Absence or Presence of Ambulatory Myocardial Ischemia in Patients with Stable Angina Pectoris and Positive Exercise Test: A Multivariate Statistical Analysis

Abstract

In 166 patients with stable angina pectoris, positive exercise test and angiographically proven coronary artery disease, determinants for the absence or presence of myocardial ischemia during 24-hour ambulatory electrocardiographic (ECG) monitoring were analyzed. Variables were derived from clinical history, electrocardiogram at rest, exercise testing, ambulatory ECG monitoring as well as from cardiac catheterization and were compared in 103 patients with (group A) and 63 patients without (group B) ambulatory myocardial ischemia. In a multiple stepwise discriminant analysis, the most powerful determinants for the presence of ambulatory myocardial ischemia were: (1) R-wave amplitude during ambulatory ECG monitoring (17.2 ± 5.3 vs. 13.8 ±4.6 mm in group A vs. group B; p < 0.001); (2) heart rate at onset of S-T-segment depression during exercise testing (112 ±17 vs. 121 ± 16 beats/ min; p < 0.001), and (3) presence of a stenosis >70% in the left anterior descending coronary artery (76 vs. 59% of the patients; p < 0.05). Furthermore, heart rates during ambulatory ECG monitoring were significantly higher in group A as compared to group B during the morning hours and in the late afternoon; during these periods, ambulatory myocardial ischemia showed a parallel increase. This study shows that the absence or presence of myocardial ischemia during ambulatory ECG monitoring is influenced by the ischemic threshold during exercise testing and involvement of the left anterior descending artery; however, R-wave amplitude and circadian heart rate profile during ambulatory ECG monitoring also play important roles.