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

Abstract

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 ischemic 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 less than 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 less than 0.002), and multivariate analysis showed that silent ischemia was the best predictor of these outcomes among the 15 variables tested (P less than 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.

A randomized, blinded, placebo-controlled trial of recombinant human tissue-type plasminogen activator in patients with unstable angina pectoris.

“…Continuous Holter electrocardiographic monitoring was performed for 72 hr from the time of entry into the study (including the preinfusion observation period). Analysis of Holter ST segment data was performed according to methods previously described by Gottlieb et al 13 Venous blood samples for routine hematologic serum chemistry, and hemostasis analysis were drawn before treatment and during the infusion. Blood samples for hemostasis analysis were drawn on 0.O1M citrate and 200 kIU aprotinin/ml of blood at 1, 5, and 12 hr after the beginning of the infusion.…”

Silent Myocardial Ischemia

“…[41][42][43][44][45] The 3-to 5-fold increase in risk of death, infarction, and revascularization has been shown to continue out to 1-and 2-year follow-up. 40,46 Transient ischemia, much of which is silent, is also detectible during Holter monitoring in the acute phase after MI, and in this setting it is associated with an adverse "in-hospital" and medium-term prognosis in terms of death and reinfarction in addition to combined end points including revascularization and angina [47][48][49][50][51][52][53][54][55][56] (Table 1).…”

Practice Standards for ECG Monitoring in Hospital Settings: Executive Summary and Guide for Implementation

“…ST-segment monitoring stud-ies of patients hospitalized with unstable angina show that although 80% to 90% of transient ischemic events are asymptomatic, they are nonetheless significant markers for unfavorable short-and long-term outcomes (Table 2). [63][64][65][66][67][68][69][70] Patients Who Present to the ED With Chest Pain or Anginal Equivalent Symptoms It is not uncommon for patients with acute ST-elevation MI to have an initial ECG that is nondiagnostic for acute ischemia. Investigators who use continuous monitoring have shown that the ST segment often is dynamic in the early hours of acute MI.…”