The effect of electro-acupuncture stimulation on rhythm of autonomic nervous system in dogs

Effects of electro-acupuncture (EA) stimulation on the rhythm of the autonomic nervous system in dogs were studied. Six healthy beagles were used in this study. Each dog was separately kept in a cage, and repeatedly exposed to light for 12 hr and dark for 12 hr alternately. Fixed subject dogs were stimulated by use of 5-V, 250-musec, 2-Hz biphasic square pulses for 15 min at the Xuan Shu (GV-5) and Bai Hui (GV-20) points on the spine. After EA stimulation, electrocardiogram was recorded for 24 hr. From the electrocardiogram data, the heart rate (HR), coefficient of variation in the R-R intervals (CVRR; index of autonomic nervous activity), power of high frequency component (HF; index of vagal nervous activity), and ratio of powers of the low and high frequency components (LF/HF; index of sympathetic nervous activity) were obtained. Cosinor analysis demonstrated that these indices exhibited a significant rhythmicity (P<0.05), irrespective of EA stimulation. In LF/HF, EA stimulation advanced the acrophase (from 22:55 to 21:33, P=0.012), and elevated the midline-estimating statistic of rhythm (from 0.653 to 0.725, P=0.006). However, there was no significant difference in HR, CVRR, or HF. In conclusion, EA stimulation markedly influenced the rhythm of sympathetic nervous system in dogs.     

Changes in heart rate and heart rate variability in Thoroughbreds during prolonged road transportation

OBJECTIVE: To determine whether evaluation of heart rate (HR) and HR variability (HRV) during prolonged road transportation in horses provides a sensitive index of autonomic stimulation. ANIMALS: Five 2-year-old Thoroughbreds. PROCEDURE: ECGs were recorded as horses were transported for 21 hours in a 9-horse van. Heart rate, high-frequency (HF) power, low-frequency (LF) power, and LF-to-HF ratio from Fourier spectral analyses of ECGs were calculated and compared with values recorded during a 24-hour period of stall rest preceding transportation. RESULTS: HR, HF power, and LF power had diurnal rhythms during stall rest but not during road transportation. Heart rate was higher and HF power and LF power lower during road transportation than stall rest, and HR, HF power, LF power, and LF-to-HF ratio all decreased with time during road transportation. Heart rate during stall rest was weakly and inversely associated with LF power, but during road transportation was strongly associated with LF power, HF power, and LF-to-HF ratio. Neither LF power nor HF power was correlated with LF-to-HF ratio during stall rest, but LF power was strongly and HF power weakly correlated with LF-to-HF ratio during road transportation. High-frequency power and LF power were significantly correlated with each other during stall rest and road transportation. Heart rate was significantly influenced by LF power and LF-to-HF ratio during stall rest (R(2) = 0.40) and by HF power and LF-to-HF ratio during road transportation (R(2) = 0.86). CONCLUSIONS AND CLINICAL RELEVANCE: HR is influenced by different sympathovagal mechanisms during stall rest, compared with during road transportation; HRV may be a sensitive indicator of stress in transported horses.     

The evaluation of autonomic nervous system activation during learning in rhesus macaques with the analysis of the heart rate variability

The aims of this study were to measure the activity of the autonomic nervous system using heart rate variability (HRV) during learning tasks and to clarify the relationship between learning to overcome a difficult situation and the autonomic nervous system in monkeys. Two young male monkeys (Macaca mulatta) were given simple discrimination learning tasks (DL) and delayed matching to samples tasks (DMTS); Holter-type electrocardiography was done, and HRV was measured. We defined the frequency bands of HRV in rhesus macaques; the low frequency (LF) was 0.01-0.15 Hz, and the high frequency (HF) was 0.15-0.50 Hz. Based on these frequency bands, the LF/HF ratios during learning tasks were analyzed, and a significant increase in the ratio was found during the tasks. The variances in the HF differed between the DL and DMTS tasks; during DMTS tasks, HF variances had a tendency to increase. Our results indicate that increased sympathetic activity accompanied learning and suggest that the parasympathetic nervous system plays a key role during learning, particularly when difficult tasks are being learned.     

