Exercise Thallium-201 Single-photon Emission Computed Tomography Research Articles

Exercise Single-Photon Emission Computed Tomography Provides Effective Risk Stratification of Elderly Men and Elderly Women

In a recent study, we reported that the Duke treadmill score was unable to effectively stratify elderly patients according to risk. The purpose of this study was to evaluate the prognostic value of exercise single-photon emission computed tomography (SPECT) in this same population and to examine results by gender. A cohort of 247 elderly (age > or =75 years) patients (108 women, 139 men, age 77+/-3 years) who underwent exercise thallium-201 SPECT were followed up for a median duration of 6.4 years. SPECT variables were significantly associated with cardiac death: summed stress score (SSS) chi2=19.5, P<0.001; summed difference score chi2=12.3, P<0.001; increased lung uptake chi2=9.6, P=0.002; and left ventricular enlargement chi2=8.3, P=0.004. The Duke score was not significantly associated with cardiac death (chi2<1, P=NS). The SSS classified most patients as low risk (49%) or high risk (35%); the Duke score classified the majority (68%) as intermediate risk. Annual cardiac mortality rates for patients categorized by SSS as low risk and high risk were 0.8% and 5.8%, respectively. Cardiac survival rates according to SSS risk categories were significantly different for both women (P=0.012) and men (P=0.003). SPECT classified most elderly patients into clinically useful low- and high-risk categories and accurately predicted outcomes in both genders. If these results can be validated in future studies, exercise SPECT rather than standard treadmill testing may emerge as the initial noninvasive testing strategy in elderly patients who are able to exercise.

Change with exercise in QT dispersion in infarct-related myocardium after angioplasty

Background: The aim of this study was to evaluate the relationship between exercise-induced QT dispersion and condition of infarct-related myocardium including myocardial scar after angioplasty assessed with exercise perfusion single photon emission computed tomography (SPECT). Methods: Exercise thallium-201 SPECT was performed 6 months after successful direct angioplasty in 67 male patients (60.6±11.5 years), who had Q wave infarction resulting from single vessel disease, and the number of perfusion defect areas (DS) was measured at rest and exercise together with QT (QTc) dispersion. Results: In 52 patients with resting perfusion defects, the exercise-induced change in DS was correlated to the change in QT (or QTc) dispersion ( r=−0.51 or r=−0.531, p<0.0001). When the patients were grouped according to the patterns of transient perfusion defect, there were significant differences in ΔQT dispersion and ΔQTc dispersion among infarct-related three groups (reverse, fixed, and partial redistributions) and normal volunteers (ΔQT dispersion; −5.7±12.7 ms in 13 patients with reverse redistribution, −16.3±13.1 ms in 30 patients with fixed redistribution, −28.9±29.5 ms in 9 patients with partial redistribution, and +3.4±20.9 ms in 12 normal volunteers, p=0.0098; ΔQTc dispersion; +18.2±20.8 ms, +1.4±16.7 ms, −15.4±30 ms, and +19±27.5 ms, p=0.0017, respectively). ΔQTc dispersion estimated the SPECT image patterns ( p=0.0002) with a sensitivity of 67.3%, a specificity of 83.7% and an accuracy of 78.2%. Conclusions: The change with exercise in QT dispersion may help detect the condition of infarct-related myocardium after angioplasty.

Exercise four hour redistribution thallium-201 single photon emission computed tomography and exercise induced ST segment elevation in detecting the viable myocardium in patients with acute myocardial infarction

ObjectiveTo investigate the specificity and sensitivity of the combination of redistribution in exercise thallium-201 single photon emission computed tomography (SPECT) and exercise induced ST elevation for detecting the viable myocardium...

Relation between the kinetics of thallium-201 in myocardial scintigraphy and myocardial metabolism in patients with acute myocardial infarction

ObjectiveTo investigate the relations between myocardial metabolism and the kinetics of thallium-201 in myocardial scintigraphy.Methods46 patients within six weeks after the onset of acute myocardial infarction underwent resting myocardial dual...

Underestimation of Extent and Severity of Coronary Artery Disease by Dipyridamole Stress Thallium-201 Single-Photon Emission Computed Tomographic Myocardial Perfusion Imaging in Patients Taking Antianginal Drugs

Objectives. This study evaluated the diagnostic value of dipyridamole plus low level treadmill exercise (dipyridamole stress) thallium-201 single-photon emission computed tomography (SPECT) in patients taking antianginal drugs.Background. Dipyridamole stress is the major substitute for maximal exercise in patients referred for myocardial perfusion imaging. Although antianginal drugs are commonly suspended before exercise, dipyridamole stress is usually performed without discontinuing these drugs.Methods. Twenty-six patients underwent two dipyridamole perfusion studies: the first without (SPECT-1) and the second with (SPECT-2) antianginal treatment. Twenty-one patients (81%) received calcium antagonists, 19 (73%) received nitrates, and 8 (31%) received beta-blockers. Eighteen of the patients underwent coronary angiography. Data are presented as the mean value ± SD.Results. Visual scoring yielded significantly larger and more severe reversible perfusion defects for SPECT-1 than for SPECT-2. Quantitative analysis showed larger perfusion defects on stress images of SPECT-1 in the left anterior descending coronary artery (LAD) (25 ± 21% vs. 17 ± 15%, p = 0.003), left circumflex coronary artery (LCx) (56 ± 35% vs. 48 ± 36%, p = 0.03) and right coronary artery (RCA) (36 ± 27% vs. 25 ± 24%, p = 0.008) territories. Individual vessel sensitivities in the LAD, LCx and RCA territories were 93%, 79% and 100% for SPECT-1 and 64%, 50% and 70% for SPECT-2, respectively. These differences were highly significant for the LAD (p = 0.004) and LCx (p = 0.00004) territories. The overall individual vessel sensitivity of SPECT-1 was significantly higher than that of SPECT-2 (92% vs. 62%, p = 0.000003). Specificity was not significantly different in SPECT-1 compared with SPECT-2 (80% and 93%, p = 0.33).Conclusions. Continued use of antianginal drugs before dipyridamole plus low level treadmill exercise thallium-201 SPECT may reduce the extent and severity of myocardial perfusion defects, resulting in underestimation of coronary artery disease.

Prediction of death and myocardial infarction by screening with exercise-thallium testing after coronary-artery-bypass grafting

The role of myocardial-perfusion imaging in calculating risk in symptom-free patients who have had coronary-artery-bypass grafting (CABG) is unclear. Practice guidelines have argued against routine screening of these patients. We sought to find out the independent and incremental prognostic value of exercise thallium-201 single-photon-emission computed tomography (SPECT) for prediction of death and non-fatal myocardial infarction (MI) in these patients. Analyses were based on 873 symptom-free patients undergoing symptom-limited exercise thallium-201 SPECT between September, 1990, and December, 1993. All had undergone CABG and none had recurrent angina or other major intercurrent coronary events. Exercise and thallium-perfusion variables were analysed to determine their prognostic importance during 3 years of follow-up. Myocardial-perfusion defects were noted in 508 (58%) patients. There were 57 deaths and 72 patients had major events (death or non-fatal MI). Patients with thallium-perfusion defects were more likely to die (9% vs 3%, p=0.0004) or suffer a major event (11% vs 4%, p=0.0002). Reversible defects were also predictive of death (12% vs 5%, p=0.002) and major events (13% vs 7%, p=0.004). The exercise variable with the strongest predictive power was an impaired (< or = 6 METs [measure of oxygen consumption equal to 3.5 mL/kg/min]) exercise capacity; poor exercise capacity was predictive of death (18% vs 4%, p<0.0001) and death or non-fatal MI (19% vs 5%, p<.00001). After adjusting for baseline clinical variables, surgical variables, time elapsed since CABG, and standard cardiovascular risk factors, thallium-perfusion defects remained predictive of death (adjusted relative risk 2.78, 95% CI 1.44-5.39) and major events (2.63, 1.49-4.66). Similarly, impaired exercise remained strongly predictive of death (4.16, 2.38-7.29) and major events (3.61, 2.22-5.87) after adjusting for confounders. In this group of patients who were symptom-free after CABG, thallium-perfusion defects and impaired exercise capacity were strong and independent predictors of subsequent death or non-fatal MI. Recommendations against routine screening exercise myocardial-perfusion studies in this setting should be reconsidered.

