Heart rate variability analysis in horses for the diagnosis of arrhythmias

Heart rate and heart rate variability in horses undergoing hot and cold shoeing

Heart rate variability (HRV) is a frequently used indicator of autonomic responses to various stimuli in horses. This study aimed to investigate HRV variables in horses undergoing cold (n = 25) or hot (n = 26) shoeing. Multiple HRV variables were measured and compared between horses undergoing cold and hot shoeing, including the time domain, frequency domain, and nonlinear variables pre-shoeing, during shoeing, and at 30-minute intervals for 120 minutes post-shoeing. The shoeing method interacted with time to change the HRV variables standard deviation of RR intervals (SDNN), root mean square of successive RR interval differences (RMSSD), very-low-frequency band, low-frequency band (LF), the LF to high-frequency band ratio, respiratory rate, total power, standard deviation perpendicular to the line of identity (SD1), and standard deviation along the line of identity (SD2). SDNN, RMSSD, and total power only increased 30 minutes after hot shoeing (all p < 0.05). Triangular interpolation of normal-to-normal intervals (TINN) and the HRV triangular index increased during and up to 120 minutes after hot shoeing (p < 0.05-0.001). TINN increased only during cold shoeing (p < 0.05). LF increased 30 and 60 minutes after hot shoeing (both p < 0.05). SD1 and SD2 also increased 30 minutes after hot shoeing (both p < 0.05). SDNN, TINN, HRV triangular index, LF, total power, and SD2 were higher in hot-shoed than cold-shoed horses throughout the 120 minutes post-shoeing. Differences in HRV were found, indicating increased sympathovagal activity in hot shoed horses compared to cold shoed horses.

Effects of pregnancy on electrocardiographic, vasovagal tonus index, and echocardiographic variables in horses

Background and Aim

Pregnancy affects maternal hemodynamics. The changes in autonomic nervous system activity for hemodynamics adaptation in pregnant horses are still unclear. Thus, this study aimed to examine the effect of pregnancy on electrocardiographic, vasovagal tonus index, and echocardiographic variables in horses.

Materials and Methods

A total of 23 Thai native crossbred mares without any cardiac abnormalities were included in this study. The animals were assigned into two groups, a non-pregnant mare group (n =12) and a pregnant mare group (n = 11). Electrocardiogram recordings (paper speed = 25 mm/s and calibration = 10 mm/mV) were performed to obtain six limb leads (leads I, II, III, aVR, aVL, and aVF). The vasovagal tonus index (VVTI) was calculated to assess variability in heart rate over short periods using just 20 consecutive beats. Cardiac structure and function were evaluated by echocardiography.

Results

Heart rate, P wave duration, PR interval, QRS duration, QT interval, and T wave duration were significantly different between non-pregnant and pregnant horses (p < 0.05). Pregnant horses had significantly lower VVTI than non-pregnant (p < 0.05). There were no significant differences in cardiac structures including % interventricular septum (IVS), % left ventricular posterior wall (LVPW), IVS in diastole, left ventricular internal diameter at end-diastole, LVPW thickness at end-diastole, IVS in systole, left ventricular internal diameter at end-systole, LVPW thickness at end-systole, and left atrium/aortic roots ratio between the two groups. However, the pregnant horses had a significantly higher cardiac output and % ejection fraction than non-pregnant horses (p < 0.05).

Conclusion

This study provided the first evidence that hemodynamic adaptations during pregnancy modified cardiac conduction, vasovagal tonus index, and echocardiographic variables in horses.

Changes in Heart Rate Variability with Induction of Gastric Ulcers in Adult Horses

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.

Validation of an Equine Smart Textile System for Heart Rate Variability: A Preliminary Study

Electrocardiograms (ECGs), and associated heart rate (HR) and heart rate variability (HRV) measurements, are essential in assessing equine cardiovascular health and fitness. Smart textiles have gained popularity, but limited validation work has been conducted. Therefore, the objective of this study was to compare HR and HRV data obtained using a smart textile system (Myant) to the gold-standard telemetric device (Televet). Simultaneous ECGs were obtained using both systems in seven horses at rest and during a submaximal exercise test. Bland-Altman tests were used to assess agreement between the two devices. Strong to perfect correlations without significant differences between the two devices were observed for all metrics assessed. During exercise, mean biases of 0.31 bpm (95% limits of agreement: -1.99 to 2.61) for HR, 1.43 ms (-11.48 to 14.33) for standard deviation of R-R intervals (SDRR), and 0.04 (-2.30 to 2.38) for the HRV triangular index (TI) were observed. A very strong correlation was found between the two devices for HR (r = 0.9993, p < 0.0001) and for HRV parameters (SDRR r = 0.8765, p < 0.0001; TI r = 0.8712, p < 0.0001). This study demonstrates that a smart textile system is reliable for assessment of HR and HRV of horses at rest and during submaximal exercise.

