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The mechanisms responsible for the development of reversible thallium-201 (TI-201) defects with dipyridamole stress in patients with coronary artery disease (CAD) is not well understood. Previous experimental animal studies have demonstrated coronary steal characterized by an absolute decrease in subendocardial flow distal to a stenosis in response to dipyridamole infusion. Accordingly, the purpose of this study was to determine if reversible TI-201 defects in response to dipyridamole infusion are reflective of myocardial ischemia or secondary to regional differences in flow reserve. Dipyridamole (0.56 mg/kg) TI-201 imaging was performed in 23 patients in whom serial electrocardiographic, hemographic, dynamic, aortic and coronary sinus lactate, and coronary sinus adenosine measurements were obtained. All patients with CAD had TI-201 redistribution (3.8 [+ or -] 2.0 defects/patient), and all patients without CAD had normal scans. Mean aortic tic pressure was similar in bath groups and did not change in response to dipyridamole non-CAD 103 [+ or -] 11 vs CAD 99 [+ or -] 15 mm Hg, p = NS). Pulmonary capillary wedge pressure was similar at baseline (non-CAD 11 [+ or -] 4 vs CAD 13 [+ or -] 5 mm Hg p = NS) and did not change in response to the drug non-CAD 11 [+ or -] 3 vs CAD 15 [+ or -] 7 mm Hg, p = NS). Lactate extraction fraction was similar at baseline non-CAD 0.22 [+ or -] 0.09 vs CAD 0.17 [+ or -] 0.14, p = NS) and decreased similarly in both groups (non-CAD 0.08 [+ or -] 0.06 vs CAD 0.05 [+ or -] 0.12, p = NS). Coronary sinus adenosine concertration was significantly higher at baseline in patients with CAD non-CAD 16 [+ or -] 4 vs CAD 35 [+ or -] 13 ng/ml, p = 0.034), presumably to maintain resting coronary blood flow, and increased significantly with a comparable percent increase in bath groups after dipyridamole (non-CAD 35 [+ or -] 10 vs CAD 69 [+ or -] 35 ng/ml, p = 0.0001). In this group of patients with multivessel CAD, dipyrid-amole-induced TI-201 perfusion abnormalities were not associated with significant myocardial ischemia by hemodynamic and metabolic criteria and appeared to be more indicative of abnormal flow reserve.

The present study used 51 patients in a prospective, crossover, blinded comparison of dipyridamole thallium-201 imaging and dobutamine echocardiography for (1) detection of coronary artery disease (CAD), (2) detection of inducible ischemia, and (3) determination of myocardial viability. The detection of CAD was based on quantitative defects on initial planar thallium-201 images and resting or inducible wall motion abnormalities on echocardiography. Detection of ischemia was based on redistribution on delayed thallium-201 images and inducible wall motion abnormality on echocardiography. The myocardium in a region with resting wall motion abnormality was considered viable if it showed either redistribution or >50% activity on delayed thallium-201 images, and if regional function either improved or worsened on echocardiography. The tests were comparable for the detection of CAD (53 and 590/o, respectively, p = 0.23). Thallium. 201 was superior to echocardiography for the detection of ischemia (35 vs 14%, respectively, p = 0.01). Although the incidence of viable myocardium was equivalent by the 2 tests (100 and 96%, respectively, p = 0.99) for each abnormally moving segment in the 24 patients with resting wall motion abnormality an echocardiography, it was greater on thallium-201 imaging (98 vs 68%, p

Scant data are available concerning the application and results of exercise thallium-201 (TI-201) scintigrephy after acute myocardial infarction (AMI) heated with thrembolytic therapy. The goals of this study were to determine the ability of exercise TI-201 scintigraphy to detect inducible Ischemia and to identify multivessel coronary artery disease (CAD) in 88 consecutive postinfarction patients who received thrombolytic therapy and underwent both predischarge noninvesive testing and coronary anglography. Exercise-nduced TI-201 redistritution on quantitative scintigraphy wes significantly more prevalent than exercise ST-segment depression (48 vs 14%, p (Am J Cardiol 1993;71:1257-1261)