Physiological effects of interactions between female dog owners with neuroticism and their dogs

The aim of this study was to investigate the physiological effects of the relationship between dog owners with neuroticism and their dogs using noninvasive procedures to measure urinary cortisol and heart rate variability (HRV). Owner personalities were tested via the NEO Five-Factor Inventory and this study focused only on the dimension of neuroticism with 12-item scales. The 24 participating owners and their dogs were randomly divided into experimental and control groups. Each participant and their dog stayed in the test room for 80 minutes. The behavioral test included 2 resting times (R1 and R2, respectively), 2 command-communication times, a separation time, and a free time. In the control group, the command-communication times were changed to noncommunication times. Each participant wore a chest heart rate transmitter and a wrist watch monitor (RS800CX; Polar Electro) during the experiment. HRV is a quantitative parameter of autonomic activity. The spectral analysis of HRV is divided into 2 major oscillatory components: the high-frequency (HF) domain, which reflects parasympathetic activity and the low-frequency (LF) domain, which reflects both sympathetic and parasympathetic activities. The LF to HF ratio reflects sympathetic activity. In the experimental group, the neuroticism scores showed a positive significant correlation with a change in the HF power and a negative correlation with the ratio of the change in the LF to HF ratio. No correlations were found in the control group. Next, all participants were divided into 2 groups according to the HRV in R1 and R2. One group included participants whose HF increased in R2, and the other included participants whose HF decreased in R2. The neuroticism scores were significantly higher in the experimental subjects whose HF increased in R2 than in those whose HF decreased in R2. High neuroticism scores indicate individuals that may be sensitive to daily stresses. Our results showed that a parasympathetic activation occurred in owners with high neuroticism scores 10 minutes after a command-communication interaction with their dogs. This suggests that daily command communication–based interactions with their dogs could improve the owner's health for the better.     

Spectral analysis of heart rate variability in dogs with mild mitral regurgitation

OBJECTIVE: To assess autonomic function in dogs with mild mitral regurgitation (MR) that did not have clinical signs of the condition. ANIMALS: 6 healthy adult Beagles. PROCEDURE: Mild MR was experimentally induced. A 24-hour ambulatory ECG was recorded before and after induction of MR. Heart rate variability was analyzed in frequency domains by use of the ambulatory ECG. Low-frequency (LF) and high-frequency (HF) power were calculated by integrating over their frequency intervals, and the ratio of LF to HF was also calculated. Measurements of frequency domains were analyzed for 4 time periods (midnight to 6 AM, 6 AM to noon, noon to 6 PM, and 6 PM to midnight). RESULTS: Dogs with experimentally induced MR were classified as International Small Animal Cardiac Health Council class Ia. The HF power of dogs with MR was significantly decreased between 6 AM and noon. The ratio of LF to HF in dogs with MR was significantly increased for the periods between midnight and 6 AM, 6 AM and noon, and noon and 6 PM. CONCLUSIONS AND CLINICAL RELEVANCE: Compensatory response through autonomic modulation was observed in dogs with mild MR that did not have abnormalities, except for cardiac murmur, during clinical examination. This result suggests that treatment during the early stages of mild MR may be beneficial. Additional studies are necessary to determine whether such treatment will delay the onset of congestive heart failure and prolong survival in dogs affected with mild MR.     

Effects of initial handling and training on autonomic nervous function in young Thoroughbreds

OBJECTIVE: To determine the effects of initial handling and training on autonomic nervous functions in young Thoroughbreds. ANIMALS: 63 healthy Thoroughbreds. PROCEDURE: All horses were trained to be handled and initially ridden in September of the yearling year and then trained until the following April by conventional training regimens. To obtain the heart rate (HR), electrocardiograms were recorded in the stable before initial handling and training and following 7 months of training; variations in HR were then evaluated from the power spectrum in terms of the low frequency (LF; 0.01 to 0.07 Hz) power and high frequency (HF; 0.07 to 0.6 Hz) power as indices of autonomic nervous activity. To evaluate the fitness, the V200 (velocity at HR of 200 beat/min), which is reflective of the aerobic capacity of the horse, was measured. RESULTS: Mean (+/- SE) resting HR decreased significantly from 41.5 +/- 0.8 to 38.7 +/- 0.4 beat/min following 7 months of training. The LF power of horses increased significantly from 1,037 +/- 128 milliseconds2 in September of the yearling year to 2,944 +/- 223 milliseconds2 in the following April. Similarly, the HF power increased significantly from 326 +/- 30 milliseconds2 to 576 +/- 39 milliseconds2 at the corresponding time points. The V200 increased significantly following training. CONCLUSIONS AND CLINICAL RELEVANCE: Increases in LF and HF powers indicate that parasympathetic nervous activity increases in horses by 7 months of training. The decrease in resting HR may be dependent on the training-induced increase of parasympathetic nervous activity in Thoroughbreds.     

