Intravenous dipyridamole thallium-201 SPECT imaging in patients with left bundle branch block

Tl-201 exercise imaging in patients with left bundle branch block (LBBB) has proven to be indeterminate for significant left anterior descending (LAD) coronary artery stenosis because of the presence of immediate septal perfusion defects with redistribution on delayed images in almost all cases. Tl-201 redistribution occurs regardless of the presence or absence of LAD stenosis. Nineteen patients having LBBB were evaluated with dipyridamole Tl-201 SPECT. Fourteen of these subjects had normal dipyridamole Tl-201 SPECT imaging. Three patients had normal coronary angiograms. None of the remaining 11 patients with normal dipyridamole Tl-201 SPECT images was found to have clinical coronary artery disease in a 5-11 month follow-up period. Five patients had abnormal septal perfusion. Four underwent coronary angiography. One had a significant LAD stenosis. The single patient with septal redistribution who refused to undergo coronary angiography died shortly thereafter of clinical coronary artery disease. This preliminary work suggests that dipyridamole Tl-201 SPECT may be more useful for excluding LAD stenosis in patients with LBBB than Tl-201 exercise imaging.     

Prognosis in patients with left bundle branch block and normal dipyridamole thallium-201 scintigraphy

Background  The presence of complete left bundle branch block (LBBB) is commonly associated with a poorer prognosis, especially in patients with coronary artery disease (CAD). In the general population with suspected CAD and normal intraventricular conduction, a normal dipyridamole-thallium scintigraphy is a strong marker of a favorable outcome. Objective  Our objective was to assess the prognosis in patients with LBBB and a normal dipyridamole thallium-201 scintigram. Population and methods  Patients with complete LBBB and normal myocardial perfusion on dipyridamole SPECT thallium-201 scintigraphy performed in our center for suspected CAD between 1988 and 1995 were monitored for clinical events. Results  Sixty-nine patients (36 women and 33 men) with a mean age of 59 years (range 56 to 61) were monitored for a mean period of 33 months (range 25 to 35). During this period, 4 patients had unstable angina, 2 of whom underwent myocardial revascularization. There were no deaths or myocardial infarction. All events occurred at least 2 years after the thallium-201 scintigraphy. Conclusion  The presence of a normal myocardial perfusion with dipyridamole thallium-201 scintigraphy in this group of patients with suspected CAD and LBBB was associated with a very good prognosis, a low rate of clinical events occurring only 2 years after the myocardial scintigraphy, and no hard events.     

Worsening of left ventricular ejection fraction induced by dipyridamole on Tl-201 gated myocardial perfusion imaging predicts significant coronary artery disease

BACKGROUND: Vasodilator stress on myocardial perfusion imaging has been found to induce ischemic stunning, which may present as transient worsening of left ventricular ejection fraction (LVEF) or regional wall motion abnormality. This study aimed to evaluate the significance of stress-induced worsening of LVEF in the diagnosis of coronary artery disease (CAD) on dipyridamole thallium 201 gated single photon emission computed tomography (SPECT). METHODS AND RESULTS: The study included 126 patients who underwent dipyridamole Tl-201 gated SPECT and coronary angiography within 3 months. Poststress and 4-hour rest images were obtained, and LVEF was calculated by use of automated software (QGS 3.0). A decrease in LVEF of 6% or greater from rest to poststress was considered significant, and this threshold was determined by the serial reproducibility assessment of Tl-201 gated SPECT. If worsening of LVEF was used as the criterion for detecting significant CAD (> or = 70% coronary stenoses in > or = 1 vessel), the sensitivity, specificity, positive predictive value, and negative predictive value were 35%, 93%, 90%, and 44%, respectively. CONCLUSION: Dipyridamole-induced worsening of LVEF, as shown by Tl-201 gated SPECT, is a valuable nonperfusion marker of significant CAD. Although the sensitivity of LVEF worsening in detecting significant CAD is only 35%, the specificity is as high as 93%.     

