12-Lead Electrocardiogram in Acute Coronary Syndrome
Association with Coronary Angiography Findings & Outcome
Acta Universitatis Tamperensis No. 1776
By Kjell Nikus
Tampere University Press
Distributed By Coronet Books
$82.50 Paper Original
Based on randomized clinical trials, the mortality of acute coronary syndrome (ACS) has been regarded as relatively low. However, the prognosis of clinical presentations of ACS in unselected “real-life” patient cohorts has not been well-documented. The significance of the electrocardiogram (ECG) ST-segment depression in ACS has been the subject for debate for many decades. Studies indicate that various manifestations of ST/T changes may have significantly different prognostic implications. Widespread ST-segment depression in combination with lead aVR ST-segment elevation is a marker of an adverse outcome in patients with non-ST-elevation (NSTE-) ACS -- perhaps because this pattern is indicative of severe coronary artery disease (CAD), including left main coronary artery (LM) stenosis. However, the prognostic value of this circumferential subendocardial ischemia (CSI) ECG pattern has not yet been established.
The aims of the present study were to investigate the significance of ST-segment depression and T-wave changes in ACS, with respect to in-hospital prognosis, troponin levels and angiographic findings (I); evaluate the prognostic significance of the three different clinical entities of ACS in prospectively collected consecutive patients from a university hospital (II); study the distribution of various ECG patterns on admission in patients with ACS and define the prognostic value of these pre-defined ECG patterns (III); compare preoperative 12-lead ECG findings during anginal pain in patients with as well as without LM disease who underwent isolated urgent or emergent bypass surgery; and, finally, study the sensitivity, specificity and predictive values for the CSI ECG pattern to predict angiographic LM disease (IV).
The study populations for all four studies were collected at Tampere University Hospital. For Study I, 50 patients with ACS were collected prospectively and consecutively. Studies II and III comprised 1,188 ACS patients admitted to the emergency department of our hospital. The original study population for Study IV consisted of 1,131 patients who had isolated bypass surgery urgently or emergently.
Patients with ST-segment depression and inverted T waves maximally in leads V4-V5 had, significantly more often, LM or LM equivalent (proximal left anterior descending and circumflex) disease, 76 vs. 8% (p<0.001), heart failure; 40 vs. 4% (p=0.005) and higher in-hospital mortality; 24 vs. 0% (p=0.02), than patients with a positive T wave in the precordial lead with maximal ST-segment depression. The troponin levels did not differ significantly between the two groups (I).
For ST-elevation myocardial infarction (STEMI), non-ST elevation myocardial infarction (NSTEMI) and unstable angina pectoris (UA) categories, in-hospital mortality was 9.6, 13 and 2.6% (p <0.001) and mortality at a median follow-up of 10 months 19, 27 and 12% (p<0.001), respectively. In multivariate Cox regression analysis age, diabetes mellitus type 1, diuretic use at admission, serum creatinine level, lower systolic blood pressure, and STEMI and NSTEMI ACS categories were associated with higher mortality during follow-up (II).
To study the distribution of ECG changes and the prognostic value of the CSI ECG pattern, the patients (n=1,188) were classified into seven ECG categories: ST-segment elevation (29%), Q waves without ST-segment elevation (23%), left bundle branch block (6%), left ventricular hypertrophy (7%), CSI ECG (8%), other ST-segment depression and/or T-wave inversion (14%) and other findings (13%). The CSI ECG pattern predicted high rate (48%) of composite endpoints (mortality, re-infarction, UA, resuscitation or stroke) at 10 months’ follow-up compared to the other ECG categories (36%) (Hazard ratio [HR] 1.78, 95% confidence interval [CI] 1.31-2.41, p<0.001). In multivariate analysis, the CSI ECG pattern was associated with a higher rate of composite endpoints at 10 months’ follow-up (HR 1.40, 95% CI 1.02-1.91, p=0.035). The multivariate analysis furthermore identified age, creatinine level and diabetes as independent predictors of prognosis (III).
In patients undergoing urgent or emergent bypass surgery, the CSI ECG pattern was found in 61 of 80 patients (76%) with and in 12 of 65 patients (19%) without angiographic LM disease. The sensitivity, specificity, positive and negative predictive values for LM disease in patients with the CSI ECG pattern were 76, 81, 84 and 74%, respectively. In multivariate analysis, the CSI ECG pattern was strongly associated with angiographic LM disease after adjusting for age, gender, diabetes, hypertension, and smoking (HR 16.0, 95% CI 6.5-39.5, p<0.001) (IV).
In conclusion, in an unselected patient cohort, short-term mortality of myocardial infarction patients, especially those classified as NSTEMI was high. In patients with NSTEMI, transient ST-segment depression and inverted T waves maximally in leads V4-V5 during anginal pain predicted LM or LM equivalent disease with high sensitivity and specificity. This CSI ECG pattern predicted an unfavourable outcome when compared to six other ECG patterns in patients with ACS. In addition, the CSI ECG pattern was strongly associated with angiographic LM disease in patients who underwent urgent or emergent coronary bypass grafting. In patients with ST-segment depression and positive T waves, there was high probability for single vessel disease and a better outcome.
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