Usefulness of silent myocardial ischemia detected by ambulatory electrocardiographic monitoring in predicting new coronary events in elderly patients

Abstract

Unrecognized myocardial infarction (MI) detected by electrocardiogram (ECG) occurred in 83 of 237 women (35%) and 130 of 469 men (28%) with initial MI in the Framingham study. 1 Unrecognized MI had as serious a prognosis as recognized MI in that study. 1 In our 1985 study, 2 we reported that unrecognized Q-wave MI detected by ECG occurred in 78 of 115 elderly patients (68%) with MI in a long-term health care facility. After instructing staff physicians on the different presenting symptoms of MI in elderly patients, the incidence of unrecognized MI detected by ECG in a prospective study was 23 of 110 MIS (21%). 3 Silent myocardial ischemia detected by ambulatory ECG monitoring is common during daily life in asymptomatic patients with coronary artery disease (CAD) and positive treadmill exercise tests. 4 In unstable angina, 80% of ischemic episodes are silent. 5 Abnormalities in regional and global left ventricular wall motion are similar in patients with CAD, with and without silent ischemia. 6 Rubidium-82 positron-emission tomographic studies have demonstrated reduced myocardial perfusion during episodes of silent myocardial ischemia detected by ambulatory ECG monitoring in patients with CAD. 7 The prognosis of asymptomatic silent ischemia in patients with CAD depends on the extent of CAD and left ventricular dysfunction. 8 The prognostic value of silent ischemia detected by ambulatory ECG monitoring has been reported in patients with unstable angina, 9–11 in high-risk postinfarction patients 12 and in patients with stable CAD. 13,14 We performed a prospective study (1) to determine the prevalence of silent ischemia in elderly patients with CAD, patients with systemic hypertension, valvular heart disease or cardiomyopathy, and in patients with no evidence of heart disease, and (2) to correlate silent ischemia with cardiac events at 26-month follow-up in these groups of patients.