Long term risk stratification of patients with acute coronary syndromes: characteristics of troponin T testing and continuous ST segment monitoring

Abstract

Objective: To examine the long term prognostic characteristics of troponin T testing and continuous multi-lead ST segment monitoring in combination with clinical and 12 lead ECG risk indicators in patients with acute coronary syndromes (ACS).

Patients and design: Patients with suspected ACS (n = 213) were studied. Troponin T was analysed in blood samples collected during the first 12 hours after admission. Continuous vectorcardiography ST segment monitoring was performed for 24 hours and the number of ST vector magnitude episodes was registered. Patients were followed up for a median of 28 months. The end point was a composite of cardiac death and acute myocardial infarction.

Results: Thirty eight (18%) patients reached the composite end point. The median (interquartile range) time from study inclusion to the time of the composite end point was longer for patients predicted to be at risk by troponin T testing (n = 27) than for those predicted to be at risk by ST segment monitoring (n = 20) (8.4 (0.2-15) months v 0.3 (0.1-4.3) months, p = 0.04). Significant univariate predictors of the composite end point were age > or = 65 years, diabetes, previous myocardial infarction, congestive heart failure, use of beta blockers or diuretics at admission, 12 lead ECG ST segment depression at admission, troponin T concentration > or = 0.10 microg/l, and > or = 1 ST vector magnitude episodes. Age > or = 65 years, previous myocardial infarction, and troponin T concentration > or = 0.10 microg/l provided independent prognostic information after multivariate analysis of potential risk variables. The prognostic value of transient ischaemic episodes in ACS seems to be confined to the short term.

Conclusions: Both biochemical and continuous ECG markers reflect an increased risk for patients with ACS; however, the methods exhibit different temporal risk characteristics.

Figure 1

Incidence of cardiac death or non-fatal acute myocardial infarction (AMI) at a median of 28 months’ follow up, according to the troponin T concentration and the number of ST-VM episodes. Median troponin T concentration and the number of patients in each group (in parentheses) are shown on the bars. p Values for trend analysis of the number of ST-VM episodes in relation to the probability of death or AMI (1) and the number of ST-VM episodes in relation to the troponin T concentration (2) are shown.

Figure 2

Occurrence of cardiac death or non-fatal AMI at a medium of 28 months’ follow up according to troponin T testing and continuous vectorcardiography ST segment monitoring. (A) Event-free probability among patients with or without troponin T ⩾ 0.10 μg/l (log rank, p  =  0.0003). (B) Event-free probability of patients with or without ST-VM episodes (log rank, p  =  0.0006).

Figure 3

Occurrence of cardiac death or non-fatal AMI at a medium of 28 months’ follow up in patients with troponin T < 0.10 μg/l and no ST-VM episodes (A, n  =  97), troponin T < 0.10 μg/l and ⩾ 1 ST-VM episodes (B, n  =  24), troponin T ⩾ 0.10 μg/l and no ST-VM episodes (C, n  =  47), and troponin T ⩾ 0.10 μg/l and ⩾ 1 ST-VM episodes (D, n  =  45). A versus B, log rank p  =  0.43; A versus C, log rank p  =  0.09; A versus D, log rank p  =  0.0001; B versus C, log rank p  =  0.61; B versus D, log rank p  =  0.02; C versus D, log rank p  =  0.01.