Changes in myocardial composition after coronary artery ligation

¹ Department of Physiology, Louisiana State University, School of Medicine, New Orleans, Louisiana

Myocardial infarction was produced by ligation of the coronary artery in a series of 20 dogs, which were killed 1, 4 1/2, 12, or 24 hours later. Each heart was divided into three parts: the infarcted area, the undamaged area, and a border zone including some of each. Each part was analyzed for its content of sodium, potassium, epinephrine, norepinephrine, and water. The water content of the infarct is detectably higher within 1 hour, reaching its ultimate concentration more rapidly than do the other changes seen. Potassium is lost from the infarct and replaced by sodium. The catecholamines progressively decrease in concentration within the infarct during the first 24 hours. No evidence of selective accumulation or loss of any of these constituents in the border zone was noted, although this zone appears to trigger the ventricular arrhythmia that occurs after coronary occlusion. The possible roles of potassium, epinephrine, and norepinephrine, as agents excitatory to such tachycardia, are discussed.