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.     

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。     

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.     

The Effect of Training on Yili Horse 1 600 m Test Results and Heart Rate Variability

【Objective】 The objective of this study was to analyze the effect of different training stages on the performance and heart rate variability(HRV) of Yili horses and to provide data for reference in the conditioning training of 1 600 m distance Yili horses.【Method】 Eight 3-year-old Yili horses (stallions) were selected as test subjects.A 3-month speed specific performance training program was conducted, and a speed test race was organized in the last week of each month of training, and HRV was collected before, immediately after, 0.5 h after, and 1 h after 1 600 m test race.Among them, the time-domain indexes included the mean of all R-R intervals (Mean RR), the standard deviation of all R-R intervals (SDNN), the mean heart rate (Mean HR), the root mean square of the difference between adjacent R-R intervals (RMSSD), the number of adjacent R-R intervals with a difference greater than 50 ms (NN50), and the percentage of adjacent R-R intervals with a difference greater than 50 ms to the total number of heartbeats (pNN50).Frequency domain metrics included very low frequency (VLF), low frequency power (LF), high frequency power (HF) and nonlinear metrics:standard deviation (Y) of all R-R-spacing (SD1), standard deviation (X) of all R-R-spacing (SD2).Consequently, the variability of HRV indexes in horses at different training stages was analyzed.【Result】 The race time in the post training period in 1 600 m speed test race of Yili horses was significantly lower than that in the early training period (P<0.05), and Mean RR, NN50 and pNN50 in the middle and post training periods were significantly lower than that in the early training period (P<0.05).Mean HR in the beginning of training was significantly lower than that in post training (P<0.05).VLF and LF in the end of training were significantly lower than that in the beginning of training (P<0.05).【Conclusion】 Under the conditions of this test, the HRV indexes of 1 600 m test race of Yili horses in different conditioning training stages were analyzed.The outcomes demonstrated that the types of neural activity in Yili horses at the beginning, middle and end of training presented some differences, showing changes of increased sympathetic excitability and decreased parasympathetic excitability, and the horses' athletic performance improved.Therefore, HRV could be considered as an effective tool to evaluate the training load and intensity of Yili horses during training.     

Electrocardiographic indicators of excitability in horses for predicting recovery quality after general anaesthesia

ObjectiveTo determine whether preoperative electrocardiographic measurements linked to sympathetic nervous activity could be used to predict recovery quality after general anaesthesia in horses.Study designProspective, clinical study.AnimalsEighteen adult client-owned horses.MethodsThe electrocardiogram (ECG) was recorded presurgery in horses under three standard conditions: stabled unattended; with a groom whilst being led along a standard course; alone in the induction box. After surgery, each animal's recovery quality was scored by eight experienced anaesthetists or technicians using Donaldson's scoring system (2000). The digitized ECG recordings were analyzed for T-wave morphology, mean heart rate (HR), HR variability (HRV) and HRV derivatives including mean R-R interval, standard deviation of normal intervals (SDNN) and the root mean square of successive intervals (RMSSD), low (LF) and high frequency (HF) activity and the LF/HF ratio in both fast Fourier transformed and autoregressive spectra. Correlations between ECG variables and recovery score were examined using Spearman's rank correlation.ResultsThere was no significant correlation between preanaesthetic ECG measurements and recovery quality.ConclusionsPredictions of recovery quality after general anaesthesia in horses cannot be based on preanaesthetic ECG variables.Clinical relevanceMeasures other than those based on the ECG should be investigated as predictors of recovery quality.     

Effect of severity of myocardial failure on heart rate variability in Doberman pinschers with and without echocardiographic evidence of dilated cardiomyopathy.

OBJECTIVE: To determine whether heart rate variability (HRV) is reduced in Doberman Pinschers with dilated cardiomyopathy. DESIGN: Case series. ANIMALS: 62 overtly healthy Doberman pinschers. PROCEDURE: Heart rate variability was analyzed in time and frequency domains from data obtained during 24-hour ambulatory electrocardiographic Holter recordings in 41 overtly healthy Doberman pinschers with normal echocardiograms and 21 overtly healthy Doberman pinschers with abnormal echocardiograms. RESULTS: Heart rate variability usually was greater during night versus day, and 2 dogs with the most severe myocardial failure had reduced HRV. CONCLUSIONS AND CLINICAL RELEVANCE: Reduced HRV was detected only in Doberman Pinschers with the most severe myocardial failure. Thus, HRV in less severely affected dogs is not reduced, or the normal sinus arrhythmia of dogs renders HRV relatively insensitive. Analysis of HRV did not provide additional information relative to the severity of left ventricular dysfunction or risk of sudden death from that which could be derived from echocardiography, analysis of Holter recordings, and signal-averaged electrocardiography.     

