Effect of Nipradilol on Exercise Electrocardiogram in Angina Pectoris: Analysis of Heart Rate-ST Segment Loop.

To study the effect of nipradilol, a new antianginal agent with vasoactive property as well as β-blocking action, on exercise electrocardiogram, multi-stage treadmill tests were performed after the administration of nipradilol and propranolol in 10 patients with stable effort angina pectoris. The effect of nipradilol on conventional measures in exercise ECG (heart rate, systolic BP, ST segment deviation, exercise duration, pressure rate product) was not significantly different from that of propranolol. An analysis of heart rate-ST loop (HR-ST loop), ST segment deviation plotted as a function of heart rate, during exercise and recovery revealed that nipradilol shifted the HR-ST loop rightward, indicating less prominent ST segment depression relative to the increase in HR when compared with propranolol. Calculated ST segment depression relative to the change in HR was smaller with nipradilol than with propranolol during exercise (ΔST/ΔHR from rest to peak exercise: nipradilol 5.57±0.81 vs propranolol 6.71±1.07μV/bpm, p<0.05) and recovery (recovery index: nipradilol 1.83±0.65 vs propranolol 3.01± 0.74μV/bpm, p<0.05). These results indicated that nipradilol may have beneficial effects on exercise ECG in angina pectoris other than β-blocking action, such as a vasoactive property.