Evaluation of heart rate and rhythm during exercise

Abstract

Summary Heart rate and rhythm can readily be monitored during exercise. Although there is considerable variation depending on the athletic discipline, exercise can be considered to be one of the most physiologically demanding times for the cardiovascular system. Assessment of heart rate during exercise typically provides information regarding fitness and the intensity of exercise, and on some occasions may provide an early indication of disease. Cardiac causes of poor performance occur relatively infrequently in comparison with disorders of the musculoskeletal and respiratory systems. Nevertheless, exercise induces cardiac hypertrophy, which predisposes athletes to valvular regurgitation and arrhythmias. Consequently cardiac murmurs and arrhythmias are frequently present in equine athletes, whereupon the clinical significance can be difficult to determine. Undertaking an exercise test to identify exercise‐induced arrhythmias is important in the assessment of poor athletic performance and the risk of sudden cardiac death during exercise. This paper describes the assessment of heart rate and rhythm during exercise. Most research has been undertaken on racehorses but, where data are available for other disciplines, they have been included. Considerations regarding the choice, type and design of exercise test were detailed in the first paper in this series.

Cardiac, respiratory and thermoregulation parameters following graded exercises in Lipizzaner horses

“…HRs increased gradually with the transitions from walk to trot, and thereafter to canter, and displayed a linear regression with gait velocity up to the maximal HR, which may exceed 200 beats/min in various horse breeds (HARGREAVES et al, 1999;SERRANO et al, 2002;VINCENT et al, 2006;HARRIS et al, 2007;MUKAI et al, 2007;PADALINO et al, 2014;ALLEN et al, 2016). Similar responses of HRs, correlating positively with speed progression, were also determined in the Lipizzaners in both months.…”

“…The response of HR to exercise is a function of exercise intensity and reflects metabolic capacity. It can be influenced by several exogenous factors, such as the characteristics of the track, environmental conditions, and the training state and health status of the horse (SLOET VAN OLDRUITENBORGH-OOSTERBAAN et al, 1991;HARGREAVES et al, 1999;KOBAYASHI et al, 1999;MUNSTERS et al, 2014;ALLEN et al 2016).…”

Irregular hearts and performance horses

“…Papers by Slack et al and Allen et al 5,6 address these issues. Both explore our understanding of what is to be expected and how we might respond as clinicians, and both work with the limitations of our current knowledge.…”

“…Both explore our understanding of what is to be expected and how we might respond as clinicians, and both work with the limitations of our current knowledge. Allen et al 6 summarise what we presently know or suspect about rhythm changes during exercise, and to make statements helpful and succinct, must deal with generalisations and extrapolations. Slack et al 5 attempt to widen our understanding by collecting contextual observational data.…”

“…“It depends,” because the output (here, heart rate and rhythm) depends so very much on the input, which in this case is the sum total of the physiologic and environmental circumstances that prevail. The predisposition of the equine heart to variations in rhythm coupled with the fact most horses are athletes and appear to share with their human counterparts a predisposition to an athletic heart, 6 together with usually benign ventricular rhythm disturbances, 7,8 means any guidance that can be obtained is very welcome. However, there is always the dilemma that you find only what you look for, and that something of even greater significance may be missed simply because we don't know to look, or how to look, or when to look.…”