Many patients with ischemic heart disease and depressed left ventricular (LV) function have asynergic zones with sustained microcirculatory perfusion and myocardial metabolic activity that exhibit improved systolic function after coronary revascularization. The 2 predominant noninvasive techniques used to determine myocardial viability in patients with severely depressed LV function are thallium-201 ([sup.201]TI scintigraphy and positron emission tomography (PET). Myocardial extraction of [sup.201]TI is unaltered under experimental conditions of myocardial stunning or short-term hibernation (characterized by decreased flow and ischemic dysfunction). Akinetic or dyskinetic LV wall segments can exhibit normal or near normal [sup.201]TI uptake as long as some residual flow is present. [sup.201]TI scintigraphy can identify viable asynergic segments when performed on patients with severe coronary artery disease who are in the resting state. Many of these patients have initial resting defects that demonstrate delayed redistribution, or mild persistent defects that show improved perfusion and function after revascularization. There is a direct correlation between the extent of [sup.201]TI uptake in zones of severe regional myocardial asynergy and the magnitude of improvement in resting LV ejection fraction after coronary bypass surgery. Rest [sup.201]TI scintigraphy may help in the selection of patients with coronary artery disease and severely depressed LV function who would benefit the most from revascularization. (Am J Cardiol 1992;70:18E-22E)

The goal of this study was to determine whether dipyridamole-induced ST-segment depression reflects more severe or extensive myocardial hypoperfusion than the absence of this electrocardiographic finding. The clinical, hemodynamic and scintigraphic correlates of ST-segment depression during intravenous dipyridamole infusion were studied in 204 consecutive patients undergoing dipyridamole stress thallium-201 (TI-201) imaging for evaluation of coronary artery disease. Of 182 patients with a diagnostic baseline electrocardiogram, 28 (15%) developed ST depression after dipyridamole. Patients with ST depression, compared with those without, were older (64 [+ or -] 1 vs 60 [+ or -] 1 years; p By multivariate logistic regression analysis, the most powerful correlate of ST depression was the number of segments having TI-201 redistribution (p

PURPOSE: The aim of this study was to (1) determine whether nonimaging variables add to the diagnostic information available from exercise thalfium-201 images for the detection of multivessel coronary artery disease; and (2) to develop a model based on the exercise thalliumstress 201 test to predict the presence of multivessel disease. PATIENTS AND METHODS: The study populations included 383 patients referred to the University of Virginia and 325 patients referred to the Massachusetts General Hospital for evaluation of chest pain. All patients underwent both cardiac catheterization and exercise thallium-201 stress testing between 1978 and 1981. RESULTS- In the University of Virginia cohort, at each level of thallium-201 abnormality no defects, one defect, more than one defect), ST depression and patient age added significantly in the detection of multivessel disease. Logistic regression analysis using data from these patients identified three independent predictors of multivessel disease: initial thallium-201 defects, ST depression, and age. A model was developed to prediet multivessel disease based on these variables. As might be expected, the risk of multivessel disease predicted by the model was similar to that actually observed in the University of Virginia population. More importantly, however, the model was accurate in predicting the occurrence of multivessel disease in the unrelated population studied at the Massachusetts General Hospital. CONCLUSION: It is, therefore, concluded that (1) nonimaging variables (age and exercise-induced ST depression) add independent information to thallium-201 imaging data in the detection of multivessel disease; and (2) a model has been developed based on the exercise thallium-201 stress test that can accurately predict the probability of multivessel disease in other populations., Treatment of coronary artery disease (CAD), or disease of the major blood vessels supplying the heart, is aimed at alleviating symptoms and prolonging the life of the patient. Revascularization, the renewal of blood supply to the heart, can be accomplished by bypass surgery, which provides an alternate route of flow to the heart by bypassing the diseased blood vessel, or by balloon angioplasty, the dilation of the narrowed blood vessel with a small inflatable balloon. Patients with multivessel disease, or CAD involving more than one coronary artery, benefit most in terms of survival from revascularization. Hence, it is important to distinguish patients with multivessel disease from those with single-vessel disease. A noninvasive method for identifying patients with multivessel disease would be the most practical approach for screening large numbers of persons for CAD. Exercise thallium-201 imaging is the most reliable noninvasive method for detecting CAD; this involves injecting dye into the bloodstream while the patient exercises and then imaging the heart for abnormalities. It is not clear whether exercise electrocardiography, the recording of the electrical activity of the heart during exercise, and clinical factors, such as age, gender, and type of chest pain, help in detecting multivessel CAD. The effectiveness of combining results from thallium-201 imaging with those of exercise electrocardiography and clinical history in diagnosis of CAD was assessed in two studies, one involving 383 patients and one involving 325 patients. The results showed that depression of the ST segment in the electrocardiogram and patient age added to the ability to detect multivessel disease using thallium-201 imaging. Three factors that predicted multivessel disease, which were age, ST depression, and defects identified by thallium-201 imaging, were used to develop a model. This model was shown to be accurate in predicting the occurrence of multivessel disease. The findings indicate that factors other than imaging results, such as age and ST depression, contribute to the detection of multivessel disease when thallium-201 imaging is also used. (Consumer Summary produced by Reliance Medical Information, Inc.)

