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PubMed1992

Effect of exercise level on the diagnostic accuracy of thallium-201 SPECT scintigraphy.

The sensitivity of electrocardiographic ST analysis for detecting coronary artery disease is markedly decreased in patients unable to exercise vigorously. To determine the diagnostic accuracy of Thallium-201 SPECT scintigraphy at various exercise levels, we evaluated 179 patients without evidence of prior myocardial infarction or other confounding factors who performed symptom-limited exercise with Thallium-201 SPECT scintigraphy. Sensitivity decreased from 89% in those patients achieving greater than or equal to 85% of maximal heart rate to 63% in those achieving less than 65%. Like ST segment analysis, Thallium 201 SPECT scintigraphy has decreased diagnostic yield at low levels of exertion.

Aged↗
PubMedDate not supplied

[Prognostic significance of thallium-201 scintigraphy in patients with previous myocardial infarct].

With the purpose of ascertaining the predictive value of residual myocardial ischemia, in stable clinical conditions at a distance after myocardial infarction, on the incidence of late cardiac events, we evaluated 55 patients 24.2 +/- 11.4 months after myocardial infarction with thallium-201 stress test imaging. All patients were either asymptomatic or with stable effort angina pectoris, well controlled with medical treatment. In the next follow-up period, whose duration has been 22.4 +/- 14.4 months, the incidence of unfavourable cardiac events, like unstable angina, reinfarction, coronary bypass surgery, sudden cardiac death has been monitored. Thirty-one patients (56.4%) presented a reversible perfusion defect (RPD) in one or more myocardial segments; 17 of these 31 showed cardiac events during follow-up. Only 2 patients of the remaining 24 without RPD had cardiac events, with a significant difference (p less than 0.01). The patients with RPD only in peri-infarct areas had a relatively smaller number of cardiac events, with respect to those patients with RPD also or only in distant areas. Fifteen of 21 patients with RPD in 2 or more segments manifested cardiac events, compared to 2 of 10 patients with RPD in only one segment (p less than 0.01). In 10/55 patients, increased lung uptake of thallium-201 activity was observed; 8 of them presented cardiac events (p less than 0.01). This analysis confirms the high predicting value of thallium-201 RPD imaging on the incidence of cardiac events in patients controlled at a distance after myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Postinfarction segmental asynergy: correction after angioplasty. Predictive value of exercise thallium scintigraphy].

The aim of this study was twofold: to evaluate the frequency of reversibility of segmental post-subendocardial infarction asynergy after coronary angioplasty, and to test the predictive value of the redistribution phenomenon during stress Thallium scintigraphy with respect to the reversibility of segmental asynergy. The inclusion criteria for this study were: previous postsubendocardial myocardial ischaemia with residual resting or effort ischaemia documented with or without the Thallium test, segmented asynergy documented by quantitative analysis of the ventriculography, complete correction of coronary angioplasty of stenotic single or double vessel disease, a balanced coronary distribution or dominant left coronary in cases of lesion of the circumflex artery. Out of 254 consecutive angioplasty procedures 39 patients met these inclusion criteria. The location of the subendocardial infarct (SEI) was anterior in 17 cases and inferior in 22 cases. The study protocol included a Thallium scintigraphy from the 10th day after SEI, ventriculography 24 hours later, angioplasty and control ventriculography 24 hours after angioplasty. Comparison of the two ventriculographies opposed Group A (reversible asynergy) and Group B (irreversible asynergy) according to criteria defined in 15 normal subjects whose average regional ejection fraction (REF) was 0.53 +/- 0.11. This result enables definition of normal segmental motion if the REF greater than 0.30 (mean--2 SD); hypokinetic if the REF greater than 0.30 or akinetic if the REF less than 0.10 (mean--4 SD). An increase of REF of 0.15 (50% of the minimal normal value) allowed definition of reversibility of asynergy. By these criteria, 19 patients (48.7%) had reversible asynergy after PTCA; 20 had definitive asynergy (51.3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Detection of viable myocardium by means of stress test with thallium 201: usefulness of delayed imaging].

Delayed imaging may help detect viable myocardium after stress Thallium scintigraphy. In 22 patients who had sustained myocardial infarction we performed a stress Thallium test followed by imaging after 24 hr. Delayed reperfusion was observed in 57% of segments showing no reperfusion at 4 hr, which is similar to findings reported in the literature. We proposed that delayed imaging should be performed in all patients showing perfusion defects at 4 hr. Even though a better image may be obtained using reinjection of Thallium, delayed imaging may be the technique of choice to reduce the cost of the test.

