Prognostic Value of Predischarge Electrocardiographic
Background: Current methods for risk stratification after acute myocardial infarction (MI) include several noninvasive studies. In this cost-containment era, the development of low-cost means should be encouraged. We assessed the ability of an electrocardiogram (ECG) MI-sizing score to predict outcomes in patients enrolled in the Economics and Quality of Life (EQOL) sub study of the Global Utilization of Streptokinase and Tissue plasminogen activator for Occluded coronary arteries -I (GUSTO-I) trial.
Methods: We classified patients by electrocardiographic Selvester QRS score at hospital discharge: those with a score 0-9 versus ≥10. Endpoints were 30-day and 1-year mortality, resource use, and quality-of-life measures.
Results: Patients with a QRS score <10 were well-matched with those with QRS score ≥10 with the exception of a trend to more anterior MI in the higher scored group. Patients with QRS score ≥10 had increased risk of death at 30-days (8.9% vs. 2.9% P < .001), and this difference persisted at 1 year (12.6% vs. 5.4%, P = .001). Recurrent chest pain, use of angiography, and angioplasty were similar during follow-up. However, there was a trend toward less coronary bypass surgery in patients with a QRS score ≥10. Readmission rates were higher at 30 days but similar at 1 year.
Conclusions: Stratification of patients after acute MI by a simple measure of MI size identifies populations with different long-term prognoses; patients with a QRS score ≥10 (approximately 30% of the left ventricle infarcted) at discharge have poorer outcomes in both the short- and long-term. The standard 12-lead ECG provides a simple, economical means of risk stratification at discharge.

The use of reperfusion therapy in patients with acute myocardial infarction (MI) has substantially reduced long-term mortality rates. The standard 12-lead electrocardiogram (ECG) remains the primary tool used by clinicians to identify an ongoing ischemia/infarction process, decide about reperfusion therapy, and assess the location and extent of myocardial necrosis.

The use of the ECG to estimate prognosis after MI is frequently based on classification into Q wave and non-Q-wave MI. Although this dichotomous nomenclature has proven useful, the definition of "Q wave MI" varies widely, and the designation of an "abnormal Q wave" is an overly simplistic method of characterizing the array of QRS changes produced in the various leads by the infarction. One of the most powerful markers of mortality after infarction appears to be the extent of necrosis that has occurred, which can be measured by biochemical markers, echocardiography, nuclear studies, and contrast ventriculography. Over the last 2 decades, methods to estimate MI size from a standard 12-lead ECG have also been developed. Selvester et al developed a QRS score, later modified twice by Wagner et al. An early 29-point version showed a high specificity, low inter-observer variability, and a good correlation with the percentage of myocardium involved.A more recent, 31-point version better quantifies inferior and posterolateral infarcts. Several authors have reported good correlation with postmortem anatomic percentage of left ventricle infarcted and left ventricular function after MI, and its prognostic capability has been validated in 2 large populations with chronic coronary disease.

The validity of the QRS score as a measure of MI size has been questioned in the thrombolytic era. Studies with fluorine 18 2-deoxyglucose and positron emission tomography show that residual viable myocardium may persist within the infarct region despite Q waves on the surface ECG, and such residual viability is more likely after thrombolysis. Correlation, mainly with imaging methodologies, has shown controversial findings. Some authors reported small correlation between QRS score and nuclear studies, and others authors reported better estimates depending on the time of measurement. However, no studies have validated the QRS score as a prognostic tool in the thrombolytic era. The purpose of this study is to determine the relationship of the complete 31-point Selvester QRS scoring system at hospital discharge with later outcomes including all cause mortality, functional status, and use of resources in patients who had received thrombolytic therapy for acute myocardial infarction.