Noninvasive stress testing of myocardial perfusion defects: head-to-head comparison of thallium-201 SPECT to MRI perfusion

Background  To evaluate the diagnostic value of magnetic resonance imaging (MRI) of myocardial perfusion in the assessment of flow-limiting epicardial stenosis in a head-to-head comparison with abnormal thallium-201 (²⁰¹TI) single photon emission tomography (SPECT) studies in patients with predominantly known coronary artery disease (CAD). Methods and Results  Twenty-one patients (mean age 65 ± 10 years) with reversible myocardial perfusion defects on ²⁰¹TI-SPECT images during dipyridamole-stimulated hyperemia were recruited for study purpose. Within 5 days of the ²⁰¹TI-SPECT study, myocardial perfusion was studied again with MRI during dipyridamole stimulation and at rest. Overall, ²⁰¹TI-SPECT identified 30 reversible regional perfusion defects. The sensitivity to detect hypoperfused segments was 70% (21/30) with the GRE-MRI perfusion analysis with ²⁰¹TI-SPECT as reference. When patients were subgrouped according to the extent of regional reversible perfusion defects on ²⁰¹TI-SPECT, mild- (SDS: 2-4), moderate- (SDS: 5-8), and severe- (SDS > 8) perfusion defects were also identified by GRE-MRI perfusion analysis in 75% (6/8), in 56% (9/16) and 100% (6/6), respectively. Conclusions  GRE-MRI first-pass stress perfusion imaging may not identify up to 30% of mild-to-moderate perfusion defects in a group of preselected patients with predominantly known CAD and abnormal ²⁰¹TI-SPECT studies.     

An attempt of thallium-201 myocardial perfusion imaging during transient coronary arterial occlusion by PTCA

To evaluate the myocardial perfusion during transient coronary occlusion, we attempted to obtain the myocardial scintigraphy during percutaneous transluminal coronary angioplasty (PTCA). Tl-201 was injected at the last inflation of angioplastic balloon and occlusion was kept on for 60 sec. Planar images or SPECT were obtained immediately after PTCA. With this protocol, myocardial perfusion defects were observed during PTCA and fully redistributed 3 hours after Tl injection. Extent of ischemic lesions were almost same as that observed during exercise in two cases without collateral vessels. In a case with well visualized collateral vessels, perfusion defect was smaller in PTCA images than that in exercise stressed images. We conclude that intravenous injection of Tl-201 during PTCA is useful to assess the alteration of myocardial perfusion due to transient coronary occlusion without increasing the risk of angioplastic procedure.     

Identification of extensive coronary artery disease: Incremental value of exercise Tl-201 SPECT to clinical and stress test variables

BACKGROUND: The ability of the size of a total myocardial perfusion defect (MPD) to detect extensive coronary artery disease (CAD) is currently suboptimal with exercise thallium 201 single photon emission computed tomography (SPECT). To improve its performance, exercise electrocardiography and indirect scintigraphic markers of extensive CAD were proposed (increased right ventricular Tl-201 uptake, lung-to-heart [L/H] ratio, and left ventricular transient ischemic dilation ratio). We aimed to determine the additive value of these criteria for the detection of extensive CAD. METHODS AND RESULTS: The population included 338 patients who underwent exercise Tl-201 SPECT and coronary angiography. Patients were classified as having extensive CAD (left main, multivessel, or 1-vessel proximal left anterior descending CAD) or limited CAD (1-vessel disease other than proximal left anterior descending CAD or no CAD). First, Tl-201 SPECT provided higher diagnostic value than exercise electrocardiography. Second, age, percent target heart rate achieved, total MPD, and L/H ratio were independent predictors of extensive CAD. Third, visually estimated abnormal right ventricular Tl-201 uptake did not present additional information. Fourth, L/H ratio presented a higher diagnostic accuracy than left ventricular transient ischemic dilation ratio. CONCLUSIONS: With exercise Tl-201 SPECT, age, percent target heart rate achieved, total MPD, and L/H ratio were independent predictors of extensive CAD.     

Transient ischemic dilation: A powerful diagnostic and prognostic finding of stress myocardial perfusion imaging

Summary  TID is an abnormal finding in stress myocardial perfusion imaging that suggests severe and extensive CAD and signifies a worse prognosis. TID has been reported with exercise and pharmacologic stress testing, planar and SPECT imaging, and Tl-201, Tc-99m, and dual-isotope protocols. Underlying mechanisms include a combination of stress-induced subendocardial hypoperfusion, ischemic systolic dysfunction, and less likely physical LV dilation with severe ischemia. TID appears to represent a significant ischemic burden and, compared with increased pulmonary Tl-201 uptake, suggests less permanent LV dysfunction and more myocardium at risk. Stress-to-rest LV volume ratios of 1.12 (epicardial) and 1.22 (endocardial) have been consistently shown to be highly specific for severe and extensive CAD.     

