speckle tracking was performed on short axis and long axis images of the LV in 29 healthy Warmblood horses and 57 Warmblood horses with AR. Radial, circumferential and longitudinal strain, strain rate and displacement were measured for each segment separately and the average was calculated over all segments. Data generated from the apical segments were not included in the analysis. Results Radial (SR) and circumferential (SC) strain were significantly higher in horses with moderate AR (average SR 75.5 ± 24.3%, SC 19.3 ± 3.2%) but not in horses with severe AR (SR 65.5 ± 26.2%, SC 16.3 ± 3.5%), compared to control horses (SR 54.5 ± 18.0%, SC 16.8 ± 3.0%). Longitudinal strain did not show significant differences, but longitudinal displacement (DL) was larger in horses with moderate (average DL 29.5 ± 4.1 cm) and severe AR (DL 32.4 ± 6.1 cm) compared to control horses (DL 25.7 ± 4.0 cm), especially in the interventricular septum. Diastolic longitudinal strain rate was lower in early diastole in horses with severe AR (0.93 ± 0.18/s) compared to controls (1.13 ± 0.13/s). Conclusions 2DST is able to detect altered myocardial motion in horses with AR, which showed significantly higher radial and circumferential strain. Further research is needed to determine whether these findings contribute to a more accurate diagnosis and prognosis in clinical cases.

BACKGROUND:Aortic regurgitation (AR) can have an important clinical impact and in some cases leads to left ventricular (LV) failure. Tissue Doppler imaging (TDI) is an echocardiographic technique that has been used in horses to detect LV dysfunction.OBJECTIVES:To examine whether TDI detects changes in radial myocardial wall motion in horses with AR compared with control horses.STUDY DESIGN:Case-control study.METHODS:Echocardiography was performed in 30 healthy Warmblood horses and 34 Warmblood horses with AR, subdivided in groups with mild, moderate or severe AR. TDI measurements were performed on six segments of the short-axis images of the LV myocardial wall. Myocardial wall motion was evaluated by measuring velocity and deformation during isovolumetric contraction, systole, early and late diastole. Timing of different events was also measured.RESULTS:In most segments, a significantly higher systolic myocardial velocity was found in horses with AR compared with controls. Horses with AR also had higher late diastolic velocity, although the difference was not significant in all segments. TDI measurement of timing intervals demonstrated less difference between groups.MAIN LIMITATIONS:There was a significant difference in age between the control group and horses with AR, which may confound the results. The assessment of AR severity was based on subjective criteria as there is no gold standard.CONCLUSIONS:TDI showed significant differences in radial systolic and late diastolic myocardial velocity in horses with AR. This could indicate an altered LV function in these horses, but further research is needed to investigate the prognostic value of these measurements.

Background: Heart rate variability (HRV) parameters, and especially RMSSD (root mean squared successive differences in RR interval), could distinguish atrial fibrillation (AF) from sinus rhythm(SR) in horses, as was demonstrated in a previous study. If heart rate monitors (HRM) automatically calculating RMSSD could also distinguish AF from SR, they would be useful for the monitoring of AF recurrence. The objective of the study was to assess whether RMSSD values obtained from a HRM can differentiate AF from SR in horses. Furthermore, the impact of artifact correction algorithms, integrated in the analyses software for HRV analyses was evaluated. Fourteen horses presented for AF treatment were simultaneously equipped with a HRM and an electrocardiogram (ECG). A two-minute recording at rest, walk and trot, before and after cardioversion, was obtained. RR intervals used were those determined automatically by the HRM and by the equine ECG analysis software, and those obtained after manual correction of QRS detection within the ECG software. RMSSD was calculated by the HRM software and by dedicated HRV software, using six different artifact filters. Statistical analysis was performed using the Wilcoxon signed-rank test and receiver operating curves. Results: The HRM, which applies a low level filter, produced high area under the curve (AUC) (>0.9) and cut off values with high sensitivity and specificity. Similar results were obtained for the ECG, when low level artifact filtering was applied. When no artifact correction was used during trotting, an important decrease in AUC (0.75) occurred. Conclusion: In horses treated for AF, HRMs with automatic RMSSD calculations distinguish between AF and SR. Such devices might be a useful aid to monitor for AF recurrence in horses.