Association between results of ambulatory electrocardiography and development of cardiomyopathy during long-term follow-up of Doberman pinschers

OBJECTIVE: To characterize ambulatory electrocardiographic results of overtly healthy Doberman Pinschers and determine associations between those results and development of dilated cardiomyopathy. DESIGN: Cohort study. ANIMALS: 114 (58 male, 56 female) overtly healthy Doberman Pinschers without echocardiographic evidence of cardiac disease on initial examination. PROCEDURE: Echocardiograms and 24-hour ambulatory electrocardiograms (Holter recordings) were obtained initially and at variable intervals. The status (live vs dead) of all dogs was known at least 2 years and as long as 10 years after initial examination (mean [+/- SD] follow-up time, 4.33 +/- 1.84 years). Associations between development of dilated cardiomyopathy and number of ventricular premature contractions (VPC), age, and sex were determined. RESULTS: 55 dogs (48%) did not have VPC on initial Holter recordings, and only 8 dogs had > 50 VPC/24 hours. The likelihood that a dog would have VPC was associated with increasing age and being male. At least 1 VPC/24 hours, and in particular, > 50 VPC/24 hours or > or = 1 couplet or triplet of VPC/24 hours, were predictive of subsequent development of dilated cardiomyopathy. Fifty-four dogs (47%) developed dilated cardiomyopathy; 12 were still alive at the end of the study, and 42 had died. Twenty-five of these 42 dogs died after the onset of congestive heart failure (CHF), 15 died suddenly before the onset of overt CHF, and 2 died of noncardiac causes. More males developed dilated cardiomyopathy than females, and dogs that died suddenly were approximately 1 year younger than those that developed CHF. CONCLUSIONS AND CLINICAL RELEVANCE: Results of high-quality Holter recordings may be used to identify overtly healthy Doberman Pinschers that are at a high risk for dilated cardiomyopathy.     

Spectral analysis of circadian rhythms in heart rate variability of dogs

OBJECTIVE: To determine characteristics of power spectral analysis of heart rate variability (HRV) during a 24-hour period in dogs and to evaluate the effects of vagal and sympathetic tone on HRV ANIMALS: 16 healthy adult Beagles. PROCEDURE: Power spectral analysis of HRV was conducted, using 24-hour ambulatory ECG recordings. Circadian rhythms were evaluated in terms of absolute units of low-frequency (LF) and high-frequency (HF) powers, their ratio (LF:HF), and their adjusted (normalized) units (LF[norm] and HF[norm]). Three or 4 dogs were used for simultaneous measurement of heart rate and respiratory waveform as well as to evaluate treatment (propranolol, atropine, or both) administered to cause blockade of the autonomic nervous system. RESULTS: Values for LF and HF powers, LF:HF, LF(norm), and HF(norm) had obvious rhythmicity in clinically normal dogs. The HF power of HRV in dogs was extremely high, compared with that of other species, and HF peaks corresponded to peaks obtained from respiratory waveforms. Blockade of the autonomic nervous system documented that HRV in dogs was mostly attributable to vagal activity. CONCLUSION AND CLINICAL RELEVANCE: We determined characteristics of power spectral analysis of HRV in dogs, including circadian rhythm of the autonomic nervous system. Power spectral analysis of HRV may provide a useful noninvasive technique for assessing the effect of drugs on activity of the autonomic nervous system in dogs.     

Heart rate variability parameters of myxomatous mitral valve disease in dogs with and without heart failure obtained using 24-hour Holter electrocardiography

Time-domain heart rate variability (HRV) parameters and the correlation between echocardiography and Holter examinations in dogs with myxomatous mitral valve disease (MMVD) were determined. Holter examination was also performed at different time frames: an entire 24-hour period, a four-hour period during sleep, and a four-hour period while awake. Ten healthy (control group) and 28 MMVD dogs, 15 with and 13 without heart failure, were evaluated. The SDANN (sd of the mean normal RR intervals for all five-minute segments during 24-hour Holter) and pNN(50) (percentage of differences between adjacent normal RR intervals that are >50 ms computed over 24-hour Holter) variables were significantly lower in the dogs with MMVD heart failure. The differences in HRV between the groups were only detected during the 24-hour evaluation period (P<0.05). There were high correlations (canonical analysis) between Holter and echocardiography examinations when considering pNN(50), SDANN, and LA/AO (left atrial to aortic root ratio) (r=0.92; P<0.05), indicating that both are important in evaluating MMVD dogs. SDANN and pNN(50) are measures of parasympathetic control of the heart, and thus, it is possible to infer that the MMVD dogs exhibit parasympathetic withdrawal during the development of heart failure.     