Aged↗
PubMed1991

Thallium myocardial scintigraphy in congenitally-corrected transposition of the great arteries.

A case of congenitally-corrected transposition of the great arteries is presented with the correlation of thallium scintigraphic results with catheterization data. The essential features of the thallium scintigrams were marked counterclockwise rotation of the heart with perfusion abnormalities of the inferior wall and apex. Since patients with congenitally-corrected transposition of the great arteries may present with the symptom of chest pain, the diagnosis of transposition of the great arteries should be considered in patients with marked counterclockwise rotation of the heart and segmental perfusion abnormalities on thallium scintigraphy.

Adult↗
PubMed1991

[An adult case of the left coronary artery anomalously originating from the pulmonary artery (BWG syndrome), demonstrating remarkable improvement in postoperative thallium-201 myocardial imaging].

Stress thallium-201 myocardial scintigraphy were performed in a 44-year-old female with BWG syndrome before and after aorto-coronary bypass surgery. Preoperative stress thallium-201 studies demonstrated anterior reversible perfusion defect and posterior persistent defect. But postoperative studies demonstrated no defects in both areas. These data suggest that preoperative anterior defect was due to transient myocardial ischemia, but the finding of posterior persistent defect wasn't due to infarction or scarring. Thus, stress thallium-201 myocardial imaging provided useful informations to clarify the myocardial perfusion patterns pre- and postoperatively.

Adult↗
PubMed1991

[Diagnosis of coronary artery disease by thallium 201 myocardial scintigraphy during atrial pacing].

Rapid atrial pacing may reveal myocardial ischemia but the sensitivity for the diagnosis of coronary artery disease is not high enough for routine use. Therefore, the value of atrial pacing coupled with Thallium 201 scintigraphy was evaluated. Sixty-two patients (53 men and 9 women) referred for investigation of angina or chest pain were divided into two groups: a control group of 13 patients (9 men and 4 women, average age: 57.1 years) with insignificant coronary lesions (less than 50%) (N = 5) or normal coronary angiography (N = 8), and a group of 49 patients (44 men and 5 women, average age: 55.5 years) 27 of whom had a history of myocardial infarction (17 posterior, 10 anterior). Coronary angiography showed single vessel disease in 44.9% of cases, double vessel disease in 34.7% and triple vessel disease in 18.4% of cases, and 1 patient with left main stem disease. All 62 patients underwent the same study protocol which comprised: incremental atrial pacing (to the calculated maximal heart rate), Thallium 201 myocardial scintigraphy immediately after pacing and during the redistribution phase, and coronary angiography. The sensitivities of anginal pain (36.7%) and ECG changes during atrial pacing (57.1%) were too low for the diagnosis of myocardial ischemia. On the other hand, Thallium 201 scintigraphy with atrial pacing was more sensitive (87.8%) and specific (84.6%) for coronary artery disease. Stenosis of the left anterior descending artery was diagnosed with a sensitivity of 96.4% and that of the right coronary artery with a sensitivity of 90.9%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Metabolic activity in the areas of new fill-in after thallium-201 reinjection: comparison with positron emission tomography using fluorine-18-deoxyglucose.

Reinjection of thallium-201 after recording the 3-hr delayed scan often demonstrates improvement in areas of persistent abnormalities. To determine the metabolic activity of these areas, the changes seen on stress/redistribution/reinjection thallium SPECT were compared with PET using fluorine-18-fluorodeoxyglucose (FDG) in 18 patients with coronary artery disease. Of 48 segments showing no redistribution on the delayed scan, the reinjection scan identified new fill-in in 20 segments (42%), all of which demonstrated FDG uptake. In contrast, only 7 of the 28 segments (25%) showing no fill-in after reinjection were PET viable (p less than 0.01). Eleven patients had coronary bypass graft surgery after the radionuclide study. The majority of the segments showing redistribution (87%) and new fill-in after reinjection (65%) improved in wall motion, whereas only eight segments (25%) without new fill-in improved after surgery. Of those without new fill-in, two segments showing PET ischemia improved in wall motion, whereas the remaining six segments showing PET scar did not improve after surgery. Thus, the segments showing new fill-in after reinjection are PET viable myocardium. However, reinjection thallium imaging still underestimates the extent of tissue viability compared to PET imaging.

