The intraindividual variability in mean electric axis referable to choice of ECG leads and augmentation ratio was investigated by means of a digital computer program. Although, in theory, the choice of leads for determining the QRS axis should make no difference, the maximum intraindividual variation in axis angle was about 50 degrees for canine and feline subjects. The angle conputed for the lead combinations I and III and I and aVF will usually fall within 5 to 10 degrees of the mean of all lead combinations, but larger variations are seen at time. The application of an "augmentation ratio" for the augmented unipolar leads was most helpful when it was individually computed. Further methods of lead-vector improvement are discussed.

Animals↗

PubMed1976

Effects of anticoagulants on packed cell volume measurement.

A comparison was made of different types of anticoagulants on packed cell volume determinations of canine, feline, rabbit, and human blood. It was found that the use of excessive amounts of anticoagulant alters the packed cell volume when measured by the standard centrifuge method. It was also found that the results vary significantly when different anticoagulants are used. The effects are not seen when the packed cell volume is indirectly measured using an electronic cell counter. A balanced combination of ethylenediaminetetraacetic acid salts ameliorates the concentration-dependent effects.

Animals↗