When the electrocardiogram fails to define site and extent of myocardial ischemia
Insights
Electrocardiogram (ECG) changes may not accurately pinpoint myocardial ischemia location. A multiparametric approach is often needed for precise characterization of ischemic and necrotic areas in the heart.
Area of Science:
- Cardiology
- Medical Imaging
- Diagnostic Electrocardiography
Background:
- The 12-lead electrocardiogram (ECG) is commonly used to identify the anatomical site of myocardial ischemia and infarction.
- However, the correlation between ECG findings and the actual location of ischemia is not always precise.
Purpose of the Study:
- To evaluate the correspondence between electrocardiographic changes and perfusion defects in patients with myocardial ischemia.
- To determine the reliability of ECG in localizing the anatomical site and extent of myocardial ischemia.
Main Methods:
- Analysis of ECG findings in correlation with perfusion defects identified by Thallium-201 scintigraphy and radionuclide ventriculography.
- Evaluation of patients with various presentations of angina, including rest and effort angina, and ST segment abnormalities.
Main Results:
- Good ECG-perfusion defect correlation was observed in patients with anterior ST elevation or T-wave normalization during rest angina.
- Transient ST depression showed less correlation with perfusion defects.
- ECG could not distinguish right or left ventricular ischemia in patients with inferior ST elevation.
- ST segment depression in effort angina failed to localize ischemia, even in single-vessel disease.
- Persistent perfusion defects were found in patients with persistent ST depression/negative T waves and necrosis, despite absent Q waves and late ECG normalization.
Conclusions:
- Electrocardiographic changes do not consistently provide accurate information on the presence, location, and extent of myocardial ischemia.
- A multiparametric approach combining ECG with other imaging modalities is often necessary for accurate characterization of ischemic and necrotic areas.
Abstract:
Information on the anatomical site of myocardial ischemia and infarction is commonly derived from the 12-lead electrocardiogram; however, correspondence between an electrocardiogram lead, showing ischemic changes and actual location of ischemia is not always present. In our experience, a good correspondence between the electrocardiogram and perfusion defects was found in patients with angina at rest and anterior ST segment elevation or normalization of negative T wave while patients with transient ST segment depression showed perfusion defects which correlated less with electrocardiographic changes. In addition, patients with ischemic episodes at rest and with inferior ST segment elevation, right or left ventricular ischemia were indistinguishable on the basis of the electrocardiogram as documented by Thallium-201 scintigraphy and radionuclide ventriculography. In effort angina, the site and extension of ST segment depression, even in patients with single vessel disease, failed to localize the actual anatomical location of myocardial ischemia. In patients with persistent ST segment depression and/or negative T waves, and clinically documented myocardial necrosis, transmural and non-transmural persistent perfusion defects were found in spite of absence of Q waves. In these patients, late normalization of the electrocardiogram did not correspond to normalization of flow. In conclusion, electrocardiographic changes do not always provide correct information regarding the presence, location and extent of myocardial ischemia and a multiparametric approach is often required in order to characterize ischemic and/or necrotic areas.
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