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Background: Biochemical markers have been an integrative part of non-invasive diagnostic strategies in cardiology for nearly 50 years, experiencing a renascence by the recently acknowledged prognostic potential of cardiac troponins in acute coronary syndromes., Diagnosis: According to the guidelines of the National Academy of Clinical Biochemistry and the International Federation of Clinical Chemistry cardiac troponin T and cardiac troponin I should be considered as the new "gold markers" of ischemic myocardial injury. One characteristic feature of these new markers is the improved diagnostic potential, reflected by the choice of two cut-off values to distinguish minor myocardial injury from acute myocardial infarction. In addition, cardiac troponins allow risk stratification in the clinical setting of acute coronary syndromes: approximately threefold higher mortality rate for patients with rest angina or ST segment elevation and cardiac troponin elevation on admission. Other indications for cardiac marker analysis are monitoring of therapeutic success in case of invasive and non-invasive reperfusion strategies and non-invasive diagnosis of non-ischemic myocardial injury (myocarditis, cardiac contusion and chemotherapy)., Conclusion: Biochemical cardiac markers are a useful tool in the diagnosis of both ischemic and non-ischemic myocardial injury. Among these, cardiac troponins seem to become the gold markers for the new millennium.

A 55-year-old man had rhabdomyolysis and myocardial damage induced by palytoxin. Weakness and myalgia of four extremities occurred five hours after eating a fish. Rhabdomyolysis developed and the serum creatine phosphokinase (CK) was elevated to 40,000 IU/l on the 3rd day. Gastric lavage with activated charcoal and forced mannitol-alkaline diuresis therapy were performed. The patient recovered with no complication such as renal failure. In this case, palytoxin was suggested to induce myocardial damage which was demonstrated by an elevation of the myosin light chain level and a change in electrocardiogram.

Acute coronary syndrome encompasses the entities acute MI, unstable AP and sudden cardiac death. The syndrome of unstable AP covers a very heterogenous group of patients. Recent pathological post-mortem investigations have revealed, that unstable AP leading to MI or sudden cardiac death is frequently preceded by microinfarctions. Despite the fact that thrombus formation is recognized as the major cause, the role of coronary artery spasm seems also important. Therefore, the pathological hallmark of ACS is at present thought to be caused by an active coronary plaque (the culprit lesion), which is often the site of intermittent occlusion and of thrombus formation, with or without vasospasm. The release of myocardial cell constituents in connection with these microinfarctions is to be expected. In order to detect these, diagnostic tools sensitive to myocardial injury and specific for myocardial tissue must be employed. According to WHO the criteria for the diagnosis of acute MI are based on clinical history, electrocardiographic changes, and enzymes in serum. Although these criteria are quite adequate in most cases, they are not present or easily discernible in all acute MI patients. The clinical symptoms are and will remain insensitive and nonspecific indicators of acute MI. Electrocardiographic alterations are carefully described, but sometimes less applicable due to non-interpretable ECG's. During the last decades, activity measurements of cardiac enzymes, and especially the isoenzymes of CK and LD, have become the final arbiters by which myocardial damage is diagnosed or excluded. However, they are not fully cardiospecific and have a low sensitivity to detect MMI, retaining a high specificity. Improved immunoassays have therefore been developed measuring the mass concentration of CK-MB instead of its catalytic activity, as well as immunoassays measuring structural proteins of the heart i.e., TnT, a tropomyosin-binding protein of the troponin regulatory complex located on the thin filament of the contractile apparatus of the myocyte; and MLC, a component of the thick filament of the contractile apparatus of the myocyte. We, and others, have shown that minor ischaemic myocardial injury can be detected by CK-MB mass immunoassays in around one-fourth to one-third of patients with unstable AP or in whom an acute MI has been ruled out. However, the prognostic significance of this identification has not been investigated. A priori, it is known that 5-20% of patients with unstable AP have a poor prognosis, with progression to acute MI or cardiac death within the first year. Additional, non-Q wave MI may also be considered a relatively unstable condition associated with a lower initial mortality but a higher risk of later MI/cardiac death. It is of further importance, that although the incidence of unrecognized MI is less than that of clinically apparent MI, the long-term prognosis for unrecognized MI appears to be similar to, and as serious as, that following detected MI. Therefore, in order to follow-up this subgroup identification based on CK-MB mass levels, we subsequently carried out a prognostic study. It demonstrated a significantly increased risk of cardiac events (i.e., non-fatal acute MI, cardiac death) in patients with significant fluctuations of CK-MB mass in serum. A similar observation has been supported by others using the rate of change in serial samples of CK-MB mass. Further, we demonstrated a good correlation between elevated CK-MB mass levels and a poor prognosis, when using a fixed discrimination limit. However, an increasing number of CK-MB mass immunoassays have been developed, and a standardization of CK-MB mass is urgently needed, as at present each laboratory determines its own reference levels and discriminatory values leading to the risk of diagnostic confusion. (ABSTRACT TRUNCATED)

In order to estimate myocardial damage after severe burn injury, the cardiac myosin light chain I (CMLC1) contents and myocardial enzyme spectrum (CK, AST and LDH) in serum were measured in rats with full thickness burn of 30% TBSA. The results showed that the CMLC1 contents in serum increased markedly at 1 h postburn and about 20 times higher than control value at 12 h postburn, remaining at high level at 24 h or 48 h postburn, and decreasing slightly at 72 h postburn. CK, AST and LDH activities were increased at 3 h postburn and tended to decrease markedly at 24 h or 48 h postburn, recovering to control level at 72 h postburn. These results suggest that high increase in CMLC1 in serum implies that myocardium is damaged after severe burn injury, and it can be used as a reliable index in the diagnosis of postburn cardiac injury with higher sensitivity and specificity than myocardial enzyme spectrum.