Background Based on its pharmacokinetic profile and electrophysiological effects in healthy horses, sotalol potentially could be used as a long‐term PO antiarrhythmic drug in horses. Objectives To evaluate the effect of sotalol on heart rate (HR), QT interval, atrial fibrillatory rate, and success of cardioversion in horses with naturally occurring chronic atrial fibrillation (AF). Animals Twenty‐eight horses referred for transvenous electrical cardioversion of AF were treated with 2 mg/kg sotalol PO q12h for 3 days before cardioversion, and 13 horses underwent the same protocol without sotalol administration. Methods Retrospective study. Before and after sotalol or no treatment, the HR was measured at rest and during an exercise test. The QT interval and atrial fibrillation cycle length (AFCL) were measured at rest using tissue Doppler velocity imaging. Results In the control group, no significant differences were found between the 2 examinations. In the sotalol group, the HR at rest and during exercise was significantly lower after sotalol treatment, whereas the QT interval and AFCL measured by tissue Doppler increased significantly. Cardioversion to sinus rhythm was achieved in 25/28 horses in the sotalol group and all horses in the control group, but the median number of shocks and energy at cardioversion were significantly lower in the sotalol group. Conclusions and Clinical Importance In horses with AF, sotalol administration results in class III antiarrhythmic effects and β‐blocking activity, with moderate HR reduction during exercise.

The disproportionate rise of pulmonary artery pressure compared to systemic blood pressure during exercise can lead to detrimental right ventricular remodelling in endurance athletes. Horses may act as an extreme model of these athletic cardiovascular adaptations, as they show a three fold increase in pulmonary pressures during exercise. Right ventricular function was examined in ten healthy horses using post-exercise and pharmacological stress echocardiography in a randomised cross-over design. Exercise testing was performed on a treadmill while pharmacological testing was performed using an atropine-dobutamine infusion. Heart rate, systemic blood pressure and cardiac output during echocardiography were similar post-exercise compared to maximal pharmacological stress. Systolic pulmonary artery pressure was significantly higher during the exercise test (121±15mmHg) and during immediate post-exercise echocardiography (93±10mmHg) compared to maximal pharmacological stress (69±12mmHg). Right ventricular diameters as well as the ratio of systolic right to left ventricular area were higher post-exercise. Right ventricular fractional area change was significantly decreased post-exercise (40.5±6.2%) compared to a significant increase during pharmacological stress echocardiography (72.6±7.3%). Serum cardiac troponin I concentration was significantly higher 2h after the pharmacological test compared to baseline values and post-exercise, although the highest value was found post-exercise in the horse with the highest systolic pulmonary artery pressure and lowest right ventricular fractional area change. Pharmacological stress testing is not recommended in further studies on right ventricular adaptations in athletic horses, as this does not reproduce the effects of exercise.

Reasons for performing studyRight ventricular (RV) function is scarcely described in horses. ObjectivesTo establish reliable echocardiographic measurements of right heart size and function in horses. Study designDescriptive study in healthy horses. MethodsTen healthy untrained adult trotter horses underwent repeated echocardiography performed by 2 sonographers from right and left parasternal standard and nonstandard views. Nonstandard views included a right parasternal view focused on the right atrium, left parasternal long-axis pulmonary artery view, left parasternal long-axis view focused on the right ventricle including anatomical M-mode of tricuspid annular motion and left parasternal pulsed wave Doppler recording of pulmonary flow. During off-line analysis, 2 observers performed two-dimensional, M-mode, pulsed wave Doppler, tissue Doppler imaging (TDI) and two-dimensional speckle tracking (2DST) measurements of RV size and function. Acquisition and measurement variability were assessed by calculating coefficients of variation (CV) from one-way repeated measures analyses of variance. The degree of variability was classified as low (CV<15%), moderate (CV 15-25%) or high (CV>25%). ResultsMost two-dimensional and M-mode measurements of RV, right atrial and pulmonary artery size showed low variability. The two-dimensional, M-mode and pulsed wave Doppler measurements of RV function showed a low to moderate variability. Right ventricular functional measurements by 2DST showed low variability, except for segmental strain rate. Right ventricular functional measurements by TDI showed a low to high variability, with a lower variability for timing than for peak measurements and a lower variability for velocity compared with deformation measurements. ConclusionsRight heart size and function can be assessed with low variability in horses.

