双核素心肌显像检测存活心肌的对比研究

目的 对比多巴酚丁胺负荷201Tl/静息99Tcm-甲氧基异丁基异腈(MIBI)双核素同步心肌断层显像及多巴酚丁胺负荷-再分布/再注射201Tl心肌断层显像法检测存活心肌的作用.方法 对160例临床怀疑有冠心病的患者予静息状态下静脉注射740 MBq99Tcm-MIBI,休息15 min后进行多巴酚丁胺负荷试验,在达到终止指标时静脉注射111 MSq201TICI.注射后观察5-lO min,分别行早期(10 min)、延迟(3 h)99Tcm-MIBI和201Tl双核素同步心肌断层显像.对早期负荷201Tl图像发现放射性缺损,延迟再分布201Tl和静息99Tcm-MIBI图像未见放射性填充的患者再注射37 MBq201TICI,30min后行再注射心肌灌注显像.负荷枷201Tl图像示放射性缺损,静息99Tcm-MIBI、再分布201Tl及再注射201Tl图像中发现任何一种放射性填充者均为存活心肌.断层显像后2周内全部患者进行了冠状动脉造影.采用SAS 6.12软件进行x2检验.结果 (1) 160例患者冠状动脉造影均发现冠状动脉狭窄.其中单支病变76例、双支病变5l例、三支病变33例.(2)152例多巴酚丁胺负荷201Tl图像发现放射性缺损的患者中,63例201Tl再分布和静息99Tcm-MIBI图像均发现放射性填充,5例201Tl再分布发现放射性填充而静息99Tcm-MIBI图像未见放射性填充,9例静息99Tcm-MIBI图像发现放射性填充而2001Tl再分布未见放射性填允,75例201Tl再分布和静息99Tcm-MIBI图像均未发现放射性填充,负荷201Tl-延迟再分布显像(66.0%,68/103)和负荷201Tl/静息99Tcm-MIBI显像(69.9%,72/103)鉴别存活心肌的灵敏度差异无统计学意义(x2=O.36,P>0.05).(3)75例201Tl再分布和静息99Tcm-MIBI图像均未发现放射性填充患者中,再注射201Tl显像后有26例放射性填充,再注射201Tl显像较单纯201Tl再分布或静息99Tcm-MIBI显像多检测出34.7%(26/75)患者有存活心肌.(4)8例多巴酚丁胺负荷201Tl、201Tl再分布图像和静息99Tcm-MIBI图像均未发现放射性稀疏,为假阴性,其中3例为三支冠状动脉病变,1例为双支冠状动脉病变(狭窄分别为90%及60%),3例为单支冠状动脉病变(狭窄<75%2例,85%1例),1例冠状动脉闭塞后有充分的侧枝循环.结论 多巴酚丁胺负荷-再分布/再注射201Tl心肌断层显像鉴别存活心肌优于多巴酚丁胺负荷201Tl/静息99Tcm-MIBI双核素同步心肌断层显像,是一种有效、无创的鉴别存活心肌的方法.     

Nitrate administration to enhance the detection of myocardial viability by technetium-99m tetrofosmin single-photon emission tomography

A comparison was performed between technetium-99m tetrofosmin myocardial perfusion tomography at baseline and after nitrate administration, using a 2-day protocol, and rest-reinjection thallium-201 single-photon emission tomography (SPET) studies in order to assess whether nitrates enhance the detection of viable myocardium with^99mTc-tetrofosmin. Fifteen patients with coronary artery disease, previous myocardial infarction and a left ventricular ejection fraction <40% underwent²⁰¹T1 rest-injection and^99mTc-tetrofosmin. baseline-postnitroglycerin (0.4 mg sublingually) SPET studies, within 48 h. Tomograms based on the three spatial planes were divided into 15 segments and regional tracer uptake was quantitatively analysed. Viability was defined as presence of tracer uptake >50% of peak activity on baseline studies or after reversibility. The percentage of peak activity of^99mTc-tetrofosmin at baseline correlated with that of 201T1 (r=0.82,P <0.001). On baseline^99mTc-tetrofosmin studies, 73 of the 225 segments that were analysed had <50% of peal. activity. Fifteen percent of these segments showed reversibility after nitrate administration, with an increase in^99mTc-tetrofosmin uptake from 40%±9% to 57%±9% of peak activity (P=0.003). All reversible segments after nitrate administration had viability criteria on²⁰¹Tl studies, but 20 segments that were non-viable on^99mTc-tetrofosmin. studies were viable on²⁰¹Tl studies. Using a threshold value of >40% of peak activity, only seven segments remained non-viable on^99mTc-tetrofosmin studies. Overall agreement between^99mTc-tetrofosmin with nitrates and²⁰¹Tl-reinjection regarding the presence of myocardial viability was 90%. Detection of myocardial viability with^99mTc-tetrofosmin. was enhanced after nitrate administration, correlating with viability criteria observed on thallium studies.     

