Assessment of exercise-induced silent myocardial ischemia by dipyridamole thallium imaging: (1) Its significance in stable angina pectoris

Abstract

To assess the clinical significance of silent myocardial ischemia (SMI) in the elderly, 113 patients with stable angina who showed ischemic ST depressions during treadmill stress testing were studied by dipyrimadole thallium imaging and coronary arteriography. They were divided into two groups: 44 patients with silent ST depressions and 69 patients with painful ST depressions. The groups were compared for scintigraphic and coronary arteriographic features as well as prognosis. There was a significantly greater proportion of older patients (≤65 years) in the group with SMI (64%) than in the group with painful ischemia (38%) (p<0.01), although there was no difference in the mean ages of the two group. The prevalence of multivessel coronary stenosis was not significantly different between the two groups (45% in the SMI group and 61% in the group with painful ischemia). Treadmill stress testing showed no differences in exercise duration, maximal heart rate, maximal systolic blood pressure, or maximal ST depression between the two group. Dipyrimadamole thalium imaging revealed similar results in the site of reversible defects (RD), i.e. 76% in the anterior area and 24% in the inferior area in patients with SMI, and 83% in the anterior area and 17% in the inferior area in patients with painful ischemia. However, the size of RD was significantly smaller in patients with SMI, i.e, 14.6 ± 6.1 segments in patients with SMI and 18.7 ± 8.3 segments in patients with painful ischemia (p<0.05). Although a significantly higher proportion of patients with painful ischemia (48%) underwent PTCA or CABG as their initial therapy as compared to those with SMI (16%), there was no significant difference in the cardiac event rate between the two groups initially treated medically. Among patients with stable angina, those with SMI may have a smaller amount of ischemic myocardium and may be older in a greater proportion than those with painful ischemia. Dipyrimadole thallium imaging is useful in the assessment of SMI in the enderly.