Electrocardiogram pattern of some exotic breeds of trained dogs: A variation study

Evaluation of the association between electrocardiogram parameters and left cardiac remodeling in dogs with myxomatous mitral valve disease

Background and Aim: Electrocardiography (ECG) is an adjunct for cardiac enlargement diagnosis. However, its efficacy in assessing left cardiac remodeling (left atrial and left ventricular enlargement) in dogs with myxomatous mitral valve disease (MMVD) remains unclear. This study aimed to evaluate the association between ECG parameters and left cardiac remodeling and to investigate whether the rate of change in ECG waveforms in the same individual reflected left cardiac remodeling in dogs with MMVD. Materials and Methods: This retrospective study included 20 healthy dogs and 140 dogs with MMVD. Data on clinical variables were obtained through physical examination, thoracic radiography, and echocardiography. The ECG parameters were the P-wave duration, PR interval, QRS complex duration, P-wave amplitude, R-wave amplitude, and mean electrical axis. Dogs with examination data that could be obtained multiple times during the study period were classified into the non-progressive and progressive groups. Results: Only the P-wave and QRS complex durations were selected as significant variables associated with imaging test parameters (p < 0.05); they had a relatively higher discriminatory ability for the left cardiac remodeling than other ECG parameters. The rates of change in the PR interval and R-wave amplitude were significantly higher in the progressive group than in the non-progressive group. Conclusion: In dogs with MMVD, the P-wave and QRS complex durations were significantly correlated with the left cardiac remodeling indicators. Furthermore, an increased rate of change in the PR interval and R-wave amplitude in the same individual may indicate left cardiac remodeling.

Assessment of age, gender, and anxiety on ECG waveform morphology in a large population of domestic dogs

Cardiovascular diseases are major causes of death in the western world and this incidence increases in the elderly population. With aging, there are physiologic changes to the cardiac structure secondary to adipose tissue deposition, calcification of valve leaflets and changes in the structure of the heart including atrial remodeling. Such changes can make the myocardium more susceptible to stress leading to a higher prevalence of cardiovascular diseases in the aging population. Studies in healthy humans have shown that these structural and molecular changes in the heart are manifested as changes on an electrocardiogram (ECG). Using animal models, similar ECG changes have been found in guinea pigs, rabbits, and mice. No veterinary study has specifically evaluated if comparable aging changes occur in canine species. In this cross-sectional retrospective study, 12,026 ECGs from apparently healthy dogs were obtained and evaluated. Age was observed to have both linear and non-linear associations with multiple ECG variables, including P wave amplitude and duration, R amplitude and QRS duration. This study confirmed that, like humans, there may be ECG changes secondary to normal physiological cardiac aging. Further studies are warranted to confirm and elaborate on these findings as canines may be a useful model for cardiac aging in humans.

How Do Avalanche Dogs (and Their Handlers) Cope with Physical Exercise? Heart Rate Changes during Endurance in a Snowy Environment

Simple Summary

Search and rescue (SAR) dogs are irreplaceable support in natural disasters. Not only are these animals required to have optimal scenting capabilities, but they are also required to have excellent physical conditions. Implementing protocols to monitor their fitness would help to optimize their performance and welfare. This study evaluated heart rate (HR) changes in avalanche SAR dogs and handlers during a 5.5 km endurance exercise in the snow, at an altitude of approximately 2000 m.a.s.l., reflecting their usual working and workload conditions. Dogs’ and handlers’ HR and activities were monitored by a global positioning satellite (GPS)/HR system. Factors influencing dogs’ and handlers’ HR changes and their possible correlation were investigated. As expected, the dog’s HR changes during the endurance activity were affected by speed, gradient, altitude, and time. The handlers’ HR changes differed and were not correlated with those recorded in the dogs. Thus, SAR handlers may not perceive the physical stress of their dog in real-time. Findings indicate that GPS/HR monitoring systems could be utilized in field conditions for monitoring SAR units’ physical fitness. A “fitness index” could be developed by incorporating HR and velocity measurements in order to target training strategies and indicate risk factors for physical distress in working dogs.