Nicotine Patch Therapy in Smoking Cessation Reduces the Extent of Exercise-Induced Myocardial Ischemia

Objectives. We sought to determine the effects of nicotine patch therapy, when used to promote smoking cessation, on myocardial ischemia in patients with coronary artery disease.Background. Nicotine patches substantially increase quit rates among cigarette smokers, but their safety in patients with myocardial ischemia who are attempting to quit smoking is unknown.Methods. This is a prospective study using exercise thallium-201 single-photon emission computed tomography (SPECT) to assess serial changes in the total and ischemic myocardial perfusion defect size at baseline while patients were smoking and during treatment with 14- and 21-mg nicotine patches. Entry criteria required that patients 1) smoked ≥1 pack of cigarettes per day; 2) had known coronary artery disease; and 3) had myocardial ischemia (i.e., ≥5% reversible perfusion defect) on SPECT. All patients performed symptom-limited treadmill exercise, and the baseline SPECT study served as its own control. We interpreted and computer quantified the SPECT images with no knowledge of the testing sequence.Results. Thirty-six of the 40 enrolled patients had exercise SPECT at baseline and during treatment with at least 14-mg nicotine patches. These patients had an initial perfusion defect size of 17.5 ± 10.6% while smoking an average of 31 ± 11 cigarettes per day for 40 ± 12 years. A significant reduction in the total perfusion defect size (p < 0.001) was observed from baseline (17.5 ± 10.6%) to treatment with 14-mg (12.6 ± 10.1%) and 21-mg (11.8 ± 9.9%) nicotine patches. This reduction occurred despite an increase in treadmill exercise duration (p < 0.05) and higher serum nicotine levels (p < 0.001). There was a significant correlation between the reduction in defect size and exhaled carbon monoxide levels (p < 0.001) because patients reduced their smoking by ∼74% during the trial.Conclusions. Nicotine patches, when used to promote smoking cessation, significantly reduce the extent of exercise-induced myocardial ischemia as assessed by exercise thallium-201 SPECT.(J Am Coll Cardiol 1997;30:125–30)

Comparison of defect size between thallium-201 and technetium-99m tetrofosmin myocardial single-photon emission computed tomography in patients with single-vessel coronary artery disease

Defect size on exercise-rest technetium (Tc)-99m tetrofosmin myocardial perfusion imaging was compared with that on exercise-reinjection thallium-201 imaging in 20 patients with 1 -vessel coronary artery disease, in each patient, exercise-reinjection thallium-201 single-photon emission computed tomography (SPECT) and exercise-rest Tc-99m tetrofosmin SPECT imaging were performed. For visual analysis of the obtained SPECT images, the left ventricular myocardium was divided into 20 segments based on 3 shortaxis slices from the apical, middle, and basal ventricular levels. For quantitative analysis, a square region of interest was placed on the center of each segment which was used for visual analysis, and relative regional activity to the normal reference region was calculated for each segment. By visual interpretation of the images, exercise Tc-99m tetrofosmin imaging showed a smaller defect size than exercise thallium-201 imaging (6.9 ± 3.9 vs 8.8 ± 3.0 segments, p < 0.01). In contrast, rest Tc-99m tetrofosmin imaging showed a defect size similar to that on reinjection thallium-201 imaging (5.9 ± 3.6 vs 5.6 ± 3.9 segments, p = NS). Similarly, the mean defect sizes during exercise determined by quantitative analysis were smaller on Tc-99m tetrofosmin SPECT than those on thallium-201 SPECT at all tested threshold cutoff points ranging from 50% to 70%, whereas there were no significant differences in defect sizes between rest Tc-99m tetrofosmin and reinjection thallium-201 imaging. These data indicate mat exercise Tc-99m tetrofosmin SPECT defect size determined either by visual analysis or by quantitative analysis may be smaller than that on exercise thallium-201 SPECT.

Arbutamine stress thallium-201 single-photon emission computed tomography using a computerized closed-loop delivery system: Multicenter trial for evaluation of safety and diagnostic accuracy

