Marcadores De Infarto

[pic]igure 1. Release of Cardiac Troponins in Acute Myocardial Infarction.
The zone of necrosing myocardium is shown at the top of the figure, followed in the middleportion of the figure by a diagram of a cardiomyocyte that is in the process of releasing biomarkers. Most troponin exists as a tripartite complex of C, I, and T componentsthat are bound to actin filaments, although a small amount of troponin is free in the cytoplasm. After disruption of the sarcolemmal membrane of the cardiomyocyte, thecytoplasmic pool of troponin is released first (left-most arrow in bottom portion of figure), followed by a more protracted release from the disintegrating myofilaments that maycontinue for several days (three-headed arrow). Cardiac troponin levels rise to about 20 to 50 times the upper reference limit (the 99th percentile of values in a referencecontrol group) in patients who have a "classic" acute myocardial infarction (MI) and sustain sufficient myocardial necrosis to result in abnormally elevated levels of theMB fraction of creatine kinase (CK-MB). Clinicians can now diagnose episodes of microinfarction by sensitive assays that detect cardiac troponin elevations above the upperreference limit, even though CK-MB levels may still be in the normal reference range (not shown).
gure 2. Mortality rates at 42 days (without adjustment for base-linecharacteristics) are shown for ranges of cardiac troponin I levels measured at base line in the Thrombolysis in Myocardial Ischemia IIIB trial, a study of patients presentingwithout ST-segment elevation on the electrocardiogram. The numbers at the bottom of each bar are the numbers of patients with cardiac troponin I levels in each range. P