The effects of oral administration of propranolol on the electrocardiogram (ECG), vector-cardiogram (VCG) and plasma potassium levels were studied in the following groups: healthy controls, and patients with neurocirculatory asthenia (NCA), ischemic heart disease (IHD), hypertension and persistent juvenile T wave pattern. ECG and VCG were taken before, 30, 60 and 90 minutes after oral administration of propranolol in a single dose of 10mg. The results were as follows: 1) RR, PQ and QT intervals were prolonged while the rate-corrected QT interval was shortened in each group. 2) The amplitude of the T wave and the magnitudes of spatial maximum T vector and of ventricular gradient (V.G.) were increased in the healthy control group. 3) In the NCA group, which was characterized by a low T wave, small T loop, small V.G. and posteriorly directed V.G. before propranolol administration, the T wave, T loop and V.G. were enlarged and V.G. was rotated toward anteriorly. 4) In the IHD group, which was characterized by a low T wave and small T loop and V.G., the changes were unremarkable after the administration of propranolol. 5) In the well controled hypertensive group the effects resembled those of the healthy control group. In the hypertensive group without sufficient treatment, the effects were similar to those of the IHD. 6) In the persistent juvenile T wave group, a typical pattern was the location of the T loop and V.G. in the left posterior quadrant. The drug rotated the T loop and V.G. anteriorly. 7) Little change was found in the R wave amplitude and spatial maximum QRS vector in each group. 8) Plasma potassium level was not effected by the drug. 9) No undesirable effects were seen during the study. 10) The maximum effects were obtained within 60 to 90 minutes after the administration of propranolol. From the above results, propranolol appears to be useful in differentiating T wave changes associate with increased beta-sympathetic tone from changes due to other causes.
nonspecific T wave change