Left ventricular function and rapid release of creatine kinase MB in acute myocardial infarction. Evidence for spontaneous reperfusion.

Intracoronary thrombolysis during acute myocardial infarction in human beings is associated with rapid release of creatine kinase and improvement of the cardiac ejection fraction. To examine the phenomenon of spontaneous coronary-artery recanalization, we studied the release of creatine kinase MB and sequential radionuclide ventriculograms in 52 patients with transmural myocardial infarction. Patients were divided into two groups according to whether the release of creatine kinase MB (time from base-line to peak serum level) was rapid (n = 24) or slow (n = 28). Patients with slow release had no significant change in global or regional ejection fraction from the time of admission to discharge. However, global ejection fraction in patients with rapid release improved from 0.38 +/- 0.09 (mean +/- S.D.) to 0.48 +/- 0.08 (P less than 0.001). The regional ejection fraction of Q-wave regions also improved, from 0.33 +/- 0.11 to 0.43 +/- 0.13 (P less than 0.001). A negative correlation (r = -0.52, P less than 0.001) existed between time to peak enzyme level and degree of improvement in ejection fraction. With increasing left ventricular damage, patients with rapid release had greater increments in creatine kinase MB than comparable patients with slow release (P = 0.03), suggesting enzyme washout. These data are consistent with the idea that spontaneous reperfusion, leading to altered enzyme release and improvement in ventricular function, is not uncommon after acute myocardial infarction.