Donkey Heart Rate and Heart Rate Variability: A Scoping Review

Heart rate (HR) and heart rate variability (HRV) are commonly used physiological measures in animals. While several studies exist on horse HRV, less information is available for donkeys. This scoping review aims to understand the extent and type of published evidence on donkey HR and HRV, their clinical and research applications, the devices used, and the analysis performed. Only quantitative primary studies published in English were considered. Four different databases were queried through the Web of Science platform, with additional evidence identified by citation chasing. After a two-stage screening phase, data were extracted considering study and population characteristics, information on HR/HRV analysis, and applications. The majority of the 87 included articles (about 80%) concerned a sample size of up to 20 individuals and were published since 2011 (about 65%). Forty-one articles employed an electronic device for signal acquisition (mainly electrocardiographs and heart rate monitors), yet only two articles reported HRV parameters. The literature on donkey HRV is lacking, and this gap can be filled by gaining knowledge on donkey characteristics and finding useful tools for welfare assessment. Comparison with what is known about the horse allows a discussion of the technical and interpretative difficulties that can be encountered with donkeys.

Sympathetic Arousal Detection in Horses Using Electrodermal Activity

The continuous monitoring of stress, pain, and discomfort is key to providing a good quality of life for horses. The available tools based on observation are subjective and do not allow continuous monitoring. Given the link between emotions and sympathetic autonomic arousal, heart rate and heart rate variability are widely used for the non-invasive assessment of stress and pain in humans and horses. However, recent advances in pain and stress monitoring are increasingly using electrodermal activity (EDA), as it is a more sensitive and specific measure of sympathetic arousal than heart rate variability. In this study, for the first time, we have collected EDA signals from horses and tested the feasibility of the technique for the assessment of sympathetic arousal. Fifteen horses (six geldings, nine mares, aged 13.11 ± 5.4 years) underwent a long-lasting stimulus (Feeding test) and a short-lasting stimulus (umbrella Startle test) to elicit sympathetic arousal. The protocol was approved by the University of Connecticut. We found that EDA was sensitive to both stimuli. Our results show that EDA can capture sympathetic activation in horses and is a promising tool for non-invasive continuous monitoring of stress, pain, and discomfort in horses.

Measuring heart rate variability using a heart rate monitor in horses (Equus caballus) during groundwork

Measuring physiological parameters of stress in horses during groundwork, for example when involved in equine-assisted interventions, is important to gain insight into the stress levels of the horses. Heart rate and heart rate variability can be used as physiological indicators of stress in horses. Heart rate monitors could be easily incorporated into practice, as they are not expensive and easy to use. However, it is questionable whether heart rate monitors present accurate heart rate variability results in exercising horses, similar to electrocardiograms. The aim of this study was to determine the accuracy of heart rate monitors for the assessment of heart rate variability in horses during groundwork exercise. Simultaneous telemetric electrocardiograms (Televet) and heart rate monitor (Polar H10 transmitter and M430 receiver, Hylofit electrodes) recordings were performed on 28 horses (15 mares and 13 geldings). Results indicate that the heart rate monitor accurately determined heart rate and time-domain heart rate variability parameters when compared to electrocardiograms during both baseline and groundwork conditions. As expected, heart rate significantly increased and the heart rate variability significantly decreased during groundwork compared to baseline conditions. This indicates that the heart rate monitor can be used to accurately determine heart rate variability during groundwork.

A life-threatening arrhythmia detection method based on pulse rate variability analysis and decision tree

Extreme bradycardia (EB), extreme tachycardia (ET), ventricular tachycardia (VT), and ventricular flutter (VF) are the four types of life-threatening arrhythmias, which are symptoms of cardiovascular diseases. Therefore, in this study, a method of life-threatening arrhythmia recognition is proposed based on pulse rate variability (PRV). First, noise and interference are wiped out from the arterial blood pressure (ABP), and the PRV signal is extracted. Then, 19 features are extracted from the PRV signal, and 15 features with highly important and significant variation were selected by random forest (RF). Finally, the back-propagation neural network (BPNN), extreme learning machine (ELM), and decision tree (DT) are used to build, train, and test classifiers to detect life-threatening arrhythmias. The experimental data are obtained from the MIMIC/Fantasia and the 2015 Physiology Net/CinC Challenge databases. The experimental results show that the DT classifier has the best average performance with accuracy and kappa coefficient (kappa) of 98.76 ± 0.08% and 97.59 ± 0.15%, which are higher than those of the BPNN (accuracy = 94.85 ± 1.33% and kappa = 89.95 ± 2.62%) and ELM (accuracy = 95.05 ± 0.14% and kappa = 90.28 ± 0.28%) classifiers. The proposed method shows better performance in identifying four life-threatening arrhythmias compared to existing methods and has potential to be used for home monitoring of patients with life-threatening arrhythmias.

