Reasons for performing study: Frequent supraventricular or ventricular arrhythmias during and after exercise are considered pathological in horses. Prevalence of arrhythmias seen in apparently healthy horses is still a matter of debate and may depend on breed, athletic condition and exercise intensity.
Objectives: To determine intra- and interobserver agreement for detection of arrhythmias at rest, during and after exercise using a telemetric electrocardiography device.
Materials and methods: The electrocardiogram (ECG) recordings of 10 healthy Warmblood horses (5 of which had an intracardiac catheter in place) undergoing a standardised treadmill exercise test were analysed at rest (R), during warm-up (W), during exercise (E), as well as during 0–5 min (PE0–5) and 6–45 min (PE6–45) recovery after exercise. The number and time of occurrence of physiological and pathological ‘rhythm events’ were recorded. Events were classified according to origin and mode of conduction. The agreement of 3 independent, blinded observers with different experience in ECG reading was estimated considering time of occurrence and classification of events.
Results: For correct timing and classification, intraobserver agreement for observer 1 was 97% (R), 100% (W), 20% (E), 82% (PE0–5) and 100% (PE6–45). Interobserver agreement between observer 1 vs. observer 2 and between observer 1 vs. 3, respectively, was 96 and 92.6% (R), 83 and 31% (W), 0 and 13% (E), 23 and 18% (PE0–5), and 67 and 55% (PE6–45). When including the events with correct timing but disagreement for classification, the intraobserver agreement increased to 94% during PE0–5 and the interobserver agreement reached 83 and 50% (W), 20 and 50% (E), 41 and 47% (PE0–5), and 83.5 and 65% (PE6–45). The interobserver agreement increased with observer experience.
Conclusions: Intra- and interobserver agreement for recognition and classification of events was good at R, but poor during E and poor-moderate during recovery periods. These results highlight the limitations of stress ECG in horses and the need for high-quality recordings and adequate observer training.