History of research in Japan on electrocardiography in the racehorse

Abstract

Since the first recording of electrocardiograms (ECGs) of a horse in Japan was carried out in 1944, studies on ECGs have been performed intensively. During the early stages of research from the 1950s to 1960s, leads to use for ECG recording were evaluated using several different approaches including unipolar leads, bipolar limb leads, and bipolar chest leads. Based on these studies, the AB lead, which is oriented along the long axis of the heart, became the standard reference method in Japan. Electrodes of the AB lead are placed on the upper 1/4th point along a straight line between the withers and the left shoulder blade (base: B), and 10 cm posterior to the left olecranon (apex: A). The incidence of equine arrhythmias among racehorses has been surveyed, and details of the electrocardiographic characteristics of several arrhythmias have been investigated. In particular, atrial fibrillation (AF) has been extensively studied, and papers have reported findings such as that paroxysmal AF occurs during racing and described electrocardiographic changes that occur at the onset of AF during exercise. Development of a radiotelemetry system for ECG recording enabled the first recording of equine ECGs during galloping in 1964, the detection of arrhythmias, and calculation of heart rate during exercise. Studies on comparative and developmental changes of ECGs have described characteristics of the equine ECGs. Future research on changes in cardiac function, including autonomic function, that occur with aging may lead to new developments in equine electrocardiography and contribute to improving the health and welfare of the horse.

Heart rates, heart rate profiles, and electrocardiograms in three killer whales, a beluga, and a pilot whale: An exploratory investigation

“…, Lorne et al . ), and with exercise in horses (Marlin and Nankervis , Hiraga and Sugano ), such changes were limited to one or the other waveforms and were small relative to the two‐ to three‐fold changes observed in the entire ECG signals of the whales. Most probably, the changes observed in the whales were secondary to a change in the relationship of the electrical vector of the heart to the location of the suction cup electrodes.…”

A novel approach for obtaining 12‐lead electrocardiograms in horses

“…The MEA of the horse heart points upward from the apex toward the base of the heart and, although no standardized method for electrode placement exists for horses, most equine clinicians place the electrodes for the standard 3-lead ECG in a similar way along the MEA, as a "modified base-apex" lead. 5,[8][9][10] Few studies have explored the use of a 12-lead ECG in horses, [11][12][13] but at the time (1950-1980) the limb lead electrodes were placed on the legs. As a result, guidelines for obtaining a 12-lead ECG in horses today 14,15 still suggest placing the electrodes on the legs, which results in the MEA being almost perpendicular to the ECG leads ( Figure 1B) leading to poor ECG quality.…”

Studies on the exercise physiology of draft horses performed in Japan during the 1950s and 1960s

“…Following these studies, a new system for recording an electrocardiogram (ECG) during exercise using radiotelemetry was developed by Nomura et al . of The University of Tokyo in order to obtain HR during exercise [9, 30, 31], and a new simplified device for measurement of HR during draft exercise was also developed [32]. …”

“…In 1960, Nomura and Tominaga [29] recorded ECG from a draft horse walking on a specially constructed treadmill while drafting 5 different weights: 1/15, 1/10, 1/8, 1/6.5, and 1/5 of the horse’s BW. Then, in 1964, Nomura had succeeded in recording ECG during field exercise, including sprint galloping, using a newly constructed radiotelemetry system [9, 30, 31, 34]. However, this system was large in scale and very expensive, and only one other similar system was available in a research facility at that time in Japan.…”