This study sought to evaluate the efficacy and safety of arbutamine when used in conjunction with thallium-201 single-photon emission computed tomography (SPECT) in a multicenter trial and to compare arbutamine stress and treadmill exercise thallium-201 SPECT for diagnostic sensitivity and myocardial perfusion pattern.Arbutamine is a potent beta-agonist developed specifically for pharmacologic stress testing.Arbutamine was administered by a novel computerized closed-loop device that measures heart rate and adjusts arbutamine infusion to achieve a selected rate of heart rate increase toward a predetermined limit. The cohort included 184 patients who underwent arbutamine stress testing, of whom 122 (catheterization group) had angiographically defined coronary artery disease ( > or = 50% diameter stenosis of a major coronary artery), and 62 had a low pretest likelihood of coronary artery disease (low likelihood group). A subset of 69 patients from the catheterization group underwent both arbutamine and exercise stress testing.Hemodynamic responses during arbutamine and exercise stress testing demonstrated no significant difference in percent increase in heart rate (81% vs. 76%) or systolic blood pressure (26% vs. 30%). The sensitivity for detecting coronary artery disease ( > or = 50% stenosis) using arbutamine thallium-201 SPECT was 87% (95% for detecting > or = 70% stenoses), and the normalcy rate in the low likelihood group was 90%. In patients completing both arbutamine and exercise stress testing, thallium-201 SPECT sensitivity for detecting coronary artery disease ( > or = 50% stenosis) was 94% and 97% (p = NS), respectively Furthermore, SPECT segmental visual score agreement (defect vs. no defect) showed a concordance of 92% between arbutamine and exercise results (kappa 0.80, p < 0.001). The stress thallium-201 SPECT segmental scores showed 83% exact agreement (kappa 0.69, p < 0.001), and analysis of the reversibility of segments with stress perfusion defects demonstrated 86% exact agreement (kappa 0.68, p < 0.001). In general, side effects associated with arbutamine were well tolerated and resolved with discontinuation of infusion.Arbutamine, administered by a closed-loop feed-back system was shown to be a safe and effective pharmacologic stress agent. Arbutamine stress thallium-201 SPECT appears to be accurate for the diagnosis of coronary artery disease with a diagnostic efficacy similar to that of treadmill exercise thallium-201 studies.

Exercise thallium-201 single photon emission computed tomography for evaluation of coronary artery bypass graft patency

Thallium-201 single photon emission computed tomography (SPECT) is superior to planar imaging for localizing native coronary stenoses, but has not yet been studied for assessing graft patency late after coronary artery bypass graft surgery (CABG). Accordingly, we studied 50 patients (40 males), aged 58 ± 9 years (mean ± SD), who presented for evaluation of angina (30 patients), atypical chest pain (20 patients), and other symptoms (9 patients), late after CABG (51 ± 47 months). Patients with prior myocardial infarction were excluded. The mean ejection fraction was 58 ± 17%. All patients underwent coronary angiography within 3 weeks of symptom-limited exercise thallium-201 SPECT. There were 119 grafts, of which 48 had >50% stenosis by angiography. Thallium-201 SPECT detected 40 of these 48 (83%) stenosed grafts. The sensitivity of thallium-201 SPECT for detecting any graft stenosis was higher than that of the exercise electrocardiogram in patients with typical recurrent angina (84% vs 24%, p < 0.0001), as well as in those with atypical symptoms (70% vs 50%, p = 0.0039). The sensitivity of thallium-201 SPECT for correctly localizing the graft stenosis site was 82% for the left anterior descending, 92% for the right coronary, and 75% for the circumflex coronary artery. In conclusion, exercise thallium-201 SPECT is an excellent method to detect and localize graft stenosis late after CABG; it is far superior to the exercise electrocardiogram alone, both in patients with and without typical recurrent angina.

Early exercise thallium‐201 single photon emission computed tomography in unstable angina: a prospective study

To evaluate the safety and diagnostic value of early symptom-limited exercise electrocardiography (ECG) and exercise thallium-201 single photon emission computed tomography (SPECT) in unstable angina (UA), 39 patients were studied prospectively soon after stabilization on medical treatment. No patient had a history of myocardial infarction (MI) or revascularization and patients with left bundle branch block were excluded. Exercise ECG and exercise thallium-201 SPECT were performed 8 +/- 4 days and 11 +/- 6 days respectively after admission to hospital. Seventeen out of 39 patients (44%) had positive exercise ECGs and 22 (56%) negative or inconclusive ones. Exercise thallium-201 SPECT was positive in 26 patients (67%) and negative in 13 patients (33%). Thirty-one patients underwent coronary arteriography and 24 of them proved to have significant coronary artery disease (CAD). The sensitivity, specificity and positive predictive value of exercise ECG in detecting CAD are 62%, 86%, and 94% respectively while the corresponding results are 96%, 100%, and 100% for exercise thallium-201 SPECT. Therefore, it is concluded that the early symptom-limited exercise test is safe in medically stabilized patients with UA. Early exercise thallium-201 SPECT is highly sensitive and predictive of the presence of significant CAD among patients in the early recovery phase of UA and can be used in selecting this group of patients for coronary angiography and other therapeutic strategies.