Abstract

This study aimed to assess the heart rate (HR) responses of avalanche SAR dogs and handlers under working field conditions. Thirteen SAR units (dogs and handlers) performed an exercise (Endurance) consisting of approximately 5.5 km of rough tracks through deep snow, at an altitude of 1991–2250 m.a.s.l. The exercise was repeated twice for each of the two different tracks. Both handlers and dogs were equipped with a global positioning satellite/heart rate (GPS/HR) system (Polar^®). Multivariable models were used to evaluate the effects of environmental (i.e., gradient, altitude, track, and time) and intrinsic (i.e., speed, repetition, and breed) factors on changes from baseline HR (Δ%HR). The dog’s Δ%HR was greater in the flat and uphill compared with downhill, and increased progressively as the speed increased (p < 0.001). Moreover, it rose at altitudes above 2100 m.a.s.l. and peaked after 30 min of the Endurance activity (p < 0.01). These findings indicated that HR monitors could be a valuable tool to contribute to the evaluation of avalanche dogs’ fitness in their real working environment. In contrast, the lack of correlation between the dogs’ and handlers’ HR changes suggests that handlers might not perceive the physical conditions of their dog in real-time. Thus, implementing protocols to monitor avalanche SAR dogs’ fitness using a GPS/HR monitoring system could help handlers to tailor the training and workload and to detect the risk factors for physical distress of working dogs.

A study on the electrocardiography in dogs: Reference values and their comparison among breeds, sex, and age groups

Aim

The present investigation was intended to generate some basic data on electrocardiography (ECG) parameters in different breeds and their alterations in respect to sex and age.

Materials and Methods

The present investigation was carried out on 239 owned dogs of 11 different breeds presented to the Institute Veterinary Clinic during 2018-2019. The animals, irrespective of breed and sex were grouped on the basis of their age groups. Recordings of rdiartR, BPL, India) at 25 mm/s paper speed and 10 mm=1 mV calibration keeping the animals on the right lateECG were performed by a single-channel ECG machine (Caral recumbence without any anesthesia. Heart rate, along with the amplitude and duration of different waves and complexes was measured.

Results

Heart rate did not vary significantly among breeds, sex, and different age groups. The highest heart rate has been reported in Doberman and the lowest in Beagle. The heart rate was lowest at the age group of 6 months-2.5 years and highest around 10.5-12.5 years irrespective of breed and sex. The incidence of sinus arrhythmia was mostly seen in older dogs. All the waves and complexes did not vary significantly between breeds, age, and sex except P duration which was significantly (p<0.05) higher in Golden retriever and Doberman breeds.

Conclusion

The present investigation generated some reference values of ECG in dogs which will help the clinicians to diagnose different cardiac abnormalities through ECG.

Assessment of cardiac variables using a new electrocardiography lead system in horses

Aim:

The objective of this study was to assess a new lead system method to improve electrocardiographic measurement in horses.

Materials and Methods:

Twenty-two horses with an average age of 8.8±0.8 years were enrolled in this study. Horses were divided into two groups, consisting of a control group (n=11) and athlete group (n=11). Electrocardiography (ECG) and echocardiography were performed to provide information on the structure and function of the heart. Two lead systems, base apex and modified precordial leads, were used for the electrocardiogram to assess the cardiac electrophysiological functions.

Results:

PR interval, QT interval, and QRS-T angle presented significant differences between the control and athlete groups when the modified precordial lead system was used. However, significant variations in the mean electrical axis were found when the base apex lead system was used. The modified precordial lead system resulted in more significant differences in cardiac electrophysiological parameters than the base apex lead system. In the athlete group, echocardiography showed cardiac adaptations such as increases in the left atrial and left ventricular dimensions and stroke volume and a decrease in heart rate in response to exercise and training. The observed differences in cardiac morphology and function between groups suggested differences in health performance in the athlete group.

Conclusion:

These data provided the first evidence that the modified precordial lead system improved statistical variation in ECG recording and provided the most reliable method for health screening in horses.

The effects of breed, age, sex, and body weight on electrocardiographic parameters in military working dogs

Aim:

This study aimed to investigate the effects of breed, sex, age, and body weight on different electrocardiographic parameters in military working dogs (Labrador Retriever and German Shepherd).

Materials and Methods:

Electrocardiographic recordings (paper speed = 25 mm/s and calibration = 10 mm/mV) were performed to obtain all the standard bipolar limb leads (leads I, II, and III) and unipolar augmented limb leads (leads aVR, aVL, and aVF). A total of 16 Labrador Retrievers and 14 German Shepherds were restrained manually in the right lateral recumbency without any tranquilizer or anesthetic drug. Amplitude and duration of P, QRS, and T wave, PR and QT interval, mean electrical axis, and heart rate were measured in each recording.

