The Effects of alpha2-Adrenergic Stimulation with Mivazerol on Myocardial Blood Flow and Function During Coronary Artery Stenosis in Anesthetized Dogs

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Abstract
The central sympatholytic effect of (Ye agonists may be beneficial during myocardial ischemia, but could be op- posed by their peripheral vasoconstrictive effect. We studied the effects of mivazerol during periods of mod- erate coronary artery stenosis in anesthetized dogs. Mivazerol decreased heart rate (from 125 + 6 to 106 5 6 bpm) and cardiac output (from 4.4 + 0.6 to 1.8 + 0.2 L/min) under normal conditions, while mean arterial pressure did not change. Mivazerol reduced blood flow in nonischemic myocardium and in the ischemic epi- cardial layer, but blood flow was preserved in the isch- emit midmyocardial and subendocardial layer. Mivaz- erol had no effect on myocardial oxygen extraction during the stenoses, and regional myocardial oxygen consumption was unchanged. However, mivazerol de- creased myocardial oxygen demand from 4.51 + 0.51 to 3.17 -C 0.24 pmol * min-' * g-', thereby reducing oxy- gen deficiency of ischemic myocardium to values sig- nificantly lower than in the placebo group (from 1.07 + 0.32 to 0.47 + 0.41 pm01 * min-' . 8-l). Mivazerol had no effect on myocardial lactate production during the stenoses. We conclude that mivazerol reduced myocar- dial oxygen demand while blood flow was preserved in the inner layers of ischemic myocardium.