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

Abstract

Although heart rate (HR) is one of the most important clinical parameters determined via physical examinations, little information is available on the normal HR in dogs, which may be related to the high variability of body weight (BW) in this species. HR is determined by the discharge rate of the sinus node, which is dependent on the autonomic nervous system and the release of catecholamines. The allometric relationship between BW and HR in different species has been described as inversely proportional; however, this relationship has been refuted. Certain authors have reported that the relationship between HR and BW in dogs is based on temperament as well as sympathetic autonomic stimulation of the sinus node in small breeds compared with large breeds. The aim of this study was to analyze the effects of weight, sex, age and temperament on the HR, heart rate variability and serum catecholamine (epinephrine and norepinephrine) levels in dogs. We evaluated 48 adult dogs of both sexes and various breeds and ages and divided the dogs into 5 BW groups: <5kg (n = 8), 5-10kg (n = 10), 10-25kg (n = 10), 25-45kg (n = 10), and >45kg (n = 10). The measured parameters were HR, breath rate (BR) and body temperature. We also performed an ambulatory electrocardiogram and electrocardiography (ECG) test for 24 hours (Holter monitor) and determined the serum levels of the catecholamines epinephrine and norepinephrine. We observed correlations between HR and sex; differences among the weight groups with respect to ECG variables and epinephrine levels; and differences among the temperament categories for certain clinical parameters, such as HR and BR. Age affected the R wave amplitude, and an allometric relationship was not observed between HR and BW in the dogs. Our results indicated that weight was associated with variations in the ECG variables; age and sex were associated with variations in HR; and temperament had a significant influence on the HR and BR of the dogs.

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

“…Variations in age were significantly associated with R wave amplitude and QRS duration in German Shepherds [18]. Body weight was also associated with variations in ECG parameters, whereas age and sex were associated with variations in HR [19].…”

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

“…Although the relationship between body weight and resting heart rate remains controversial in veterinary medicine, 54–59 dogs with a lower body weight were noted to have significantly longer CRTs in this study. This finding may represent an impairment in the ability of smaller dogs with a higher resting heart rate to manifest compensatory tachycardia in order to maintain adequate cardiac output in the face of shock.…”

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

“…We therefore conclude that despite the differences in wolf and dog body mass and age, our comparisons of HR over different contexts are still valid. Such concerns do not affect HRV in a similar way as this parameter seems even more independent of body size or motor activity than HR (Cruz Aleixo et al, 2017).…”

“…Hezzell et al (2013) indeed found that HR scaled negatively with body mass, whereas Hamlin et al (1967) reported that Great Danes HR frequencies exceeded that of miniature poodles. A recent study contributes to these contrasting results by reporting only a limited effect of body mass on HR (Cruz Aleixo et al, 2017). We presently controlled for body mass and age by adding them into the statistical model and found an influence of body mass on HR, while age affected both HR and HRV.…”