Coronary Circulation↗
PubMed1991

Orbit-related variation in spatial resolution as a source of artifactual defects in thallium-201 SPECT.

The cause of 180-degree diametrical artifactual defects in clinical thallium-201 SPECT imaging was investigated using phantom simulation. This artifact was observed on SPECT images acquired with a "body contour" or "peanut" orbit. It was hypothesized that this artifact was caused by differences in spatial resolution that occur when the heart-to-detector distance changes employing noncircular orbits. To test this hypothesis, a series of planar static images of a normal cylindrical phantom was obtained at varying distances from the camera detector head. From these images, tomographic acquisition files were created that simulated tomographic data acquired with circular orbits and elliptical orbits. The reconstructed phantom short-axis slices showed no artifacts for circular orbits. However, for various elliptical orbits, significant regional nonuniformity, similar to the artifacts noted in patients, was observed. The degree of nonuniformity correlated with the long-short axis ratio of elliptical orbits (r = 0.98). In addition, circular orbits with the phantom in an eccentric position resulted in similar nonuniformities. It is concluded that a noncircular tomographic orbit can create characteristic artifacts on thallium-201 SPECT images. For rotational thallium 201 SPECT, a circular orbit with the heart in the center of rotation should be employed.

Coronary Disease↗
PubMed1990

[Quantification of the extent of myocardial infarction by thallium-201 single photon emission computed tomography: comparisons with post-mortem findings].

A circumferential profile analysis with a two-dimensional polar representation of thallium(Tl)-201 myocardial single photon emission computed tomograms (SPECT) is an objective and quantitative method to evaluate myocardial infarction (MI). However, the diagnostic capability depends on the normal range of thallium distribution. Therefore, the quantitative analysis of Tl-201 myocardial SPECT was correlated with the pathological findings of the heart in 50 autopsy cases (28 with MI; 22 without MI) to determine the lower normal limits at which we can precisely determine the extent of MI on a quantitative basis. For correctly detecting the extent of MI, the lower normal limits were 2.5 standard deviations below the mean values calculated using profiles normalized to the maximum pixel count observed in each profile. Using this lower normal limit, the sensitivity was 63.8%; specificity was 87.4%; and accuracy was 80.7% for determining the extents of ischemic lesions, though these values were lower than those obtained by visual analysis. However, for detecting MI, the sensitivity by quantitative analysis was 97% which was higher than that by visual analysis. A medium sized (2.5 cm) non-transmural infarction, undetectable by visual analysis, was detectable by two-dimensional polar representations. However, the specificity of detecting MI was low (59%), and most of the false positive studies were observed in cases of valvular disease, coronary artery disease or other cardiac complications. The detectability of the extent of MI varied according to the location of the lesion. False negative lesions were most frequently observed in the septal region; false positive lesions were most frequently observed at the posterolateral regions of the dilated hypertrophic hearts. The septal region located at the peripheral portion of the MI and septal hypertrophy in cases of hypertension, were the likely negative cases, thus, these pathological characteristics may explain the high incidence of false negative results in the septal region quantitatively as well as by visual analysis. In cases with dilated hearts, the radioactivity of the thallium at the posterolateral region was more reduced by absorption compared with that in the non-dilated hearts. This reduction in counts was empirically regarded as abnormal lesions by visual analysis, however, the same situation can objectively and automatically be recognized as false positive by quantitative analysis. We concluded that quantitative analysis by Tl-201 myocardial SPECT is useful for evaluating myocardial infarction automatically, but care must be exercised concerning possible false positive diagnosis in cases with dilated hypertrophic hearts.

Aged↗
PubMedDate not supplied

[Thallium poisoning. Experience with 50 patients].

We have studied fifty cases of thallium intoxication during the past nine years. Twenty-eight occurred in women and twenty-two in men. One of the patients was a new born whose mother had this type of intoxication during her third trimester of pregnancy. The ages varied from one day to 84 years and in all cases the source of thallium was ingestion of rat poison, except for the baby who received it across the placenta and an other patient whose source was transdermal. Twenty-three of the cases of intoxication were accidental, twenty-one were suicidal attempts and five were homicidal. One case did not know the source of intoxication. Thallium levels were measured in the urine of all the patients, some were measured in blood, as well as cerebrospinal fluid. The main clinical manifestation was a mixed type of severe peripheral neuropathy, with abdominal pain, nausea, vomiting and alopecia and some cases had psychiatric manifestations. Electrophysiological studies and nerve biopsy examined with electron microscopy in three patients. Magnetic nuclear resonance, computerized axial tomography of the abdomen and cranium were performed in two patients. There was only one death and the rest of the patients recovered almost completely. Pathophysiology and pharmacological management of this type of neurointoxication are revised.