Fundamental quantitative planar imaging techniques, evolved over the years, have been adapted to maximaize the efficiency and clinical effectiveness of technetium-99m (Tc-99m) sestamibi imaging. To ensure reproducible image interpretation, the Society for Motion Picture and Television Engineers test pattern is used to obtain the necessary standardization of video and hard copy images. A standardized intensity scale intuitively relates count density to perceived brightness. Data are accumulated via standard 16-frame multiple gated acquisition and can be viewed in cine mode to assess wall motion. The images are then automatically summed for quantitative analysis of myocardial perfusion. Excessive extracardiac Tc-99m activity is automatically suppressed by the computer program to prevent suboptimal display of the heart. Due to the difference in heart bachground ratio and shape of the extracardiac background between resting and exercise Tc-99m sestamibi images, a modified interpolative background subtaction algorithm was developed. Image registration is necessary for accurate comparison of the rest and exercise images to detect redistribution. This is automatically accomplished by adjusting the position of the background-subtracted and centered images so as to maximize the cross-correlation coefficient. Profiles are generated to sample the myocardial count distribution and can be compared to a normal database, subject to confirmation by a competent interpreter. Rest redistribution is defined by a change in the myocardial distribution of Tc-99m sestamibi between exercise and rest images. Flashback display is used to identify subtle regions of redistribution that often signify residual viability within an infarct zone. In this technique, which maintins standard anatomic images for the interpreter, exercise and rest background-corrected images are brought into registration and each scaled to its maximum count so that alternate images can be flashed on the screen in the same position. Redistribution in a myocardial segment will appear as a sudden shift of intensity relative to the remainder of the image during flashback. (Am J Cardiol 1990;66:16E-22E)

