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PubMed1980

Clinical decision-making with treadmill testing and thallium 201.

Fifty patients were prospectively evaluated for myocardial ischemia utilizing treadmill testing and thallium-201 imaging. By coronary angiography, 43 had significant coronary stenosis and seven were normal. The sensitivity, specificity, accuracy and predictive value of treadmill testing alone (81 per cent, 71 per cent, 80 per cent and 95 per cent) did not statistically differ from that of thallium-201 imaging (70 per cent, 86 per cent, 72 per cent and 97 per cent). Combined treadmill testing and thallium-201 imaging (84 per cent, 71 per cent, 80 per cent and 98 per cent) did not significantly affect the results of treadmill testing alone. Thallium-201 imaging failed to identify a number of patients with high risk lesions. The high prevalence of disease, the presentation of typical angina, preselection bias, multiple lead monitoring and exclusion of patients with abnormalities on the resting electrocardiogram probably accounted for failure of thallium-201 imaging to improve the results obtained with treadmill testing. The use of thallium-201 imaging in certain subsets of patient (resting electrocardiographic abnormalities, nondiagnostic treadmill testing, atypical chest pain or asymptomatic patients with abnormalities on treadmill testing) may be of value. However, the use of thallium-201 imaging as a routine screening procedure for myocardial ischemia in patients with typical angina, without due consideration of the prevalence of the disease in the population, is not justified.

Angina Pectoris↗
PubMed1988

Superiority of quantitative exercise thallium-201 variables in determining long-term prognosis in ambulatory patients with chest pain: a comparison with cardiac catheterization.

The purpose of this study was to determine the prognostic utility of quantitative exercise thallium-201 imaging and compare it with that of cardiac catheterization in ambulatory patients. Accordingly, long-term (4 to 9 years) follow-up was obtained in 293 patients who underwent both tests for the evaluation of chest pain: 89 had undergone coronary artery bypass graft surgery within 3 months of testing and were excluded from analysis, 119 experienced no cardiac events and 91 had an event (death in 20, nonfatal myocardial infarction in 21 and coronary artery bypass operations performed greater than 3 months after cardiac catheterization in 50). When all variables were analyzed using Cox regression analysis, the quantitatively assessed lung/heart ratio of thallium-201 activity was the most important predictor of a future cardiac event (chi 2 = 40.21). Other significant predictors were the number of diseased vessels (chi 2 = 17.11), patient gender (chi 2 = 9.43) and change in heart rate from rest to exercise (chi 2 = 4.19). Whereas the number of diseased vessels was an important independent predictor of cardiac events, it did not add significantly to the overall ability of the exercise thallium-201 test to predict events. Furthermore, information obtained from thallium-201 imaging alone was marginally superior to that obtained from cardiac catheterization alone (p = 0.04) and significantly superior to that obtained from exercise testing alone (p = 0.02) in determining the occurrence of events. In addition, unlike the exercise thallium-201 test, which could predict the occurrence of all categories of events, catheterization data were not able to predict the occurrence of nonfatal myocardial infarction. The exclusion of bypass surgery and previous myocardial infarction did not alter the results. In conclusion, data from this study demonstrate that exercise thallium-201 imaging may be superior to data from both exercise testing alone and cardiac catheterization data alone for predicting future events in ambulatory patients who have undergone both exercise thallium-201 imaging and catheterization for the evaluation of chest pain.

Adult↗
PubMed1989

Effect of ischemia and postischemic dysfunction on myocardial uptake of technetium-99m-labeled methoxyisobutyl isonitrile and thallium-201.

The myocardial uptake of a new technetium-99m-labeled myocardial perfusion agent, methoxyisobutyl isonitrile (Tc-99m MIBI), and thallium-201 was correlated with microsphere flow in an open chest canine model of low coronary flow and postischemic dysfunction. Eighteen dogs were given an injection of thallium-201 (0.5 mCi) and Tc-99m MIBI (5 mCi) either after 40 min of partial left anterior descending artery occlusion (Group I, 10 dogs) or during reperfusion after 15 min of left anterior descending artery occlusion (Group II, 8 dogs). Regional dysfunction was documented during injection in both groups by quantitative two-dimensional echocardiography. Regional blood flow was assessed by radiolabeled microspheres. The heart was excised 15 min after radionuclide injection and the left ventricle divided into 96 segments for gamma well counting. Among Group I dogs, central ischemic thallium-201 and Tc-99m MIBI activity (expressed as a percent of the activity in the corresponding nonischemic zone) was comparable, respectively, for endocardial (54 +/- 17% and 52 +/- 17%), mid-wall (71 +/- 20% and 69 +/- 17%) and epicardial (89 +/- 13% and 94 +/- 9%) segments and increased proportionally with flow. There was a good linear correlation among these endocardial segments between flow and both thallium-201 (r = 0.78) and Tc-99m MIBI (r = 0.85) activity. Among Group II dogs, central ischemic endocardial flow (59 +/- 14%) was comparable to thallium-201 (70 +/- 18%) and Tc-99m MIBI (74 +/- 12%) activity. Similarly, relative endocardial flow in the intermediate ischemic region (71 +/- 11%) was comparable to thallium-201 (77 +/- 11%) and Tc-99m MIBI (81 +/- 10%) activity. Thus, myocardial uptake of Tc-99m MIBI and thallium-201 is comparable under conditions of low coronary flow and postischemic dysfunction and closely parallels flow alterations.

Animals↗
PubMed1995

Rest-redistribution thallium-201 scintigraphy to determine myocardial viability early after myocardial infarction.

OBJECTIVES: This study attempted to determine the utility of early rest-redistribution thallium-201 imaging in detecting residual myocardial viability after myocardial infarction. BACKGROUND: The early detection of myocardial viability after myocardial infarction would have clinical relevance. METHODS: Thirty-one patients with acute myocardial infarction had early (mean [+/- SD] 2 +/- 1 day) rest-redistribution thallium-201 imaging followed by radionuclide and coronary angiography. Late studies included stress-redistribution-reinjection thallium-201 imaging or radionuclide angiography, or both. Viability was defined by the rest thallium-201 scan as an initial mild rest defect or any defect that demonstrated redistribution. RESULTS: Group 1 (n = 15) was predicted to have viable and Group 2 (n = 16) nonviable myocardium in the infarct zone. Group 1 patients were more likely to have a patent infarct-related artery (15 of 15 vs. 10 of 16, p < 0.03), higher initial ejection fraction (61 +/- 12% vs. 53 +/- 9%, p < 0.05), higher infarct wall motion score (p < 0.0001) and fewer abnormal thallium-201 segments (p < 0.0001). On follow-up studies, ejection fraction improved in Group 1 (from 57 +/- 13% to 66 +/- 10%, p < 0.05, n = 9) and deteriorated in Group 2 (from 53 +/- 10% to 46 +/- 8%, p < 0.05, n = 13). On late stress testing with thallium-201 reinjection, Group 1 patients had fewer abnormal segments (p < 0.03) and higher infarct zone counts during exercise (p < 0.05) and after reinjection (p < 0.05) than Group 2 patients. CONCLUSIONS: If confirmed by larger studies, early rest-redistribution thallium-201 imaging may be a useful technique for identifying residual viability after myocardial infarction.

Aged↗
PubMed1995

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. The International Arbutamine Study Group.

OBJECTIVES: 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. BACKGROUND: Arbutamine is a potent beta-agonist developed specifically for pharmacologic stress testing. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Adult↗
PubMed1996

The importance of work-up (verification) bias correction in assessing the accuracy of SPECT thallium-201 testing for the diagnosis of coronary artery disease.

Noninvasive testing is often evaluated by the sensitivity and specificity in comparison with a more invasive, but more definitive "gold" standard. However, work-up or verification bias, which occurs when the results of a noninvasive test impact the decision to perform the gold standard invasive test, increases the "observed" sensitivity and decreases the "observed" specificity of the noninvasive test. Most large clinical studies utilizing a noninvasive technique to diagnose coronary artery disease have biases, particularly work-up bias. To obtain more accurate measurements of sensitivity and specificity, we determined the observed sensitivity and specificity of stress (exercise and dipyridamole) single photon emission computed tomographic (SPECT) thallium testing for the detection of coronary artery disease by angiography, and then applied previously published equations to correct for work-up bias. From a computerized data base, reports of 4354 stress SPECT thallium studies from January 1, 1986 through December 31, 1992 were reviewed. All patients with a known history of myocardial infarction or prior coronary angiography were excluded, leaving 2688 patients. From this total, 471 patients underwent coronary angiography within 90 days following stress SPECT thallium testing. Coronary artery disease was defined as a visually assessed stenosis of a coronary artery or a major branch > 50%. Of the 2688 stress SPECT thallium studies, 1265 were normal and 1423 were abnormal. For the 471 patients who underwent catheterization within 90 days following stress SPECT thallium testing. the "observed" sensitivity and specificity were 98 and 14%, respectively. After correction for work-up bias, the corrected sensitivity and specificity were 82 +/- 6% and 59 +/- 2%, respectively. Most studies utilizing noninvasive technologies for the detection of coronary artery disease include patients with known coronary artery disease and have work-up bias as well. By knowing the thallium results of patients with and without catheterization, we were able to correct for work-up bias. These data provide better estimate of the sensitivity and specificity of stress SPECT thallium testing.

Bias↗
PubMed1993

Thallium-201 for oncological imaging in children.

Many pediatric centers are beginning to accumulate a large experience in the use of thallium-201 (201Tl) imaging with 201Tl requires a state-of-the-art high-resolution gamma camera computer system with single photon emission computed tomography (SPECT) capability and a physician-directed tailored examination. Tumor imaging with 201Tl, with its multifactorial localization mechanisms that are different from those for gallium-67, offers a distinct advantage over gallium tumor imaging with a short total imaging time. Tumors are variable in avidity and intensity of thallium uptake. Primary and metastatic disease can be detected with 201Tl scintigraphy. Baseline pretreatment determination of thallium avidity is crucial to its efficacy in therapeutic response assessment. Adjunctive SPECT imaging provides greater sensitivity for lesion detection and direct comparison of physiology (thallium uptake) with anatomy (computed tomography and magnetic resonance imaging). The sensitivity and specificity for detection of pediatric brain tumors has been reported as 77% and 93%, respectively. Thallium-201 brain SPECT also provides a less expensive and more readily available alternative to positron emission tomography for assessing the functional state of pediatric brain tumors. Extremity osteogenic sarcoma and Ewing's sarcoma have 100% sensitivity for 201Tl uptake pretreatment. Early results confirm an association between 201Tl uptake and histological tumor response. The determination of residual/recurrent disease versus thymic rebound and other nonneoplastic change in thallium-avid lymphoma, rhabdomyosarcoma, and germ cell tumors that involve the thorax can be confirmed with a 201Tl SPECT examination. Soft-tissue tumors elsewhere in the body may be detected with 201Tl scintigraphy. Thallium-201 does not exhibit 100% specificity for tumors. False-positive 201Tl uptake has been seen in histiocytosis X, benign bone tumors, stress fractures, and inflammation.

Bone Neoplasms↗
PubMed1983

Effects of reduced coronary flow on thallium-201 accumulation and release in an in vitro rat heart preparation.

To study the relation between myocardial thallium-201 (TI-201) uptake, TI-201 release, and reduced coronary flow, isolated Langendorff rat hearts (n = 8) were perfused for 3 hours at constant flows ranging from physiologic (12 ml/min) to severely ischemic (1.5 ml/min); thallium activity was monitored with a scintillation probe. Each heart was perfused for 1 hour with thallium buffer, followed by 2 hours with thallium-free buffer at the same flow rate. Accumulation curves for all 4 flows were monoexponential. However, release curves during the 2 hours of washout with thallium-free buffer demonstrated a biexponential configuration. The early fast release component decreased with reductions in coronary flow, and the later slow release component did not vary significantly with flow. These data show that thallium clearance has at least 2 components: a rapid (possibly extracellular) component related to coronary flow and a slow (possibly intracellular) component independent of coronary flow. These findings should be useful in providing a better understanding of thallium redistribution observed clinically.

Animals↗
PubMed1996

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 with 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 short-axis 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 that exercise Tc-99m tetrofosmin SPECT defect size determined either by visual analysis or by quantitative analysis may be smaller than on exercise thallium-201 SPECT.

Aged↗
PubMed1998

Thallium scintigraphy compared with 18F-fluorodeoxyglucose positron emission tomography for assessing myocardial viability in patients with moderate versus severe left ventricular dysfunction.

Thallium-201 reinjection imaging and positron emission tomography provide concordant information regarding myocardial viability in many patients with coronary artery disease and left ventricular (LV) dysfunction. It is unclear whether this concordance applies to patients with severe, as well as those with moderate, LV dysfunction. We studied 44 patients with chronic coronary artery disease and LV dysfunction, subgrouped on the basis of severity of dysfunction: 23 patients had moderate and 21 had severe dysfunction (ejection fractions 34 +/- 6% and 19 +/- 6%). Patients underwent exercise thallium single-photon emission computed tomography (SPECT) with 3- to 4-hour redistribution and reinjection imaging, as well as positron emission tomography (PET) imaging with 18fluorodeoxyglucose and 15O-water. Data were analyzed quantitatively in aligned transaxial PET and SPECT tomograms. A myocardial region was considered nonviable by PET if 18fluorodeoxyglucose activity was <50% of that in a normal region, associated with proportional reduction in blood flow. Similarly, regions were considered nonviable by thallium if activity was <50% of activity in normal regions on redistribution and reinjection studies. Thallium SPECT and PET data were concordant regarding viability in 98% and 93% of myocardial regions, respectively, in patients with moderate and with severe LV dysfunction. Lower concordance was observed only when regions with severe irreversible thallium perfusion defects on redistribution images were considered in both groups: 86% and 78%, respectively (p <0.01). Thus, thallium SPECT with reinjection yields information regarding regional myocardial viability that is similar to that provided by PET in patients with severe as well as moderate LV dysfunction. However, there is discordance in >20% of regions manifesting severe irreversible thallium defects in patients with severely reduced LV function.

Aged↗
PubMed1999

Long-term prognostic value of preoperative dipyridamole thallium imaging and clinical indexes in patients with diabetes mellitus undergoing peripheral vascular surgery.

The objective of this study is to assess the prognostic impact of preoperative dipyridamole thallium imaging and clinical variables on the long-term outcome of diabetic patients undergoing peripheral vascular surgery. Complete follow-up was obtained in 101 consecutive patients with diabetes mellitus undergoing routine dipyridamole thallium scintigraphy before vascular surgery (mean 4.2 +/- 3.2 years, range 1 month to 11 years). Low risk was defined by diabetes alone with a normal resting electrocardiogram. High risk was defined as a history of angina, myocardial infarction, congestive heart failure, or resting electrocardiogram abnormalities. There were 71 deaths in 98 patients discharged alive from the hospital (median survival 4.4 years). Age, the presence of resting electrocardiogram abnormalities, and an abnormal thallium scan were independent predictors of late death. After adjusting for age >70 years and thallium abnormalities, high-risk patients had a death rate 4.8 times (95% confidence interval 1.7 to 13.4, p <0.002) greater than low-risk patients. The presence of >2 reversible thallium defects was useful in further risk stratification of both low- and high-risk patients. Low-risk patients with >2 reversible defects had a median survival of 4.0 years compared with 9.4 years in those with < or =2 reversible defects (p <0.001). Similarly, high-risk patients with < or =2 reversible defects had an intermediate median survival rate of 4.7 years compared with 1.8 years in the group with >2 reversible defects (p <0.001). Therefore, advanced age and the presence of resting electrocardiographic or thallium abnormalities identifies a subset of diabetic patients with a poor long-term outcome after vascular surgery. Combined clinical and thallium variables may identify a population in whom intensive medical or surgical interventions may be warranted to reduce both perioperative and late cardiac events.

Aged↗
PubMed1991

Comparison of technetium-99m teboroxime tomography with automated quantitative coronary arteriography and thallium-201 tomographic imaging.

Technetium-99m (Tc-99m) teboroxime is a new perfusion tracer that is highly extracted and rapidly cleared by the myocardium. To determine the feasibility of Tc-99m teboroxime imaging in the diagnosis of patients with suspected coronary artery disease, 30 patients underwent single photon emission computed tomography imaging with Tc-99m teboroxime (25.2 +/- 1 mCi) at peak exercise and again 60 min later at rest. All patients underwent either a thallium stress test (n = 26) or automated quantitative coronary arteriography (n = 25), or both, without intervening revascularization or infarction. Images were reviewed by two investigators who had no knowledge of clinical data. Coronary lesions with greater than or equal to 50% diameter narrowing by quantitative coronary arteriography were considered significant. Both thallium and Tc-99m teboroxime detected disease in all patients with two or three vessel disease. One vessel disease was detected with Tc-99m teboroxime in 9 of 10 patients and with thallium in 8 of 10 (p = NS). In patients without angiographically significant disease. Tc-99m teboroxime demonstrated normal perfusion in six of eight patients and thallium in three of five (p = NS). Overall, when presence or absence of disease detected by Tc-99m teboroxime or thallium was compared with quantitative coronary arteriography, there was no difference between Tc-99m teboroxime and thallium. These results suggest that Tc-99m teboroxime is comparable to thallium as an imaging agent. The rapid biologic half-life, 5.3 min, allows studies to be completed in 60 to 90 min.

Angiography↗
PubMed1984

Effect of decreased blood flow and ischemia on myocardial thallium clearance.

To determine the effect of reduced coronary blood flow on myocardial thallium-201 clearance over a range of flows, miniature radiation detectors were inserted into the left ventricular apex and positioned against the anterior and posterior endocardial walls in 21 dogs. Thallium was administered intravenously and myocardial tracer activity was monitored continuously for 1 hour in both walls. A balloon occluder was then partially inflated around the left anterior descending coronary artery in 19 dogs, producing a range of anterior wall blood flow reductions as assessed by the microsphere technique. Thallium activity was monitored continuously for 3 hours in both walls. Two dogs served as control animals and had no coronary artery occlusion at 1 hour. At the end of the 4 hour experiment, the dogs were sacrificed and the hearts counted in a well counter. The 19 dogs with coronary artery stenosis were divided into three groups (mild, moderate and severe flow reduction groups) on the basis of their poststenosis anterior/posterior wall regional myocardial blood flow ratios. The two control dogs had similar thallium clearances in the anterior and posterior left ventricular walls during the 3 hour period, as assessed by the radiation detectors, and by a final anterior/posterior wall thallium ratio near unity. All three groups of dogs with coronary stenosis had comparable fractional thallium clearances from the anterior and posterior walls before and after the balloon occluder inflation. The final anterior/posterior left ventricular wall thallium ratios were not significantly different than unity for all three groups of dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Quantitation of myocardial infarct size from thallium-201 images: validation of a new approach in an experimental model.

A new computer-based method has been developed to quantitate myocardial infarct size from the size of the regional thallium-201 deficit. The operator outlines the left ventricular myocardial activity with an ellipse. The program then plots the background-corrected activities of the highest mean value in a 3 pixel myocardial band perpendicular to and within the ellipse. The approach uses a new interpolative background correction. To determine the accuracy of this approach in assessing regional thallium deficit size, acute myocardial infarction was produced in six dogs by 24 hour occlusion of the proximal left anterior descending coronary artery. Infarct size was assessed from planar thallium images of the dog heart in three views, each with the chest opened and closed and with the heart excised and placed in a cradle. Before removal of the heart, triphenyltetrazolium chloride was infused to delineate normal from infarct tissue. Transverse slices of left ventricle were made and thallium images of the slices acquired. Infarct size delineated by triphenyltetrazolium chloride staining was expressed as a percent of the total left ventricular slice surface area (planimetric infarct size). Infarct size from whole heart and left ventricular slice thallium images was expressed as a percent of the total length of the left ventricular perimeter (perimetric infarct size). This was determined from points below a certain percent of normalized peak thallium activity in the computer-generated thallium activity curve.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Assessment of single vessel coronary artery disease: results of exercise electrocardiography, thallium-201 myocardial perfusion imaging and radionuclide angiography.

The sensitivity of the commonly used stress tests for the diagnosis of coronary artery disease was analyzed in 46 patients with significant occlusion (greater than or equal to 70% luminal diameter obstruction) of only one major coronary artery and no prior myocardial infarction. In all patients, thallium-201 perfusion imaging (both planar and seven-pinhole tomographic) and 12 lead electrocardiography were performed during the same graded treadmill exercise test and radionuclide angiography was performed during upright bicycle exercise. Exercise rate-pressure (double) product was 22,307 +/- 6,750 on the treadmill compared with 22,995 +/- 5,622 on the bicycle (p = NS). Exercise electrocardiograms were unequivocally abnormal in 24 patients (52%). Qualitative planar thallium images were abnormal in 42 patients (91%). Quantitative analysis of the tomographic thallium images were abnormal in 41 patients (89%). An exercise ejection fraction of less than 0.56 or a new wall motion abnormality was seen in 30 patients (65%). Results were similar for the right (n = 11) and left anterior descending (n = 28) coronary arteries while all tests but the planar thallium imaging showed a lower sensitivity for isolated circumflex artery disease (n = 7). The specificity of the tests was 72, 83, 89 and 72% for electrocardiography, planar thallium imaging, tomographic thallium imaging and radionuclide angiography, respectively. The results suggest that exercise thallium-201 perfusion imaging is the most sensitive noninvasive stress test for the diagnosis of single vessel coronary artery disease.

Adult↗
PubMed1986

Abnormal thallium kinetics in postoperative coarctation of the aorta: evidence for diffuse hypertension-induced vascular pathology.

After operative correction of congenital coarctation of the aorta, patients continue to have excess cardiovascular mortality, including manifestations of ischemic heart disease. Previous morphologic studies support the concept of direct hypertensive vascular injury in these patients. To determine whether abnormalities of myocardial perfusion were present in an asymptomatic group of patients with coarctation repair, 18 men and 9 women with a mean age of 26 years (range 19 to 41) were studied between 2 and 25 years after operative correction. Stress electrocardiography and quantitative thallium imaging by a circumferential profile technique were used. These patients were compared with a normal group, statistically defined as having a less than 1% prevalence of significant obstructive coronary artery disease. The postoperative coarctation group demonstrated a reduction in global thallium redistribution in each view analyzed. As compared with findings in the control subjects, thallium washout in the anterior view (41.9 versus 48.6%, p = 0.02) and left anterior oblique projection (40.5 versus 48.2%, p = 0.007) was significantly diminished. Although the postoperative coarctation group had a lower thallium redistribution rate in the lateral view (41.4 versus 46.3%, p = 0.09) this difference did not reach statistical significance because of the intrinsic variability of this projection. Plots of the median percent thallium washout revealed independence from circumferential profile angle, indicating global abnormalities in perfusion. No correlation between clinical variables and thallium kinetics could be established, suggesting marked individual variability in the development of this vascular lesion. The observation of abnormal thallium kinetics in patients with coarctation repair may have consequences for long-term follow-up and therapy.