Abnormalities, Multiple↗
PubMed1990

The incidence of serious hemodynamic changes in physically-limited patients following oral dipyridamole challenge before thallium-201 scintigraphy.

Dipyridamole has liberalized referrals for stress TI-201 chloride (thallium) studies at the Iowa City Veterans Administration Medical Center. Seventy-five percent of referrals now receive dipyridamole and, unlike patients who tolerate conventional exercise testing, these patients are often quite debilitated. Therefore, the hemodynamic consequences of dipyridamole were reviewed in 120 consecutive, physically-limited patients referred for thallium scintigraphy following an average oral dose of 5.4 mg/kg. Each patient's blood pressure was measured every 5 minutes for 1 hour after dipyridamole and compared with several clinical factors to determine if blood pressure change was predictable. In all patients, blood pressure changed from 136 +/- 21/83 +/- 15 (mean +/- 1 SD) to 117 +/- 25/72 +/- 15 following dipyridamole administration. One hundred nine of the 120 patients had a blood pressure decline from 137 +/- 21/82 +/- 12 to 113 +/- 21/70 +/- 13. Of the 109, 43% (N = 47) had a systolic blood pressure decline greater than 20 mmHg, 16% (n = 18) greater than 40 mmHg, and 13% (n = 14) greater than 50 mmHg. Thirteen percent (n = 14) required emergent reversal of the dipyridamole with aminophylline. Significant hypotension is relatively common but generally unpredictable after oral dipyridamole. Therefore, patient eligibility criteria should be carefully considered; strict hemodynamic monitoring must be routine in the usual patient undergoing thallium scintigraphy after oral dipyridamole challenge.

Administration, Oral↗
PubMed1990

Superiority of dipyridamole over exercise testing when exercise thallium imaging is limited by angina.

The extent of jeopardized myocardium can be underestimated on stress thallium myocardial perfusion images when exercise tolerance is limited by angina pectoris. A patient's tolerance for pain can influence the degree of myocardial ischemia observed on myocardial perfusion images during effort angina. A case is reported of a patient with angina pectoris showing mild ischemia limited to one myocardial segment on exercise thallium images, but severe and extensive reversible perfusion defects during dipyridamole-thallium imaging, and a 70% stenosis of the left main coronary artery on coronary angiography.

Angina Pectoris↗
PubMed1990

Risk stratification in patients with non Q wave myocardial infarction: a role for thallium exercise testing.

The ability of maximal exercise thallium testing to stratify patients after non Q wave myocardial infarction was prospectively examined in 20 patients. Patients were enrolled in the study if there was no evidence of residual ischemia nor congestive heart failure during initial hospitalization. The thallium exercise test showed four patients to be at high risk, three of whom had successful revascularization. The remaining 16 patients were considered to be at low risk. There were no re-admissions for unstable angina, no myocardial infarctions and no deaths in the follow-up period (average 15 months). Thus patients with no evidence of early ischemia, no signs of left ventricular failure and a negative maximum thallium exercise test are at low risk following non Q wave myocardial infarction.

Adult↗
PubMed1989

[Reverse redistribution in the stress thallium scan--correlation of coronary blood flow and myocardial damage].

In order to make clear 'reverse redistribution (RR)' phenomenon in stress thallium scan we investigated 477 consecutive patients who were consisted of 74 cases with PTCA (PTCA group), 86 cases with coronary artery bypass graft (CABG group) and 317 cases without any revascularization (N group). RR was detected in 12 cases out of PTCA group (16%), in 11 cases out of CABG group (13%) and in 10 cases out of N group (3.2%), and the incidence of RR in PTCA or CABG group was higher than that of N group (p less than 0.01). In 33 patients with RR the cases without significant coronary artery stenosis were more than those with stenosis (p less than 0.01) and the cases with myocardial damage were more than those without damage (p less than 0.01). In quantitative analysis washout rate at the RR areas showed relatively high value, but it was not significant compared with normal value (53 +/- 9.0% vs. 49 +/- 1.9%). In conclusion, RR had a tendency to appear in the condition of normal myocardium mingled with scar and of sufficient coronary blood flow. The mechanism of the phenomenon was thought to be that initial uptake of thallium in the partially scarred area was as high as in the normal myocardium, but washout of thallium from its remaining normal myocardium is normal or faster so that the defect appears at the myocardium mingled with scar. Therefore existence of reverse redistribution suspects the myocardium mingled with scar and sufficient coronary blood flow to the remaining normal myocardium.