Results:

There was no significant difference in electrocardiographic parameters across breed and sex. However, QRS duration tended to alter by breed (p<0.1) in Labrador Retrievers (0.04±0.005 s), which is lower than German Shepherds (0.05±0.005 s). PR interval was influenced by sex (p<0.1). PR interval was higher in females (0.13±0.005 s) than males (0.11±0.008 s). In addition, electrocardiographic values were not significantly affected by age and body weight, except that the amplitude of R wave was statistically affected by age (p<0.05). A correlation was found between the decrease in R wave amplitude and increase in age of dogs.

Conclusion:

Different electrocardiographic parameters were within the normal range. A significant effect of age was seen on amplitude of R wave. However, the effect of breed, sex, and body weight was not significant on different electrocardiographic parameters in Labrador Retriever and German Shepherd dogs.

Left shift of the ventricular mean electrical axis in healthy Doberman Pinschers

In canine electrocardiography, the reference interval of the ventricular mean electrical axis (MEA) is between +40° and +100°. MEA values in dogs can be influenced by the patient position as well as by the shape of the thorax. The aim of this study was to evaluate the MEA in healthy Doberman Pinschers, hypothesizing that some present a left shift of the MEA. In this retrospective study, 41 healthy, client-owned Doberman Pinschers were included. Echocardiography and standard six-lead ECG examination were performed in all dogs. The MEA was calculated using the isoelectric method. The morphology of the QRS complex and the Q/R ratio in lead II were also evaluated. The median MEA was +45° and ranged from −45° to +90°. MEA was deviated in 16/41 dogs (39%), all presenting a left axis deviation (range, −45° to + 30°). Age was significantly associated with the MEA (P=0.008), showing a negative linear correlation. A deep Q wave in lead II was present in 26/41 (63%) dogs. The Q/R ratio was higher in dogs presenting left shift of the MEA (0.66; range, 0.28–1.35) in comparison to dogs with a MEA within reference range (0.44; range, 0.04–0.73; P<0.001). In conclusion, a significant number of healthy Doberman Pinschers present a left shift of the MEA compare to the reference range, and dogs with MEA deviation show a higher Q/R ratio in lead II. This data should be considered when electrocardiographic evaluation is performed in Doberman Pinschers.

Effects of resistance training on electrocardiographic and blood parameters of police dogs

The aims of this study were to evaluate effects of a 6 week resistance training on electrocardiographic (ECG) and blood parameters of police dogs. Our hypothesis was that this training protocol improves fitness, contributing to the welfare of these animals. Nine dogs, 18.56±0.53 months old, were evaluated before (M1) and six weeks after (M2) a training protocol using treadmill. Their training program was performed 2 times/week, and included 20 min of treadmill activity on a speed compatible with 60-80% of HRmax on weeks 1 and 2, same exercise of weeks 1 and 2 with a 5% grade added between 7.5 and 12.5 min in weeks 3 and 4, and, finally, same exercise of weeks 3 and 4 with three short bursts of strenuous exercise, 60 min after the end of treadmill activity. On both moments, animals were examined before (T0) and after (T1) an incremental effort test, and at 30 (T2) and 120 min (T3) of recovery, measuring heart rate, respiratory rate and body temperature. Blood samples were taken to determine erythrogram, aspartate aminotransferase, creatine kinase, triglycerides, lactate and glucose. Electrocardiographic variables were analysed at T0 and T1. All variables were analysed by one-way ANOVA and Tukey tests, with P≤0.05. After training, there was an increase on the length of work on treadmill of 41.5% for the German Shepherd (P=0.0139) and 21.4% for the Belgian Malinois (P=0.0085) along with a increase of maximal speed of 34.0% for the German Shepherd (P=0.0084) and 15.9% for the Belgian Malinois (P=0.0241). It was observed in physiological, blood and ECG parameters differences between M1 and M2 (P<0.05). Other findings included a lower rest QTc value at T0 after training (P=0.0194). The chosen training led to a better fitness of the police dogs as all of them worked more intensively with a low cardiovascular requirement in M2. In conclusion, current exercise protocol in a treadmill improved dogs fitness, when we analysed ECG, physiological and blood parameters, making possible that animals may be used in more extended and multiple missions, contributing welfare of these animals.