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Heart rate variability is an established risk factor for mortality in both healthy dogs and animals with heart failure. The aim of this study was to compare short-term heart rate variability (ST-HRV) parameters from 60-min electrocardiograms in dogs with sick sinus syndrome (SSS, n=20) or chronic mitral valve disease (CMVD, n=20) and healthy controls (n=50), and to verify the clinical application of ST-HRV analysis. The study groups differed significantly in terms of both time - and frequency- domain ST-HRV parameters. In the case of dogs with SSS and healthy controls, particularly evident differences pertained to HRV parameters linked directly to the variability of R-R intervals. Lower values of standard deviation of all R-R intervals (SDNN), standard deviation of the averaged R-R intervals for all 5-min segments (SDANN), mean of the standard deviations of all R-R intervals for all 5-min segments (SDNNI) and percentage of successive R-R intervals >50 ms (pNN50) corresponded to a decrease in parasympathetic regulation of heart rate in dogs with CMVD. These findings imply that ST-HRV may be useful for the identification of dogs with SSS and for detection of dysautonomia in animals with CMVD.

Heart rate variability (HRV) is a well established mortality risk factor in both healthy dogs and those with heart failure. While the standards for short-term HRV analysis have been developed in humans, only reference values for HRV parameters determined from 24-hour ECG have been proposed in dogs. The aim of this study was to develop the reference values for short-term HRV parameters in a group of 50 healthy dogs of various breeds (age 4.86 ± 2.74 years, body weight 12.2 ± 3.88 kg). The ECG was recorded continuously for at least 180 min in a dark and quiet room. All electrocardiograms were inspected automatically and manually to eliminate atrial or ventricular premature complexes. Signals were transformed into a spectrum using the fast Fourier transform. The HRV parameters were measured at fixed times from 60-min ECG segments. The following time-domain parameters (ms) were analyzed: mean NN, SDNN, SDANN, SDNN index, rMSSD and pNN50. Moreover, frequency-domain parameters (Hz) were determined, including very low frequency (VLF), low frequency (LF) and high frequency (HF) components, total power (TP) and the LF/HF ratio. The results (means ± SD) were as follows: mean NN = 677.68 ± 126.89; SDNN = 208.86 ± 77.1; SDANN = 70.75 ± 30.9; SDNN index = 190.75 ± 76.12; rMSSD = 259 ± 120.17, pNN50 = 71.84 ± 13.96; VLF = 984.96 ± 327.7; LF = 1501.24 ± 736.32; HF = 5845.45 ± 2914.20; TP = 11065.31 ± 3866.87; LF/HF = 0.28 ± 0.11.

The purpose of this study was to develop prognostic models for heart failure in dogs with dilated cardiomyopathy (DCM). The prospective study included 26 dogs with DCM and 58 healthy dogs. The ervation time median was 250 days (1-600 days). All the dogs were clinically examined, had echocardiography, electrocardiography, and morphological and biochemical blood sampling. Twenty four deaths were found in the group of dogs with DCM and 1 demise in the healthy dog's group. There was a significant increase in the level of NT-pro-BNP and cTnI (p<0.0005) in the group of dogs with DCM and a significant higher level of NT-pro-BNP and cTnI (p<0.0005) in the dead dogs from group with DCM that died or were euthanized up to the 60'th day of observation, compared to the animals that outlasted over 60 days of observation. The median level of NT-pro-BNP in the dogs which had short survival period (no more than 60 days) was 4865 pmol/L and the median level of cTnI in the same group of dogs was 0.63 ng/ml. The median level of NT-pro-BNP in the group of dogs with DCM, which lived longer than 60 days of observation was 978 pmol/l and the median level of cTnI in this group was 0.1 ng/ml. The level of NT-pro-BNP (r=0.79) and cTnI (r=0.4) correlated with the dogs' death. NT-pro-BNP and cTnI measurements could be useful to evaluate the survival the dogs with DCM. Increased level of NT-pro-BNP and cTnI is a bad prognosis. In the performed analysis of the Cox hazard regression it was found that cTnI level has a significant impact of the survival of the dogs (HR=8.54; Cl 1.1-46.6; p=0.02).

