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Altered myocardial perfusion in patients with angina pectoris or silent ischemia during exercise as assessed by
J J Mahmarian1, C M Pratt, M K Cocanougher
1Department of Internal Medicine, Baylor College of Medicine, Methodist Hospital, Houston, TX 77030.
Insights
Silent ischemia is common in coronary artery disease (CAD) and presents similarly to symptomatic ischemia. Quantitative SPECT perfusion defects were similar in patients with and without chest pain during exercise.
Area of Science:
- Cardiology
- Nuclear Medicine
- Diagnostic Imaging
Background:
- Chest pain during exercise is a common symptom of coronary artery disease (CAD).
- Silent myocardial ischemia, or ischemia without chest pain, is also a recognized manifestation of CAD.
- Distinguishing between symptomatic and silent ischemia is important for patient management.
Purpose of the Study:
- To compare the extent of abnormally perfused myocardium in patients with and without chest pain during treadmill exercise.
- To evaluate the diagnostic performance of quantitative single-photon emission computed tomography (SPECT) for detecting CAD.
- To assess the prevalence and characteristics of silent versus symptomatic ischemia in a low-risk patient population.
Main Methods:
- Quantitative thallium-201 SPECT was performed on 356 patients referred for treadmill exercise testing.
- Coronary angiography was used to assess the severity of CAD.
- Patients were categorized based on the presence or absence of chest pain during exercise and CAD severity.
Main Results:
- Chest pain during exercise was equally frequent in patients with normal coronary arteries and those with significant CAD.
- Silent ischemia was fivefold more common than symptomatic ischemia in patients with significant CAD.
- The extent of SPECT perfusion defects was nearly identical in patients with and without exertional chest pain.
- Quantitative SPECT demonstrated higher sensitivity for detecting CAD compared to stress electrocardiography (87% vs. 65%).
- SPECT was superior to stress electrocardiography in detecting silent myocardial ischemia (52% vs. 35%).
Conclusions:
- The majority of patients with CAD experiencing ischemia during exercise are asymptomatic.
- Asymptomatic and symptomatic ischemic events show similar angiographic profiles and myocardial perfusion defects.
- Quantitative SPECT is a valuable tool for detecting CAD and silent myocardial ischemia.
Abstract:
The extent of abnormally perfused myocardium was compared in patients with and without chest pain during treadmill exercise from a large, relatively low-risk consecutive patient population (n = 356) referred for quantitative thallium-201 single-photon emission computed tomography (SPECT). All patients had concurrent coronary angiography. Patients were excluded if they had prior coronary angioplasty or bypass surgery. Tomographic images were assessed visually and from computer-generated polar maps. Chest pain during exercise was as frequent in patients with normal coronary arteries (12%) as in those with significant (greater than 50% stenosis) coronary artery disease (CAD) (14%). In the 219 patients with significant CAD, silent ischemia was fivefold more common than symptomatic ischemia (83% versus 17%, p = 0.0001). However, there were no differences in the extent, severity, or distribution of coronary stenoses in patients with silent or symptomatic ischemia. Our major observation was that the extent of quantified SPECT perfusion defects was nearly identical in patients with (20.9 +/- 15.9%) and without (20.5 +/- 15.6%) exertional chest pain. The sensitivity for detecting the presence of CAD was significantly improved with quantitative SPECT compared with stress electrocardiography (87% versus 65%, p = 0.0001). Although scintigraphic and electrocardiographic evidence of exercise-induced ischemia were comparable in patients with chest pain (67% versus 73%, respectively; p = NS), SPECT was superior to stress electrocardiography for detecting silent myocardial ischemia (52% versus 35%, respectively; p = 0.01). The majority of patients in this study with CAD who developed ischemia during exercise testing were asymptomatic, although they exhibited an angiographic profile and extent of abnormally perfused myocardium similar to those of patients with symptomatic ischemia. The prognostic significance of quantified perfusion defects detected by SPECT remains to be assessed.