Clinical evaluation of Tl-201 ECG-gated myocardial SPECT--comparison with ECG-gated blood pool SPECT

In order to evaluate the clinical usefulness of the Tl-201 ECG-gated myocardial single photon emission computed tomography (SPECT), we compared the wall motion and the grade of the Tl-201 uptake of the ECG-gated myocardial SPECT with the wall motion of the ECG-gated blood pool SPECT. Materials were 87 patients of 50 old myocardial infarctions (OMIs), 19 hypertrophic cardiomyopathies (HCMs), 2 dilated cardiomyopathies (DCMs) and 16 others. After intravenous injection of 111-185 MBq (3-5 mCi) of Tl-201 at rest, the projection data were acquired using a rotating gamma-camera through 180 degrees, from RAO 45 degrees in 24 directions, each of which consisted of 80-100 beats. For the reconstruction of ED, ES and non-gated images, R-R interval was divided into about 20 (18-22) fractions. In 348 regions of interest (anterior, septal, lateral and inferior wall) in 87 cases, wall motion and the Tl-201 uptake were evaluated to three grades (normal, hypokinesis and akinesis; normal, low and defect, respectively), which were compared with the wall motion of the ECG-gated blood pool SPECT. The wall motion and the grade of the Tl-201 uptake of the ECG-gated myocardial SPECT correlated well with the wall motion of the ECG-gated blood pool SPECT (96.6% and 87.9%, respectively). In conclusion, the ECG-gated myocardial SPECT can provide clear perfusion images and is a very useful diagnostic strategy to evaluate the regional wall motion and perfusion simultaneously.     

Thallium-201 myocardial SPECT in a patient with mirror-image dextrocardia and left bundle branch block

A 53-year-old male patient with a previous diagnosis of situs inversus with mirror-image dextrocardia underwent thallium-201 (Tl-201) stress-redistribution myocardial perfusion single photon emission computed tomography (SPECT). Electrocardiogram (ECG) obtained on right hemithorax revealed constant complete left bundle branch block. Tl-201 stress-redistribution SPECT images revealed abnormal perfusion with reversible ischemia in the anteroseptal, septal and inferoseptal walls. Coronary angiography performed 1 month after SPECT study was normal. This case illustrates that false positive reversible perfusion defects can be seen in patients with mirror-image dextrocardia associated with constant complete left bundle branch block. To our knowledge, this is the first reported case of mirror-image dextrocardia and constant complete left bundle branch block with false positive Tl-201 SPECT findings.     

Quantitation of infarct size in patients with chronic coronary artery disease using rest-redistribution tl-201 myocardial perfusion spect: Correlation with contrast-enhanced cardiac magnetic resonance

Background  Rest and rest-redistribution thallium 201 myocardial perfusion single photon emission computed tomography (SPECT) (MPS) has been incompletely validated in patients for determination of the total amount of scarred myocardium. We sought to determine whether rest or redistribution Tl-201 MPS provides an accurate determination of infarct size as defined by delayed contrast-enhanced cardiac magnetic resonance (CMR). Methods and Results  We studied patients (n ± 44) with chronic coronary artery disease referred for rest-redistribution Tl-201 MPS, who were also studied by contrast-enhanced CMR within 3 ± 4 days. Patients were considered retrospectively based on a series of patients referred for clinically indicated MPS. Defect size, as a percent of left ventricular mass (% LV), was determined by quantitative perfusion SPECT (QPS) and compared with the volume of delayed hyperenhancement on contrast-enhanced CMR, normalized to LV mass. Infarct size varied from 0% to 43% LV. Rest QPS defect size correlated with the amount of nonviable myocardium assessed by contrast-enhanced CMR (r ± 0.76; mean difference, 4.3% ± 8.0% LV). When delayed thallium data were considered, redistribution QPS was superior to rest QPS for determination of infarct size (redistribution r ± 0.90; mean difference, 2.4% ± 5.2% LV; P ± .03 vs rest). Conclusion  Rest-redistribution Tl-201 MPS provides a more accurate measurement of total infarct size than rest-only Tl-201 MPS and correlates with contrast-enhanced CMR.     

A comparison of Tl-201 stress-reinjection-prone SPECT and Tc-99m-sestamibi gated SPECT in the differentiation of inferior wall defects from artifacts

The frequency of false positive results obtained from the inferior myocardial region using single photon emission computed tomography (SPECT) myocardial perfusion scintigraphy is significantly higher than that obtained from other regions. Several methods, such as prone-position imaging, have been proposed to overcome this diagnostic problem. The aim of the present study was to compare the results of Tc-99m-sestamibi gated SPECT and Tl-201 prone SPECT in the differentiation of inferior wall artifacts from true defects. For this purpose, 38 subjects, whose coronary anatomies were documented on angiography, underwent same-day stress-rest Tc-99m-sestamibi gated SPECT and Tl-201 stress-reinjection-prone (whose standard supine images demonstrated fixed defects on the inferior wall) SPECT. Gated SPECT was performed by 8 frames per cycle acquisition over a 180 degree rotation on 30 projections. Four gated SPECT slices were obtained on mid-ventricular vertical long axis, horizontal long axis and apical and basal short axis planes, and displayed in cine-format. Both Tl-201 prone imaging and Tc-99m-sestamibi gated analysis increased the specificity of inferior wall disease detection remarkably from 54% to 85% and 46% to 82%, respectively (P<0.05). The difference between diagnostic accuracies was not significant (80% and 82%, respectively) (P > 0.05). The positive predictive values for true defects were 96% for Tl-201 prone imaging and 94% for Tc-99m-sestamibi gated imaging. Based on segmental analysis, the two modalities showed fair agreement (kappa = 0.44 for standard supine protocols, kappa = 0.46 for Tl-201 prone and Tc-99m-sestamibi gated SPECT). It can be concluded that Tc-99m-sestamibi gated SPECT, requiring only two-step acquisition, may potentially increase the test specificity for coronary artery disease (CAD) of the inferior wall as well as does Tl-201 stress-reinjection-prone SPECT. By giving functional information, it seems the most practical method in daily use for supplying the most extensive information about patients with suspected or known CAD.     

Direct comparison of adenosine and adenosine 5-triphosphate as pharmacologic stress agents in conjunction with Tl-201 SPECT: Hemodynamic response, myocardial tracer uptake, and size of perfusion defects in the same subjects

Background  Adenosine 5-triphosphate (ATP), a potent and inexpensive coronary vasodilator, was introduced as a pharmacologic stress agent for thallium 201 single photon emission computed tomography (SPECT). However, there has been no direct comparison of ATP and adenosine as myocardial stressors in the same subjects. Methods and Results  Thirty-six patients underwent consecutive Tl-201 SPECT imaging with adenosine and ATP in a randomly assigned order. There were no changes in clinical status and no invasive procedures were performed between the two tests. The hemodynamic response and side effects were monitored, and myocardial tracer uptake was assessed by use of a visual grading system and quantitative analysis via a CEqual map. The hemodynamic changes and adverse effects did not differ significantly between the two groups. There were no changes in the detection of any perfusion defect on a per-subject basis, except in one. The exact agreement rate for the visual grading of the myocardial tracer uptake was 84.8%. However, the average extent of the perfusion defect and the severity score were higher with adenosine. Conclusion  The hemodynamic changes and the degree of myocardial uptake were similar between the adenosine and ATP infusion. However, quantitative analysis by use of a CEqual map revealed smaller perfusion defects and lower severity scores in subjects undergoing Tl-201 SPECT with ATP. This work was supported by grants in aid from the Atomic Energy Research Fund of the Korea Institute of Science and Technology Evaluation, Ministry of Science, Seoul, South Korea.     

