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Effects of myocardial alpha 1-adrenergic receptor stimulation and blockade on contractility in humans

J S Landzberg1, J D Parker, D F Gauthier

  • 1Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115.

Circulation
|October 1, 1991
PubMed

Insights

Stimulating myocardial alpha-adrenergic receptors in humans causes a positive inotropic effect, but does not affect basal contractility. This effect is reduced in heart failure patients.

Area of Science:

  • Cardiology
  • Pharmacology

Background:

  • Alpha-adrenergic receptors are present in human heart muscle.
  • Their role in human heart contractility is not fully understood.
  • These receptors mediate positive inotropic effects in other species.

Purpose of the Study:

  • To determine if alpha-adrenergic receptor stimulation affects human left ventricular contractility in vivo.
  • To investigate if these receptors contribute to basal contractile state.

Main Methods:

  • Infusion of alpha-adrenergic agents (phentolamine, phenylephrine) into the left main coronary artery.
  • Study included patients with normal left ventricular function and heart failure.
  • Left ventricular contractility assessed by measuring peak positive dP/dt.

Main Results:

  • Phenylephrine caused a concentration-related positive inotropic effect in both normal and failing ventricles.
  • Alpha-adrenergic effect was significantly attenuated in heart failure patients.
  • Phentolamine alone did not alter left ventricular contractility.

Conclusions:

  • Myocardial alpha-adrenergic receptors do not maintain basal left ventricular contractility in humans.
  • Stimulation of these receptors does produce a positive inotropic effect.
  • The magnitude of this effect may be reduced in heart failure.
Abstract

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