[Determination of the range of physiologic variation of the electrical axes using P, QRS, and T waves in pregnancy].

Since functional overload in pregnancy frequently induces the appearance of symptoms that could arouse suspicion of myocardiopathy, it is important to analyse and characterize all electrocardiographic modifications during a healthy subject's pregnancy. Variations of the mean electrical axis (A) of P, QRS and T waves were evaluated in 52 healthy volunteers, 17-37 years, during pregnancy. The A values were measured, in the frontal plane, at the end of both I and III quarter of pregnancy, using a method of scalar determination. The As in I and III quarters was compared with those observed in the post-partum (at 5th day) and statistical evaluations were performed (Student t-test for paired observations). In the I quarter the mean A was 40 +/- 3 degrees for P, 40 +/- 16 degrees for QRS and 32.5 +/- 9 degrees for T wave, whereas in the III quarter the mean A changed to 37 +/- 2 degrees for P, 34 +/- 18 degrees for QRS and 31 +/- 9 degrees for T. During pregnancy, all mean As significantly diverted to the left side, AP about 3 degrees, AQRS about 6 degrees and AT about 1.5 degrees. These results were also confirmed by analysis of A frequency distribution histograms. In the post-partum (5th day) the A resumed basal values (I quarter's values). These results show: i) the physiological range of AP, AQRS and AT, during pregnancy; ii) left deviation of all three As at the end of III quarter. It is possible to conclude that variation over this range, particularly for QRS, could give evidence of the onset of cardiopathy.