Diagnostic accuracy of simultaneous acquisition of transmission and emission data with technetium-99m transmission source on thallium-201 myocardial SPECT

PURPOSE: This study evaluates not only the clinical usefulness but also the problems in attenuation correction for thallium-201 (Tl-201) myocardial SPECT by means of simultaneous transmission and emission data acquisition in the detection of coronary artery disease (CAD). METHODS: A three-detector SPECT system equipped with a Tc-99m line source and fan-beam collimators was used for simultaneous transmission and emission data acquisition for Tl-201 myocardial SPECT in 73 patients (18 patients for normal database and 55 patients for the evaluation of diagnostic accuracy). Attenuation-corrected (AC) images and non-attenuation-corrected (NC) images were reconstructed with an iterative maximum-likelihood estimation-corrected (ML-EM) algorithm. Both sets of images were reoriented into the short axis. Normal database polar maps were constructed from the AC and NC images for quantitative analysis. RESULTS: There was a significant difference in specificity between NC and AC images in the RCA territory and those in specificity and accuracy in the LCX territory. There was no significant difference in sensitivity found between NC and AC images in either territory, but sensitivity in both territories tended to decrease with attenuation correction. In the LAD territory, there were various changes in sensitivity and specificity observed with attenuation correction in cases with each quantitative criterion. CONCLUSIONS: Diagnostic performance of significant stenosis in the RCA and LCX territories quantitatively improved with attenuation correction because of an increase in specificity, but no significant improvement in diagnostic performance was obtained in the LAD territory with attenuation correction. We recommend combined interpretation of AC and NC images and careful evaluation of any SPECT image by means of transmission computed tomography.     

Left bundle branch block and coronary artery disease: Accuracy of dipyridamole thallium-201 single-photon emission computed tomography in patients with exercise anteroseptal perfusion defects

Background  Reduced septal or anteroseptal uptake of thallium-201 during exercise is frequently observed in patients with left bundle branch block (LBBB) even in the absence of left anterior descending (LAD) coronary artery disease. The purpose of this study was to evaluate prospectively the accuracy of dipyridamole²⁰¹TI single-photon emission computed tomography (SPECT) in detecting LAD coronary artery disease in patients with LBBB and septal or anteroseptal perfusion defects on exercise²⁰¹TI SPECT. Methods and Results  Twelve consecutive patients (10 men and two women) with complete LBBB and septal or anteroseptal perfusion defects on exercise²⁰¹TI SPECT underwent dipyridamole²⁰¹TI SPECT. The delay between dipyridamole and exercise was 2 to 30 days. Coronary angiography was performed during this period in all patients. Six (50%) of 12 patients with exercise perfusion defects showed normal perfusion after dipyridamole; all had normal coronary angiograms. The remaining six patients also had positive results of dipyridamole studies, two with moderate and four with severe septal or anteroseptal perfusion defects. Coronary angiography showed significant (>50%) LAD coronary artery stenosis in three patients; three patients with severe septal or anteroseptal perfusion defects after dipyridamole had normal coronary angiograms. Neither the evaluation of apical involvement nor the presence of dilated ventricles, decreased left ventricular ejection fraction, or wall motion abnormalities could help to identify (or explain) false-positive results. Conclusion  This study confirms that dipyridamole is more accurate than exercise in excluding LAD coronary artery disease. However, there are still false-positive results and the severity of the septal or anteroseptal perfusion defect does not add additional information to identify LAD coronary artery disease. Coronary angiography is thus necessary for positive dipyridamole study results to identify coronary artery disease as a major prognostic factor in patients with LBBB.     

Etiology and pathophysiology of new-onset heart failure: Evaluation by myocardial perfusion imaging

Objective  The IMAGING in Heart Failure study was a prospective, multi-national trial designed to explore the role of single-photon emission computed tomographic (SPECT) myocardial perfusion imaging (MPI) as an initial investigative strategy in patients hospitalized with new-onset heart failure. Methods  We recruited 201 patients (age 65.3 ± 14.5 years, 43% women) hospitalized with their first episode of heart failure. Rest/stress gated SPECT Tc-99m sestamibi MPI was performed during or within 2 weeks of the index hospitalization, in addition to standard care. Results  SPECT MPI revealed a broad range of ejection fractions with preserved systolic function in 36% of patients. Forty-one percent of patients had normal perfusion. In the remaining patients, perfusion abnormalities were predominantly due to prior myocardial infarction, with extensive ischemia seen only in 6%. Among patients who underwent coronary angiography, SPECT performance characteristics revealed excellent negative predictive value (96%) for extensive coronary artery disease (CAD). In multivariable analyses, the extent of perfusion abnormality and advancing age predicted the presence of extensive CAD. Conclusions  These preliminary data derived from a non-randomized observational cohort suggest potential diagnostic utility of MPI for ischemic LV dysfunction in new-onset HF, and sets the stage for a prospective randomized study to confirm these findings. The results were presented in part at the 2004 Annual Scientific Sessions of the American Society of Nuclear Cardiology, and the American College of Cardiology.     

