The Effects of β-Adrenergic Blockade on Systemic Hemodynamics at Rest and during Exercise

The effects of proranolol and pindolol on systemic hemodynamics at rest and during bicycle exercise with work load at 27 watts were studied in 22 outpatients. Cardiac output was measured by dye dulution method. Twelve lead electrocardiograms were taken and blood pressure was measured by cuff method. The dosages used were 20 mg of propranolol and 5 mg of pindolol. There was no significant difference in effect on heart rate between propranolol and pindolol. Propranolol significantly decreased blood pressure only on exercise, while pindolol did it at rest as well as on exercise. Propranolol decreased cardiac output on exercise to the same extent than at rest while pindolol did it only on exercise. There was no significant change in stroke index on administration of propranolol, but a significant decrease on exercise with pindolol. Propranolol decreased cardiac work index on exercise to the extent than at rest while pindolol decreased it only on exercise. There was no significant difference in effect on double products between propranolol and pindolol, both of which decreased double products at rest as well as on exercise. Although propranolol increased peripheral vascular resistance at rest as well as on exercise, pindolol did not significantly change it.This data indicates that pindolol exerts more influence on hemodynamics on exercise than at rest except for blood pressure and double products, both of which are decreased at rest as well as on exercise.