Left axis deviation: diagnostic contribution of stress testing and post-exercise systolic time intervals.
The response to graded submaximal upright bicycle ergometry combined with resting and postexercise systolic time intervals (STIs) was investigated in ten ambulatory subjects (study group) with normal electrocardiograms except for a frontal plane axis of greater than or equal to -30 degrees, or left axis deviation (LAD) mean -40 degrees); and eight age-matched volunteers (control group) with a normal ECG and frontal plane axis (mean +35 degrees). Following a 12-lead resting ECG, supine STIs were measured. The subjects then exercised on a bicycle ergometer at progressive workloads with ECG and blood pressure monitoring until a heart rate based on 85 percent of tha age-predicted maximum was attained or an abnormal end point was noted. STIs were repeated immediately postexercise. Prolongation of left ventricular ejection time corrected for heart rate (LVETc) of 8 msecs or more from rest to post-exercise. (deltaLVETc) was considered an abnormal STI response. The deltaLVETc can elicit left ventricular dysfunction and possible latent organic heart disease in patients with isolated left axis deviation.
D000328:Adult; D001794:Blood Pressure; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged