Scaling Relationships Among Heart Rate, Electrocardiography Parameters, and Body Weight

Retrospective evaluation of the respiratory rate-oxygenation index to predict the outcome of high-flow nasal cannula oxygen therapy in dogs (2018-2021): 81 cases

OBJECTIVE

To evaluate the respiratory rate-oxygenation index (ROX), modified ROX index (ROX-HR), and the ratio of pulse oximetry saturation (Spo2) to Fio2 (SF) to determine if these indices over time are predictive of outcome in dogs treated with high-flow nasal cannula oxygen therapy (HFNC).

DESIGN

Retrospective study.

SETTING

Two university teaching hospitals.

ANIMALS

Eighty-one client-owned dogs treated with HFNC for hypoxemic respiratory failure.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The ROX was defined as the SF divided by the respiratory rate (RR), and the ROX-HR was defined as the ROX divided by the heart rate multiplied by 100. The overall success rate of HFNC was 44% (n = 36/81). Dogs weaned from HFNC had a significantly higher ROX (P < 0.0001) at 1-3, 5-10, 12, and 15 hours than dogs that failed HFNC. Both the ROX and SF showed excellent discriminatory power in predicting HFNC failure at 6 hours, with an area under receiver operating curve of 0.85 (95% confidence interval: 0.72-0.99; P < 0.002) and 0.86 (95% confidence interval: 0.73-0.99; P < 0.001), respectively. The optimal cutoff values for predicting HFNC failure at 6 hours were a ROX ≤3.68 (sensitivity 72%, specificity 92%) and an SF ≤143 (sensitivity 79%, specificity 93%).

CONCLUSIONS

These results suggest that similar to people, the ROX and SF are useful predictors of HFNC failure. These indices are easy to measure at the bedside and may have clinical use. Future prospective studies are warranted to confirm the findings and to optimize cutoff values in a larger population of dogs undergoing HFNC.

Comparative electrocardiographic study of the Asian freshwater box turtle Cuora flavomarginata and the Asian yellow pond turtle Mauremys mutica using non-invasive methods

Background

Evaluation of cardiac function is an integral part of clinical examination of chelonians. However, information about electrocardiography (ECG) in turtles and tortoises is limited and fragmentary. Its application is limited due to the lack of ECG reference values. This study aimed to compare specific ECG parameters using non-invasive methods in the Asian box turtle Cuora flavomarginata (CF) and the Asian yellow pond turtle Mauremys mutica (MM).

Methods

We included 116 clinically healthy and conscious turtles. Two non-invasive methods, using adhesive patches or crocodile clips, for ECG were applied where possible. The ambient temperature was within the preferred optimum temperature zone of both species. We used specific digital ECG monitoring equipment to record the ECG data and analysed the data using specific software.

Results

The MM group showed better ECG quality and lower heart rate than the CF group. Comparing both methods, the adhesive patches method yielded higher ECG quality in the CF group, while the crocodile clips method yielded higher ECG quality in the MM group.

Conclusions

The study population was selected as presumed healthy turtles; the presence of systemic or cardiac disease could not be excluded completely due to limited investigation. Both ECG methods were clinically potentially useful for obtaining ECG parameters; the ECG quality was influenced by the method used.

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.

Standardized capillary refill time and relation to clinical parameters in hospitalized dogs

OBJECTIVE

To assess the relationship between various physical and clinicopathologic parameters and the capillary refill time (CRT) using a standard method; to evaluate the influence of emergency room (ER) versus ICU hospital location on CRT; and to identify latent subgroups among the CRT distribution.

DESIGN

Prospective, observational study.

SETTING

University teaching hospital.

ANIMALS

Client-owned dogs in the ER (n = 40) and ICU (n = 71).

INTERVENTIONS

The CRT was defined as the duration required for the oral mucosa of the upper lip to return to its original color after blanching for 4 seconds. The CRT was recorded in seconds to the 10ths place by a single observer using an automated recording device.

MEASUREMENTS AND MAIN RESULTS

Median CRT for all dogs was 1.1 seconds (ER, 1.2 s; ICU, 1.1 s; P = 1.000). The CRT was significantly associated with rectal temperature (P = 0.004), systolic blood pressure (P = 0.028), body weight (P = 0.031), mucous membrane color (P = 0.007), skin turgor (P = 0.039), and acute patient physiologic and laboratory evaluation mentation score (P = 0.019) for all dogs. The CRT was related to a greater number of variables in the ER than in the ICU patient population. In general, the total population of dogs had CRTs belonging to 1 of 2 groups: either ≤1.2 or ≥1.7 seconds. A statistically significant association was found between body weight CRT ≥1.3 seconds (P = 0.02).

CONCLUSIONS

A CRT following blanching for 4 seconds may provide insight into the hydration status and hemodynamic stability of canine patients. Further research into its clinical application is warranted.

