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Postexercise changes of the QTc interval in patients with recent myocardial infarction
E Macieira-Coelho1, M Garcia-Alves, A P de Lacerda
1St. Mary University Hospital, Department of Cardiology and Nuclear Medicine, Lisboa, Portugal.
Insights
A lack of QTc ratio decrease during maximal exercise may indicate exercise-induced ischemia in post-myocardial infarction patients. QTc interval changes during exercise ECGs effectively identify residual ischemic myocardium noninvasively.
Area of Science:
- Cardiology
- Exercise Physiology
- Diagnostic Imaging
Background:
- Exercise-induced ischemia is a critical concern in patients with coronary artery disease.
- Assessing residual ischemic myocardium post-myocardial infarction is vital for patient management.
- Traditional methods like ST-segment depression have limitations in sensitivity and specificity.
Purpose of the Study:
- To evaluate the utility of QTc interval changes during exercise stress tests for identifying residual ischemic myocardium in patients after myocardial infarction.
- To compare the diagnostic value of QTc variations with thallium-201 scintigraphy and coronary angiography.
Main Methods:
- Fifty-one patients with recent myocardial infarction underwent exercise stress tests, coronary angiographies, and exercise thallium-201 scintigraphy.
- QTc interval changes were analyzed from resting and post-exercise electrocardiograms.
- Myocardial perfusion defects were assessed using thallium-201 scintigraphy, and coronary arteries were evaluated for patency.
Main Results:
- Patients with reversible thallium-201 defects showed QTc interval prolongation or no change post-exercise.
- Patients with fixed perfusion defects exhibited a QTc interval shortening.
- QTc variations demonstrated higher diagnostic value compared to ST-segment depression for detecting residual ischemia.
Conclusions:
- QTc interval variations at the end of exercise electrocardiograms are a valuable, noninvasive, and low-cost tool for identifying residual ischemic myocardium.
- This method offers a practical approach for risk stratification in patients post-myocardial infarction.
- QTc changes provide a sensitive indicator of exercise-induced ischemia when compared to traditional ECG markers.
Abstract:
A lack of the QTc ratio decrease at maximal exercise is considered as an index of exercise-induced ischemia in patients with coronary artery disease. The authors studied 51 patients with recent myocardial infarction in order to evaluate the QTc changes with exercise in assessing the presence of remaining ischemic myocardium. All patients were submitted to exercise stress tests, coronary angiographies, and exercise thallium 201 scintigraphies within 3-5 months of the myocardial infarction. Of the patients studied, 18 showed one-vessel disease and 33 showed multivessel disease. All vessels were classified as patent or occluded. In all patients with reversible thallium 201 defects both at distance and in the infarct zone, the QTc interval following exercise either showed a prolongation or no change from the resting electrocardiogram. In patients with only fixed perfusion defects, the QTc shortened at the end of the test. This study showed a low sensitivity and specificity for inducible ST-segment depression compared with the delayed redistribution on the postexercise thallium 201 scintigram. QTc variations at the end of exercise electrocardiograms are valuable as a noninvasive, low-cost identification of residual ischemic myocardium in patients after myocardial infarction.