[Cardiac troponin I in unstable angina].

BACKGROUND

Unstable angina implies high risk of myocardial infarction and sudden death. Increased levels of cytoplasmatic enzymes and proteins (creatine phosphokinase, MB creatine phosphokinase troponin T, etc.) were described in unstable angina, providing information about incoming major coronary events. Cardiac troponin I (cTn-I) is a structural protein inhibiting the actinomyosine ATPase; it is only found in myocardial cells. Serum titration of cTn-I has been recently introduced into clinical practice as a sensitive and specific marker of myocardial cellular necrosis.

OBJECTIVES

The aim of our prospective study was to assess the presence of cTn-I in blood samples of patients with unstable angina and no signs of myocardial necrosis. Furthermore we intended to test the possible use of cTn-I in unstable angina as a prognostic marker of major coronary events on short and middle term.

METHODS

We studied 33 consecutive patients admitted to our CCU for unstable angina. According to unstable angina Braunwald's classification, 6 patients were included in the first class, 4 patients in the second class and 23 patients in the third class. We excluded patients with acute or recent myocardial infarction. Blood samples of all patients were obtained at the time of CCU admission and every eight hours in the first and second day. Serum cTn-I titration was performed with the sandwich immunoenzymometric method, recently introduced by Diagnostic Pasteur. Two months follow-up was carried out in order to survey major coronary events and revascularization procedures, either angioplasty or coronary artery bypass surgery.

RESULTS

No patients with unstable angina exhibited cTn-I in their blood samples; accordingly, cTn-I was not found in the first blood sample of a patient who underwent myocardial infarction during hospitalization. During the follow-up 2 patients died of myocardial infarction, 9 patients had surgical revascularization and 5 patients angioplasty.

CONCLUSIONS

CTn-I is a sensitive and specific marker of myocardial necrosis. It is not found in patients with unstable angina; therefore it has no role as a prognostic marker of major coronary events.