Cardiac troponin I in systemic diseases. A possible role for myocardial strain.

Cardiac troponin I levels are frequently above normal values in several disease states in which myocardial necrosis is not a prominent aspect, particularly in pulmonary embolism, heart failure, liver cirrhosis, septic shock, renal failure and arterial hypertension. Sub-clinical myocardial necrosis has been postulated to be the cause of the phenomenon. Studies performed so far have not included pathological data to confirm this hypothesis. Increased troponin I plasma levels may be the result of myocardial strain, especially the type of strain that accompanies some forms of cardiac dilatation or hypertrophy. Troponin I may act as a marker of myocardial strain, either acute (in pulmonary embolism, septic shock and acute heart failure) or chronic (in chronic cardiac, renal and hepatic failure, as well as in arterial hypertension). The apparent paradox of elevated levels of troponin I without elevated levels of creatine kinase in several disease states might be solved if troponin I could be released from myocardial cells without the disruption of myocardial cell plasma membranes. Precise pathological studies are needed to elucidate whether increased troponin I with normal CK is associated with myocyte death, and, if so, with necrosis or with apoptosis.