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At least 811 records · Page 45Linked to original sources
PubMed1987

Dipyridamole-thallium scanning in patients undergoing vascular surgery. Optimizing preoperative evaluation of cardiac risk.

Dipyridamole-thallium imaging has been suggested as a method of preoperatively assessing cardiac risk in patients undergoing major surgery. To define more clearly its proper role in preoperative assessment, we prospectively evaluated 111 patients undergoing vascular surgery. In the first set of 61 patients, our data confirmed the value of preoperative dipyridamole-thallium scanning in identifying the patients who suffered postoperative ischemic events. Events occurred in eight of 18 patients with reversible defects on preoperative imaging, compared with no events in 43 patients with no thallium redistribution (confidence interval for the risk difference: 0.624, 0.256). The results also suggested that clinical factors might allow identification of a low-risk subset of patients. To test the hypothesis that patients with no evidence of congestive heart failure, angina, prior myocardial infarction, or diabetes do not require further preoperative testing, we evaluated an additional 50 patients having vascular procedures. None of the 23 without the clinical markers had untoward outcomes, while ten of 27 patients with one or more of these clinical markers suffered postoperative ischemic events (confidence interval for the risk difference: 0.592, 0.148). In the clinical high-risk subset, further risk stratification is achieved with dipyridamole-thallium scanning.

Aged↗
PubMed1987

Correlates of lung/heart ratio of thallium-201 in coronary artery disease.

We studied 306 patients with chest pain (262 with coronary artery disease and 44 with no coronary artery disease) to determine which of 23 clinical, exercise, thallium, and angiographic variables best discriminate between patients with increased lung/heart ratios of thallium versus those with normal ratios. Normal lung/heart ratio values were defined using an additional 45 subjects with less than 1% probability of coronary artery disease. The number of diseased vessels was the best discriminator between patients with increased ratios versus those with normal ratios. Double product at peak exercise, number of segments with abnormal wall motion, patient gender, and duration of exercise were also significant discriminators. Using discriminant function analysis these variables could correctly identify 81% of cases with increased lung/heart ratios and 72% of cases with normal ratios. These results indicate that an increased lung/heart ratio of thallium reflects exercise-induced left ventricular dysfunction and affords a better understanding of why this thallium parameter is a powerful prognostic indicator in patients with chest pain.

Adult↗
PubMed1986

Effect of exercise position during stress testing on cardiac and pulmonary thallium kinetics and accuracy in evaluating coronary artery disease.

We compared the effects of symptom-limited upright and supine exercise on 201Tl distribution and kinetics in the heart and lungs of 100 consecutive patients. Our analysis was based on data obtained with a digital gamma camera in the 45 degrees left anterior oblique position at 5, 40, 240, and 275 min postadministration of [201Tl]chloride. We found significant differences in the results at the 5- and 40-min intervals; viz, higher cardiac and lower pulmonary thallium activity after upright exercise in 94 subjects at both intervals, and greater variability in total and regional cardiac thallium kinetics after supine exercise. With supine exercise, the relatively low initial cardiac activity, relatively high lung activity, and the greater variability in thallium kinetics combined to make interpretation of quantitative data and cardiac images difficult and less accurate with respect to detection of coronary artery disease. These observations have important implications for the interpreting physician when thallium stress tests are performed in the supine position.

Coronary Disease↗
PubMedDate not supplied

Flavor aversions induced by thallium sulfate: importance of route of administration.

Flavor aversions induced by intraperitoneal (IP) and oral (PO) administration of thallium sulfate were compared in a repeated trial, two-bottle preference test. Male Long-Evans rats (N = 6/group) were given 30-min access to a 0.1% saccharin solution followed 20-min later by either IP or PO thallium sulfate (2.5, 5, 10 or 20 mg/kg), vehicle or nothing. Non-treated and vehicle-treated rats consistently preferred the saccharin solution, with relative saccharin intakes ranging from 0.65 to 0.85 over the three choice trials. On the first choice trial, flavor aversions produced by IP-administered thallium sulfate were marginal and occurred only at the highest dosage. In contrast, on the first choice trial, PO-administered thallium sulfate led to pronounced aversions at all but the lowest dosage. Saccharin preferences on the second and third choice trials resembled those obtained on the first choice trial. These results suggest that failure to obtain toxicant-induced flavor aversions may be due in part to the particular route by which the toxicant is administered.

Administration, Oral↗
PubMed1985

Prognostic implications of normal exercise thallium 201 images.

We studied 455 patients (mean age, 51 years) in whom exercise thallium 201 scintigrams performed for suspected coronary artery disease were normal. Of those, 322 (71%) had typical or atypical angina pectoris and 68% achieved 85% or more maximal predicted heart rate. The exercise ECGs were abnormal in 68 patients (15%), normal in 229 (50%), and inconclusive in 158 (35%). Ventricular arrhythmias occurred during exercise in 194 patients (43%). After a mean follow-up period of 14 months, four patients had had cardiac events, sudden cardiac death in one and nonfatal myocardial infarctions in three. None of the four patients had abnormal exercise ECGs. Two had typical and two had atypical angina pectoris. Normal exercise thallium 201 images identify patients at a low risk for future cardiac events (0.8% per year), patients with abnormal exercise ECGs but normal thallium images have good prognoses, and exercise thallium 201 imaging is a better prognostic predictor than treadmill exercise testing alone, because of the high incidence of inconclusive exercise ECGs and the good prognosis in patients with abnormal exercise ECGs.

Adult↗
PubMed1985

[Assessment of coronary stenosis by myocardial scintigraphy with thallium-201 after dipyridamol infusion].

After a 4 minute i.v. dipyridamole infusion (0.14 mg/Kg/min) serial Thallium-201 scans were obtained in 45 patients, without myocardial necrosis, undergoing coronarography. Twelve patients had effort angina, 6 rest angina, 14 effort associated with rest angina, 13 had atypical chest pain. Thirty-two patients had a 50% or greater stenosis of 1 or more coronary artery (8 had three vessels disease, 7 two vessels, 17 one vessel); 13 patients had no significant coronary stenosis ("control group"). The test induced electrocardiographic signs of ischemia in 18 patients, all with significant coronary stenosis, 15 of them experienced angina too. Sensitivity of Thallium-201 for detecting coronary artery stenosis was 94% (30 of 32) and specificity was 85% (11 of 13). In the group of the 17 patients with one vessel disease we obtained a sensitivity and specificity of 100% (17 of 17). We conclude that Thallium-201 myocardial imaging after pharmacologic vasodilatation with dipyridamole is a highly sensitive and specific test for detecting coronary artery stenoses without necessary overt ischemia. In fact dipyridamole, as consequence of its important coronary vasodilatation, produces differences in myocardial perfusion with relative perfusion defects detectable with Thallium-201 imaging.

Adult↗
PubMed1977

Thallium-201: non-invasive determination of the regional distribution of cardiac output.

Sapirstein (1) employed cationic radiopotassium to determine the fractional distribution of cardiac output to several organs. Thallium-201 can substitute for radiopotassium in myocardial imaging, and was evaluated in the present studies to determine the distribution of cardiac output in the anesthetized dog in comparison with tracer microspheres, both under control circumstances and following the infusion of norepinephrine in a dose sufficient to raise the blood pressure 20 mm Hg above control levels. The concentrations of thallium-201 and microspheres were similar in the heart, kidney, thyroid, and skeletal muscle in both control and norepinephrine-treated animals (r=0.93). Thallium concentration in the liver and lung exceeded that of microspheres, however, and probably is not related solely to the regional distribution of arterial perfusion. These data suggest that in the heart, kidney, thyroid, and skeletal muscle, thallium-201 distribution reflects the fractional distribution of cardiac output.

Animals↗
PubMed1983

[Evaluation of myocardial infarction by thallium emission computed tomography].

Thallium myocardial emission computed tomography (ECT) using a rotating gamma camera was undertaken to assess three-dimensional thallium distribution in the myocardium in cases with myocardial infarction (MI). Ninety-one cases with MI and 29 normal persons were examined by thallium ECT and the conventional planar imaging. Diagnostic performance and quantification of MI, and characterization of non-transmural MI were also investigated. In the detection of a perfusion defect, the ECT imaging showed significantly higher sensitivity (96%) than the planar imaging (77%) (p less than 0.001), especially in those with inferior wall MI (95% vs 73%, p less than 0.02) and nontransmural MI (82% vs 27%) (p less than 0.01). The specificity was the same in both techniques (90%), and therefore, higher overall accuracy was obtained by the ECT imaging (94%) than by the planar imaging (80%) (p less than 0.01). The receiver operating characteristic (ROC) curves were obtained from three independent observers for quantitative evaluation of observer detection performance. The ECT curves in each observer were situated in the upper left corner, indicating excellent diagnostic performance. Infarct size was estimated from the extent of the perfusion defect expressed as a percentage of the planar imaging (% defect) and as a volume of the infarcted myocardium (infarct volume). Those parameters were significantly correlated with peak CPK (r = 0.80 and 0.94, respectively), and inversely correlated with left ventricular ejection fraction (r = -0.78 and -0.85, respectively). Thus, the infarct volume calculated from the ECT is considered to permit estimation of infarct size more accurately than % defect from the planar imaging. To characterize nontransmural MI, 11 cases with nontransmural MI were examined by ECT and the findings were compared with those of transmural MI. A perfusion defect was detected in nine of the 11 patients (82%). As compared to those with transmural MI, infarct volume was smaller and the residual activity in an infarct region was higher in cases with nontransmural MI. Thus, the thallium ECT imaging, providing any-angle multisection of the myocardium, permits qualitative and quantitative evaluation of MI accurately.

Humans↗
PubMed1983

[Myocardial 201-thallium uptake after hydralazine in coronary disease].

UNLABELLED: Following injection of hydralazine, a benign coronary-artery-dilating drug, myocardial blood flow increased by 25%. Myocardial 201-thallium uptake at rest and after intravenous injection of 12 mg hydralazine was quantitatively investigated in 28 patients. In patients with essential hypertension or coronary artery stenoses of up to 90%, myocardial 201-thallium uptake increased by 19%-30% in nonischemic areas. In 9 of 14 patients with regional imaging defects, thallium uptake also increased in these ischemic areas; 4 of these patients had asynergies in the area of imaging defects. In 3 patients with a complete obstruction of a major branch of a coronary artery perfusion defects developed following hydralazine application. CONCLUSION: An increased 201-thallium uptake in an ischemic area indicates reperfusion; this could be helpful for deciding whether coronary surgery should be performed or not.

Coronary Circulation↗
PubMed1984

Thallium scintigraphy in experimental toxic pulmonary edema: relationship to extravascular pulmonary fluid.

Pulmonary fluid volumes (PBV = lung blood volume; EVLW = extravascular lung water) were examined to define the effects of oleic acid injury and then to examine the relationship between edema formation and accumulation of pulmonary thallium. In six dogs, pulmonary fluid compartments were monitored during the induction of pulmonary injury by oleic acid (0.15 cc/kg i.v.). By 30 min after the injection, EVLW had doubled (p less than 0.01); it continued to increase slowly for 180 min, whereas PBV declined. In six anesthetized dogs, we made similar measurements in an identical preparation and compared pulmonary fluid volumes with pulmonary counts derived from sequential thallium (1-1.3 mCi) scintigrams obtained after the injection of oleic acid (0.12-0.15 ml/kg). Measures of EVLW and PBV were obtained sequentially along with thallium scintigrams. There was a linear relationship between EVLW and pulmonary counts alone, or when pulmonary counts were normalized to myocardial activity. We conclude that sequential thallium scintigrams provide useful information about the degree of change of EVLW over time in a model of noncardiogenic pulmonary edema.

Animals↗
PubMed1980

[Comparison of stress testing and thallium 201 testing in the diagnosis of coronary insufficiency according to the functional class of angina. 154 cases with coronary angiography].

154 patients investigated for chest pain underwent 12 lead exercise electrocardiography and also exercise 201-Thallium myocardial scintigraphy performed at coronary angiography. 92 patients had typical angina; in this group the sensitivity and specificity of exercise electrocardiography was good (91% and 86% respectively) and exercise myocardial scintigraphy did not give significantly better results. On the other hand, in cases when exercise electrocardiography was negative (27%) exercise myocardial scintigraphy was positive in 75%. 201-Thallium did not discriminate between ischaemia and necrosis in patients with previous myocardial infarction, ischaemia alone causing hypofixation on basal myocardial scintigraphy. 62 patients had atypical chest pain. The low incidence of coronary artery disease in this group (30%) increases the value of exercise 201-Thallium scintigraphy as it is both more sensitive (59% compared to 21%, p less than 0,05) and more specific than exercise electrocardiography (43% compared to 85%, p less than 0,1). 29% monotruncular lesions had negative exercise electrocardiography and myocardial scintigraphy. However, multivessel and left main coronary disease may be excluded with great probability by a negative exercise 201-Thallium scintigraphy.

Adult↗
PubMed1980

[Myocardial scintigraphy with thallium-201 for evaluation of the patency of aorto-coronary bypasses in multiple vessel disease and multiple bypasses (author's transl)].

The reliability of myocardial scintigraphy with thallium-201 in evaluating the patency of aorto-coronary bypasses was examined. In addition to coronary angiography and ventriculography in 16 patients (42 stenosed vessels, 36 bypasses of which 22 were patent) quantitative myocardial scintigraphy was performed after maximum exercise and at rest, pre- and postoperatively. In general, 12 patients with postoperatively improved angina showed an improvement in their scintigram. The analysis of myocardial areas with a bypass showed a decrease of thallium uptake at rest in 39%, regardless of patency occlusion of the bypass. In 85% of these regions an increased thallium uptake was seen after exercise, again independent of the function of the bypass. The data show that myocardial scintigraphy with thallium-201 cannot be utilized in patients with multiple vessel disease and multiple bypasses to evaluate the patency of a particular bypass, but a general assessment is possible, whether myocardial perfusion has improved.

Adult↗
PubMed1980

Thallium-201 scintigraphy at rest in ischemia and infarction.

Serial imaging of the myocardium in the resting state after intravenous administration of thallium-201 can be employed to differentiate between ischemia or under-perfusion and myocardial infarction or scar. Redistribution of thallium with filling-in of defects on delayed images or rest can be observed in myocardial regions supplied by stenotic coronary arteries (greater than or equal to 70% narrowing). These myocardial segments usually exhibit normal or hypokinetic wall motion. Persistent defects over a two to three hour imaging period at rest correlate highly with Q waves on the electrocardiogram and akinetic or dyskinetic wall motion on ventriculography. Thallium scintigraphy can be successfully utilized for detecting and localizing acutely infarcted myocardium. Sensitivity for infarct detection is higher in the first 24 hours after the onset of chest pain, although with computer-assisted quantitative analysis of images sensitivity for late detection (ten to fourteen days post myocardial infarction) may be improved. Multivessel disease can be predicted in many patients with acute inferior myocardial infarction by demonstrating anteroseptal wall defects with delayed redistribution on rest images prior to hospital discharge. Patients who demonstrate inferior wall persistent defects (infarction) with anterior wall redistribution (hypoperfusion/ischemia) have a worse prognosis characterized by an increased frequency of recurrent angina and infarction compared to the group with only inferior defects. Thallium scintigraphy may also be useful in assessing myocardial infarct size. Patients with large defects during the acute phase of infarction have significantly higher early and late mortality.

Acute Disease↗
PubMed1980

[Investigation of obliterative arterial disease of the lower limbs, by muscular scintigraphy using thallium (author's transl)].

The behaviour of thallium is similar to that of potassium. It participates in transmembrane exchanges and accumulates within the cells, in particular muscle cells. The subjects being at rest or at the maximum phase of an effort test, an injection of 2 mCi of thallium 201 as given. Quantitative scintigraphies were performed during the minutes following injection. Ten control subjects were studied in this way. Uptake of thallium in the muscle masses of the lower limbs was symmetrical and homogeneous and was more marked after effort. Acute ischemia for a few minutes was obtained using a tourniquet in a volunteer. The ischemic area was clearly seen on the early scintigraphy. There was redistribution of thallium in the later scintigraphic studies. Fifteen patients with obliterative arterial disease underwent scintigraphy at rest and after effort. Good agreement was found between arteriography, measurement of pressures, plethysmography and deficiencies demonstrated by scintigraphy. The effort test, by inducing transient ischemia, was useful in detecting moderate circulatory disturbances.

Adult↗
PubMedDate not supplied

Effect of ionic and nonionic contrast media on regional distribution of thallium-201 in rabbits.

Cardiac output is effectively redistributed to each part of the body by regional changes in vascular resistance. Thallium-201 distribution reflects the fractional distribution of cardiac output and parallels regional blood flow. The side effects of iodinated contrast media in different organs have been well documented in animal experiments and clinical studies. However, no simultaneous assessment of regional blood flow change in each part of the body after the administration of contrast media has been reported. Using a double-dose thallium-201 method, we investigated the effect of contrast media on the regional distribution of thallium-201 in each organ as an estimate of regional blood flow change in rabbits. The distribution of 201T1 and 99mTc-MAA was similar in the heart, spleen, kidneys, and leg muscles in the control animals (r = 0.99). The regional distribution of thallium-201 significantly increased in the heart and leg muscle, but decreased in the liver in the nonionic (Iohexol) and ionic (Iothalamate) contrast medium groups as compared with the control group. There were no significant changes in the kidneys or intestine in these three groups in our study. The intravenous infusion of contrast media in rabbits causes uneven redistribution of regional blood flow in the heart, leg muscle and liver. These changes are more prominent in the ionic contrast medium group.

Animals↗
PubMed1995

[Effectiveness and safety of coronary vasodilation with adenosine triphosphate with thallium-201 for the diagnosis of coronary disease].

OBJECTIVE: To evaluate the accuracy and safety of pharmacologic stress testing with adenosine triphosphate (ATP) associated with thallium-201 scintigraphy for detection of coronary artery disease. PATIENTS: We studied 44 patients, 35 male and 9 female with a mean age of 59 + 9 years. Previous myocardial infarction was present in 15 patients. Thirty-two patients underwent coronariography that revealed coronary artery disease in 28 patients. METHODS: ATP (Stryadine) was infused at a rate of 140 micrograms/kg/min for 6 minutes and 2 mCi of thallium-201 was injected at the third minute. Stress and redistribution SPECT acquisitions were performed respectively 5-10 minutes and 4-6 hours after ATP infusion. RESULTS: The incidence of side effects was 77% and chest pain was the most frequent (45%). Dyspnea occurred in 2 patients and only one patient presented transient first degree AV block. No serious or severe side effect occurred. In patients without myocardial infarction 14 of 16 patients with significant coronary artery disease had reversible perfusion defects demonstrated by ATP thallium-201 scintigraphy (sensitivity 88%) and all of 4 patients without significant coronary artery disease had normal myocardial perfusion (specificity 100%). The overall accuracy for detecting the presence of coronary artery disease was 90%. The test demonstrated an overall accuracy of 88% for detecting left anterior descending artery disease, 91% for circumflex artery disease and 80% for right coronary artery disease. CONCLUSIONS: Pharmacologic stress with ATP associated with thallium-201 scintigraphy, is a safe and high accurate alternative to dipyridamole and adenosine for the diagnosis of coronary artery disease.

Adenosine Triphosphate↗
PubMed1995

Variability of normal coronary anatomy: implications for the interpretation of thallium-SPECT myocardial perfusion images in single-vessel disease.

UNLABELLED: Standard criteria for assigning perfusion defects to a specific vascular territory often result in mistaken identification of the affected coronary artery due to the normal variability of coronary anatomy. A retrospective study was performed to determine the frequency of this type of error and to identify the most common perfusion patterns associated with specific coronary lesions. METHODS: Records were reviewed of all patients with single-vessel coronary artery disease (CAD) who had exercise or dipyridamole thallium SPECT myocardial perfusion studies since 1987. Patients with coronary artery bypass grafts and an interval between the two studies greater than 6 wk or interval change in medical status were excluded. Ninety-three studies were available for review. The size, severity and location of all perfusion defects were noted by three observers who had no knowledge of the angiographic data. Significant CAD was defined as luminal diameter stenosis greater than 50%. RESULTS: The diseased vessel was correctly identified in 85% of positive studies. Thallium SPECT, however, mistakenly predicted additional vessel involvement in 29% of those studies. Another 15% correctly predicted single-vessel disease but identified the wrong artery. Using standard criteria, thallium SPECT correctly predicted the arteriogram findings in only 56% of studies. Most of these findings could be correlated with variations in individual coronary anatomy. CONCLUSION: The accurate localization of coronary stenoses by thallium SPECT imaging requires close correlation with arteriography owing to the significant variability in normal coronary anatomy.

Coronary Disease↗
PubMed1994

Safety of pharmacological (intravenous dipyridamole) stress for Thallium-201 perfusion imaging in patients with coronary artery disease unable to exercise.

Exercise Thallium-201 myocardial perfusion imaging is a sensitive technique for detection of CAD. However, in patients unable to perform exercise pharmacological stress with intravenous dipyridamole can be used to dilate coronaries. Out of 125 patients (21 men and 104 women; mean age 52.03 years) evaluated, 110 were considered to be unable to perform adequate stress by their physician while remaining 15 had LBBB. One hundred and seven patients had chest pain with or without a remote MI while 18 individuals were clinically asymptomatic but had ECG abnormalities. Intravenous dipyridamole was administered at a rate of 0.142 mg/kg/min for 4 min. After 3 min an i.v. bolus of T1-201 was given. Diffuse or occipital headache of mild to moderate intensity occurred in 50 (40%) cases; 39 patients experienced chest pain and had either a positive thallium scan (26 cases) suggestive of CAD or a normal thallium study (15 cases). Complete relief from dipyridamole induced symptoms was brought by i.v. aminophylline and sublingual nitrate in 51 of 54 cases (94%) and 11 of 18 (61%) respectively. We, therefore, conclude: 1) i.v. dipyridamole-thallium scintigraphy offers a safe, effective and reliable method for evaluating CAD in those who are unable to perform adequate exercise and 2) parenteral aminophylline is very effective antidote to dipyridamole.

Aminophylline↗