[Comparison of different electrocardiographic techniques for the detection of arrhythmias in horses]

The aim of the study was to extend the range of the electrocardiographic examination in horses, evaluating the practicability of special electrocardiographic techniques (exercise- and Holter-ECG) and comparing these with more common techniques (resting-ECG) in equine medicine.

Electrocardiographic examination (resting-ECG for 1 minute, exercise-ECG and Holter-ECG) was performed in 20 horses without any clinical or echocardiographic findings and in 80 patients with abnormal findings (valvular regurgitation and/or atrial fibrillation).

In comparison with the resting-ECG, the exercise-ECG demonstrated more atrial and ventricular premature beats, while the Holter-ECG had a higher detection rate of 2nd degree atrioventricular or sinuatrial blocks, and of ventricular and atrial premature depolarisations (p < 0.001). In comparison to the exercise-ECG, the Holter-ECG registered more 2nd degree atrioventricular blocks (p < 0.001) and ventricular (p < 0.001) or atrial premature contractions (p < 0.01). Atrial fibrillation was detected in every recorded ECG-type, but Holter-ECG provided additional information. Three of 16 horses with atrial fibrillation had R-on-T-episodes during Holter-monitoring. In addition to more common findings in the ECG, Holter-monitoring detected a 2nd degree atrioventricular block associated with an adjacent ventricular escape beat in a horse without any clinical or echocardiographic findings. An accelerated idioventricular rhythm was identified in a horse without any clinical or echocardiographic findings and in a horse with mitral valve insufficiency.

The Holter-ECG is a useful tool in the evaluation of heart disease and could supply additional information when compared to the usual diagnostic electrocardiographic procedures used in horses. Exercise-ECG should not be replaced by Holter-ECG, however, Holter-EGC can provide additional diagnostic value.