Denervation supersensitivity of refractoriness in noninfarcted areas apical to transmural myocardial infarction.

Denervation supersensitivity was demonstrated in anesthetized dogs 5 to 10 days after transmural myocardial infarction produced by latex embolization of a diagonal branch of the left anterior descending coronary artery. Sympathetic efferent denervation in noninfarcted myocardium apical to the infarction was demonstrated by a 90% depletion of myocardial norepinephrine content in the apical (45 +/- 15 pg norepinephrine/g tissue) vs basal (437 +/- 76 pg/g tissue) regions and by the lack of effective refractory period (ERP) shortening during bilateral ansae subclaviae stimulation in 34% of sites apical to the infarction. Supersensitivity in the area apical to the infarction was manifested by an exaggerated shortening of the ERP during both norepinephrine and isoproterenol infusions, with an upward and leftward shift in the dose-response curves in the apical vs basal regions (p less than .001). The cellular mechanism for denervation supersensitivity did not involve detectable changes in the beta-adrenergic rec...