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Transient ST-segment depression as a marker of myocardial ischemia during daily life
Insights
Transient ST depression indicates myocardial ischemia in coronary artery disease (CAD) patients, often occurring silently. Continuous monitoring can reveal more disease activity than previously understood.
Area of Science:
- Cardiology
- Nuclear Medicine
- Ischemic Heart Disease
Background:
- Patients with coronary artery disease (CAD) and angina experience frequent, often asymptomatic, transient ST-segment depression.
- ST-segment depression is a potential indicator of myocardial ischemia, but its diagnostic utility, especially in silent episodes, requires further investigation.
Purpose of the Study:
- To investigate transient ST-segment depression as a marker of myocardial ischemia in patients with chronic stable angina and CAD.
- To compare ischemic responses during provoked (exercise, cold pressor) and unprovoked ST depression events.
Main Methods:
- Positron tomography using rubidium-82 was employed to assess regional myocardial uptake in 30 patients with chronic stable angina and CAD.
- Myocardial perfusion was evaluated before, during, and after exercise tests, cold pressor tests, and episodes of unprovoked ST depression.
- ST-segment changes, pain, and perfusion defects were recorded and analyzed in relation to clinical events and in comparison to 16 normal subjects.
Main Results:
- ST depression occurred during exercise (58 episodes, 53 with angina) and cold pressor tests (15 episodes, 3 with pain).
- Tomography confirmed myocardial ischemia in 97% of episodes with angina and 100% of painless ST depression episodes.
- Perfusion defects were consistently located in the same myocardial segments during both painful and painless ST depression, differing significantly from normal subjects.
Conclusions:
- Transient ST depression, including painless episodes, is a reliable indicator of myocardial ischemia in patients with typical angina, exercise-induced ST depression, and proven CAD.
- Continuous monitoring for ST depression provides a broader understanding of CAD activity, highlighting a higher prevalence of silent myocardial ischemia than previously recognized.
Abstract:
Patients with angina and coronary artery disease (CAD) have many episodes of transient ST-segment depression during ordinary daily life, and these are often asymptomatic. To investigate this signal as a marker of myocardial ischemia, 30 patients with chronic stable angina and CAD underwent positron tomography, recording the regional myocardial uptake of rubidium-82, pain and ST-segment changes before, during and after 59 technically satisfactory exercise tests, 35 cold pressor tests and 22 episodes of unprovoked ST depression. Exercise resulted in 53 episodes of ST depression with angina and in 5 episodes without pain. After cold pressor tests, there were 3 episodes of ST depression and pain and 12 of painless ST depression. Only 9 episodes of unprovoked ST depression were accompanied by pain. Tomography showed independent evidence of ischemia in 63 (97%) of the total 65 episodes of ST depression with angina and in all 30 episodes of painless ST depression. In each patient perfusion defects occurred in the same myocardial segment during painful and painless ST depression and responses were significantly different from those in 16 normal subjects studied in the same way. These findings support the use of transient ST depression in continuous monitoring to assess the activity of CAD, but only in patients with typical angina pectoris, ST depression during exercise and proved CAD. They strengthen the evidence derived from ambulatory monitoring for a wider picture of the disease than is generally appreciated, with more frequent episodes of silent myocardial ischemia than of angina pectoris.