EFFECTS OF RIGHT VENTRICULAR PACING ON QRST ISOINTEGRAL MAPS IN PATIENTS WITH AND WITHOUT MYOCARDIAL-INFARCTION - BODY-SURFACE DISTRIBUTIONOF SIGNIFICANT CHANGES IN QRST AREA COMPARED TO SUPRAVENTRICULAR COMPLEX

To assess the effects of right ventricular (RV) pacing on body surface QRST distributions, we recorded QRST isointegral maps (I-maps) during sinus rhythm and RV pacing in 25 patients with anterior myocardial in farction (MI), 19 with inferior MI, and 14 without MI. The QRST values at each lead point recorded during sinus rhythm and RV pacing with an 87-lead system were analyzed with a paired t-test in each patient. An abnormal decrease in the QRST value of the I-map was assessed by the difference map, which indicated a ''-2SD area,'' where the QRST integr al value was less than the normal range (mean - 2SD) calculated from 6 08 normal individuals. The I-maps were similar during the two activati on sequences in patients with and without MI. However, during RV pacin g, QRST values significantly decreased over the upper right anterior c hest and increased over the lower left anterior chest and back. The SI GMADMs (sum of QRST integral values below the normal range) for both a ctivation sequences were strongly correlated in patients with anterior MI and with inferior MI (r = 0.91 and r = 0.92, respectively; P < 0.0 01). Although small but significant changes in QRST values were detect ed, the distribution of the ''-2SD area'' and the SIGMADM were similar during both activation sequences in patients with prior MI. Thus, the se findings demonstrate that an altered activation sequence produces s mall but significant changes in QRST values but that I-maps still prov ide information that is useful for the diagnosis of MI during RV pacin g.