Results of ambulatory electrocardiography in overtly healthy Doberman Pinschers with echocardiographic abnormalities

OBJECTIVE: To identify, by means of 24-hour ambulatory electrocardiography, electrocardiographic abnormalities in overtly healthy Doberman Pinschers in which results of echocardiography were abnormal. DESIGN: Clinical case series. ANIMALS: 56 (35 male, 21 female) overtly healthy Doberman Pinschers with echocardiographic evidence of cardiomyopathy on initial examination that subsequently died of cardiomyopathy. PROCEDURE: Twenty-four-hour ambulatory electrocardiographic (Holter) recordings obtained at the time of initial examination were reviewed. For all dogs, scan quality was > 90%. RESULTS: Initial Holter recordings of all 56 dogs contained ventricular premature contractions (VPC). Thirty-six (65%) dogs had > 1,000 VPC/24 h, 17 (31%) had > 5,000 VPC/24 h, and 11 (19%) had > 10,000 VPC/24 h. Fifty-four (96%) dogs had couplets of VPC, 37 (66%) had triplets of VPC, and 36 (64%) had episodes of nonsustained (< 30 seconds) ventricular tachycardia. Number of VPC/24 h during the initial Holter recordings was positively correlated with numbers of couplets and triplets of VPC and number of ventricular escape beats and negatively correlated with left ventricular fractional shortening. Twenty-eight dogs died suddenly prior to the putative onset of congestive heart failure. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that along with echocardiography, 24-hour ambulatory electrocardiography can be used to help identify overtly healthy Doberman Pinschers with cardiomyopathy.     

Holter monitoring in clinically healthy Cavalier King Charles Spaniels, Wire-haired Dachshunds, and Cairn Terriers

Background: Few reported studies describe normal values from 24‐hour ECG (Holter) recordings of small breed dogs. Objectives: To investigate influence of breed, age, sex, body weight, degree of recording artifact, and mitral valve prolapse (MVP) on Holter recordings of 3 breeds of small dogs that have differing predispositions for myxomatous mitral valve disease. The study also assessed if heart rate (HR) at clinical examination (HRex) was associated with HR during Holter monitoring and evaluated the reproducibility of Holter variables. Animals: Fifty clinically healthy, privately owned dogs of the breeds Cavalier King Charles Spaniel (CKCS), Wire‐haired Dachshund (wD), or Cairn Terrier (CT). Methods: Prospective, longitudinal observational study. Dogs were recruited for clinical examination, echocardiography, and Holter monitoring. In 8 CKCS, Holter recordings were performed twice with a 7‐day interval. Arrhythmia and heart rate variability (HRV) analysis (time and frequency domain analysis) were performed on Holter recordings. Results: Fifteen out of 27 Holter derived variables were significantly associated with breed (P < .03), but not with age (P > .7), sex (P > .2), body weight (P > .7), degree of recording artifact (P > .4), or MVP (P > .6). During Holter recording, minimum (P= .0001) and mean HR (P= .0001) were higher in CKCS compared with wD. CKCS had significantly lower values than wD, CT, or both in 10 out of 13 HRV variables (P < .03). Minimum and mean HR during Holter recording were correlated with HRex (r= 0.55, P= .0003). HR and time domain variables had a coefficient of variation <10%. Conclusions and Clinical Importance: There is an influence of breed on Holter‐derived variables in 3 breeds of small dogs. Arrhythmia and HRV analysis can be performed on 24‐hour ambulatory ECG (Holter) recordings. Arrhythmia analysis includes HR measurements and identification of arrhythmias.     

Results of ambulatory electrocardiography in overtly healthy Doberman Pinschers with equivocal echocardiographic evidence of dilated cardiomyopathy

