Exercise haemodynamic effects of beta-blockade and intrinsic sympathomimetic activity |
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Authors: | P. A. Ades E. E. Wolfel W. R. Hiatt C. Fee R. Rolfs H. L. Brammell L. D. Horwitz |
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Affiliation: | (1) Division of Cardiology and Internal Medicine, University of Colorado Health Sciences Center, Denver, CO, USA;(2) Cardiology Unit, McClure 1, Medical Center Hospital of Vermont, Burlington, VT, USA |
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Abstract: | Summary Beta-adrenergic blockade with intrinsic sympathomimetic activity (ISA) causes less depression of resting and submaximal heart rate (HR) than non-ISA beta-blockers. The effects of these drugs on exercise haemodynamics have not been well studied. We evaluated effects of pindolol, propranolol and placebo during rest and steady-state exercise on cardiac output, oxygen consumption, calf blood flow, HR and blood pressure in 18 healthy subjects.Pindolol 5 mg and propranolol 80 mg given twice daily, reduced maximal exercise HR by 50 and 52 beats·min–1 respectively, confirming similarity of beta1-blockade. Resting cardiac output was unchanged in all three groups after one week of therapy.Cardiac output, measured during steady-state exercise decreased in the propranolol group (18.3 vs 15.6 l·min–1) with no significant changes in pindolol (15.7 vs 16.0 l·min–1) or placebo (18.6 vs 17.3 l·min–1). The rise in cardiac output, from rest to exercise, was similarly attenuated by propranolol but not by pindolol or placebo. Exercise stroke volume increased 12% on pindolol (123–140 cc) and decreased 7% on propranolol (143–133 cc).Neither drug had a detrimental effect on exercise calf blood flow compared to placebo. Thus, unlike propranolol, pindolol with ISA, maintains a normal cardiac output during submaximal exercise.Presented in part at the National meeting of the American Federation for Clinical Research, Washington, D.C., May, 1985 |
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Keywords: | beta-receptor blockade intrinsic sympathomimetic activity exercise haemodynamics |
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