Normal electro- and vectorcardiographic data in the growing Friesian calf using a semi-orthogonal lead system.

This study derives normal values for electro- and vectorcardiographic parameters, as generated by the Holmes semi-orthogonal lead system, in healthy growing calves. Sixty-four electrocardiograms were recorded from healthy Friesian calves aged from one week to one year. Waveform and duration were analysed and compared in the X-, Y- and Z-leads. The modal P, QRS and T tridimensional vectors were graphically constructed and their magnitude and orientation were calculated. The duration of waves and intervals were similar to data previously reported in the bovine species. Differences from data reported in other species were attributed to heart rate. The duration of waves and QT and ST intervals significantly lengthened with the decrease in heart rate which occurred during growth. PR interval significantly lengthened with physical maturation, and this change was independent of the decrease in heart rate. The magnitude and the orientation of the spatial modal vectors were approximately similar to the few data previously reported in cattle and in other ungulates and were not affected by somatic growth.