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Electrocardiographic evaluation of reperfusion therapy in patients with acute myocardial infarction
1Department of Medicine B, Rigshospitalet, Copenhagen.
Insights
This study developed an "ST score" using electrocardiograms (ECGs) to estimate myocardial damage in acute myocardial infarction (AMI) patients. A 20% ST-segment elevation decrease accurately predicted coronary artery patency after thrombolytic therapy.
Area of Science:
- Cardiology
- Medical Imaging
- Clinical Research
Background:
- Thrombolytic therapy improves outcomes in acute myocardial infarction (AMI).
- Accurate assessment of ischemic myocardium is crucial for evaluating AMI therapies.
- Noninvasive methods are needed to evaluate the effectiveness of interventions limiting AMI size.
Purpose of the Study:
- To develop noninvasive methods for assessing myocardial ischemia in AMI patients.
- To create an "ST score" for estimating the amount of myocardium at risk during AMI.
- To evaluate the accuracy of ST-segment changes in predicting coronary artery patency after thrombolytic therapy.
Main Methods:
- Analysis of serial ECGs in 267 AMI patients admitted within 12 hours.
- Quantitative ST-segment measurements in the acute phase compared to Selvester QRS score.
- Validation against independent noninvasive and invasive methods.
- Development of "ST score" formulas based on ST-segment elevation magnitude and leads involved.
- Assessment of ST-segment normalization post-thrombolytic therapy for predicting coronary artery patency.
Main Results:
- Acute ST-segment elevation can predict final AMI size in patients not receiving reperfusion therapy.
- The developed "ST score" estimates the amount of myocardium in jeopardy.
- ST-segment deviation correlates with regional and global left ventricular dysfunction.
- A 20% decrease in ST-segment elevation accurately predicts coronary artery patency (PPV 88%, NPV 80%).
Conclusions:
- The "ST score" is a valuable noninvasive tool for assessing myocardial ischemia in AMI.
- Serial ECG ST-segment changes can reflect infarct artery patency status.
- ST-segment normalization is a reliable indicator of successful reperfusion therapy in AMI.
Abstract:
The present thesis is based on 6 previously published clinical studies in patients with AMI. Thrombolytic therapy for patients with AMI improves early infarct coronary artery patency, limits AMI size, improves left ventricular function and survival, as demonstrated in large placebo-controlled clinical trials. With the advent of interventions aimed at limiting AMI size it became important to assess the amount of ischemic myocardium in the early phase of AMI, and to develop noninvasive methods for evaluation of these therapies. The aims of the present studies were to develop such methods. The studies have included 267 patients with AMI admitted up to 12 hours after onset of symptoms. All included patients had acute ECG ST-segment changes indicating subepicardial ischemia, and patients with bundle branch block were excluded. Serial ECG's were analyzed with quantitative ST-segment measurements in the acute phase and compared to the Selvester QRS score estimated final AMI size. These ECG indices were compared to and validated through comparisons with other independent noninvasive and invasive methods, used for the purpose of evaluating patients with AMI treated with thrombolytic therapy. It was found that in patients with first AMI not treated with reperfusion therapies the QRS score estimated final AMI size can be predicted from the acute ST-segment elevation. Based on the number of ECG leads with ST-segment elevation and its summated magnitude, formulas were developed to provide an "ST score" for estimating the amount of myocardium in jeopardy during the early phase of AMI. The ST-segment deviation present in the ECG in patients with documented occlusion of the infarct related coronary artery, was subsequently shown to correlate with the degree of regional and global left ventricular dysfunction. Because serial changes in ST-segment elevation, during the acute phase of AMI were believed to reflect changes is myocardial ischemia and thus possibly infarct artery patency status, the summated ST-segment elevation present on the admission ECG was compared to that present after administration of intravenous thrombolytic therapy, and immediately prior to angiographic visualization of the infarct related coronary artery. The entire spectrum of sensitivities and specificities, derived from different cut-off values for the degree of ST-segment normalization, was described for the first time. It was found that a 20% decrease in ST-segment elevation could predict coronary artery patency with a high level of accuracy: positive predictive value = 88% and negative predictive value = 80%.(ABSTRACT TRUNCATED)