Exercise echocardiography versus thallium-201 SPECT for assessing patients before and after PTCA.

This study was designed (1) to assess the relationship between stress exercise echocardiography (echo) and 201-Tl single photon emission computed tomography (SPECT) applied simultaneously in 23 patients who were candidates to percutaneous transluminal coronary angioplasty (PTCA), (2) to assess the relationship between the development of exercise-induced wall motion abnormalities, transient perfusion defects and the severity of quantitatively assessed coronary stenoses and (3) to compare the functional improvement after PTCA by exercise echo and SPECT. Before PTCA there was an agreement of 78% between stress echo (new wall motion abnormalities) and SPECT (transient perfusion defects) results. All patients with a percentage diameter stenosis greater than 70% had a positive echo and SPECT, while they were both negative if the percentage diameter stenosis was less than 50%. In 19 patients re-studied 4 weeks after PTCA, an ischaemic response at stress echo was found in two of the 13 patients who had a positive stress echo test before PTCA, and SPECT was still positive in three of the 10 patients who had a positive SPECT study before PTCA. Echo and SPECT were concordant in 17/19 cases. It is concluded that exercise echo and 201-Tl SPECT are useful non-invasive tools for the functional assessment of patients before and after PTCA, and that they provide highly concordant results.

Submaximal exercise thallium-201 SPECT for assessment of interventional therapy in patients with acute myocardial infarction

Submaximal thallium-201 stress testing has been shown to provide important diagnostic and prognostic information in patients with acute myocardial infarction. The purpose of this investigation was to evaluate the diagnostic value of early submaximal stress testing and thallium-201 single photon emission computed tomography (SPECT) after interventional therapy. Scintigraphic results from 56 patients with infarctions, who underwent acute thrombolytic therapy, angioplasty, or both, were compared with late (6 weeks) functional outcome as assessed by radionuclide ventriculography and with results of discharge coronary angiography. A linear correlation was found between the extent of thallium-201 SPECT perfusion defect and late ventricular function ( r = 0.74, p < 0.01). Forty-two percent of patients with large SPECT perfusion defects had normal left ventricular ejection fractions, suggesting an overestimation of infarct size by early imaging. Sensitivity and specificity of thallium-201 SPECT for detection of coronary artery stenosis in noninfarct territories was 57% and 46%, respectively, indicating limited diagnostic definition of extent of underlying coronary artery disease. Results of follow-up coronary angiography showed a significant relationship between the size of the initial perfusion defect and early restenosis or reocclusion of the infarct artery. Thus the extent of early thallium-201 perfusion defects correlates with late functional outcome but appears to overestimate the degree of injury. Submaximal thallium-201 stress testing allows only limited characterization of underlying coronary artery disease. Early assessment of infarct size may identify a patient population at high risk for reocclusion of the infarct artery.

Thallium-201 single-photon emission computed tomography with intravenous dipyridamole to diagnose coronary artery disease

To determine the ability of thallium-201 single-photon emission computed tomography (SPECT) after dipyridamole infusion (0.71 mg/kg body weight) to detect coronary disease and predict individual coronary stenoses, 76 patients unable to exercise adequately underwent thallium-201 SPECT and quantitative analysis with bull's eye polar maps immediately after dipyridamole infusion and again 4 hours later. Bull's eye maps were compared with files compiled from gender-matched normal patients who had less than 5% probability of coronary artery disease while undergoing exercise thallium-201 SPECT. All patients underwent coronary arteriography. Test sensitivity in detecting coronary disease (> 50% diameter stenosis of any vessel) was 89%, with sensitivities of 73% to 82% in detecting stenoses of individual vessels. Specificity for coronary artery disease was 47% (83% to 88% for individual vessels). However, 5 of the 8 patients with false-positive thallium-201 SPECT had 30% to 40% stenoses. The results, from a comparison of patients who underwent dipyridamole infusion with patients who exercised, indicate that dipyridamole infusion is a satisfactory alternative to exercise for thallium-201 SPECT. Coronary stenosis of less than 50% is a frequent cause of scan abnormalities