Evaluation of normal variations in S-T segment patterns by body surface isopotential mapping: S-T segment elevation in absence of heart disease.

S-T segment elevation is commonly observed in the electrocardiogram of normal persons. To study the possible origins of such patterns, 45 normal volunteers were examined. Electrocardiographic potentials were registered from 150 torso electrodes and processed to construct isopotential maps at 2 ms intervals throughout the QRS-T interval. The maximal potentials recorded from any of the 150 electrodes were 198 +/- 76.4 and 272.1 +/- 84.2 microV at instants 40 and 80 ms into the S-T segment, respectively. Maximal voltages recorded by the six standard precordial V leads at these respective time points were 109.7 +/- 57.0 and 163.6 +/- 66.9 microV. Torso maximal potentials were significantly stronger than were those sensed by V leads; the two were significantly correlated but predictability was limited. The duration of overlap between the onset of ventricular recovery and the end of the excitation was determined from isopotential maps and ranged rom 4 to 16 ms. There was no significant correlation (p greater than 0.05) between these values and either torso or V lead potentials at either 40 or 80 ms into S-T segment. These data suggest that (1) standard precordial leads do not accurately predict maximal torso potentials during the S-T segment, and (2) the degree of overlap between repolarization and depolarization is not a major determinant of precordial voltage. Hence, the rationale for use of the term "early repolarization" to describe this clinical condition is not substantiated.