BACKGROUND Atrial fibrillation (AF) is the most common pathological arrhythmia in horses. After successful treatment, recurrence is common. Heart rate monitors are easily applicable in horses and some devices offer basic heart rate variability (HRV) calculations. If HRV can be used to distinguish between AF and sinus rhythm (SR), this could become a monitoring tool for horses at risk for recurrence of AF. OBJECTIVES The purpose of this study was to assess whether in horses AF (before cardioversion) and SR (after cardioversion) can be differentiated based upon HRV parameters. STUDY DESIGN Cohort study with internal controls. METHODS Six HRV parameters were determined in 20 horses, both in AF and in SR, at rest (2- and 5-min and 1- and 4-h recordings) and during exercise (walk and trot, 2-min recordings). Time-domain (standard deviation of the NN intervals, root mean squared successive differences in NN intervals and triangular index), frequency domain (low/high frequency ratio) and nonlinear parameters (standard deviation of the Poincaré plot [SD]1 and SD2) were used. Statistical analysis was done using paired Wilcoxon signed rank tests and receiver operating characteristic curves. RESULTS HRV was higher during AF compared to SR. Results for the detection of AF were good (area under the receiver operating characteristic curve [AUC] 0.8-1) for most HRV parameters. Root mean squared successive differences in NN intervals and SD1 yielded the best results (AUC 0.9-1). Sensitivity and specificity were high for all parameters at all recordings, but highest during exercise. Although AUCs improved with longer recordings, short recordings were also good (AUC 0.8-1) for the detection of AF. In horses with frequent second degree atrioventricular block, HRV at rest is increased and recordings at walk or trot are recommended. MAIN LIMITATIONS Animals served as their own controls and there was no long-term follow-up to identify AF recurrence. CONCLUSIONS AF (before cardioversion) and SR (after cardioversion) could be distinguished with HRV. This technique has promise as a monitoring tool in horses at risk for AF development.

Atrial fibrillation (AF) is the most common clinically important arrhythmia in horses. Monitoring cardiac rhythm in successfully treated patients is important because recurrence may occur, but it might be challenging to the owner. Heart rate monitors are user-friendly, can be applied by owners and may offer basic heart rate variability (HRV) parameters such as root mean square of the successive differences (RMSSD) that might differentiate AF from sinus rhythm. The purpose of this study was to assess if RMSSD, automatically generated by a heart rate monitor, can distinguish between AF and sinus rhythm (SR), based upon a short recording. In 14 horses a 2-minute recording with a heart rate monitor (Polar V800) was made at rest, walk and trot, both in AF and after treatment when back in SR. RMSSD was obtained from the heart monitor’s software after importing the recordings. Statistical analysis was performed using ANOVA and receiver operating curves. At all recording points, RMSSD was significantly higher in AF compared to SR ( P < 0.001). Area under the curves were high (> 0.9) and cut-off values at rest, walk and trot were set at 134ms (100% sensitivity, 93% specificity), 55.5ms (94% and 73%) and 14ms (100% and 87%), respectively. We concluded that RMSSD obtained from a 2-minute heart rate monitor recording is an easy-to-use tool to monitor horses at risk for developing AF. Recordings at rest revealed best results. Loss of electrode contact and movement artifacts are possible confounders that increase RMSSD and may lead to false positive results.

BackgroundThe electrocardiographic differentiation between atrial (APDs) and ventricular (VPDs) premature depolarizations is important. P wave prematurity and normal QRS and T wave morphology generally are used as discriminating criteria for APDs.Hypothesis/ObjectivesThe aim of this study was to determine whether P, Q, R, S, and T wave amplitude, PQ interval, QRS and P wave duration and P and T wave morphology differ between APDs and sinus beats. To determine the relationship between the RR coupling interval and the change in S wave amplitude between sinus beats and APDs.MethodsCase–control study. From a modified base‐apex configuration of 30 horses with APDs at rest, sinus beat and APD associated preceding RR interval, P, PQ and QRS duration and P, R, S, and T wave amplitudes were measured. Linear mixed models and logistic regression were used to determine the effect of APDs on the ECG variables studied.ResultsIn comparison to sinus beats, APDs were associated with a significant (P < .001) change in P amplitude (−0.03 ± 0.01 mV) and increase in S (0.20 ± 0.02 mV) and T (0.08 ± 0.03 mV) amplitude. PQ (−20.3 ± 5.2 ms) and RR (−519 ± 14 ms) interval and P duration (−21.1 ± 3.0 ms) decreased (P < .001). APDs were significantly associated with a singular positive P wave (OR: 11.0, P < .001) and were more likely to have a monophasic positive T wave (OR: 9.2, P < .001). A smaller RR coupling interval was associated with an increased relative difference in S amplitude (P < .01).ConclusionsAtrial premature depolarizations may lead to changes in QRS and T wave morphology. Knowledge of these changes is important to avoid interpreting certain APDs as VPDs.

