Left stellate stimulation: regional myocardial flows and ischemic injury in dogs

The effects of left stellate ganglion stimulation (LSGS) on regional myocardial blood flow (RMBF) and epicardial S-T segment were investigated in the normal and ischemic myocardium of anesthetized dogs. In nonischemic myocardium LSGS decreased calculated coronary resistance, increased RMBF, and reduced the endocardial-to-epicardial (endo-to-epi) ratio. These effects were reversed after atenolol (1 mg/kg) and abolished after combined atenolol and phenoxybenzamine (3 mg/kg) treatments. In ischemic myocardium LSGS did not change RMBF but increased S-T segment. However, after atenolol, LSGS increased ischemic RMBF and the ischemic-to-nonischemic areas flow ratio (reverse coronary steal phenomenon), these effects being abolished by phenoxybenzamine. We conclude that 1) LSGS increases RMBF and decreases endo-to-epi ratio in nonischemic areas by beta 1-adrenergic stimulation through metabolic autoregulation, 2)beta 1-adrenergic blockade in nonischemic areas unmasks alpha-adrenergic vasoconstriction inducing a redistribution of flow towards ischemic areas, and 3) further elevation of S-T segment by LSGS is due to oxygen requirements enhancement by beta 1-adrenoceptors stimulation.