The influence of spasmolytic agents on heart rate variability and gastrointestinal motility in normal horses

The effects of hyoscine-N-butylbromide (hyoscine) and propantheline-bromide (propantheline) on heart rate (HR), HR variability (HRV) and gastrointestinal tract (GIT) contractions in the normal horse were determined. Five adult horses had ECG recordings for 180min after treatment with propantheline (100mg), hyoscine (120mg) or saline. Both propantheline and hyoscine reduced GIT sounds, with propantheline having a longer duration of effect (?120min). Both drugs elevated HR relative to the control baseline period (P<0.05), with the effects of propantheline again being of longer duration. HRV analysis indicated that propantheline suppressed Total Power (P<0.05), and both the high frequency (HF) and low frequency (LF) components of the power spectral analysis for up to 60-90min post treatment. Hyoscine had no effect on HRV Total Power but reduced the HF component for 30min after drug injection. Time domain variables correlated with Total Power and HF data (P<0.01). The marked effect of these compounds on parasympathetic control of cardiac and GIT function in normal horses should be taken into consideration when evaluating a clinical response to these agents.     

Does Acupuncture Acutely Affect Heart Rate Variability in Horses?

One of the mechanisms by which acupuncture (AP) exerts its purported effects involves modulation of the autonomic nervous system. Heart rate variability (HRV) noninvasively and quantitatively assesses autonomic nervous system activity. We hypothesized that AP treatment would acutely affect HRV by affecting autonomic tone. Eleven horses received three treatments in random order on different days: AP, placement of AP needles at eight AP points; sham AP (SAP), placement of eight AP needles at non-AP points; and control, no needles inserted. A Holter monitor recorded an electrocardiogram for 40 minutes during each treatment session and was analyzed over three periods: 10 minutes of initial “baseline” before AP and/or SAP, the first 10 minutes of a 20-minute AP/SAP/control “treatment”, and the first 10 minutes “post”-AP/SAP/control. RR intervals were measured during each period after the electrocardiograms were inspected and filtered, and mean heart rate (HR), low-frequency (LF) power (0.01–0.07 Hz), high-frequency (HF) power (0.07–0.6 Hz), and LF-to-HF ratio were calculated for each period. Baseline HR decreased with sequential experiments. Within experiments, HF decreased and LF-to-HF ratio increased reciprocally with time. These results suggest that parasympathetic tone decreased over the course of the experiment, perhaps, because of the stress of being restrained. Consequently, HRV indices were either not acutely affected by AP over the intervals studied or autonomic responses to being restrained may have masked any autonomic response to AP.     

Heart rate variability in Doberman Pinschers with and without echocardiographic evidence of dilated cardiomyopathy

OBJECTIVE: To characterize the salient variables of the time-domain analysis of heart rate variability (HRV) in clinically normal Doberman Pinschers and to compare those variables with those of Doberman Pinschers with cardiomyopathy and mild to moderate myocardial failure. ANIMALS: 46 Doberman Pinschers. PROCEDURE: HRV was analyzed in the time-domain from 24-hour Holter recordings obtained from 28 Doberman Pinschers with normal echocardiograms and 18 Doberman Pinschers with echocardiograms consistent with mild to moderate myocardial failure. RESULTS: Significant differences in HRV variables between the 2 groups of dogs were not detected. The HRV was greater during the nighttime (12 AM to 6 AM), compared with the 24-hour day and an 18-hour (6 AM to 12 AM) period. CONCLUSIONS AND CLINICAL RELEVANCE: HRV of dogs with mild to moderate myocardial failure was not different from that of clinically normal dogs, because there were no disturbances of autonomic balance, baroreceptor function, and other factors that influence HRV in the dogs with cardiomyopathy, or the sensitivity of time-domain analysis was overwhelmed by normal sinus arrhythmia. The techniques now used to study HRV have important limitations, especially in dogs, and better noninvasive tests of autonomic function are needed.     

Correlations among time and frequency measures of heart rate variability recorded by use of a Holter monitor in overtly healthy Doberman pinschers with and without echocardiographic evidence of dilated cardiomyopathy.

