EFFECTS OF SOTALOL AND VAGAL-STIMULATION ON ISCHEMIC MYOCARDIAL BLOOD-FLOW DISTRIBUTION IN THE CANINE HEART

  • 1 January 1981
    • journal article
    • research article
    • Vol. 216  (2) , 347-351
Abstract
A comparison was made of the effect of equivalent decreases in heart rate produced by sotalol and bilateral vagal stimulation on regional myocardial blood flow and coronary perfusion pressure distal to a severe left circumflex coronary artery stenosis in anesthetized dogs. Tissue blood flow was measured with radioactive microspheres (15 .mu.). Vagal stimulation or .beta.-adrenergic blockade produced by sotalol (1.0 mg/kg i.v.) reduced heart rate .apprx. 35 beats/min. This decrease in rate was accompanied by nearly equivalent increases (P < 0.05) in diastolic perfusion time and subendocardial blood flow and in the ischemic region. Both interventions significantly increased the O2 supply-demand balance (distal diastolic pressure time index divided by the tension time index) in the ischemic region. These values returned to control after cessation of vagal stimulation or during atrial pacing to predrug heart rate. Coronary perfusion pressure distal to the stenosis increased significantly only in the sotalol-treated group. A decrease in heart rate and increase in diastolic perfusion time appear to be important factors in the favorable redistribution of ischemic myocardial blood flow and increase in the O2 supply-demand balance observed after .beta.-adrenergic blockade with sotalol or after vagal stimulation. Whether these beneficial actions are solely due to the prolonged diastolic perfusion period or to reduced O2 demand and a return to autoregulation in the ischemic area cannot be determined with certainty.