Silent Ischemia as a Marker for Early Unfavorable Outcomes in Patients with Unstable Angina

We examined the prevalence and prognostic importance of silent myocardial ischemia detected by continuous electrocardiographic monitoring in 70 patients with unstable angina. All the patients received intensive medical treatment with nitrates, beta-blockers, and calcium-channel blockers. Continuous electrocardiographic recordings were made during the first two days in the coronary care unit to quantify the frequency and duration of asymptomatic ischémie episodes, defined as a transient ST-segment shift of 1 mm or more. Thirty-seven patients (Group 1) had at least one episode of silent ischemia, and the other 33 patients had no silent ischemia (Group 2). Over the subsequent month, myocardial infarction occurred in 6 patients in Group 1 and in only 1 in Group 2 (P<0.01); bypass surgery or angioplasty was required for recurrent symptomatic angina in 10 patients in Group 1 and only 3 in Group 2 (P = 0.02). Survival-curve analysis demonstrated that silent ischemia was associated with these outcomes (P<0.002), and multivariate analysis showed that silent ischemia was the best predictor of these outcomes among the 15 variables tested (P<0.002). Patients in Group 1 with 60 minutes or more of silent ischemia per 24 hours had a worse prognosis than those with under 60 minutes per 24 hours (P = 0.04). Silent ischemia occurred in more than 50 percent of our patients with unstable angina, despite intensive medical therapy, and it identified a subset who were at high risk for early unfavorable outcomes. (N Engl J Med 1986; 314:1214–9.), UNSTABLE angina is a common ischemic condition characterized by symptoms of recent onset, a crescendo pattern, or the occurrence of symptoms at rest. Patients with angina at rest treated medically have the poorest short-term and long-term prognosis, and they have a high incidence of sudden death, myocardial infarction, and persistent angina requiring revascularization.^{1 2 3 4} Symptoms of chest pain are often controlled with medical therapy in the coronary care unit, but one third or more of such patients nevertheless have an unfavorable outcome within a period of one to two months.^1,5,6 Although coronary arteriography contributes important clinical information,^1,2,7,8 it is difficult to.