Cardiac Troponin and Creatine Kinase MB Monitoring during In-Hospital Myocardial Reinfarction

Abstract

Cardiac troponin monitoring for detection of myocardial injury has been designated the new standard for differentiating the diagnosis of unstable angina and non-ST-elevation myocardial infarction (NSTEMI) in acute coronary syndrome patients (1)(2)(3)(4). Increased cardiac troponin I (cTnI) or T (cTnT) in the clinical setting of ischemia is defined as an acute MI and has been endorsed by the European Society of Cardiology, American College of Cardiology, the American Heart Association, the IFCC, and the Epidemiology World Council (1)(2)(3)(4)(5)(6). One of the challenges that confronts cardiac troponin monitoring encompasses the clinical setting of myocardial reinfarction within a short time period after an initial MI. Because cardiac troponins can remain increased in the circulation for up to 5 (cTnI) or 10 days (cTnT) after an acute MI, in theory, the role for monitoring cardiac troponins during reinfarction has been questioned. The European Society of Cardiology/American College of Cardiology consensus document notes that in the clinical setting of a reinfarction, creatine kinase MB (CKMB) may be more useful for monitoring for MI because CKMB remains increased for only 2–4 days after an acute MI (1)(2)(3)(4). There are only two case reports in the literature, both from a previous report from our laboratory, that readdressed the role of cardiac troponin monitoring in reinfarction (7). The purpose of this study was to compare the patterns of increases and decreases in cTnI and CKMB mass in a series of nine MI patients who experienced an in-hospital myocardial reinfarction (MI extension) within 4 days of the initial MI event. Over a period of 16 months (September 1999 through February 2001), nine MI patients were identified who experienced a myocardial …