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  • Title: Variable effects of intracoronary nitroglycerin on myocardial blood flow and segmental shortening according to dose and degree of coronary occlusion.
    Author: Weintraub WS, Akizuki S, Agarwal JB, Bodenheimer MM, Banka VS, Helfant RH.
    Journal: Am Heart J; 1984 Apr; 107(4):707-10. PubMed ID: 6422731.
    Abstract:
    The effects of intracoronary nitroglycerin were determined in 21 open-chest dogs. Six dogs with severe stenosis (25 mm Hg diastolic perfusion pressure) and nine dogs with moderate stenosis (40 mm Hg) received a 12 micrograms bolus followed by 44 micrograms/min intracoronary nitroglycerin. In addition, six dogs with moderate stenosis (40 mm Hg) received 5 micrograms followed by 5 micrograms/min nitroglycerin. Myocardial blood flow was measured with radioactive microspheres and segment shortening with ultrasonic crystals. At 40 mm Hg, high-dose but not low-dose nitroglycerin raised epicardial blood flow, while at 25 mm Hg nitroglycerin had no effect. Subendocardial blood flow was not affected in any group. Partial occlusion resulted in a decrease in segment shortening in the 25 mm Hg group but not at 40 mm Hg. High-dose nitroglycerin had no effect on shortening at either level of occlusion. Thus, in the presence of coronary vascular reserve, high-dose nitroglycerin may overcome coronary autoregulation. A dose equivalent to one that simulates the amount of nitroglycerin delivered to the coronary circulation by a systemic infusion did not affect myocardial blood flow. In addition, even a large dose of nitroglycerin did not affect segment shortening.
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