MYOCARDIAL ACTIVITIES OF LACTATE-DEHYDROGENASE ISOENZYMES IN RELATIONTO TISSUE COMPOSITION OF CHRONICALLY INFARCTED HUMAN MYOCARDIUM - A STUDY OF 21 PREOPERATIVELY EXCISED CARDIAC ANEURYSMS

We analyzed tissue creatine kinase, lactate dehydrogenase (LDH), and L DH isoenzyme activities as well as tissue composition in terms of livi ng cells (myocytes, nonmuscle cells) and extracellular material (like collagen) in left ventricular aneurysms obtained at surgery from 21 pa tients with chronic myocardial infarction because of angina pectoris ( 13 patients), chronic heart failure (7 patients), and ventricular arrh ythmias (1 patient). In patients with chronic heart failure, aneurysm tissue was characterized by a small volume fraction of myocytes (6 +/- 1%), a small volume fraction of nonmuscle cells (15 +/- 1%), and a la rger volume fraction of extracellular material (78 +/- 1%). Aneurysm t issue of patients operated upon for angina pectoris contained a larger volume fraction of myocytes (11 +/- 1%), a larger volume fraction of nonmuscle cells (19 +/- 1%), and a smaller volume fraction of extracel lular material (70 +/- 2%). In the patient with ventricular arrhythmia s, aneurysm tissue contained a relatively large volume fraction of non muscle cells (51 +/- 4%) in combination with a relatively small volume fraction of extracellular material (35 +/- 5%). The composition of my ocardial tissue in terms of volume fractions of myocytes and nonmuscle cells is reflected biochemically by the relative and absolute activit ies of LDH isoenzymes. The LDH isoenzyme profiles (LDH-1:LDH-2:LDH-3:L DH-4:LDH-5) are 57:35:8:0:0 in myocytes and 2:3:14:41:40 in nonmuscle cells.