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Analysis of ST-segment changes in normal subjects: implications for ambulatory monitoring in angina pectoris
Insights
Transient ST depression was rare in asymptomatic individuals, supporting its use for monitoring coronary artery disease (CAD) activity in patients with angina and proven CAD outside the hospital.
Area of Science:
- Cardiology
- Clinical Electrophysiology
Background:
- Asymptomatic ST-segment depression on electrocardiogram (ECG) monitoring in coronary artery disease (CAD) patients suggests silent myocardial ischemia.
- Understanding the prevalence of these ECG changes in healthy individuals is crucial for accurate interpretation.
Purpose of the Study:
- To determine the frequency of transient ST depression in asymptomatic normal subjects.
- To differentiate normal ECG variations from pathological changes indicative of CAD.
Main Methods:
- Frequency-modulated ambulatory ECG recordings in 80 asymptomatic volunteers (aged 20-50+ years) and 20 patients with normal coronary arteries.
- Treadmill exercise testing in subjects over 40 years old.
- Analysis of transient ST depression (≥0.1 mV, ≥80 ms, >30 seconds duration).
Main Results:
- Transient ST depression meeting specific criteria was rare in the normal population.
- Upsloping ST depression during tachycardia was common (36%) but more frequent in younger subjects.
- No patient with normal coronary arteries exhibited significant ST depression.
Conclusions:
- The low incidence of significant ST depression in healthy individuals supports its utility as a marker for CAD activity.
- Ambulatory ECG monitoring can effectively track coronary artery disease progression and treatment response in patients with angina.
Abstract:
Continuous monitoring of the electrocardiogram in patients with angina pectoris and coronary artery disease (CAD) has shown episodes of asymptomatic ST-segment depression, suggesting frequent silent myocardial ischemia during normal daily life. Interpretation of this new finding depends on whether similar changes occur in normal subjects. Frequency-modulated ambulatory electrocardiographic recordings were performed in 80 asymptomatic normal volunteers (20 from each decade between 20 and 50 years and, 20 more than 50 years old) and in 20 patients with noncardiac pain, negative exercise and provocative tests and angiographically normal coronary arteries. Treadmill exercise testing was performed in all subjects more than 40 years old. Episodes of T-wave change were identified in 53 subjects. Five subjects younger than 40 years had episodes of ST elevation that were prolonged; they usually occurred at night. In 3 patients they could be reproduced by postural change. Only 2 subjects, both older than 40 years had planar ST depression during tachycardia; one of these subjects had a positive exercise test response. No patient with normal coronary arteries had significant ST depression. Tachycardia was frequently associated with upsloping ST depression (36%), which was more common in younger subjects: Five subjects also showed isolated single complexes with ST depression during baseline instability. With use of frequency-modulated recordings, transient ST depression of 0.1 mV or greater that lasted 80 ms or longer and more than 30 seconds in duration, was rare in a normal population. This finding supports the use of this signal to follow the activity of CAD out of the hospital, specifically in patients with typical angina and proved CAD.