Evaluation of a novel ambulatory electrocardiogram monitor (the Carnation Ambulatory Monitor) for use in horses

Introduction: Short-term electrocardiogram (ECG) examinations of horses may not detect paroxysmal arrhythmias. Twenty-four hour Holter equipment can be unwieldy and inconvenient for long-term use. This study evaluated a novel long-term ECG patch recorder, the Carnation Ambulatory Monitor (CAM) in horses, determining ideal placement, practicality, durability and performance.

Animals: Twenty-one adult mixed-breed horses.

Methods: Prospective observational study. Three horses had ECG patches fitted at selected sites (phase 1); the two most promising sites were used for further wear testing (phase 2) and the best site was chosen for a trial in 18 horses (phase 3), 16 of which had presented for evaluation of cardiac disease. In phase 1, the CAM was compared with a standard telemetric ECG. The CAM ECGs were analysed using proprietary software.

Results: The most promising sites for CAM placement were the ventral midline caudal to the xiphisternum and left thorax caudal to the girth. The ventral midline was chosen for further evaluation. The CAM provided reliable and generally excellent ECG quality at rest (median quality score 4.5/5, range 3-5), over extended periods, allowing detection of arrhythmias. The ECG quality was poor during exercise (median quality score 1, range 1-5), except in three horses. In 15/17 placements in the standing horse, greater than 85% of the potential recording time was achieved.

Conclusions: The CAM is a convenient and well-tolerated device for evaluating equine cardiac rhythm at rest over long periods. Further evaluation of the ideal placement site during exercise may increase its diagnostic utility.