Adult↗
PubMed1989

[Thallium-201 myocardial perfusion imaging during transient coronary occlusion at the time of PTCA: comparison with stress imaging].

To evaluate myocardial perfusion during transient coronary arterial occlusion, thallium-201 was administered intravenously during percutaneous transluminal coronary angioplasty (PTCA) in 12 patients with effort angina, and the resulting perfusion images were compared with those of exercise stress obtained before PTCA. Thallium-201 was injected at the last inflation of an angioplastic balloon and occlusion was maintained for 60 to 90 sec. Three projections of planar images were obtained immediately after PTCA, using a portable gamma camera in an angiography room. These perfusion images obtained during PTCA and exercise were visually interpreted and compared. Myocardial perfusion defects due to the responsible vessel occlusion were observed at early imaging after PTCA, and were fully redistributed three hrs post injection. In 10 patients without angiographically imaged collateral vessels, there were no significant differences in perfusion between images during PTCA and during exercise. Two patients whose collaterals were observed during coronary angiography before PTCA had higher perfusion scores during PTCA than during exercise. We concluded that intravenous injection of thallium-201 during PTCA is a useful means for assessing alteration of myocardial perfusion due to transient coronary occlusion without increasing the risk of angioplastic procedures, and that it provides more precise information about the jeopardized myocardium, perfused by antegrade blood flow.

Angioplasty, Balloon↗
PubMedDate not supplied

Effect of antianginal medications on the prognostic value of exercise thallium scintigraphy.

Whether administration of antianginal medications at the time of exercise thallium scintigraphy reduces the prognostic value of this test was retrospectively examined using two year follow-up of 201 patients. Sensitivity, specificity, positive and negative predictive values and accuracy of five test outcomes for prediction of coronary events (unstable angina, myocardial infarction, cardiac death) were compared between groups of patients either taking or not taking antianginal medications. Specificity and negative predictive value of exercise and redistribution thallium scores for prediction of coronary events were greater in patients not taking antianginal medication (P less than 0.05). It was concluded that normal exercise thallium scintigraphy affords greater assurance against future coronary events in patients tested while not taking antianginal medications.

Adrenergic beta-Antagonists↗
PubMed1989

[Radial long-axis tomography: a new reconstructing algorithm for thallium-201 myocardial SPECT].

The long-axis (L-A) tomograms of the heart in thallium-201 SPECT have been conventionally reconstructed as those parallel to the midventricular vertical or horizontal L-A plane. We developed a new algorithm for reconstructing the rotated L-A tomograms around the L-A to longitudinally observe thallium-201 myocardial distribution and to provide an optimal view of the cardiac apex. After determining the orientation of the L-A and reconstructing the short-axis (S-A) tomograms using standard techniques, the coordinates of the S-A planes were transformed to the polar coordinates whose origin is located at the position of the L-A in each plane. Then, "radial L-A tomograms", i.e. midventricular L-A planes oriented at the angle of every 6 degrees to the midventricular horizontal L-A plane, were reconstructed. Also, we developed a new technique for analyzing thallium-201 distribution of the L-A tomograms. For the basal 2/3 regions, two profiles which consist of the pixels with maximum count on the upper and lower myocardial portions of the lines (spaced at 1 pitch) vertically to the L-A were computed. For the remaining apical 1/3 regions, the semi-circumferential maximum-count profile from the values of 30 radii spaced at 6 degrees interval were computed. Based on these profiles, a 2D polar representation was then generated. From the study using a cardiac phantom with an apical small infarction, the usefulness of this new tomographic method for the detection of apical myocardial ischemia was demonstrated. The application to the exercise/redistribution studies in patients with effort angina indicated that radial long-axis tomography provides precise information about the longitudinal extent of perfusion defects, particularly in the apical regions.

Algorithms↗