OBJECTIVE: To determine correlations between time-domain and frequency-domain variables of heart rate variability (HRV) derived from 24-hour recordings obtained by use of an ambulatory electrocardiographic recorder (Holter monitor). ANIMALS: 59 overtly healthy Doberman Pinschers (41 without echocardiographic evidence of cardiomyopathy and 18 with precongestive heart failure attributable to cardiomyopathy). PROCEDURE: The HRV was analyzed from 24-hour recordings. Variables were calculated from the entire 24-hour recording as well as 4 user-selected time epochs. Comparisons were made for total power to SD of normal beat-to-normal-beat (NN) intervals (SDNN), ultra-low frequency power to SD of the means of NN intervals, low-frequency power and very-low-frequency power to mean of the SD of NN intervals, and high-frequency (HF) power to the root mean square successive difference of NN intervals (RMSSD) and percentage of NN intervals that varied from the previous NN interval by > 50 milliseconds (PNN50). RESULTS: 58 of 66 (88%) comparisons revealed significant values, indicating that relationships between variables were not random (r > 0.7 in 41 of 66 [62%)) comparisons). Strong correlations (r > 0.8) were found between the square root of total power and SDNN and between HF power and RMSSD. CONCLUSIONS AND CLINICAL RELEVANCE: Time-domain surrogates for variables of frequency-domain analysis variables that correlated in the dogs reported here are the same ones that reportedly correlate in humans. When 24-hour recordings obtained by use of a Holter monitor are used to calculate HRV, SDNN and total power as well as RMSSD and HF power are interchangeable.     

Effects of repeated atropine injection on heart rate variability in Thoroughbred horses.

To investigate the effects of repeated atropine injection on heart rate (HR) variability in resting Thoroughbred horses, two microg/ kg of atropine as parasympathetic nervous blockade was injected intravenously every 6 min to a total of 8 microg/kg after intravenous administration of 0.2 mg/kg of propranolol as sympathetic nervous blockade. We recorded electrocardiograms and obtained the HR, then evaluated variation in HR from the power spectrum in terms of low frequency (LF, 0.01-0.07 Hz) power and high frequency (HF, 0.07-0.6 Hz) power. Administration of atropine decreased parasympathetic nervous activity in a dose-dependent manner, affecting first the LF power, then the HF power and finally HR. These responses may provide valuable information for evaluating autonomic nervous activity in Thoroughbred horses.     

The beneficial effects of horse trekking on autonomic nervous activity in experienced rider with no disability

The aim of this study was to determine whether autonomic nervous activity of a rider with no disability was altered by one practical and applicable horse trekking (HT) exercise. Changes in autonomic nervous activity were analyzed by heart rate variability (HRV). Twenty‐three participants with no disability rode horses along a predetermined HT course at trotting and walking for 60 min. HRV was sampled at 60 min before and immediately, following 60 min, and 120 min after HT. As a control, the same measurements were performed for 22 age‐matched participants during their rest. Only in the HT group, the value of normalized unit in high frequency component (HF nu), an index of parasympathetic nervous activity, was higher at 120 min after treatment than before HT (P < 0.05). The low / high frequency ratio (LF / HF), believed to reflect sympathetic nervous activity, was lower in the HT group than those in the control group at 60 min (P < 0.05) and 120 min after treatment (P < 0.01). These findings suggest that a single HT shifted the autonomic nervous balance of a rider toward parasympathetic dominance. The results obtained by the present study could accelerate the use of horses for human health.     

