Myocardial Infarction Following Coronary Ligation in Dogs

In the subacute phase of myocardial infarction following coronary ligation in dogs, a relationship was noted between the extent of infarction and the degree of elevation of left ventricular end-diastolic pressure. Left ventricular filling pressure was consistently increased when 25% or more of the left ventricle was infarcted. Isoproterenol infusion resulted in enhanced left ventricular function in both control and infarcted dogs, but the response was clearly weakened in those animals in which more than 20% of the left ventricle was infarcted. Acetylstrophanthidin caused no improvement in left ventricular function in infarcted dogs as judged by the relationship between filling pressure and cardiac output. The peak rate of rise of left ventricular pressure did increase in animals with infarcts, but was less than that in controls. Animals with infarcts had a lowered threshold for production of ventricular tachycardia by acetylstrophanthidin. These results in dogs suggest the need for further assessment of the role of digitalis in the treatment of heart failure following acute myocardial infarction.