Aortic regurgitation (AR) in horses can lead to left ventricular (LV) eccentric hypertrophy, ventricular arrhythmia and heart failure. Objective quantification of the severity of regurgitation is difficult. The aim of this study was to evaluate dimensional measurements, systolic time intervals and blood flow velocities, acquired by standard 2D, M-mode and pulsed wave Doppler echocardiography, for quantification of AR. Echocardiography was performed in 32 healthy horses and 35 horses with AR that were subdivided in three groups (mild, moderate or severe AR). From the recorded images LV, left atrial and aortic dimensions, systolic time intervals and aortic blood flow velocities were measured. Diastolic run-off in the aorta (AoDiastDecr) was calculated as the difference in aortic diameter between early diastole and late diastole. Stroke volume (SV) was calculated from pulsed wave Doppler measurements, by the bullet method (SVbullet) and by the area-length method. Pre-ejection period (PEP) and ejection time (LVET) were determined from the M-mode images. Horses with AR showed enlargement of the LV, left atrium and aorta compared to the control group. The SV, the AoDiastDecr and the rate of AoDiastDecr were significantly larger than controls. PEP decreased significantly in horses with AR, whereas LVET did not change. PEP and the newly defined variable AoDiastDecr proved to be easy to measure parameters that provided a good indication of AR severity. There was increased SV in horses with AR using all three methods, but SVbullet was superior for the detection of increased AR severity.

“Brain natriuretic peptide” (BNP) wordt gebruikt in de humane geneeskunde voor de diagnose van congestief hartfalen. Vermits er geen BNP-test voor paarden beschikbaar is, werd BNP nog nooit bepaald bij paarden. Op basis van de 90% homologie tussen equine en porciene BNP, werd in de voorliggende studie het plasma BNP-gehalte van gezonde paarden (groep 1; n=20), paarden met een hartaandoening zonder (groep 2a; n=8) en met atriale dilatatie (n=8), ventriculaire dilatatie (n=1) of beide (n=1) (groep 2b; n=10) bepaald met een porciene BNP “enzyme-linked immunoassay” (ELISA). Er werd geen significant verschil gevonden tussen de BNP-concentratie van groep 1 (77,79; 37,20-513,36 pg/mL), groep 2a (52,02; 24,69-268,37 pg/mL) of 2b (94,73; 42,88-470,66 pg/mL). In deze pilootstudie wordt aangetoond dat deze porciene BNP ELISA-test geen accurate detectie van BNP bij paarden toelaat. Een specifieke equine BNP-test zou dus ontwikkeld moeten worden om de BNP-concentratie bij paarden te meten.

Although cardiac troponin T (cTnT) assays have been used to detect myocardial damage in horses, a cTnT assay has not been analytically validated, to our knowledge. The aims of this study were to estimate the precision of a high-sensitivity cTnT assay in horses and determine the effect of hemolysis on the measured cTnT concentration. Serum samples from horses were mixed in 3 different pools. Pool 1 consisted of samples from 3 healthy horses, pool 2 from 6 horses with heart failure or atypical myopathy, and pool 3 from 10 horses with atypical myopathy. The within- and between-run coefficients of variation were determined for each pool. Pools 2 and 3 were diluted to estimate linearity. To study the influence of sample hemolysis, serum was collected from 4 horses with a high cTnT concentration, in which hemolysis was mechanically induced. In addition, ethylenediamine tetra-acetic acid blood tubes were collected from 3 other horses, from which hemolysate was prepared and added to plasma at different concentrations. The within- and between-run coefficients of variation of all pools were <10%, and a good linearity was found. Three out of 4 hemolyzed serum samples had a decreased serum cTnT concentration. Plasma samples with a high hemolysis index showed a negative interference, resulting in a lower cTnT concentration. Results of the high-sensitivity cTnT assay were highly reproducible. Because samples from horses with musculoskeletal damage were included, further studies should test the possible cross-reactivity between troponin T of musculoskeletal and cardiac origin before the assay can be used in equine clinical practice.

