title: Left axis deviation: diagnostic contribution of stress testing and post-exercise systolic time intervals.
abstract: 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.
mesh_terms: D000328:Adult; D001794:Blood Pressure; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged