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PubMed1996

Gender and referral for coronary angiography after treadmill thallium testing.

Considerable controversy exists regarding whether women are less likely than men to be referred to coronary angiography after an abnormal noninvasive test. This prospective cohort study analyzed consecutive subjects (2,351 men and 1,318 women) with no prior history of invasive cardiac procedures who were referred for treadmill thallium testing at the Cleveland Clinic Foundation. The primary end point was performance of coronary angiography within 90 days of treadmill thallium testing. A secondary end point was all-cause mortality during 1.8 years of follow-up. Women were less likely than men to undergo coronary angiography (6% vs 14%, odds ratio [OR] 0.42, 95% confidence interval [Cl] 0.33 to 0.54, p < 0.001), but were also less likely to have an abnormal thallium scan (8% vs 29%, p < 0.001). In logistic regression analyses with adjustment for thallium result and age, women were as likely as men to be referred for coronary angiography (adjusted OR 1.00, 95% Cl 0.75 to 1.34, p > 0.9). Women were less likely to have severe coronary disease on angiography (15% vs 30%, p = 0.006). During 1.8 years of follow-up there were 26 deaths (2%) among women and 84 deaths (4%) among men. After adjusting for age, thallium abnormalities, and clinical characteristics in Cox regression analyses, women had a lower mortality rate than men (relative risk 0.58, 95% Cl 0.36 to 0.94, p = 0.03). Thus, gender-related differences in referral for coronary angiography after treadmill thallium testing can be explained by a higher rate of abnormal tests in men. No evidence of a post-test gender bias was detected, but a pretest bias affecting referral to nuclear testing cannot be excluded. Furthermore, women have a lower prevalence of severe coronary disease and a lower adjusted mortality rate.

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PubMed1996

Prediction of late cardiac events by dipyridamole thallium scintigraphy in patients with intermittent claudication and occult coronary artery disease.

Concomitant coronary artery disease often occurs in patients with peripheral vascular disease, but it may be asymptomatic. Despite being asymptomatic, cardiovascular events are the main source of morbidity and mortality in this group of patients. Dipyridamole thallium scintigraphy has been shown to be of prognostic value in patients with peripheral vascular disease and symptomatic coronary artery disease, but its effect on the long-term outcome in the asymptomatic group of patients is less defined. Eighty-four consecutive patients with peripheral vascular disease and no symptoms of coronary artery disease were therefore evaluated by clinical assessment, dipyridamole thallium imaging, radionuclide ventriculography, and cardiac catheterization and followed for a mean of 66 months. Abnormal perfusion patterns were found on thallium scintigraphy in 48 patients (57%); fixed, mixed, and reversible defects were present in 14 (17%), 11 (13%), and 23 (27%) patients, respectively. Significant coronary artery disease was present in 52 patients (69%) and mean left ventricular ejection fraction was 44%. During the follow-up period, 23 patients had a cardiac event (nonfatal myocardial infarction or cardiac death). Univariate analysis of 15 clinical, scintigraphic, radionuclide, and angiographic variables revealed that age, angiographic extent of coronary artery disease, and an abnormal thallium scan were significant predictors of subsequent cardiac events. Multivariate stepwise logistic regression analyses selected fixed and mixed thallium defects and diffuse coronary artery disease as the only significant independent predictors of outcome. Thus, the present study shows the value of dipyridamole thallium scintigraphy as a valuable prognostic indicator for long-term event-free survival in a cohort of patients with peripheral vascular disease and no history or symptoms of coronary artery disease.

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PubMed1996

Additive value of thallium single-photon emission computed tomography myocardial imaging for prediction of perioperative events in clinically selected high cardiac risk patients having abdominal aortic surgery.

