Characteristics of silent and symptomatic myocardial ischemia during daily activities

Abstract

In 191 patients with proven coronary artery disease, 24-hour Holter monitoring detected 587 transient episodes of ST depression during daily activities. Of that total, 424 episodes were silent (72.3%) and 163 were symptomatic (27.7%). There were no statistically significant differences between silent and symptomatic episodes as to their mean duration (15.1 vs 14.3 minutes, respectively), heart rate at onset of ST depression (93 vs 96 beats/min, respectively), heart rate at the time of maximal ST depression (114 beats/min, both) and mean maximal ST depression (1.9 vs 2.0 mm, respectively).Of the 191 patients, 104 (55%) had only silent episodes, 33 (17%) only symptomatic episodes and 54 (28%) had both types (“mixed”). All patients, regardless of episode type, were of similar age, received comparable medical therapy, had a similar extent of angiographically documented coronary artery disease and similar episode characteristics. However, mixed-episode patients had significantly more ischemic episodes per day (4.8) than silent-episode (2.6) and symptomatic-episode (1.9) patients (p < 0.001 for both) and a longer total period of daily ischemia (60 minutes), than the other 2 groups (36 and 28 minutes, respectively, p < 0.001 for both).Of the 191 patients, 97 (51%) had had a previous myocardial infarction. The characteristics of their silent and symptomatic episodes were similar to the 94 (49%) patients without infarction, except for a longer duration of the silent episodes. Postinfarction patients had a higher frequency of silent episodes (75%) than noninfarction patients (65%, p < 0.02). Thus, silent and symptomatic ischemic episodes during daily activities had similar characteristics and were associated with a similar extent of coronary artery disease. Patients who had both silent and symptomatic ischemia had more episodes and a longer ischemic daily period. Postinfarction patients had silent transient ischemia more frequently, although their episodes had characteristics similar to those of patients without infarction.