This study was designed to elucidate the basic changes in electrocardiogram during phase I study. Lead II electrocardiograms were recorded from 10 healthy male volunteers (Group P) with placebo administration and blood sampling, and 16 healthy male volunteers (Group N) with no placebo and no blood sampling by the time schedules of phase I study of some cardiovascular drugs. The RR intervals were significantly prolonged (P<0.01) before lunch and then shortened (P<0.05) by taking lunch, in both groups. Prolongation of RR interval was more pronounced in Group N. Maximum prolongation was observed at 3 hr (9.6%) in Group P, and at 2. 67 hr (12. 5%) in Group N. The PR intervals and QRS width revealed no significant change during observation period. The QT interval was significantly prolonged (P<0.05) before lunch in Group N, but not in group P, and significantly shortened (P<0.05) after lunch in Group P but not in Group N, whereas the QTc was significantly shortened (P<0.05) in both groups before lunch. These results indicated that the RR interval was lengthened with bed rest but this effect was attenuated by drawing blood sample, and suggested that rate-dependent QT prolongation and dis cordant shortening of QTc before lunch resulted in overcorrection by Bazett's formula The T wave amplitude was significantly increased (P<0.01) by 4 hr-check up point and then suddenly reduced by taking lunch. This suggests that T wave amplitude might be controlled by blood glucose level.
It should be noted that the electrocardiographic effects of phase I study of cardiovascula: drugs might be affected by these changes.