Data comparing myocardial thallium-201 imaging after exercise and intravenous dipyridamole infusion in the same patients are scarce. Accordingly, this study is a segment-by-segment quantitative analysis of regional uptake and washout of thallium-201 after dipyridamole (0.56 mg/kg) and symptom-limited exercise testing in 21 patients (ages 58 [plus or minus] 9.2 Years) with chest pain studied 2.5 [plus or minus] weeks apart. Thallium-201 activity in 9 myocardial segments was measured in initial and delayed anterior and 45 [degrees] left anterior oblique views, producing 184 pairs of segments in the distribution of 63 coronary supply regions for direct comparison. The number of segments with normal thallium-201 uptake 201 and the number of numerically significant defects were similar with exercise and dipyridamole (76 vs 73%, 24 vs 27%, respectively, difference not significant). A slightly higher proportion of redistribution defects was found after dipyridamole infusion compared to exercise (17 vs 10%, p [less than] 0.05). Agreement between 87% (165 of 189) of segment pairs was found when each was classified as either normal or abnormal. Although 24 of 189 segments were discordant, agreement was observed in 92% (61 of 63) of coronary supply regions determined to be normal (41 of 41) or abnormal 20 of 22). In 15 patients who underwent cardiac catheterization, exercise and dipyridamolethallium-201 scintigraphy detected 61% (16 of 26) vs 61% (16 of 26) of stenoses [greater than] 50%, (difference not significant) and 100%, (19 of 19) vs 100% (19 of 19) (difference not significant) normal vessels, respectively. These data indicate that exercise and dipyridamole-thallium-201 imaging in the same patients are comparable in detecting and localizing normal or abnormal scan segments. (Am J Cardiol 1989;64:871-877), In thallium-201 scintigraphy, radioactive thallium is injected into the body and accumulates at certain body sites. Emissions from thallium accumulated in tissue result in the production of an image of that tissue. Circulation disorders within the heart, such as disease of the coronary arteries, can be detected by thallium-201 scintigraphy during exercise. Dipyridamole, a drug which dilates blood vessels, may be used as an alternative to physical exercise for evaluating blood flow within the heart using thallium-201 scintigraphy. The characteristics of thallium-201 imaging after exercise and after intravenous dipyridamole were examined and compared in 21 patients with chest pain. Exercise and intravenous dipyridamole revealed similar numbers of segments with normal and defective thallium-201 uptake. Defects in redistribution of blood flow were detected more often with dipyridamole than with exercise. However, exercise or intravenous dipyridamole were similar in classifying segments of heart tissue as normal or abnormal in terms of blood flow and supply. Both exercise and intravenous dipyridamole were equally effective in detecting stenoses (narrowing of blood vessels) and identifying normal vessels. The results show that exercise and intravenous dipyridamole are equally effective in detecting and localizing normal and abnormal segments of heart tissue using thallium-201 imaging. (Consumer Summary produced by Reliance Medical Information, Inc.)

This study describes a simplified approach for the interpretation of electrocardiographic and thallium-201 imaging data derived from the same patient during exercise. The 383 patients in this study had also undergone selective coronary arteriography within 3 months of the exercise test. This matrix approach allows for multiple test outcomes (both tests positive, both negative, 1 test positive and 1 negative) and multiple disease states (no coronary artery disease vs 1-vessel vs multivessel coronary artery disease). Because this approach analyzes the results of 2 test outcomes simultaneously rather than serially, it also negates the lack of test independence, if such an effect is present. It is also demonstrated that ST-segment depression on the electrocardiogram and defects on initial thallium-201 images provide conditionally independent information regarding the presence of coronary artery disease in patients without prior myocardial infarction. In contrast, ST-segment depression on the electrocardiogram and redistribution on the delayed thallium-201 images may not provide totally independent information regarding the presence of exercise-induced ischemia in patients with or without myocardial infarction., Investigators have developed a new diagnostic method of determining the probability of multiple coronary disease states using a matrix approach. ECG (electrocardiograph) results were analyzed in conjunction with the results of the Exercise Thallium-201 Stress Test, a diagnostic procedure involving the injection of an isotope of the element thallium to produce a clear visual outline of the areas under examination. A study was done of 383 patients who had selective coronary arteriography performed within the prior three-month period. Factors predictive of heart disease were looked for, as were any changes in disease states using data recorded during exercise by the patients. The thallium test can detect exercise-induced ischemia, an insufficient blood supply to the heart muscle. Special attention was given to the ST-segment depression area, a particular wave pattern segment, on the ECG and to thallium-201 images. This approach was distinct from previous methods in two important respects: the procedure allowed for the simultaneous analysis of the results of two tests and the evaluation took into consideration the possible interdependence of the data derived from the two tests. An appendix provides the formula used for the 'Derivation of the Probability Correction Factor'. It was concluded that there exist advantages, both theoretical and practical, to this approach over conventional methods. Its simplicity makes the technique clinically useful and practical. However, the full utility of this method has yet to be determined.