Exercise electrocardiographic mapping in normal subjects

To investigate the spectrum of change in multiple-lead exercise electrocardiograms, 120-lead body surface potential maps (BSPM) in normal adult subjects during upright, graded, submaximal exercise testing were recorded. Results showed that in the normal group, exercise was associated with substantial electrocardiographic changes on the body surface, many of which persisted during early recovery. The QRS waveform was minimally altered during exercise. Despite, however, no change in QRS duration, there was significant reduction in QRS potential range with consequent reduction QRS integral value. The ST waveforms changed markedly with exercise, showing abbreviated duration and increased slope. This was reflected by significantly increased ST potential range from rest to immediate cessation of exercise, which returned towards resting value during recovery. The effect of the altered ST-segment waveform was also reflected in torso potential distributions at two time instants during the ST-segment. When a spatially-fixed position on the ST-T waveform was evaluated (ST-segment offset), exercise resulted in small potential changes, especially over the torso area occupied by the standard V1 to V6 chest leads. However, when a temporally-fixed point (80 ms after QRS offset) was evaluated, there were large increases in potential over the precordium with exercise. Isointegral ST-segment maps, which reflect both spatial and temporal ST properties, showed that exercise was associated with substantial decreases in values over the precordium and inferior torso, and although diminished, they tended to persist through five minutes of recovery. Thus, electrocardiographic repolarization parameters are particularly affected by physiological exercise and, although the underlying causes of these changes remain undefined, they should be taken into account when evaluating the population at risk.