OBJECTIVE: To determine results of ambulatory electrocardiography in and outcome of overtly healthy Doberman Pinschers with equivocal echocardiographic evidence of dilated cardiomyopathy. DESIGN: Case series. ANIMALS: 44 overtly healthy (25 male, 19 female) Doberman Pinschers. PROCEDURE: 24-hour ambulatory electrocardiographic (Holter) recordings with > 90% scan quality obtained the same day that echocardiography was performed were reviewed. RESULTS: Holter recordings from 42 of 44 (95%) dogs contained ventricular premature complexes (VPC). Fifteen of 44 (34%) dogs had > 100 VPC, 9 (20%) had > 500 VPC, and 5 (11%) had > 1,000 VPC. Nonsustained (< 30 seconds) ventricular tachycardia was detected in 4 dogs. Eighteen of 27 (67%) dogs with > 100 VPC, any couplets or triplets of VPC, or ventricular tachycardia developed dilated cardiomyopathy within 1 year, compared with 8 of 17 (47%) dogs with < 100 VPC, no couplets or triplets of VPC, and no ventricular tachycardia. Of the 18 dogs that did not develop dilated cardiomyopathy within 1 year, 11 (61%) did so within 3 years. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that a high percentage of Doberman Pinschers with equivocal echocardiographic evidence of dilated cardiomyopathy will be found to have VPC during 24-hour ambulatory electrocardiography and that most will develop echocardiographic abnormalities indicative of cardiomyopathy.     

Behavioral and cardiac responses by dogs to physical human–dog contact

Measures of behavioral responses and cardiovascular parameters to evaluate and assess animal well-being are well established. A major aspect of companion animal well-being seems to originate from direct human–animal interaction. For pet dogs, the manner in which they obtain and respond to petting and hugs could interfere with the development of a pleasant human–dog companionship. Therefore, the purpose of this study was to evaluate cardiovascular responses by dogs to physical human–dog contact and to assess these physiological responses in relation to the dogs' behavioral responses. Noninvasive measurements of privately owned dogs' (N = 28) cardiovascular parameters and behavioral responses were carried out during 9 physical human–dog interactions (e.g., petting the dog on its back, holding a forepaw of the dog). The behavioral responses were grouped in categories, for example, redirected behavior, displacement activity, and appeasement gesture. The mean heart rate (HR) and 2 cardiac activity parameters, standard deviation of normal-to-normal R–R intervals (SDNN) and root mean square of successive heartbeat interval differences/SDNN (RMSSD/SDNN) ratio, differed significantly among the human–dog interactions. Petting and holding the dog around the head was associated with an increased SDNN. An increased vagal tone was the dogs' responses to being petted at the chest. Displacement activities correlated negatively with all cardiovascular parameters (HR, SDNN, RMSSD, and RMSSD/SDNN ratio). Appeasement gestures were positively correlated with HR and occurred less under an increased vagal tone. The behavioral strategies, that is, freezing (standing motionless with all legs on the floor) and withdrawal (moving backward without any agonistic display) were negatively associated with the cardiac activity parameters, RMSSD and RMSSD/SDNN ratio. The dogs' behavioral and physiological responses suggest that some common physical human–dog interactions perceived as unpleasant by dogs. Emphasis on human signaling in human–dog interactions encourages development of recommendations for pleasant and safe human–dog contact to enhance dogs' well-being and the human–dog relationship.     

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.     

Intratesticular and subcutaneous lidocaine alters the intraoperative haemodynamic responses and heart rate variability in male cats undergoing castration

ObjectiveTo evaluate the usefulness of intratesticular and subcutaneous lidocaine in alleviating the intraoperative nociceptive response to castration, measured by pulse rate (PR) and mean arterial pressure (MAP), and to test the applicability of heart rate variability (HRV) analysis in assessing this response.Study designRandomized, controlled, observer-blinded experimental trial.AnimalsThirty-nine healthy male cats admitted for castration.MethodsOne group received general anaesthesia and served as control group (GA), while the treatment group (LA) additionally received local anaesthesia (lidocaine 2 mg kg^?1) intratesticularly and subcutaneously. PR and MAP were recorded at anaesthesia baseline (T0), treatment (T1), incision left testicle (T2), traction on spermatic cord (T3), tightening of the autoligature and resection of the cord (T4), incision on the right side (T5), traction on spermatic cord (T6), and tightening of the autoligature and resection of cord (T7). HRV analysis was divided into three 5-minute intervals: baseline (H0), treatment (H1), and surgery (H2).ResultsThere were significant increases in PR and MAP for both groups during surgery from T3 onwards; however, the increase in the treatment group (LA) was significantly lower than for the control group (GA). For HRV analysis, significant differences were found between groups in the following parameters during surgery: TP (total power), VLF (very low frequency), SDNN (standard deviation of NN intervals [=the interval between two consecutive R-waves in the ECG]), and TI (triangular index), which were lower in the LA group. Mean NN was significantly lower in the GA group, whereas LF (low frequency) and LFn (low frequency, normalized value) were lower in the LA group. HF (high frequency) and HFn (high frequency, normalized value) decreased significantly from H1 to H2 in both groups.Conclusions and clinical relevanceThe study showed that the nociceptive response to surgery was alleviated by the use of intratesticular and subcutaneous lidocaine and that HRV analysis is a promising research tool to estimate intraoperative nociception in cats during general anaesthesia.     