The present study was designed to prospectively evaluate whether reinjection thallium-201 single-photon emission computed tomography (SPECT) has a significant additive predictive value for occurrence of perioperative cardiac events in clinically selected patients at high cardiac risk undergoing abdominal aortic surgery. Of a group of 517 consecutive patients referred, 134 had > or = 2 of the following clinical or electrocardiographic cardiac risk variables: age > 70 years; history of myocardial infarction, angina, or congestive heart failure; diabetes mellitus; hypertension with severe left ventricular hypertrophy; and Q waves or ischemic ST-segment abnormalities on electrocardiogram at rest. Operation was performed after thallium SPECT study. Twelve patients (9%) had major perioperative events (cardiac death or nonfatal myocardial infarction) and 18 patients had other cardiac events (unstable angina, congestive heart failure, or severe ventricular tachyarrhythmia). Variables correlated with the occurrence of major events were history of myocardial infarction (p < 0.05) and the presence (p < 0.001) and number of segments with thallium reversible defects (p < 0.001). In multivariate analysis, history of myocardial infarction (p < 0.05) and the number of segments with reversible thallium defects (p < 0.001) were independent predictors. When all the cardiac events were taken into consideration, all the previous variables, as well as Q waves and ischemic ST abnormalities on the electrocardiogram, showed significant predictive value in both univariate and multivariate analyses. Furthermore, thallium SPECT imaging has an additive predictive value for major cardiac events over clinical and electrocardiographic risk factors. When performed on clinically selected patients at high cardiac risk undergoing abdominal aortic surgery, thallium SPECT demonstrates significant prognostic value for cardiac events over that provided by clinical variables alone.

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PubMed1999

Comparison of dobutamine echocardiography, dobutamine sestamibi, and rest-redistribution thallium-201 single-photon emission computed tomography for determining contractile reserve and myocardial ischemia in ischemic cardiomyopathy.

Both dobutamine stress echocardiography (DSE) and myocardial perfusion scintigraphy are used to assess myocardial viability. Few studies have compared the data on myocardial viability and ischemia by low and peak dose DSE and myocardial perfusion imaging in the same patients. Fifty-four patients (45 men and 9 women aged 65 +/- 9 years) with ischemic cardiomyopathy (mean ejection fraction 24 +/- 9%) underwent rest 4-hour redistribution thallium-201 single-photon emission computed tomography (SPECT), low and peak dose DSE, and dobutamine sestamibi SPECT. A total of 864 segments were analyzed (16 segments/patient). Wall motion abnormality was present in 796 segments (92%), and contractile reserve during dobutamine infusion was seen in 400 of these segments (50%). Contractile reserve was seen in 331 of 509 hypokinetic segments (65%) and 69 of 287 akinetic/dyskinetic segments (24%) (p <0.001). Contractile reserve was more frequent in segments with normal thallium uptake (64%), reversible thallium defects (42%), or mild to moderate fixed thallium defects (48%) than severely fixed defects (22%) (p <0.05 each). Concordant information about viability by thallium imaging and DSE was obtained in 62% of segments. Dobutamine sestamibi ischemia was seen in 518 of 796 segments (65%) compared with 265 segments (33%) by DSE (p <0.001). Scintigraphic ischemia was noted in 126 of 195 segments (65%) demonstrating biphasic response, 129 of 205 segments (63%) showing sustained improvement, 42 of 70 segments (60%) deteriorating during dobutamine infusion, and 221 of 326 (68%) demonstrating no change (p = NS). Thus, in patients with ischemic cardiomyopathy, contractile reserve is more frequent in hypokinetic segments than akinetic/dyskinetic segments. The number of segments with normal or near-normal thallium uptake or with scintigraphic ischemia is significantly greater than the number of those capable of increasing contractile function or demonstrating an ischemic response during dobutamine echocardiography.

Adult↗

PubMed1999

Prognostic value of thallium-201 single-photon emission computed tomography for patients with multivessel coronary artery disease after revascularization (the Emory Angioplasty versus Surgery Trial [EAST]).

The aim of this study was to investigate the relation between reversible thallium single-photon emission computed tomography (SPECT) myocardial perfusion defects at 1-year after revascularization and quantitative indexes in Emory Angioplasty versus Surgery Trial (EAST) and outcomes 3 years after revascularization in 336 patients. EAST was a randomized controlled trial assessing cardiac outcomes for angioplasty versus bypass surgery for patients with multivessel coronary artery disease. During this prospective trial, a substudy included the evaluation of the prognostic value of reversible defects on quantitative thallium SPECT. At 1-year after revascularization, 336 patients underwent SPECT thallium-201 stress myocardial perfusion and 3-hour delayed imaging. Subsequent events, percutaneous transluminal coronary angioplasty, coronary artery bypass graft surgery, myocardial infarction, and death, were recorded at 3 years. A stress-induced reversible thallium-201 defect was defined using a quantitative index of a reversibility score >30% and severity score >500. Reversible defects were observed more frequently in the percutaneous transluminal coronary angioplasty than in the coronary artery bypass graft surgery treatment groups (46% vs 27%, p <0.001). A total of 123 patients had stress-induced, reversible thallium defects and more events than patients with other perfusion results (freedom from all events was 81.3% vs 94% [p <0.001], and freedom from myocardial infarction and death 88.3% vs 95.5% [p = 0.031]). Quantitative thallium SPECT at 1 year after revascularization risk stratifies patients as to their likelihood of major cardiac outcomes.

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PubMed1995

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.

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PubMed1995

Symptom-limited arm exercise increases detection of ischemia during dipyridamole tomographic thallium stress testing in patients with coronary artery disease.

Exercise combined with dipyridamole during thallium stress testing in patients with coronary artery disease (CAD) increases the frequency of angina and ischemic ST changes in the electrocardiogram. Evidence for an increase in thallium abnormalities has been inconclusive. We prospectively examined 54 consecutive patients who underwent coronary angiography and tomographic thallium with dipyridamole (0.57 mg/kg) alone and combined with symptom-limited dynamic arm exercise. Most patients presented with a history of chest pain and 49 had angiographic evidence of significant coronary stenosis (50% diameter narrowing). Thallium abnormalities were scored blindly by consensus. The number of abnormal segments (total and ischemic) and indexes of left ventricular dysfunction, such as increased lung uptake or ischemic dilation, were compared in the 49 patients with CAD. During arm exercise more patients had evidence of ischemia (39 vs 30; p < 0.001), and the number of ischemic segments increased significantly from 1.3 +/- 1.5 to 2.5 +/- 2.2 (p < 0.001). There was also a significant increase in the indexes of left ventricular dysfunction, ischemic dilation (10 vs 4 patients; p < 0.03) and increased lung uptake (16 vs 5 patients; p < 0.001). Patients who exercised had increased thallium evidence of extent and severity of ischemia and more frequent indexes of left ventricular dysfunction. Thus, symptom-limited arm exercise improves detection of extent and severity of ischemia in patients with CAD undergoing dipyridamole thallium stress testing.

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PubMed1986

Thallium-induced testicular toxicity in the rat.

Reproductive tract functions were studied in adult male Wistar rats given 10 ppm thallium as thallium sulfate in the drinking water. After 60 days of treatment, spermatozoa isolated from the cauda epididymides and vas deferens showed reduced motility and immature germ cells were found in the tubular lumen. Histological examination of testes in thallium-treated animals revealed disarrangement of the tubular epithelium and ultrastructural changes in the Sertoli cells with cytoplasmic vacuolation and distension of the smooth endoplasmic reticulum. The activity of testicular beta-glucuronidase was significantly reduced whereas acid phosphatase and sorbitol dehydrogenase activities were unchanged. Plasma testosterone levels were within normal limits. No abnormalities in testicular morphology and biochemistry were seen in animals sacrificed at the end of the first month of thallium exposure. These findings indicate that the male reproductive system is a susceptible target site to toxic effects of thallium under chronic exposure. They also suggest a major involvement of Sertoli cells in the mechanism underlying thallium-induced testicular damage.

Acid Phosphatase↗

PubMed1997

Sestamibi versus thallium subtraction scintigraphy in parathyroid localization: a prospective comparative study in patients with predominantly mild primary hyperparathyroidism.

BACKGROUND: Technetium 99m sestamibi was recently introduced for the preoperative localization of abnormal parathyroid glands in patients with primary hyperparathyroidism with promising results. However, the sensitivity of sestamibi and thallium to detect abnormal parathyroid glands is partly dependent on the gland size. In this study we compared the sensitivity of sestamibi subtraction scintigraphy with thallium subtraction scintigraphy in patients with predominantly mild increase in serum calcium level. METHODS: Thirty-nine patients with primary hyperparathyroidism were included. The mean (+/-SD) serum level of calcium was 2.75 +/- 0.17 mmol/L. In 28 (72%) of the patients the serum level of calcium was less than 2.85 mmol/L. These patients were classified as having mild abnormalities in serum calcium. All patients were investigated before operation with both sestamibi and thallium subtraction scintigraphy. RESULTS: In two patients autonomous thyroid adenomas precluded subtraction scintigraphy. Sestamibi subtraction scintigraphy correctly localized 31 (86%) of 36 parathyroid adenomas compared with only 17 (47%) of 36 by thallium subtraction scintigraphy (p < 0.001). There was one false-positive result in the sestamibi group because of a thyroid adenoma, and two of the scans were negative. Both the sestamibi and the thallium subtraction scintigraphy localized one single enlarged gland in all three patients with multiple gland involvement. In no case was multiglandular disease predicted. CONCLUSIONS: Sestamibi subtraction scintigraphy is superior to thallium subtraction scintigraphy and has a high sensitivity to localize a solitary parathyroid adenoma in patients with mild increase in serum calcium level. The sensitivity decreases in patients with multiglandular parathyroid disease and concomitant thyroid nodular abnormalities.

Adenoma↗

PubMed1998

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

BACKGROUND: 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. METHODS: 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. FINDINGS: 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. INTERPRETATION: 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.

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PubMed1986

Regional variability in the myocardial clearance of thallium-201 and its importance in determining the presence or absence of coronary artery disease.

There are several limitations in using absolute myocardial clearance of thallium-201 for the detection of coronary artery disease. Noncardiac factors such as peak exercise heart rate and blood level of thallium can affect its absolute myocardial clearance. However, because all myocardial segments in a given heart are exposed to the same noncardiac factors, a relative difference in myocardial clearance of thallium between segments could reflect the presence of coronary artery disease. Accordingly, myocardial clearance of thallium was analyzed in 370 patients. Patients in Group I (n = 45) had less than 1% probability of having coronary artery disease, patients in Group II (n = 44) had normal coronary arteries and patients in Group III (n = 281) had coronary artery disease. Although mean myocardial clearance of thallium in 15 myocardial segments in three views in Group I subjects was 3.4 +/- 0.7 hours, the variability between the slowest and fastest clearing segments in the same subject was as much as 98%. This variability was systematic, suggesting technical reasons associated with imaging as the cause of the variability: 78% of the slowest clearing segments were basal whereas 53% of the fastest clearing segments were apical (p less than 0.01). When Group II and III patients were compared based on Group I values, the absolute myocardial clearance of thallium had a sensitivity and specificity of 92 and 16%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗

PubMed1986

Noninvasive identification of left main and triple vessel coronary artery disease: improved accuracy using quantitative analysis of regional myocardial stress distribution and washout of thallium-201.

