Reduction of myocardial infarct size by early intracoronary thrombolysis as assessed by serum cardiac myosin light chains and left ventricular function

Cardiac myosin light chains are released from the infarcted myocardium soon after the onset of infarction, and the level of myosin light chains in the serum reflects infarct size, regardless of the presence of early coronary reperfusion. In this study, we used serum myosin light chains and assessed changes in left ventricular function to evaluate the effects of intracoronary thrombolysis on infarct size, with special reference to the interval between the onset of infarction and the time of reperfusion. Forty patients with acute myocardial infarction who underwent coronary angiography and intracoronary thrombolysis for the left anterior descending artery (LAD) early after the onset of infarction were categorized in four groups: in group A (n = 9) the LAD was already patent at the start of intracoronary thrombolysis, in group B (n = 12) antegrade flow in the LAD was achieved within three hours of the onset of symptoms, in group C (n = 10) antegrade flow was achieved later than three hours after the onset of symptoms, and in group D (n = 9) antegrade flow in the LAD was not achieved. The peak appearance time of creatine phosphokinase (CPK) in group D was significantly later than in the other groups. The total release of CPK in group C (3,119 +/- 414 IU/l) was greater than that in group A (1,332 +/- 346 IU/l) (p less than 0.01), but the total CPK release in group D (2,525 +/- 525 IU/l) was not statistically different from those of any other group. In all four groups myosin light chain I appeared in the serum from the first day on and reached their peak values between the third and fifth days. The peak values of myosin light chain I were 14.7 +/- 2.1 ng/ml for group A, 16.3 +/- 2.3 ng/ml for group B, 24.6 +/- 2.4 ng/ml for group C, and 25.1 +/- 1.8 ng/ml for group D. The peak myosin light chain levels in groups A and B were less than those in groups C and D. Twenty-nine of the 40 patients had no previous episodes of infarction, and these 29 patients were classified in two groups according to the Forrester's subset class on the first day: four of seven patients in group D were in subsets II, III or IV; whereas, the majority of patients in groups A, B and C were in subset I.(ABSTRACT TRUNCATED AT 250 WORDS)