Two Methods for 24-hour Holter Monitoring in Horses: Evaluation of Recording Performance at Rest and During Exercise.

Continuous electrocardiography (ECG) monitoring is the gold standard for diagnosing arrhythmias that occur intermittently or under exercise. The aim of this study was to compare two different methods for 24-hour Holter monitoring in horses, a 7-electrode system (7-ES) versus a 4-electrode system (4-ES), assessing the recording performance at rest and during exercise. Six standardbred horses were included in the present prospective study. Two different methods for 24-hour Holter monitoring were used in each horse with a washout period of one week between each recording method. In the first 15 minutes of the 24-hour Holter monitoring, a standard exercise test was performed. Holter recordings were analyzed in terms of the number of recorded hours; the number of detached electrodes (DEs); and total duration of artifacts over the 15-minute exercise. The number of recorded hours was significantly higher in the 7-ES (24 hours, range: 23-24 hours) than the 4-ES (6.5 hours, range: 1.2-20 hours; P < .05). The number of DEs was not significantly different between the two systems. The total duration of artifacts over the 15-minute exercise was significantly higher in the 7-ES (155 seconds, range: 35-378 seconds) than in the 4-ES (25 seconds, range: 10-32 seconds; P < .05). Our results showed a better recording performance during exercise using the 4-ES because of the lower number of artifacts. The 7-ES showed a better performance in terms of recording duration. In conclusion, we suggest using the 4-ES for exercise tests and the 7-ES when a longer ECG recording at rest is required.