Effects of a coronary α1-constriction on transmural left ventricular flow and contractile function

P. A. Gwirtz, O. J.M. Dodd, H. F. Downey, H. J. Mass, B. A. Barron, A. G. Williams, C. E. Jones

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16 Scopus citations

Abstract

Modulation of myocardial contractile function and perfusion by α1- adrenergic receptors were examined in anesthetized dogs during left stellate ganglion stimulation. In 11 dogs, stellate stimulation significantly increased heart rate, mean arterial pressure, left ventricular systolic pressure, maximal rate of left ventricular pressure generation, segmental shortening and rate of shortening in anterior and posterior ventricular regions, and myocardial oxygen extraction. Myocardial lactate extraction decreased. The selective α1-adrenergic antagonist prazosin (0.5 mg) injected into the circumflex artery during stellate stimulation caused significant additional increases in maximal rate of left ventricular pressure generation by 19 ± 5% and in rate of shortening in posterior subendocardium by 20 ± 6%. No changes were observed in posterior subepicardial or anterior subendocardial segmental contractile function. Myocardial oxygen and lactate extractions returned to their control values following prazosin injection. Regional left ventricular perfusion was measured using tracer microspheres in five additional dogs. Stellate stimulation increased subepicardial and subendocardial perfusion by 30%. Prazosin increased both subepicardial and subendocardial perfusion by an additional 36%. Stellate stimulation increased norepinephrine concentration in the coronary sinus, but no further increase was noted after blockage of α1-receptors by prazosin. Thus, during sympathetic stimulation, an α1-vasoconstriction existed uniformly across the left ventricular wall. However, blockade of this vasoconstriction was associated with an increase in contractile function only in the deeper muscle layers.

Original languageEnglish
Pages (from-to)H965-H972
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume262
Issue number4 31-4
StatePublished - 1992

Keywords

  • coronary circulation
  • myocardial function
  • prazosin
  • sympathetic stimulation
  • α-adrenergic blockade
  • α-adrenoceptor

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    Gwirtz, P. A., Dodd, O. J. M., Downey, H. F., Mass, H. J., Barron, B. A., Williams, A. G., & Jones, C. E. (1992). Effects of a coronary α1-constriction on transmural left ventricular flow and contractile function. American Journal of Physiology - Heart and Circulatory Physiology, 262(4 31-4), H965-H972.