Time course and clinical significance of marked left axis deviation in airline pilots.

The purpose of this study was to examine the time course and evaluate the clinical significance of marked left axis deviation (LAD) in airline pilots. The study group consisted of 30 Japan Airlines' pilots with marked LAD, identified from a group of 1,700 who are now 35 years of age or older. The mean age at examination was 48.5 +/- 5.7 years [corrected] and the mean observation period was 22.6 +/- 5.6 years [corrected]. The prevalence rate of marked LAD was 1.8%. In 20%, the axis remained unchanged, and in 70%, LAD progressed either gradually or suddenly. All subjects were examined by exercise testing and 26 had echocardiograms. Two pilots (6.7%) were found to have organic heart disease (hypertension), which was much lower than the rate reported previously. In these individuals, the onset of marked LAD was noted more than 10 years before hypertension was detected. No progression to complete left bundle branch block, nor any form of AV block, was observed among these subjects. No cardiac events or death occurred during the study period.