Adult↗
PubMed1987

Myocardial thallium-201 kinetics and regional flow alterations with 3 hours of coronary occlusion and either rapid reperfusion through a totally patent vessel or slow reperfusion through a critical stenosis.

Myocardial thallium-201 kinetics and regional blood flow alterations were examined in a canine model using 3 hours of coronary occlusion and different methods of reperfusion. Group I comprised 10 dogs undergoing a 3 hour left anterior descending artery occlusion and no reperfusion. Group II comprised seven dogs undergoing 3 hours of left anterior descending artery occlusion and rapid reperfusion through a totally patent vessel. Group III comprised 10 dogs undergoing 3 hours of left anterior descending artery occlusion and slow reperfusion through a residual stenosis. All dogs received 1.5 mCi of thallium-201 after 40 minutes of coronary occlusion. During occlusion and 2 hours of reperfusion, serial hemodynamic, blood flow and myocardial thallium-201 activity measurements were made. The relative thallium-201 gradient (normal zone minus ischemic zone activity when initial normal activity is expressed as 100%) during left anterior descending coronary occlusion was similar in all groups. Group I, 87 +/- 3%; Group II, 78 +/- 6%; Group III, 83 +/- 6% (p = NS). After 2 hours of either method of reperfusion, the final relative gradient had decreased to a similar level (Group II, 51 +/- 9%; Group III, 42 +/- 6%). These values were not significantly different from the final relative thallium-201 gradient seen in dogs undergoing a sustained 3 hour occlusion (Group I, 55 +/- 5%). After 2 hours of reperfusion, both methods of reflow were associated with similar degrees of "no reflow." Transmural flows in the central ischemic zone were 89 +/- 10% of normal in Group II and 71 +/- 6% of normal in Group III after reperfusion, with both flows substantially higher than the relative thallium-201 activities in these dogs. Infarct size (percent of left ventricle) determined with triphenyltetrazolium chloride was similar in all groups (Group I, 24 +/- 4%; Group II, 29 +/- 4%; Group III, 25 +/- 4%). Thus, in this experimental canine model, 3 hours of coronary occlusion followed by either rapid reperfusion through a totally patent vessel or slow reperfusion through a critical stenosis resulted in little delayed thallium-201 redistribution or myocardial salvage as assessed histologically, despite significant recovery of regional flow.

Animals↗
PubMed1987

Relative prognostic value of rest thallium-201 imaging, radionuclide ventriculography and 24 hour ambulatory electrocardiographic monitoring after acute myocardial infarction.

Rest thallium-201 scintigraphy, radionuclide ventriculography and 24 hour Holter monitoring are acceptable methods to assess myocardial necrosis, performance and electrical instability. This study examined the relative value of the three tests, when obtained a mean of 7 days after acute myocardial infarction, in predicting 1 year mortality in 93 patients. Planar thallium-201 images were obtained in three projections and were scored on a scale of 0 to 4 in 15 segments (normal score = 60). Patients were classified as having high risk test results as follows: thallium score less than or equal to 45 (33 patients), left ventricular ejection fraction less than or equal to 40% (51 patients) and complex ventricular arrhythmias on Holter monitoring (36 patients). During the follow-up of 6.4 +/- 3.4 months (mean +/- SD), 15 patients died of cardiac causes. All three tests were important predictors of survival by univariate Cox survival analysis; the thallium score, however, was the only important predictor by multivariate analysis. The predictive power of the thallium score was comparable with that of combined ejection fraction and Holter monitoring (chi-square = 21 versus chi-square = 22). Thus, rest thallium-201 imaging performed before hospital discharge provides important prognostic information in survivors of acute myocardial infarction which is comparable with that provided by left ventricular ejection fraction and Holter monitoring. Patients with a lower thallium score (large perfusion defects) are at high risk of cardiac death during the first year after infarction.

Adult↗