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Character of transient ischemia in angina pectoris
Insights
Silent myocardial ischemia is rare in healthy individuals but common in coronary artery disease (CAD) patients. Ambulatory ECG monitoring reveals frequent, often asymptomatic, ischemic episodes in CAD, rarely triggered by heart rate increases.
Area of Science:
- Cardiology
- Diagnostic Medicine
Background:
- Silent myocardial ischemia is increasingly recognized for its therapeutic and prognostic implications in coronary artery disease (CAD).
- Ambulatory electrocardiographic (ECG) monitoring is a key tool for detecting myocardial ischemia.
Purpose of the Study:
- To investigate the prevalence and characteristics of silent myocardial ischemia in healthy individuals and patients with documented CAD.
- To assess the utility of Holter monitoring in identifying ischemic episodes and their triggers.
Main Methods:
- Holter monitoring was performed on 100 healthy subjects and 30 patients with CAD over 18 months.
- ECG data were analyzed for ST-segment depression, and episodes were correlated with symptoms and positron emission tomography (PET) findings.
- Heart rate changes preceding ischemic events were also examined.
Main Results:
- Significant ST-segment depression (silent ischemia) was found in only 2% of healthy subjects, none with normal coronary arteries.
- Patients with CAD exhibited frequent, variable, and often asymptomatic ischemic episodes (24% associated with angina).
- Ischemic episodes in CAD patients were rarely triggered by heart rate increases (>10 beats/min) and showed comparable perfusion changes whether symptomatic or asymptomatic.
Conclusions:
- Silent myocardial ischemia is uncommon in individuals without CAD.
- Patients with stable CAD experience frequent, variable, and often asymptomatic ischemic episodes detected by ECG, with limited association with heart rate changes.
- These findings have significant therapeutic and prognostic implications for managing CAD.
Abstract:
There is growing interest in the possible therapeutic and prognostic significance of silent myocardial ischemia in coronary artery disease (CAD) and its detection by ambulatory electrocardiographic (ECG) monitoring. In 100 apparently healthy normal subjects (20 with angiographically normal coronary arteries), Holter monitoring revealed significant ST-segment depression in only 2 (both over 40 years, one with positive treadmill test, the other with risk factor for CAD). No significant ECG changes were found in those with normal coronary vessels. In 30 patients with documented CAD, significant ST-segment depression during 1,934 episodes over 446 days of monitoring over 18 months was found. Only 24% of the episodes were associated with angina. Asymptomatic and symptomatic episodes were associated with comparable changes in perfusion detected by positron emission tomography. Heart rate increases greater than 10 beats/min preceding the onset of the ST-segment changes occurred in only 23% of the episodes. There was considerable variability in the ST-segment changes in the same patient monitored serially over long periods of time. The data indicate that it is extremely uncommon for patients without CAD to exhibit silent myocardial ischemia, whereas patients with stable angina exhibit frequent, variable and often asymptomatic ECG evidence of myocardial ischemia rarely triggered by increases in heart rate. These findings are likely to be of therapeutic and prognostic significance.