Twenty healthy male subjects (age range, 15-25 years; median, 21 years
) underwent magnetocardiography during physical exercise. Significant
ST-segment displacements of the magnetic signal were found during exer
cise at a heart rate of 120 beats/min compared to the magnetic signal
at rest (P < .001). Since no significant ST-segment changes were found
in the electrocardiogram recorded simultaneously with the magnetocard
iogram, it is concluded that the magnetocardiogram shows junctional ST
-T segment changes earlier than the electrocardiogram.