Reasons for performing study: In human medicine, oesophageal electrocardiography (ECG) is a well-established technique that magnifies P waves with respect to the QRS complex.
Objectives: To investigate the feasibility of oesophageal ECG recording in horses and its ability to produce larger P waves compared with base-apex and unipolar recordings.
Methods: Bipolar and unipolar ECG were performed using oesophageal and surface electrodes. Oesophageal ECG was obtained from 6 different recording configurations at different oesophageal depths. Amplitudes of P, Q, R, S and T waves were measured from 3 different cardiac cycles for each recording configuration and depth.
Results: Oesophageal ECG was feasible in all horses. For all oesophageal recording configurations, significantly larger P waves were recorded from a depth that equalled ‘height of the withers + 10 cm’ (HW+10) than from any other depth. P/QRSmagn, the ratio between the P wave and QRS complex magnitudes, was largest for intraoesophageal recordings with an interelectrode distance of 10 cm, at HW+10, where it was significantly larger than base-apex and unipolar recordings. Base-apex recording resulted in significantly smaller P waves than all other recording configurations and significantly smaller P/QRSmagn ratios than all other recording configurations except one combined oesophageal-surface recording (E/Slow).
Conclusions: Oesophageal ECG recording is feasible in horses and effective in magnifying P wave amplitude.
Potential relevance: The procedure is promising for diagnosis of supraventricular tachydysrhythmias and might be used in electrophysiological studies and for cardiac pacing.