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Silent ischemia during daily life is an independent predictor of mortality in stable angina
1Department of Medicine, UCSF Program/VAMC 93703.
Insights
Silent myocardial ischemia, detected by ambulatory electrocardiogram monitoring, is common in stable angina patients. This silent ischemia independently predicts a higher risk of cardiac death, even with conventional treatment.
Area of Science:
- Cardiology
- Preventive Cardiology
Background:
- Stable angina patients on antianginal agents may still experience silent myocardial ischemia.
- Ambulatory electrocardiogram (ECG) monitoring can detect these silent ischemic episodes during daily life.
Purpose of the Study:
- To investigate the prognostic significance of silent myocardial ischemia in patients with stable angina.
- To determine if silent ischemia is an independent predictor of cardiac mortality.
Main Methods:
- Prospective study of 107 stable angina patients with symptom control.
- Ambulatory ECG monitoring to detect myocardial ischemia.
- Kaplan-Meier survival analysis and multivariate Cox's hazard function analysis.
Main Results:
- 46 patients had silent myocardial ischemia (group 1), 61 did not (group 2).
- Group 1 experienced significantly more cardiac deaths (11 vs. 5) during follow-up (p=0.023).
- Silent ischemia was the strongest independent predictor of cardiac mortality (p=0.01).
Conclusions:
- Silent myocardial ischemia is frequent in treated stable angina patients.
- Detecting silent ischemia identifies a high-risk subset for cardiac mortality.
- Ambulatory ECG monitoring is crucial for risk stratification in stable angina.
Abstract:
We prospectively examined the prognostic significance of silent myocardial ischemia detected by ambulatory electrocardiogram (ECG) monitoring during daily life in 107 patients with long-term stable angina who were symptomatically controlled on conventional antianginal agents. Forty-six patients (group 1) demonstrated one or more episodes (87% silent) of myocardial ischemia; the remaining 61 patients (group 2) had no ischemic ST segment changes. During the mean follow-up period of 23 +/- 8 months, 11 cardiac deaths (five sudden and six nonsudden) occurred in group 1, and five cardiac deaths (all nonsudden) occurred in group 2. Kaplan-Meier survival analysis between the groups confirmed that patients with silent ischemia (group 1) had worse prognoses during the follow-up period (p = 0.023). Although the higher incidence of hypertension, smoking, hypercholesterolemia, and diabetes in our patients might reflect a more sickly population of stable angina patients, the multivariate Cox's hazard function analysis of these and other variables including Q waves on ECG, exercise parameters, and ambulatory ECG findings revealed presence of silent ischemia during daily life as the most powerful and independent predictor of cardiac mortality (p = 0.01). These data indicate that, in such patients with stable angina, silent myocardial ischemia occurs frequently during treatment with conventional antianginal drugs and identifies a subset of patients who are at high risk of cardiac death.