The shape of enzymatic curves during acute myocardial infarction: relationship to the progression of necrosis and implications for thrombolysis.

BACKGROUND: During acute myocardial infarction, the ascending branch of creatine kinase curves has a sigmoidal course whose inflection point marks the maximum rate of enzymatic increase in serum. This study was performed to assess the relationship between these morphologic characteristics of creatine kinase curves and the progression of myocardial necrosis. METHODS AND RESULTS: In isolated rat hearts exposed to different degrees of ischemia (coronary flow of 0.6 or 0.2 ml/g/min), the total quantity of creatine kinase released in the effluent had a sigmoidal course similar to the ascending branch of the curves from patients with acute myocardial infarction. Other rat hearts were frozen (which causes maximum damage to cell structures), thawed and then perfused. The resulting enzymatic curves had a downward concave ascending trend, similar to the portion beyond the inflection point of sigmoidal curves (the rate of creatine kinase release was maximum at the onset of perfusion and then decreased progressively). Finally, in some experiments ischemic rat hearts were further damaged by the perfusion, at different times, with highly concentrated catecholamines and without oxygen and substrates. This damaging perfusate was able to increase the rate of creatine kinase release (p = 0.0001) only when it was started before the inflection point of enzymatic curves. In 25 creatine kinase curves from patients with acute myocardial infarction (19 men and 6 women, age range 42 to 68 years), who were not treated with thrombolysis, the time of inflection varied from 1 to 12 hours from the onset of symptoms, with a maximum frequency between the 7th and the 8th hour. CONCLUSIONS: Based on these data, a biological model with 3 compartments has been suggested to explain the shape of creatine kinase curves, according to which the inflection point would occur after the completion of myocardial necrosis. The variability of the time of inflection might account for the cases of beneficial late thrombolysis reported in literature.