Macroscopic Enzyme-mapping Verification of Large, Homogeneous, Experimental Myocardial Infarcts of Predictable Size and Location in Dogs

Difficulty is frequently experienced in producing a large homogeneous myocardial infarct in the dog heart because of the extensive network of coronary anastomoses. This problem may be overcome by combining the ligation of the left anterior descending coronary artery with agar injection into the distal coronary vasculature to obliterate anastomotic channels. All infarcts produced in this manner occupied a constant area in the anterior wall of the left ventricle. From our results in 25 dogs, the individual infarct averaged 12.3 Gm. in weight (range 9.4 to 13.5), representing 25 to 30 per cent of the total left ventricular muscle mass. The homogeneity of the infarct was verified by a simple, macroscopic enzyme-mapping technique based on the inability of the ischemic (dehydrogenase-deficient) myocardium to reduce triphenyl tetrazolium chloride and by detailed histologic studies. Apart from providing ample raw material for comprehensive morphologic, chemical, histochemical, and radioisotopic analyses, a large myocardial infarct also serves as a useful experimental model for various physiological and hemodynamic studies of cardiogenic shock and left ventricular akinesis.