Exercise-rest Tc-99m tetrofosmin SPECT in patients with chronic ischemic left ventricular dysfunction: Direct comparison with Tl-201 reinjection

BACKGROUND: This study was designed to compare the results of exercise-rest technetium-99m tetrofosmin single photon emission computed tomography (SPECT) with those of thallium-201 reinjection at rest after exercise-redistribution imaging in the same patients with chronic ischemic left ventricular (LV) dysfunction. METHODS: Within 1 week, 33 patients with chronic myocardial infarction and LV dysfunction underwent exercise-rest tetrofosmin SPECT and Tl-201 reinjection at rest after exercise-redistribution imaging. In each patient, regional tetrofosmin and Tl-201 activity was quantitatively measured in 22 myocardial segments. Regional LV function was assessed in corresponding segments by echocardiography. RESULTS: Agreement in the evaluation of regional perfusion status between tetrofosmin and Tl-201 imaging was observed in 78% of the 726 total segments, with a kappa value of 0.61. In segments with normal function at echocardiography (n = 436), no difference between Tl-201 and tetrofosmin uptake was observed. In hypokinetic segments (n = 138), exercise tetrofosmin uptake was lower (P < .01) as compared with exercise Tl-201 activity, whereas no difference was observed between tetrofosmin uptake at rest as compared with Tl-201 activity on redistribution and reinjection images. In segments with severe functional impairment (akinetic or dyskinetic, n = 152), tetrofosmin uptake on exercise images was reduced (P < .01) as compared with exercise Tl-201 activity; furthermore, tetrofosmin uptake at rest was lower (P < .01) as compared with Tl-201 activity on both redistribution and reinjection images. In these segments, concordance in the detection of myocardial viability between tetrofosmin and Tl-201 imaging was observed in 138 (91%) of the 152 segments, with a kappa value of 0.77. CONCLUSIONS: In patients with chronic coronary artery disease and LV dysfunction quantitative exercise-rest tetrofosmin and Tl-201 reinjection SPECT provide similar information in the assessment of perfusion status and in the detection of myocardial viability.     

Characteristics of Tl-201 myocardial SPECT images of patients with coronary artery lesion of diagonal branch

Noninvasive detection of coronary artery lesion of diagonal branch is important. Utility of Tl-201 myocardial SPECT images for this purpose was studied in 9 patients with angina pectoris and 4 patients with myocardial infarction, in whom localized stenosis more than 75% was noted at diagonal branch. Position of basal margin of abnormal region in the coronal images lay between -30 degree and 30 degree and basal abnormal region was very narrow. Width of mid portion of abnormal region lay from 5 degree to 70 degree. Abnormal region due to diagonal branch was not noted in septal region. These results showed the utility of Tl-201 myocardial SPECT images for detecting coronary artery lesion of diagonal branch.     

Comparative performance of gated perfusion SPECT wall thickening, delayed thallium uptake, and F-18 fluorodeoxyglucose SPECT in detecting myocardial viability

To evaluate the comparative abilities of gated single photon emission computed tomography (SPECT) wall thickening, delayed thallium-201 (Tl-201) SPECT, and F-18 fluorodeoxyglucose (FDG) SPECT in detecting myocardial viability, 23 patients with previous myocardial infarction and clinically suspected viability were studied. Each patient had at least 1 extensive fixed perfusion defect on rest/stress technetium-99m sestamibi SPECT. A total of 41 major vascular territories had fixed defects. The mean (+/- 1 SD) left ventricular ejection fraction determined from gated perfusion SPECT was 26% +/- 11%. Wall thickening was assessed in a semiquantitative fashion by the regional increase in myocardial intensity during systole and was considered normal when a > or = 20% increase was observed. Tl-201 SPECT was acquired 4 hours after resting tracer injection was administered. Viability was considered present when regional defect Tl-201 count density, determined by quantitative analysis, was > 20% greater than that on the resting sestamibi scan. FDG SPECT was performed independently with a 10 mCi F-18 FDG dose after oral glucose loading was performed. A camera equipped with ultrahigh energy collimation was used. Quantitative criteria for viability were the same as for Tl-201. In the 23 patients viability within the fixed sestamibi defects was manifest by preserved wall thickening in 8 patients, delayed Tl-201 uptake in 10 patients, and FDG uptake in 18 patients. Nine major vascular territories with fixed defects were judged viable by wall thickening, 11 by Tl-201 SPECT, and 24 by FDG SPECT (P = .0009). We conclude that FDG SPECT demonstrates more evidence of myocardial viability than either gated sestamibi wall thickening or delayed Tl-201 SPECT.     

