Influence of R-wave amplitude on exercise-induced ST XXXX : need for a "gain factor" correction when interpreting stress electrocardiograms.

@entity1 @entity4214 @entity308 @entity741
Does 2 mm of ST @entity308 induced by exercise have the same clinical significance in a @entity1 with a 30-mm R wave as a @entity1 with a 10-mm R wave in the same monitored lead? To answer this question the exercise responses of 85 @entity1 were compared by 2 quantitative methods of assessing @entity741 . A computer-derived treadmill exercise score, based largely on the characteristics of exercise-induced @entity308 , was compared with a thallium exercise score. Both scores correlated well over a wide range of values (r = 0.71, p less than 0.001). Then, the treadmill exercise score was corrected (by adjusting the magnitude of the ST @entity308 to a standardized R-wave amplitude of 12 mm in V5 and 8 mm in aVF) to determine if this would improve its correlation with the @entity4214 exercise score. The @entity1 were separated into 2 groups by R-wave amplitude: 53 had an RV5 of 9 to 17 mm and 32 had an RV5 less than 9 or greater than 17 mm. Correction of the treadmill exercise score for R-wave amplitude did not change the slope and intercepts of the regression line for @entity1 with an RV5 amplitude of 9 to 17 mm, but did for those with an RV5 amplitude less than 9 or greater than 17 mm. In this latter group, R-wave correction changed the regression line from one that differed significantly from that of @entity1 with less extreme RV5 voltage to one that was indistinguishable from it. Correction of the treadmill exercise score also increased the correlation coefficient from 0.54 to 0.68 in this group.(ABSTRACT TRUNCATED AT 250 WORDS)