The capabilities of visual and quantitative analysis of stress redistribution thallium-201 scintigrams, exercise electrocardiography and exercise blood pressure response were compared for correct identification of extensive coronary disease, defined as left main or triple vessel coronary artery disease, or both (50% or more luminal diameter coronary narrowing), in 105 consecutive patients with suspected coronary artery disease. Extensive disease was present in 56 patients and the remaining 49 had either less extensive coronary artery disease (n = 34) or normal coronary arteriograms (n = 15). Although exercise blood pressure response, exercise electrocardiography and visual thallium-201 analysis were highly specific (98, 88 and 96%, respectively), they were insensitive for identification of patients with extensive disease (14, 45 and 16%, respectively). Quantitative thallium-201 analysis significantly improved the sensitivity of visual thallium-201 analysis for identification of patients with extensive disease (from 16 to 63%, p less than 0.001) without a significant loss of specificity (96 versus 86%, p = NS). Eighteen (64%) of the 28 patients who were misclassified by visual analysis as having less extensive disease were correctly classified as having extensive disease by virtue of quantitative analysis of regional myocardial thallium-201 washout. When the results of quantitative thallium-201 analysis were combined with those of blood pressure and electrocardiographic response to exercise, the sensitivity and specificity for identification of patients with extensive disease was 86 and 76%, respectively, and the highest overall accuracy (0.82) was obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

Prognostic value of computer-quantitated exercise thallium imaging early after percutaneous transluminal coronary angioplasty.

To develop an approach to predicting adverse events after percutaneous transluminal coronary angioplasty (PTCA), 50 patients had thallium-201 exercise testing within 1 month after successful single vessel coronary angioplasty and were followed up for a mean of 18 months. Adverse events were: 1) clinical events consisting of recurrent angina (17 patients) and myocardial infarction (1 patient); 2) treatment events consisting of repeat coronary angioplasty (10 patients) and coronary bypass surgery (1 patient); and 3) restenosis, defined as a greater than 30% increase in luminal stenosis (15 of 38 recatheterized patients). There were no deaths. Of the clinical, exercise, angiographic and thallium scan variables analyzed by stepwise logistic regression, postangioplasty gradient greater than 20 mm Hg predicted clinical events and treatment events, and the number of segments with slower thallium clearance predicted clinical events, treatment events and restenosis. Using Cox Hazards model regression of survival without events, the number of transient qualitative thallium defects also predicted clinical events and restenosis. At 1 year after angioplasty, 24% of patients with these variables had restenosis compared with only 6% of those without these variables and 36% of patients with these variables had a clinical or treatment event compared with 8% of patients without these variables. Three measures of the adequacy of myocardial perfusion (post-angioplasty gradient, reduced thallium clearance and transient thallium defects) were additive predictors of adverse events after coronary angioplasty with the relative risk being approximately four times greater in patients with these variables than in those without. Such adverse events, therefore, are usually a consequence of inadequate revascularization.

Adult↗

PubMed1997

Adenosine thallium-201 tomography in evaluation of graft patency late after coronary artery bypass graft surgery.

OBJECTIVES: We sought to ascertain the utility of adenosine thallium-201 tomography for assessing graft stenoses late after coronary artery bypass graft surgery. BACKGROUND: Although pharmacologic perfusion imaging has been increasingly used in the assessment of patients with coronary artery disease, the value of this stress modality for detecting coronary artery bypass graft stenosis late after surgery is unknown. METHODS: We studied 109 patients who underwent both adenosine thallium-201 tomography and coronary angiography at 6.7 +/- 4.8 (mean +/- SD) years after coronary artery bypass graft surgery. Adenosine thallium-201 tomography was assessed quantitatively by computer-generated polar maps of the myocardial thallium-201 activity. RESULTS: On coronary angiography, significant graft stenoses were present in 68 patients, 65 of whom had a corresponding perfusion defect as shown by thallium-201 tomography (sensitivity 96%). Significant stenoses were present in 107 (37.8%) of 283 grafts. The overall specificity by quantitative tomography was 61%. Seventy percent of the apparently false positive perfusion defects could be explained on the basis of unbypassed native disease or by the presence of fixed defects in patients with previous myocardial infarction. CONCLUSIONS: Thus, results of adenosine thallium-201 tomography are nearly always abnormal in patients with late coronary graft stenosis. Most of the false positive defects appear to be due to either unbypassed native disease or a previous myocardial infarction.

Adenosine↗

PubMed1998

Thallium reinjection versus standard stress/delay redistribution imaging for prediction of cardiac events.

