Evaluation of precordial orthogonal vectorcardiographic lead ST-segment magnitude in the assessment of myocardial ischemic injury.

Relationship has been established between epicardial ST-segment elevation, considered a reliable estimate of ischemic injury in experimental myocardial damage, and ST changes by multiple-lead precordial electrocardiography. However, 35-lead precordial mapping is time-consuming and suitable only for anterior infarctions. An alternate, more rapid method for recording ST segments is an external 3-lead orthogonal vectorcardiographic (VCG) system which also can assess the entire ventricle. Accordingly, validity of VCG ST magnitude was evaluated by direct comparison with changes in epicardial ST magnitude (EST) induced by occlusion of major coronary arteries, reperfusion, and pharmacologic interventions in 15 closed-chest dogs. A total of 404 data points (average 27/dog), 20 epicardial grid and 3 Frank XYZ leds each, demonstrated close correlation (least squares linear regression) between VCG ST and EST changes (r = 0.921 +/- 0.02 SEM). These data document the accuracy of precordial VCG ST in noninvasive assessment of ischemic injury in various areas of myocardium and its practicality for clinical application.