Electrocardiogram of the racing pigeon (Columba livia domestica).

Using standard limb leads electrocardiograms (ECGs) were recorded in 60 pigeons. The greatest amplitude of the P wave was observed in lead II in the majority of ECGs. The predominant pattern of the P wave was positive in leads I and II, biphasic (-/+) in lead III, negative in aVR, biphasic (+/-) in aVL and positive in aVF. A Ta wave was observed in 50 out of 60 tracings. Wenckebach's phenomenon was observed in three different pigeons. In lead I the QRS pattern was rs or qs. In leads II, III and aVF the waveform was rS or QS. In leads aVR and aVL this pattern was R or qR. The highest voltage was observed in lead II. ST elevation and ST slurring were common findings. The T wave was always discordant, except for lead I, where the T wave was isoelectric. Reference values for electrocardiographic parameters were established.