OBJECTIVES: The purpose of this study was to compare thallium reinjection with standard stress/delay redistribution for the prediction of cardiac events. BACKGROUND: Although thallium reinjection enhances the detection of viable myocardium, its contribution to prognosis over stress/delay redistribution in a general referral population has not been clearly evaluated. METHODS: This retrospective analysis included 366 consecutive patients with coronary artery disease who underwent stress/delay redistribution imaging and thallium reinjection scintigraphy, with a mean follow-up of 33+/-12 months. RESULTS: Cardiac events occurred in 48 patients (40 deaths, 8 myocardial infarctions). Of the 366 original patients, 159 demonstrated ischemia by stress/delay redistribution, 107 showed ischemia by reinjection only, and 100 showed infarction only. Cardiac events occurred in 20 patients (12.6%) with stress/delay redistribution, 13 patients (12%) with ischemia detected by thallium reinjection only and 15 patients (15%) with infarction only. The size of the reversible thallium defect by either stress/delay redistribution imaging or reinjection scintigraphy did not predict cardiac events. Independent predictors of cardiac events included left ventricular cavity size, the size of the abnormal perfusion defect and patient age. CONCLUSIONS: Thallium reinjection does not contribute independent prognostic utility for cardiac events when compared with stress/delay redistribution. Left ventricular dilation and the size of the post-stress defect were predictors of cardiac events.

Aged↗

PubMedDate not supplied

The value of perioperative clinical indexes and dipyridamole thallium scintigraphy for the prediction of myocardial infarction and cardiac death in patients undergoing vascular surgery.

BACKGROUND: Dipyridamole thallium scintigraphy has previously been shown to have predictive value for both perioperative and late cardiac events in patients undergoing vascular surgery. However, despite the prognostic utility of this technique, the relative importance of clinical factors and scintigraphic information is not well known. The purpose of this study was to evaluate the value of commonly used clinical risk indexes, composed of historic variables, and dipyridamole thallium scintigraphy for predicting perioperative cardiac event-free survival rates. METHODS AND RESULTS: Clinical and scintigraphic variables in 360 patients undergoing vascular surgery were analyzed for their predictive utility for perioperative and late (up to 5 years) cardiac events (nonfatal myocardial infarction or cardiac death) by means of chart review and telephone contact. Patients were correctly categorized as being at low, moderate, or high risk for perioperative cardiac events based on two clinical indexes. Thallium redistribution, however, was a more powerful predictor of cardiac events than these indexes. Even in a clinically low-risk patient cohort, the odds ratio for an event increased by 6- to 8-fold (p < 0.05) if thallium redistribution was noted. These indexes also demonstrated prognostic utility for late cardiac event-free survival rates by life-table analysis (p < 0.001). The presence of a fixed thallium defect was associated with an increased risk of late cardiac events (p < 0.01). When stratified by risk index, in those patients at moderate to high risk who had a fixed defect the odds ratio increased by 3.9- to 5.4-fold (p < 0.001). Likewise, the low-risk subgroup had a 3.9- to 8.2-fold increase in the risk of a late cardiac event when a fixed perfusion defect was present. CONCLUSIONS: Preoperative clinical indexes are predictive of both perioperative and late cardiac events in patients undergoing vascular surgery. However, dipyridamole thallium scintigraphy is more powerful prognostically than these clinical indexes and provides supplemental value to clinical risk stratification.

Adult↗

PubMed2001

New class of oligonuclear platinum-thallium compounds with a direct metal-metal bond. 5. Structure determination of heterodimetallic cyano complexes in aqueous solution by EXAFS and vibrational spectroscopy.

