There have been several attempts to identify the patients with unstable coronary artery disease (CAD) who will benefit the most from various treatment options. Some studies have assessed examining the admission electrocardiogram (ECG) to determine if quantitative measurements of ST-T segments provide similar or better prognostic information than troponin measurements in patients with acute coronary syndromes. In other trials, qualitative analysis of the ECG data alone or in combination with troponin T levels predicted treatment outcomes. There are currently defined troponin levels that can be used as predictors in patients with acute coronary syndromes, but the quantitative levels for an admission ECG have not been established. The objective of this study by Holmvang and associates was to evaluate which patients with non–ST-segment elevation acute coronary syndromes might benefit the most from an early invasive treatment strategy.
The trial was a sub-study of the Fast Revascularization during InStability in Coronary artery disease trial (FRISC-II), a randomized study to evaluate early invasive intervention versus noninvasive intervention in patients with unstable CAD. Patients were enrolled if they had chest pain within the past 48 hours with elevation of the cardiac biomarkers, ST-segment depression, or T-wave inversion on the admission ECG. In the invasive arm, patients received revascularization procedures within seven days of admission, while patients in the noninvasive arm received intervention only if they had refractory or recurrent symptoms or failed a discharge exercise test. An ECG was obtained on admission, at randomization, after the intervention, and at three-month and six-month follow-up visits. The ECGs were analyzed for the presence and amount of ST-segment deviation and T-wave amplitudes. These ECGs were then placed into quartiles based on the amount of cumulative ST-segment deviation and the number of leads where this deviation was present. Summed ST-deviation was divided into three groups: zero to 2.5 mm, 3 to 5.5 mm, and 6 mm or larger. The number of leads where this deviation occurred was divided into three groups: zero to 4 leads, 5 to 7 leads, and 8 or more leads. Primary end points were death or myocardial infarction at six months. Secondary outcomes were hospital re-admission, angina, myocardial revascularization, and bleeding.
There were 2,201 patients who met the inclusion criteria for the study. In terms of the primary outcomes of death and myocardial infarction, the intermediate and major ST-segment deviation groups (defined by the total amount of ST-segment deviation or the number of leads with ST-segment deviation) benefited more from the invasive strategy than from the noninvasive strategy. The invasive strategy in these groups provided an approximate 50 percent reduction in mortality and myocardial infarction rates. This finding was true even when other variables such as gender, age, smoking, diabetes, hypertension, previous myocardial infarction, and elevated troponin levels were controlled for in the analysis. The invasive strategy reduced mortality rates in all ECG subgroups except in patients with a cumulative total of ST-segment deviation of zero to 2.5 mm.
The authors conclude that complete quantitative analysis of the admission ECG in patients with acute coronary syndrome can identify the patients who would best benefit from invasive treatment strategy. They add that this is a readily available, easy, and inexpensive method of risk stratifying patients with acute chest pain. When ECG data is evaluated carefully, it provides independent information on patient prognosis and the benefits of treatment.