不同妊娠状态伊犁马心率变异性变化规律研究

【目的】研究流产伊犁马与正常分娩伊犁马在妊娠期心率变异性(HRV)的变化规律,以防止不良妊娠结局的发生。【方法】选取妊娠时间为29孕周的伊犁马21匹(其中流产5匹,正常分娩16匹)及7匹空怀伊犁马,分别在妊娠中期第30孕周,妊娠后期第45孕周及分娩前后1天对母马进行24 h HRV采集,包括时域指标:全部R-R间期的平均值(Mean RR)、全部R-R间距的标准差(SDNN)、平均心率(Mean HR)、相邻R-R间期差值的均方根(RMSSD)、相邻R-R间距差＞50 ms的个数(NN50)和相邻R-R-间距差＞50 ms的个数占总心跳次数的百分比(pNN50);频域指标:极低频率(VLF)、低频功率(LF)和高频功率(HF);非线性指标:全部R-R间距的标准差(Y)(SD1)、全部R-R间距的标准差(X)(SD2)。【结果】时域指标中,流产组和正常分娩组Mean RR、SDNN、RMSSD、NN50、pNN50极显著或显著低于空怀组(P＜0.01;P＜0.05),Mean HR极显著高于流产组和正常分娩组(P＜0.01);频域指标中,流产组和正常分娩组HF、LF极显著低于空怀组(P＜0.01),流产组和空怀组母马VLF极显著高于正常分娩组(P＜0.01)。非线性指标中,流产组和正常分娩组SD1和SD2极显著或显著低于空怀组(P＜0.01;P＜0.05),正常分娩组母马SD2/SD1极显著高于流产组和空怀组(P＜0.01)。【结论】伊犁马心率变异性在不同妊娠状态下均呈波动变化,Mean HR、Mean RR、SD2/SD1值在妊娠母马中出现上升,母马在妊娠过程中副交感神经占主导,自主神经系统受到抑制,流产母马VLF指标出现升高,在流产发生前后交感神经占主导,自主神经系统产生兴奋。     

Decreased sympathetic tone after short-term treatment with enalapril in dogs with mild chronic mitral valve disease

Heart rate variability (HRV) and echocardiography were performed in 14 dogs with mitral regurgitation (MR) before and after 14 days of 0.5 mg/kg/day of enalapril treatment. All dogs were in heart failure stages B1 and B2. After enalapril treatment, left ventricular end diastolic diameter (LVEDd), left ventricular end diastolic diameter normalized for body weight (LVEDdN) and percent mitral regurgitant jet decreased (P < 0.05). The diastolic blood pressure decreased (P < 0.05). Increased time domain parameters of HRV were found. For frequency domain analysis, the total frequency (TF) increased significantly (P < 0.05). The normalized low frequency (LF norm) decreased while normalized high frequency (HF norm) increased causing significant reduction in LF/HF (P < 0.05). Before enalapril treatment, LF was correlated with end diastolic volume (EDV) (P < 0.01) and LVEDd (P < 0.05). In conclusion, MR dogs receiving enalapril treatment for 14 days had increased cardiac parasympathetic tone while sympathetic tone was suppressed. The decreased sympathetic activity corresponded to the reduction in cardiac preload and afterload.     

Changes in heart rate variability in horses during immersion in warm springwater

OBJECTIVE: To determine the effects of immersion in warm springwater (38 degrees to 40 degrees C) on autonomic nervous activity in horses. ANIMALS: 10 male Thoroughbreds. PROCEDURE: Electrocardiograms were recorded from horses for 15 minutes during a warm springwater bath after being recorded for 15 minutes during stall rest. Variations in heart rate (HR) were evaluated from the power spectrum in terms of low frequency (LF, 0.01 to 0.07 Hz) power and high frequency (HF, 0.07 to 0.6 Hz) power as indices of autonomic nervous activity. RESULTS: Mean (+/- SE) HR during stall rest and immersion in warm springwater was 31.1 +/- 1.7 and 30.3 +/- 1.0 beat/min, respectively. No significant difference was found between the HR recorded during stall rest and that recorded during immersion in warm springwater. The HF power significantly increased from 1,361 +/- 466 milliseconds2 during stall rest to 2,344 +/- 720 milliseconds2 during immersion in warm springwater. The LF power during stall rest and immersion in warm springwater was 3,847 +/- 663 and 5,120 +/- 1,094 milliseconds2, respectively, and were not significantly different from each other. Similarly, the LF:HF ratio did not change during immersion in warm springwater. The frequency of second-degree atrioventricular block, which was observed in 2 horses, increased during immersion in warm springwater, compared with during stall rest. CONCLUSIONS AND CLINICAL RELEVANCE: Increases in HF power indicates that the parasympathetic nervous activity in horses increases during immersion in warm springwater. Thus, immersion in warm springwater may provide a means of relaxation for horses.     