Een zestienjarige Friese ruin werd aangeboden op de vakgroep Interne Geneeskunde van de Grote Huisdieren, Faculteit Diergeneeskunde (UGent), met klachten van inspanningsintolerantie, bleke mucosae, tachycardie en een onregelmatig hartritme. Uit het algemeen onderzoek bleek een demping van hart- en ventrale longgeluiden. Dit, in combinatie met een lage hematocriet, deed het vermoeden van hemothorax rijzen. De diagnose van hemothorax kon bevestigd worden aan de hand van thoracale echografie en thoracocentesis. Daar het een Fries paard betrof werd onmiddellijk gedacht aan een aortopulmonale fistel, maar dit kon echter uitgesloten worden aan de hand van uitgebreid echocardiografisch onderzoek. Uit het elektrocardiogram kon afgeleid worden dat het onregelmatig hartritme te wijten was aan atriale extrasystolen. Het paard werd gehospitaliseerd en conservatief behandeld met breedspectrumantibiotica. Daar zowel de hematocriet als het echografische beeld gunstig evolueerde, mocht het paard na vijftien dagen de kliniek verlaten. Bij controle zes weken later werden geen afwijkingen meer gevonden.

A 16-year-old Friesian gelding was admitted to the Faculty of Veterinary Medicine (Ghent University) with complaints of exercise intolerance, pale mucous membranes, tachycardia and an irregular heart rate. General examination revealed decreased heart sounds and bronchovesicular sounds in the ventral lung fields, combined with a low hematocrit, which led to the suspected diagnosis of hemothorax. The diagnosis of hemothorax was confirmed by ultrasonographic examination of the thoracic cavity and thoracocentesis. Because it was a Friesian horse, aorto-pulmonary fistulation was suspected, but this was excluded by thorough echocardiographic examination. The electrocardiogram showed that the irregular heart rate was caused by atrial premature contractions. The horse was hospitalized and was treated conservatively with broad spectrum antibiotics. Because both the hematocrit and the ultrasonographic images evolved well, the horse could leave the clinic after 15 days. Re-examination after six weeks showed no more abnormalities.

BackgroundDifferent cardiac troponin I (cTnI) assays give different results. Only 1 manufacturer has marketed troponin T (cTnT) assays. Therefore, cTnT often is preferred for detection of myocardial infarction in human patients. Studies of cTnT in horses are limited.ObjectivesTo compare a cTnI and a high‐sensitive cTnT assay (hs‐cTnT) in horses.AnimalsCardiac troponin I and cTnT were determined in 35 healthy horses (group 1), 23 horses suspected to have primary myocardial damage (group 2a), and 41 horses with secondary myocardial damage caused by structural heart disease (group 2b).MethodsAll cTnI samples were analyzed at laboratory A (limit of detection [LOD]: 0.03 ng/mL), whereas cTnT samples were analyzed at 2 laboratories with the same hs‐cTnT assay (laboratory B, LOD: 10.0 pg/mL; laboratory C, LOD: 4.0 pg/mL).ResultsThe median cTnI concentration in group 2a (0.90 ng/mL; range, 0.03–58.27 ng/mL) was significantly higher (P < .001) than in group 1 (0.03 ng/mL; range, 0.03–0.09 ng/mL) or group 2b (0.05 ng/mL; range, 0.03–30.92 ng/mL), and the optimal cut‐off for detection of primary myocardial damage was 0.095 ng/mL (sensitivity: 90.5%, specificity: 100%). Using an LOD of 10.0 pg/mL for all cTnT samples, a cut‐off value of 10.5 pg/mL was found, but sensitivity was low (42.9%). When only samples analyzed at laboratory C (n = 58) were included, a cut‐off of 6.6 pg/mL was found (sensitivity: 81%, specificity: 100%).Conclusions and Clinical ImportanceDespite large quantitative differences, cTnI and cTnT are both useful for detection of myocardial damage in horses.

A 16-year-old Friesian gelding was admitted to the Faculty of Veterinary Medicine (Ghent University) with complaints of exercise intolerance, pale mucous membranes, tachycardia and an irregular heart rate. General examination revealed decreased heart sounds and bronchovesicular sounds in the ventral lung fields, combined with a low hematocrit, which led to the suspected diagnosis of hemothorax. The diagnosis of hemothorax was confirmed by ultrasonographic examination of the thoracic cavity and thoracocentesis. Because it was a Friesian horse, aorto-pulmonary fistulation was suspected, but this was excluded by thorough echocardiographic examination. The electrocardiogram showed that the irregular heart rate was caused by atrial premature contractions. The horse was hospitalized and was treated conservatively with broad spectrum antibiotics. Because both the hematocrit and the ultrasonographic images evolved well, the horse could leave the clinic after 15 days. Re-examination after six weeks showed no more abnormalities.