Heart rate turbulence (HRT) is modulated by the baroreceptor reflex and it was suggested that it could be used as a measure of autonomic dysfunction. Impaired HRT is of a significant prognostic value in humans after myocardial infarction, suffering from dilated cardiomyopathy and patients with heart failure. So far no studies were performed assessing the importance of HRT in dogs. The aim of this study was to prospectively evaluate the HRT turbulence onset (TO) and the turbulence slope (TS) in healthy dogs and in dogs with DCM and to compare the HRT in dogs with DCM that died during the first 30 days of observation and dogs with DCM that survived the first 30 days after the HRT analysis. The current study was aimed at determining reference value of the TO and TS of HRT in healthy dogs (control group) and dogs with dilated cardiomyopathy (DCM group). The tests were carried out on 30 healthy dogs and 30 dogs with DCM composed of Boxers, Doberman pinschers and Great Danes, of different sexes and body weights from 22 to 72 kg, aged between 1.5 and 11.5 years, submitted to the 24-hour Holter monitoring. HRT parameters were calculated using an HolCard software algorithm. TO is a percentage difference between the heart rate immediately following ventricular premature complex (VPC) and the heart rate immediately preceding VPC. TS corresponds to the steepest slope of the linear regression line for each sequence of five consecutive normal intervals in the local tachogram. The average TO in healthy dogs was determined as -13.55 ± 11.12%, TS was 21.33 ± 9.66 ms/RR. TO in dogs with DCM was determined as - 2.61 ± 2.1% and TS was 6.15 ± 3.86 ms/RR. Parameters of HRT were statistically significantly decreased (p<0.01) in dogs with DCM. HRT TO and TS were statistically significantly decreased in dogs with DCM. Dogs with DCM that survived more than 30 days of observation had HRT statistically significantly decreased in comparison to dogs with DCM that died after the 30’th day of observation. Decreased HRT parameters in dogs with DCM suggest an autonomic neuropathy which principally consists of the withdrawal of the cardiac parasympathetic tone. The more the autonomic neuropathy is advanced the faster the death of the dog with DCM might occur, with no correlation with the level of the heart failure.

The aim of the study was to analyse the influence of enrofloxacin and pradofloxacin administered orally for 14 days on the ECG in dogs. The ECG was performed before and after a 14 day period of quinolone administration. There was an increase in the QTc and the TpTe interval in the group treated with quinolones. QTc was prolonged by 24 ms (p=0.001). The TpTe interval was shortened, on average, by 6.55 ms (p=0.048). In the group treated with enrofloxacin, QTc was prolonged by 16.27 ms (p=0.006) and the TpTe interval was shortened by 9.64 ms (p=0.050), the TpTe/QT index was reduced by 0.034 (p=0.050) on average. In dogs treated with pradofloxacin, QTc was prolonged by 21.55 ms (p=0.012) on average. The results suggest that a prolonged administration of quinolones can increase the risk of arrhythmias. Furthermore, different generations of these drugs increase this risk to various degrees. The study proved that second generation quinolones, such as enrofloxacin, significantly change the phase of depolarization and repolarization of the ventricles, at the same time increasing the risk of ventricular arrythmia. Pradofloxacin does not change the TpTe and TpTe/QT values, so it is safer in use.

Heart rate turbulence (HRT) is a new electrocardiographic parameter used in human medicine to predict the possibility of death in patients with cardiac diseases. There is no information about HRT in healthy dogs and those with cardiac diseases. The aim of the present study was to compare the HRT in healthy Boxers dogs with Boxers with mild and moderate subaortic stenosis (SAS), to disclose the relationship between HRT and specific echocardiographic parameters and to evaluate if HRT can be used as a prognostic value in dogs with aortic stenosis. The study revealed significantly lower values of turbulence onset (TO) and turbulence slope (TS) HRT dogs with SAS (TO = -0.76 ± 2.6, TS = 7.1 ± 3.21) in compared with healthy dogs (TO = -7.45 ± 9.72, TS = 14.33 ± 8.76). TO values correlated with the left ventricular mass (LVM)/body mass factor (r = 0,32; p = 0.048). Based on the results obtained it can be stated that dogs with SAS have a compromised baroreceptor response, which can influence the mortality of the animals with described cardiac defect.

The study has focused on the retrospective analysis of cases of coexisting congenital aortic stenosis (AS) and pulmonary artery stenosis (PS) in dogs. The research included 5463 dogs which were referred for cardiological examination (including clinical examination, ECG and echocardiography) between 2004 and 2014. Aortic stenosis and PS stenosis were detected in 31 dogs. This complex defect was the most commonly diagnosed in Boxers - 7 dogs, other breeds were represented by: 4 cross-breed dogs, 2 Bichon Maltais, 3 Miniature Pinschers, 2 Bernese Mountain Dogs, 2 French Bulldogs, and individuals of following breeds: Bichon Frise, Bull Terrier, Czech Wolfdog, German Shepherd, Hairless Chinese Crested Dog, Miniature Schnauzer, Pug, Rottweiler, Samoyed, West Highland White Terrier and Yorkshire Terrier. In all the dogs, the murmurs could be heard, graded from 2 to 5 (on a scale of 1-6). Besides, in 9 cases other congenital defects were diagnosed: patent ductus arteriosus, mitral valve dysplasia, pulmonary or aortic valve regurgitation, tricuspid valve dysplasia, ventricular or atrial septal defect. The majority of the dogs suffered from pulmonary valvular stenosis (1 dog had supravalvular pulmonary artery stenosis) and subvalvular aortic stenosis (2 dogs had valvular aortic stenosis). Conclusions and clinical relevance - co-occurrence of AS and PS is the most common complex congenital heart defect. Boxer breed was predisposed to this complex defect. It was found that coexisting AS and PS is more common in male dogs and the degree of PS and AS was mostly similar.