Preliminary clinical results of photon energy recovery in simultaneous rest Tl-201/stress Tc-99m sestamibi myocardial SPECT

BACKGROUND: The purpose of this study is to report the first clinical results obtained with the spectral deconvolution technique photon energy recovery (PER) for crosstalk correction in simultaneous rest thallium 201/stress technetium 99m sestamibi myocardial perfusion single photon emission computed tomography (SPECT). METHODS AND RESULTS: Thirty-four patients with suspected coronary artery disease received Tl-201 (111-130 MBq) at rest, followed by single SPECT. Tc-99m sestamibi (444-518 MBq) was then injected at stress, followed by dual SPECT. Single SPECT data were processed to obtain the following data sets: single raw (conventional) Tl-201 and single PER (scatter-corrected) Tl-201. Dual SPECT data were processed to obtain the following data sets: dual raw Tl-201, dual PER (scatter- and crosstalk-corrected) Tl-201, dual raw Tc-99m, and dual PER (scatter-corrected) Tc-99m. All data sets were automatically analyzed with Cedars-Sinai Quantitative Perfusion SPECT software to derive the relative segmental uptake, the summed score, and the summed difference score. The relative segmental uptake, the summed score, and the number of patients with significant reversibility (summed difference score >2) were 74.84% +/- 12.79%, 3.44 +/- 3.07, and 13, respectively, for single raw Tl-201; 80.5% +/- 10.18%, 1.97 +/- 2.25, and 20, respectively, for dual raw Tl-201; 69.47% +/- 14.08%, 6.41 +/- 3.68, and 17, respectively, for single PER Tl-201; and 69.99% +/- 13.39%, 6.58 +/- 3.63, and 17, respectively, for dual PER Tl-201. The differences between single and dual raw Tl-201 data sets were highly significant, whereas there was no significant difference between PER-corrected Tl-201 data sets. CONCLUSIONS: PER is quantitatively efficient to correct for crosstalk in patients investigated with simultaneous rest Tl-201/stress Tc-99m sestamibi myocardial SPECT.     

Study of sympathetic nervous function under effort induced ischemia in patients with angina pectoris with I-123 metaiodobenzylguanidine (MIBG) myocardial SPECT images

I-123 metaiodobenzylguanidine (MIBG) is a norepinephrine analog, which can be used to study the sympathetic nervous function of the heart. With MIBG myocardial SPECT images sympathetic nervous function under effort induced ischemia were studied in 18 patients with significant coronary artery lesions. In 5 patients with effort induced ischemic region in stress T1-201 myocardial images rest MIBG images were collected and then exercise stress test was performed. Patients continued exercising for 3 minutes after onset of symptom. Post-stress MIBG images were collected. Definite ischemic region was noted in stress Tl-201 myocardial images, however no differences were noted between rest and post-stress MIBG images. These results suggested that exercise induced ischemia did not enhance release of uptaken MIBG. In 13 patients with significant coronary artery lesions symptom-limited exercise stress test was performed MIBG and Tl-201 were simultaneously injected at onset of symptom and patients continued exercising for an additional one minute. In 6 cases (46%, 6/13) MIBG defects with Tl-201 uptake were noted. These results showed that exercise induced ischemia depressed net MIBG uptake and that sympathetic nervous function (MIBG images) may be more sensitive to ischemic damage than muscle (Tl-201 images). It is suggested that exercise induced ischemia depressed reuptake of norepinephrine at sympathetic nervous endings. MIBG myocardial SPECT images may be useful for evaluating sympathetic nervous function under ischemia.