Social Context Influences Resting Physiology in Dogs

Simple Summary

Wolves became dogs over the past 35,000 years. It has been suggested that through domestication, the cooperative nature of wolves and their dependence on pack mates has been re-directed towards humans. This has also affected the social orientation of dogs towards conspecifics. In contrast to wolves, dogs in free-ranging packs are not monogamous and are less cooperative with their pack members. In a previous paper, we found that dogs resting isolated from their pack members were less relaxed/more alert than wolves in the same situation. As social context may affect such results, we replicated this study with pack-living and enclosure-kept dogs resting alone or close to pack members. Specifically, we measured heart rate and heart rate variability as physiological proxies of alertness. We found that dogs were less relaxed/more alert when resting alone than with pack members, but that this may be modulated by social status, i.e., high-ranking dogs being less relaxed than low-ranking individuals. We conclude that relaxation/alertness of dogs during rest depends on social context and that, as in wolves, conspecific pack members still have a role in this. This indicates that domestication has only partially re-directed social orientation in dogs from conspecific pack members to human partners.

Abstract

Domestication has affected the social life of dogs. They seem to be less dependent on their pack members than wolves, potentially causing dogs to be more alert towards their environment, especially when resting. Such a response has been found in dogs resting alone compared to wolves in the same situation. However, as this may be influenced by social context, we compared alertness (i.e., degree of activation along the sleep–wake continuum—measured via cardiac parameters) of pack-living and enclosure-kept dogs in two conditions: (1) alone, and (2) with pack members, and in two states of activation: (1) inactive wakefulness, and (2) resting. We found that when dogs were resting alone, alertness was higher than when resting in the pack; individual alertness was potentially influenced by social rank. However, alertness was similar in the two conditions during inactive wakefulness. Thus, depending on social context, familiar conspecifics may still provide support in dogs; i.e., domestication has probably only partly shifted the social orientation of dogs from conspecifics to humans. We suggest that cardiac responses of dogs may be more flexible than those of wolves because of their adaptation to the more variable presence of humans and conspecifics in their environment.

Context-Specific Arousal During Resting in Wolves and Dogs: Effects of Domestication?

Due to domestication, dogs differ from wolves in the way they respond to their environment, including to humans. Selection for tameness and the associated changes to the autonomic nervous system (ANS) regulation have been proposed as the primary mechanisms of domestication. To test this idea, we compared two low-arousal states in equally raised and kept wolves and dogs: resting, a state close to being asleep, and inactive wakefulness, which together take up an important part in the time budgets of wolves and dogs. We measured arousal via cardiac output in three conditions: alone, with a familiar human partner, or with pack members (i.e., conspecifics). Specifically, we compared heart rate (HR) and heart rate variability (HRV) of six wolves and seven dogs. As patterns of resting can vary adaptively, even between closely related species, we predicted that dogs would be generally more aroused than wolves, because living with humans may come with less predictable contexts than living with conspecifics; hence, dogs would need to be responsive at all times. Furthermore, we predicted that due to the effects of domestication, emotional social support by familiar people would reduce arousal more in dogs than in equally human-socialized wolves, leading to more relaxed dogs than wolves when away from the pack. Overall, we found a clear effect of the interactions between species (i.e., wolf versus dog), arousal state (i.e., resting or awake inactive) and test conditions, on both HR and HRV. Wolves and dogs were more aroused when alone (i.e., higher HR and lower HRV) than when in the presence of conspecifics or a familiar human partner. Dogs were more relaxed than wolves when at rest and close to a familiar human but this difference disappeared when awake. In conclusion, instead of the expected distinct overall differences between wolves and dogs in ANS regulation, we rather found subtle context-specific responses, suggesting that such details are important in understanding the domestication process.

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.

Does socio-ecology drive differences in alertness between wolves and dogs when resting?

Variation in resting behaviour across animals may be driven by adaptations towards their environment. Wolves and dogs seem promising models to examine this idea as they share a common ancestor, but occupy different socio-ecological niches. While wolves generally avoid humans, hunt, defend their territory, and raise offspring cooperatively, most dogs live in human-shaped environments. Hence, we hypothesized wolves to be more alert towards their environment than dogs, i.e. the degree of activation along the sleep-wake continuum (alertness) should be greater in wolves than in dogs. We estimated alertness via cardiac output. We tested similarly raised and kept pack-living wolves and dogs in two different behavioural conditions: (1) inactive wakefulness: animal is lying, head in an upward position with eyes opened, (2) resting: animal is lying, head in downward position with eyes mainly closed. In contrast to our expectations, we found that in both conditions wolves had a lower heart rate and higher heart rate variability than dogs, i.e. wolves might be less alert/more relaxed than dogs. Although our results are preliminary, we suggest that the higher alertness of dogs compared to wolves is potentially driven by differences in their socio-ecology (i.e. domestication) causing greater attention of dogs to human behaviour.