The effect of autonomic manipulation on heart rate variability in dogs

Beat‐to‐beat variation of heart rate is reflective of autonomic balance and has been used to assess pain and stress in human beings. The purpose of this investigation was to pharmacologically manipulate the autonomic nervous system and to determine the effect of these manipulations on heart rate variability (HRV) in dogs. Four adult male hound dogs (27 ± 1 kg) were used in the investigation. Each dog was given five treatments: Parasympathetic blockade (glycopyrrolate; 0.01 mg kg^–1 IV and 0.01 mg kg^–1 IM), parasympathetic stimulation (phenylephrine; 0.005 mg kg^–1 IV + 0.05 mg kg^–1hour^–1), sympathetic blockade (propranolol; 0.11 mg kg^–1 IV), sympathetic stimulation propranolol; 0.01 μg kg^–1 minute^–1), and saline control. At least 48 hours were allowed between treatments. ECG recordings were obtained using an ambulatory ECG monitor. A 5‐minutes period of continuous recording obtained ~30 minutes after initiation of drug administration was used for data analysis. Changes in HRV were evaluated by time and frequency‐domain analysis. The standard deviation of normal R‐R intervals (SDNN), as well as the standard deviation of successive differences in RR intervals (SDSD) were assessed for each treatment. Low frequency (LFP; 0.05–0.15 Hz), high frequency (HFP; 0.15–0.35 Hz), and total (TP; 0.017–0.5 Hz) spectral power were also determined. The LFP:HFP ratio was also evaluated. A two‐way anova with a Tukey's test was used to detect differences (p < 0.05). Administration of glycopyrrolate or isoproterenol increased HR and decreased SDNN and SDSD below control levels. Phenylephrine or propranolol administration were without effect. LFP was diminished by glycopyrrolate and isoproterenol, but was unaffected by phenylephrine and propranolol. HFP, TP, and LFP:HFP were unaffected by treatment. Both branches of the autonomic nervous system influence SDNN and LFP. SDSD, in contrast, is altered primarily by parasympathetic activity. Thus, it appears that parasympathetic activity modulates HRV in the resting dog, as either withdrawal of parasympathetic influence or accentuated sympathetic activity led to significant changes in these measures of HRV. Conversely, augmentation of parasympathetic activity or withdrawal of sympathetic tone minimally affected HRV.     

Frequency domain analysis of heart rate variability in horses at rest and during exercise

The pattern of variation in heart rate on a beat-to-beat basis contains information concerning sympathetic (SNS) and parasympathetic (PNS) contributions to autonomic nervous system (ANS) modulation of heart rate (HR). In the present study, heart period (RR interval) time series data were collected at rest and during 3 different treadmill exercise protocols from 6 Thoroughbred horses. Frequency and spectral power were determined in 3 frequency bands: very low (VLF) 0-< or = 0.01, low (LO) >0.01-< or = 0.07 and high (HI) >0.07-< or = 0.5 cycles/beat. Indicators of sympathetic (SNSI = LO/HI) and parasympathetic (PNSI = HI/TOTAL) activity were calculated. Power in all bands fell progressively with increasing exercise intensity from rest to trot. At the gallop VLF and LO power continued to fall but HI power rose. SNSI rose from rest to walk, then fell with increasing effort and was lowest at the gallop. PNSI fell from rest to walk, then rose and was highest at the gallop. Normalised HI power exceeded combined VLF and LO power at all gaits, with the ratio HI to LO power being lowest at the walk and highest at the gallop. ANS indicators showed considerable inter-horse variation, and varied less consistently than raw power with increasing physical effort. In the horses studied, the relationship between power and HR changed at exercise intensities associated with heart rates above approximately 120-130 beats/min. At this level, humoral and other non-neural mechanisms may become more important than autonomic modulation in influencing heart rate and heart rate variability (HRV). HRV at intense effort may be influenced by respiratory-gait entrainment, energetics of locomotion and work of breathing. HRV analysis in the frequency domain would appear to be of potential value as a noninvasive means of assessing autonomic modulation of heart rate at low exercise intensities, only. The technique may be a sensitive method for assessing exercise response to experimental manipulations and disease states.     