The comparative study of the acid-base balance (ABB) parameters has been performed on 20 clinically healthy mature Małopolski horses. An arterial blood sample from the facial artery and a sample of venous blood from the external cervical vein were colected from each animal. In the samples tested, the blood pH, pCO2, tCO2, HCO3-, concentration of Na+, K+, Cl-, and a value of the anion gap were determined. The difference among pCO2, tCO2, and HCO3- in both samples tested was statistically significant, whereas the pH of the arterial blood and the pH of the venous blood did not differ significantly. The anion gap in both types of blood did not differ significantly. Conclusions: 1) ABB parameters such as pCO2, HCO3-, and tCO2 determined in the arterial and venous blood of the Małopolski horses differ from each other significantly. 2) In spite of the lack of the differences between pH of the arterial and venous blood, the ABB parameters in horses should be determined in the arterial blood, because the comparative study performed proves that the analysis of the ABB parameters determined for the venous blood of a healthy horse may lead to a wrong diagnosis of the compensated respiratory acidosis. 3) The mean value of anion gap in horses aged 8-12 years amounts to 20.9 mmol/l for the arterial blood and 19.93 for the venous blood; the difference between the two values is not statistically significant.

The duration of electrocardiographic (ECG) parameters: PQ, QT and R-R intervals change during long-term and short-term observation as the consequence of the fluctuations in autonomic nervous system activity among others dependent on the exercise and resting. There is no data of horse breed influence on these parameters. The aim of the study was to assess the duration and the variability of the PQ, QT and R-R intervals in the resting conditions and after exercise testing in Anglo-Arabian horses. 27 healthy Anglo-Arabian horses aged 3.4 +/- 1.0 years (15 male, 12 female) had ECG examination in the standing position using Einthoven system of leads. The longest and the shortest PQ, QT and R-R intervals were measured after night rest and after exercise testing and the means were calculated. 1) In Anglo-Arabian horses the difference between the longest and the shortest PQ interval at rest vs. after exercise is 0.06 +/- 0.05 vs. 0.03 +/- 0.02, QT interval is 0.04 +/- 0.03 vs. 0.04 +/- 0.04, R-R interval 0.19 +/- 0.15 vs. 0.08 +/- 0.11. 2) The PQ and R-R intervals reveal high short-term variability either at the resting conditions or after exercise testing. 3) After exercise testing PQ, QT and R-R intervals are shorter than at the resting conditions. The delta PQ and R-R are 2 times smaller in contrast to delta QT which is constant. 4) The PQ and R-R interval variability was greater at the baseline condition than after exercise testing. The QT variability was similar at baseline condition to that after exercise testing.

Ventricular tachycardia may lead to haemodynamic deterioration and, in the case of long term persistence, is associated with the development of tachycardiomyopathy. The effect of ventricular tachycardia on haemodynamics in individuals with tachycardiomyopathy, but being in sinus rhythm has not been studied. Rapid ventricular pacing is a model of ventricular tachycardia. The aim of this study was to determine the effect of rapid ventricular pacing on blood pressure in healthy animals and those with tachycardiomyopathy. A total of 66 animals were studied: 32 in the control group and 34 in the study group. The results of two groups of examinations were compared: the first performed in healthy animals (133 examinations) and the second performed in animals paced for at least one month (77 examinations). Blood pressure measurements were taken during chronic pacing--20 min after onset of general anaesthesia, in baseline conditions (20 min after pacing cessation or 20 min after onset of general anaesthesia in healthy animals) and immediately after short-term rapid pacing. In baseline conditions significantly higher systolic and diastolic blood pressure was found in healthy animals than in those with tachycardiomyopathy. During an event of rapid ventricular pacing, a significant decrease in systolic and diastolic blood pressure was found in both groups of animals. In the group of chronically paced animals the blood pressure was lower just after restarting ventricular pacing than during chronic pacing. Cardiovascular adaptation to ventricular tachycardia develops with the length of its duration. Relapse of ventricular tachycardia leads to a blood pressure decrease more pronounced than during chronic ventricular pacing.