Exercise haemodynamic effects of beta-blockade and intrinsic sympathomimetic activity.
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 beta 1-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 16.01.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.
Ades
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Division of Cardiology and Internal Medicine, University of Colorado Health Sciences Center, Denver.
Wolfel
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Hiatt
W R
WR
Fee
C
C
Rolfs
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R
Brammell
H L
HL
Horwitz
L D
LD
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004311:Double-Blind Method; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D007866:Leg / Q000098:blood supply; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D005082:Physical Exertion; D010869:Pindolol / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology*; D011897:Random Allocation; D012039:Regional Blood Flow / Q000187:drug effects
D011433:Propranolol; D010869:Pindolol