Importance of the Location of Myocardial Infarction and Ventricular Aneurysm on Left Ventricular Function

This experimental study was performed to evaluate the possibility that the site per se of infarction or ventricular aneurysm after acute myocardial infarction had a unique important role in left ventricular function.Acute myocardial infarction and ventricular aneurysm were made in either the anterior or the inferior wall of the left ventricle using 24 dogs. Infarction was made by the multiple ligation method. The weight of the infarcted area was 23.1±3.9% of the left ventricular free wall in the anterior wall group (12 dogs), and was 23.8±4.8% in the inferior wall group (12 dogs). Ventricular aneurysm was made of right atrial homograft. The capacity of ventricular aneurysm, measured by casts, was 37.8±7.7% of the left ventricular cavity in the anterior wall group and was 38.3±7.3% in the inferior wall group. There was no significant difference in either the size of infarction or the capacity of ventricular aneurysm between 2 groups (p=0.05).Ventricular function curves were obtained before infarction (control), after infarction, and after the creation of ventricular aneurysm, plotting left ventricular stroke work (LVSW) per body weight against left atrial mean pressure (LAMP). The change in ventricular function curves after infarction and the creation of ventricular aneurysm was not different significantly between 2 groups.In the anterior wall group, LVSW/LAMP decreased to 47.8±9.8% of the control after infarction, and further to 27.1±6.9% after the creation of ventricular aneurysm. In the inferior wall group, it lowered to 47.6±12.5% and again to 26.5±6.4%, respectively. There was no difference in these values between 2 groups statistically (p=0.05).From the result of this experiment, it was concluded that the impairment of left ventricular function was equal between these 2 groups not only after infarction but also after the creation of ventricular aneurysm and that the anterior wall would not have more important contribution to the pumping ability of the left ventricle as compared with the inferior wall.