Vitamin C augments the inotropic response to dobutamine in humans with normal left ventricular function.
BACKGROUND
We studied the effect of an antioxidant, the intracoronary infusion of vitamin C, on basal and dobutamine-stimulated left ventricular (LV) contractility.


RESULTS
Nineteen patients with normal ventricular function participated in this study. A micromanometer-tipped catheter was inserted into the LV. In the experimental group (n=10), an infusion catheter was positioned in the left main coronary artery. LV peak +dP/dt (LV +dP/dt) was measured in response to the intravenous infusion of dobutamine before (Dob) and during (Dob+vit C) the intracoronary infusion of vitamin C. The intracoronary infusion of vitamin C had no effect on basal LV +dP/dt or any other hemodynamic parameter. The infusion of vitamin C augmented the LV +dP/dt response to dobutamine by 22+/-4% (Dob, 1680+/-76 mm Hg/s; Dob+vit C, 1814+/-97 mm Hg/s, P<0.01). In the control group (n=9), LV +dP/dt was measured in response to sequential infusions of dobutamine (Dob, Dob-2) given at the same time intervals as in the experimental group but without the intracoronary infusion of vitamin C. In contrast to the experimental group, no difference in LV +dP/dt was observed between the 2 infusions of dobutamine (Dob, 1706+/-131 mm Hg/s; Dob-2, 1709+/-138 mm Hg/s, P=NS).


CONCLUSIONS
The administration of the antioxidant vitamin C augments the inotropic response to dobutamine in humans. This suggests that redox environment contributes to the adrenergic regulation of ventricular contractility.
Mak
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Bayer Cardiovascular Clinical Research Laboratory, Division of Cardiology, Mount Sinai Hospital, University of Toronto, Ontario, Canada. gary.newton@utoronto.ca
Newton
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D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D006328:Cardiac Catheterization; D002316:Cardiotonic Agents / Q000494:pharmacology*; D003327:Coronary Disease / Q000628:therapy; D003331:Coronary Vessels; D003924:Diabetes Mellitus, Type 2 / Q000628:therapy; D004280:Dobutamine / Q000494:pharmacology*; D004357:Drug Synergism; D005260:Female; D006439:Hemodynamics; D006801:Humans; D006973:Hypertension / Q000628:therapy; D007261:Infusions, Intra-Arterial; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000187:drug effects; D010084:Oxidation-Reduction; D016277:Ventricular Function, Left / Q000187:drug effects*
D000318:Adrenergic beta-Agonists; D000975:Antioxidants; D002316:Cardiotonic Agents; D004280:Dobutamine; D001205:Ascorbic Acid