Evaluation of stability over time for measures of heart-rate variability in overtly healthy Doberman Pinschers

OBJECTIVE: To determine whether results of analysis of heart-rate variability (HRV) in overtly healthy Doberman Pinschers remain stable over time. ANIMALS: 24 overtly healthy client-owned Doberman Pinschers. PROCEDURE: The HRV was analyzed in time- and frequency-domains from 24-hour ambulatory electrocardiographic (Holter) monitor recordings. Activity during paired tests (tests 1 and 2) was similar (17 dogs) or nearly identical (7). Holter recordings and HRV analyses of those 17 dogs were repeated at a mean +/- SD of 65 +/- 50 weeks (median, 51 weeks; range, 10 to 177 weeks), whereas it was repeated for the other 7 dogs at 3 to 9 weeks (mean, 73 +/- 2.1 weeks). RESULTS: Differences between test 1 and test 2 were not significantly different, except for 24-hour means of the normal beat-to-normal beat (NN) intervals in all 5-minute segments. Strongest correlations were for SD of all NN intervals and root mean square successive difference between adjacent NN intervals of the time-domain analyses and total power, very-low frequency power, and high-frequency power of the frequency-domain analyses. When activity during tests 1 and 2 in 7 dogs was stringently controlled, the differences were not significantly different, and correlation factors for the 24-hour HRV analyses exceeded 0.83. CONCLUSIONS AND CLINICAL RELEVANCE: Variables from sequential HRV analyses in overtly healthy Doberman Pinschers with normal echocardiograms are moderately stable when physical activity is not stringently controlled and extremely stable for at least 3 to 9 weeks when physical activity is stringently controlled.     

The association between heart rate, heart rate variability, endocrine and behavioural pain measures in horses suffering from laminitis

The objective of this study was to compare the stress response of horses suffering from laminitis after short- and long-term treatment with the intent to evaluate power spectral analysis of heart rate variability (HRV) for pain monitoring. Data were collected from 19 horses with acute or chronic exacerbating laminitis without known primary disease before and after treatment with non-steroidal anti-inflammatory drugs (NSAID). Recordings were carried out the day after admission to the equine hospital. Measurements were repeated on day 7 of the treatment. The recorded parameters included a clinical orthopaedic index (OLPI: Obel-grade plus hoof tester score), frequency of weight-shifting between contralateral limbs, mean beat-to-beat interval (R-R) duration, standard deviation of continuous R-R intervals, low- (LF) and high-frequency (HF) components of HRV, sympatho-vagal balance (LF/HF), and plasma concentration of cortisol, adrenalin and noradrenalin. The LF represents mainly sympathetic influences on the heart whereas HF is mediated by the parasympathetic tone. Weight-shifting and OLPI decreased significantly with treatment. The LF normalized units (n.u.) decreased after NSAID from 60.41 +/- 21.42 to 51.12 +/- 19.81 and was 49.33 +/- 22.64 on day 7, whereas HF n.u. increased from 35.07 +/- 20.02 to 43.14 +/- 18.30 and was 45.98 +/- 23.00 on day 7. Hormone levels showed no tendency to change with treatment. The OLPI was only correlated with LF/HF, LF and HF (R = 0.57, 0.55 and -0.54 respectively). Significant negative correlations existed between HFn.u. and weight-shifting frequency (R = -0.37), HFn.u. and adrenalin (R = -0.47), and HFn.u. and noradrenalin (R = 0.33). The LFn.u. only correlated positively with adrenalin. Cortisol levels were poorly associated with the other parameters. Determination of the sympatho-vagal influences on cardiac function may offer complementary information for reliable assessment of pain and may represent a valuable alternative method to catecholamine measurements.     

The influence of spasmolytic agents on heart rate variability and gastrointestinal motility in normal horses

The effects of hyoscine-N-butylbromide (hyoscine) and propantheline-bromide (propantheline) on heart rate (HR), HR variability (HRV) and gastrointestinal tract (GIT) contractions in the normal horse were determined. Five adult horses had ECG recordings for 180 min after treatment with propantheline (100 mg), hyoscine (120 mg) or saline. Both propantheline and hyoscine reduced GIT sounds, with propantheline having a longer duration of effect (⩾120 min). Both drugs elevated HR relative to the control baseline period (P < 0.05), with the effects of propantheline again being of longer duration. HRV analysis indicated that propantheline suppressed Total Power (P < 0.05), and both the high frequency (HF) and low frequency (LF) components of the power spectral analysis for up to 60–90 min post treatment. Hyoscine had no effect on HRV Total Power but reduced the HF component for 30 min after drug injection. Time domain variables correlated with Total Power and HF data (P < 0.01). The marked effect of these compounds on parasympathetic control of cardiac and GIT function in normal horses should be taken into consideration when evaluating a clinical response to these agents.