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 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.     

Incidence of post-anaesthetic arrhythmias in dogs

OBJECTIVES: To assess the use of Holter monitoring for evaluating the incidence of post-anaesthetic cardiac arrhythmias and associated anaesthetic risk for two different anaesthetic protocols. METHODS: Patients undergoing orthopaedic surgery were randomly divided into two groups with different anaesthetic regimens (group A, isoflurane n = 30; group B, propofol n = 30). Two 24-hour Holter recordings were performed for each patient: the first directly following anaesthesia and the second, as a comparison, on the fifth postoperative day. RESULTS: Although all dogs were healthy on pre-anaesthetic cardiac evaluation, 56 dogs showed arrhythmias in the two 24-hour (Holter) electrocardiograms performed. However, the number of arrhythmias recorded was low in most cases (less than 10 supraventricular extrasystoles and less than 100 ventricular extrasystoles). One patient in group A showed 94 supraventricular extrasystoles during the second monitoring period. Three patients in each group developed more than 100 ventricular extrasystoles during both Holter recordings. There were no statistically significant differences between the two anaesthetic regimens or between the two recordings in both groups. CLINICAL SIGNIFICANCE: The two anaesthetic protocols investigated in this study did not induce an increased incidence of severe arrhythmias in healthy dogs in the post-anaesthetic phase.     

Competition Horses Housed in Single Stalls (II): Effects of Free Exercise on the Behavior in the Stable, the Behavior during Training, and the Degree of Stress

Although housing horses in single stalls limits their natural behavior to a great extent, this housing system is widespread in Germany, especially for competition horses. To improve the welfare of this system, free exercise on pastures or paddocks is deemed suitable, but it is also feared because of injuries and decreased willingness or motivation to perform. In the present study, three treatments were investigated with regard to their effect on the behavior of six competition horses in the stable, behavior during training, and on their degree of stress: daily training without free exercise (no turnout [NT]), solitary turnout for 2 hours after training, and 2-hour turnout in groups of two after training (group turnout). The horses’ behavior in the stable was continuously analyzed through video recordings (2 pm to 6 am) on 3 days at the end of each treatment. The degree of stress was evaluated daily by heart rate variability at rest. The behavior during training was evaluated by a questionnaire answered by the riders, and the distance covered during training was measured by global positioning system. When NT was allowed, the horses showed less lying in the stable compared with the treatments with turnout. Heart rate variability measurements resulted in great individual differences, but generally, there was a higher degree of stress shown with the treatment NT according to the following parameters: standard deviation of inter-beat-intervals (SDNN), square root of the mean of the sum of the squares of differences between successive inter-beat-intervals (RMSSD), and ratio between low frequency and high frequency (LF/HF). The willingness to perform was evaluated as being slightly better in the treatments with turnout than in the treatment without turnout.     

Heart rate variability and plasma norepinephrine concentration in diabetic dogs at rest

Cardiac autonomic neuropathy in dogs with diabetic mellitus (DM) was evaluated using measurement of heart rate variability (HRV) and plasma norepinephrine (NE) concentration. Dogs were divided into 2 groups; the control non-DM group (n?=?13) and the diabetic group (n?=?22) which was further divided into the well-controlled DM (n?=?11) and the poorly-controlled DM subgroups (n?=?11) according to their fasting plasma fructosamine concentrations. The electrocardiogram (ECG) was recorded continuously for at least 30?min to yield HRV. The results showed that in the poorly-controlled DM subgroup, the average of normal R-R interval (mean N-N), SD of the mean of all 5-min segments of normal RR intervals (SDANN) were lower than the control group while heart rate was higher (P?<?0.05). The NNA, SDNN, SDNN index and pNN50% were significantly lower when compared with the well-controlled DM subgroup (P?<?0.05). The high frequency (HF) and total power were significantly lower while the ratio of low to high frequency (LF/HF) was higher (P?<?0.05) when compared with the well-controlled DM subgroup. Moreover, in the poorly-controlled DM subgroup, plasma NE concentration was lower than the control group (210?±?37 vs. 479?±?74?pg/ml, P?<?0.05). There was a significantly negative correlation between plasma NE and plasma fructosamine concentrations. It is concluded that cardiac autonomic neuropathy occurred in poorly-controlled DM dogs. The sympathetic activity was suppressed as shown by decrease in both plasma NE concentration and LF component.