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Small vessel and total coronary blood volume during intracoronary adenosine

G J Crystal, H F Downey, F A Bashour

    The American Journal of Physiology
    |August 1, 1981
    PubMed

    Insights

    Intracoronary adenosine dilates larger coronary vessels, increasing blood flow and oxygen tension, but does not affect small-vessel blood volume or oxygen consumption. This suggests adenosine primarily impacts larger arterioles, not precapillary sphincters.

    Area of Science:

    • Cardiovascular Physiology
    • Microcirculation Research
    • Myocardial Metabolism

    Background:

    • Understanding coronary circulation regulation is crucial for treating ischemic heart disease.
    • Adenosine is a potent vasodilator, but its precise effects on different levels of the coronary vasculature remain debated.

    Purpose of the Study:

    • To investigate the impact of intracoronary adenosine on total and small-vessel coronary blood volume, hematocrit, and oxygen supply-demand dynamics in canine myocardium.
    • To determine whether adenosine affects precapillary sphincters or larger resistance vessels.

    Main Methods:

    • Anesthetized open-chest dogs were used to measure coronary blood volume (CBV), small-vessel blood volume (MSVBV), and hematocrit (MSVHct) using radiolabeled red blood cells and plasma.
    • Coronary blood flow (CBF), myocardial oxygen consumption (MVO2), and myocardial oxygen tension (MPO2) were also measured.

    Main Results:

    • Adenosine significantly increased CBV by 75%, CBF by 574%, and MPO2 by 122%.
    • MSVBV, MSVHct, and MVO2 remained largely unaffected by adenosine infusion.
    • Myocardial small-vessel hematocrit (MSVHct) was consistently lower than large-vessel hematocrit.

    Conclusions:

    • Intracoronary adenosine causes vasodilation primarily in vessels larger than 100 micrometers, not precapillary sphincters.
    • Increased MPO2 may counteract adenosine's effect on precapillary sphincters during high flow.
    • Accurate MSVBV measurements necessitate using both red blood cell and plasma labels.

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