The structures of three closely related heterodimetallic cyano complexes, [(NC)(5)Pt-Tl(CN)(n)()](n)()(-) (n = 1-3), formed in reactions between [Pt(II)(CN)(4)](2)(-) and Tl(III) cyano complexes, have been studied in aqueous solution. Multinuclear NMR data ((205)Tl, (195)Pt, and (13)C) were used for identification and quantitative analysis. X-ray absorption spectra were recorded at the Pt and Tl L(III) edges. The EXAFS data show, after developing a model describing the extensive multiple scattering within the linearly coordinated cyano ligands, short Pt-Tl bond distances in the [(NC)(5)Pt-Tl(CN)(n)()](n)()(-) complexes: 2.60(1), 2.62(1), and 2.64(1) A for n = 1-3, respectively. Thus, the Pt-Tl bond distance increases with increasing number of cyano ligands on the thallium atom. In all three complexes the thallium atom and five cyano ligands, with a mean Pt-C distance of 2.00-2.01 A, octahedrally coordinate the platinum atom. In the hydrated [(NC)(5)Pt-Tl(CN)(H(2)O)(4)](-) species the thallium atom coordinates one cyano ligand, probably as a linear Pt-Tl-CN entity with a Tl-C bond distance of 2.13(1) A, and possibly four loosely bound water molecules with a mean Tl-O bond distance of about 2.51 A. In the [(NC)(5)Pt-Tl(CN)(2)](2)(-) species, the thallium atom probably coordinates the cyano ligands trigonally with two Tl-C bond distances at 2.20(2) A, and in [(NC)(5)Pt-Tl(CN)(3)](3)(-) Tl coordinates tetrahedrally with three Tl-C distances at 2.22(2) A. EXAFS data were reevaluated for previously studied mononuclear thallium(III)-cyano complexes in aqueous solution, [Tl(CN)(2)(H(2)O)(4)](+), [Tl(CN)(3)(H(2)O)], and [Tl(CN)(4)](-), and also for the solid K[Tl(CN)(4)] compound. A comparison shows that the Tl-C bond distances are longer in the dinuclear complexes [(NC)(5)Pt-Tl(CN)(n)()](n)()(-) (n = 1-3) for the same coordination number. Relative oxidation states of the metal atoms were estimated from their (195)Pt and (205)Tl chemical shifts, confirming that the [(NC)(5)Pt-Tl(CN)(n)()](n)()(-) complexes can be considered as metastable intermediates in a two-electron-transfer redox reaction from platinum(II) to thallium(III). Vibrational spectra were recorded and force constants from normal-coordinate analyses are used for discussing the delocalized bonding in these species.

Chemical Phenomena↗

PubMed1999

Comparison of dobutamine stress echocardiography and exercise stress Thallium-201 SPECT for detection of myocardial ischemia after acute myocardial infarction treated with thrombolysis.

In order to compare the ability of dobutamine stress echocardiography (DSE) and exercise Thallium-201 SPECT to detect myocardial ischemia in patients with myocardial infarction (MI) treated with thrombolysis, 43 prospectively selected patients with MI treated with thrombolysis underwent within 1 month from MI DSE, stress-redistribution-reinjection Thallium-201 SPECT and coronary angiography. The echocardiographic and scintigraphic images were analyzed for the presence of myocardial ischemia using a 11-segment left ventricular model. DSE and exercise Thallium-201 SPECT detected myocardial ischemia in the infarct zone in 72% and 72% (31/43) of patients and ischemia at a distance in 12% (5/43) and 19% (8/43) of patients with a concordance of 67% and 88%, respectively. A significant agreement between DSE and exercise Thallium SPECT was found in the evaluation of the extent of both myocardial necrosis and stress-induced myocardial ischemia. DSE and exercise Thallium SPECT showed similar sensitivity (79 vs 76%), specificity (60 vs 60%) and accuracy (77 vs 74%) for detection of a critical stenosis of the infarct-related artery; there was also no significant difference between the tests in sensitivity, specificity and accuracy for detection of the multivessel disease. In conclusion, initially after thrombolyzed MI, DSE and exercise Thallium-201 SPECT detect myocardial ischemia in the infarct zone in a high proportion of patients and show a similar accuracy for the diagnosis of a critical stenosis of the infarct-related coronary artery and of the multivessel disease.

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