Risk Factors for Exercise-Associated Sudden Cardiac Death in Thoroughbred Racehorses

Cardiac arrhythmias resulting in sudden cardiac death (SCD) are an important cause of racehorse fatalities. The objective of this study was to determine risk factors for SCD in Thoroughbreds by evaluating a sample with a policy of mandatory post-mortem following racing or training fatalities. Risk factors were compared between case horses with SCD (n = 57) and control horses with other fatal injury (OFI, n = 188) by univariable and multivariable logistic regression. Survival in years for horses with SCD was compared to OFI using the Kaplan−Meier method with log rank test. The following variables were most important in the multiple logistic model: Horses with SCD were more likely to die during training than during racing, SCD (42/57, 74%) vs. OFI (82/188, 44%; odds ratio [OR], 95% confidence interval [CI], 2.5, 1.2−5.4; p = 0.01), had fewer lifetime starts, median (interquartile range [IQR]), SCD (3.0 [0.0−9.0]) vs. OFI (9.0 [0.0−22.8]; OR, 95% CI, 0.96, 0.9−1.0; p = 0.02 and were less likely to be entire (uncastrated) males, SCD 9/57 (16%) vs. OFI (46/188, 25%; OR, 95% CI, 0.47, 0.1−0.9; p = 0.03). Survival in years (median (IQR)) for horses with SCD was 3.6 (3.1−4.4), which was shorter than OFI (4.5 [3.1−6.0], hazard ratio, 95%CI, 1.6,1.2−2.3; p < 0.001). SCD occurs more commonly in training than racing, which suggests exercise intensity is less important in precipitating this fatality. In this study, SCD occurred early in the careers of affected horses.

Golden Standard or Obsolete Method? Review of ECG Applications in Clinical and Experimental Context

Cardiovascular system and its functions under both physiological and pathophysiological conditions have been studied for centuries. One of the most important steps in the cardiovascular research was the possibility to record cardiac electrical activity. Since then, numerous modifications and improvements have been introduced; however, an electrocardiogram still represents a golden standard in this field. This paper overviews possibilities of ECG recordings in research and clinical practice, deals with advantages and disadvantages of various approaches, and summarizes possibilities of advanced data analysis. Special emphasis is given to state-of-the-art deep learning techniques intensely expanded in a wide range of clinical applications and offering promising prospects in experimental branches. Since, according to the World Health Organization, cardiovascular diseases are the main cause of death worldwide, studying electrical activity of the heart is still of high importance for both experimental and clinical cardiology.

Inflammatory Response and Electrocardiographic Examination in Horses Vaccinated against Equine Herpesvirus (Ehv-1)

Simple Summary

Equine herpesvirus 1 (EHV-1) is an alphaherpesvirus that infects horses, causing respiratory, neurologic, and abortion syndromes in pregnant mares. Vaccination induces an immune response that reduces the risk of infection, the severity of clinical signs, and viral excretion. This study aimed to evaluate and describe the clinical and electrocardiographic findings, and changes in cardiac troponin I (cTnI) and inflammatory biomarkers (serum amyloid A (SAA) and C-reactive protein (CRP)) occurring after vaccination against herpesvirus in healthy horses.

Abstract

This study aimed to evaluate possible abnormalities in electrocardiographic findings, and changes in cardiac troponin I (cTnI) and inflammatory biomarkers (serum amyloid A (SAA) and C-reactive protein (CRP)) after inactivated herpesvirus vaccine administration. Eighteen healthy horses were included. All animals were vaccinated with Pneumoequine^® (Merial, France) according to the protocol provided by the manufacturer. They were evaluated 1 day before the first dose of vaccination (D0), and 7 days (D1) and 14 days (D2) afterwards. At D0, D1, and D2, a blood sample was taken for the evaluation of SAA, cTnI, and CRP. An electrocardiographic examination was also performed. The data obtained suggested the possible involvement of the myocardium following vaccination against herpesvirus 1, mostly related to an inflammatory response.