Electrocardiographic parameters of normal alpacas (Lama pacos).

The electrocardiographic parameters of 40 healthy alpacas (Lama pacos) were recorded with a base-apex lead system to establish the normal resting electrocardiographic parameters in this species. The following parameters were measured: heart rate and rhythm, QRS and T morphology, ST segment position, P amplitude and duration, QRS duration and PQ and QT intervals. The heart rate varied between 50 and 110 bpm, with a mean (sd) of 80 (17.8) bpm, and no significant differences were observed between males and females or between alpacas of different ages. Sinus arrhythmia was observed in 35 of the animals, and a regular sinus rhythm was recorded in the other five. The QRS morphology was variable, with an 'rS' pattern observed in 29 animals, 'RS' in six, 'Rs' in three and 'QS' in the other two. A variable morphology was also observed for the T wave, which was positive in 27 animals, negative in seven and biphasic in the other six. All the electrocardiographic parameters were normally distributed and no significant differences were observed between the sexes, except that the amplitude of the P wave was higher in males. The PQ interval was significantly shorter in animals less than six months old.