A comparison of rest sestamibi and rest-redistribution thallium single photon emission tomography: Possible implications for myocardial viability detection in infarcted patients

Thirty patients (26 men, 4 women, mean age 61 ± 8 years) who had suffered myocardial infarction 15 ± 6 months previously, were submitted to (1) standard stress-redistribution thallium-201 single photon emission tomography (SPET), (2) rest-redistribution²⁰¹Tl SPET and (3) stress-rest technetium-99m sestamibi SPET. Uptake modifications in relation to exercise-induced defects were evaluated in a total of 390 myocardial segments. Tracer uptake was scored as normal (=0), mildly reduced (=1), apparently reduced (=2), severely reduced (=3) or absent (=4). Comparison of stress studies failed to show any statistical difference (58% segmental abnormalities with sestamibi vs 61% with thallium). Uptake abnormalities (score 1–4) were detected in 55% of the segments wiliest sestamibi, 55% with standard thallium redistribution, 55% with early imaging after thallium injection at rest and 54% with 3-h delayed rest imaging (P = NS). Absence of tracer uptake (score = 4) under resting conditions was recorded in 75 (19%) segments with standard²⁰¹Tl redistribution, 75 (19%) with rest sestamibi, 70 (18%) with rest²⁰¹Tl imaging and 62 (16%) with rst-rdistruion²⁰¹Tl (P<0.05 vs other imaging modalities). Thus, 3-h delayed rest thallium imaging detected reversibility of uptake defects in a significantly higher number of myocardial segments. This finding might have important implications for both tracer and technique selection when myocardial viability is the main clinical issue.     

Fluorine 18-labeled fluorodeoxyglucose myocardial single-photon emission computed tomography: An alternative for determining myocardial viability

The identification of hibernating myocardium in patients with poor ventricular function has become increasingly important as investigators demonstrate an improvement in ventricular performance in patients with injured but viable myocardium who undergo surgical revascularization. Modifications of ²⁰¹Tl redistribution protocols and rest/stress ^99mTc-labeled hexakis-2-methoxy-2-methyl propylisonitrile perfusion studies continue to underestimate myocardial viability compared with resting ¹⁸F-labeled fluorodeoxyglucose (¹⁸FDG) positron emission tomography. The combined data from multiple investigators suggest that ¹⁸FDG single-photon emission computed tomograpy used in combination with cardiac perfusion agents, either sequentially or with simultaneous dual-isotope acquisition, may provide an acceptable alternative to positron emission tomographic imaging for the detection of hibernating myocardium.     

Enhanced detection of reversible myocardial hypoperfusion by technetium 99m-tetrofosmin imaging and first-pass radionuclide angiography after nitroglycerin administration

Background  Reversal of ischemia after myocardial infarction by revascularization is worth-while only if viability exists in a sufficiently large portion of the left ventricle. Methods and Results  To determine myocardial hypoperfusion reversibility and its influence on segmental and global function, we studied 50 patients after myocardial infarction. Three technetium 99m-tetrofosmin scintigraphies were performed: 1 at rest, 1 after 0.6 mg sublingual nitroglycerin (NTG), and 1 after injection at peak stress. First-pass multigated radionuclide angiography was obtained at rest and after NTG. Each patient also underwent a stress redistribution-reinjection thallium-201 scintigraphy. During stress ^99mTc-tetrofosmin, 104 segments had normal uptake, 51 showed moderately reduced uptake, and 186 had severely reduced uptake. Of these 186 segments, 33 (18%) improved at rest, and 41 (22%) improved only after NTG. Fifty-nine (79%) of these segments with improved uptake were also found to have reversible defects on ²⁰¹Tl imaging. In the 26 patients with ventricular dysfunction, a 73% agreement was found between the functional and ^99mTc-tetrofosmin uptake post-NTG improvement, whereas a 69% agreement was found with thallium reinjection. No significant differences were seen between ^99mTc-tetrofosmin and ²⁰¹Tl imaging. Conclusion  Nitroglycerin administration during ^99mTc-tetrofosmin scintigraphy improves the detection of myocardium with reversible hypoperfusion in patients with a previous myocardial infarction.     

Technetium 99m-labeled sestamibi imaging reliably identifies retained contractile reserve in dyssynergic myocardial segments

Background

Recently there has been considerable controversy regarding the use of ^99mTc-labeled sestamibi as an agent for the detection of viable myocardium. In this study we have used dobutamine-induced left ventricular wall thickening by echocardiography in regions with evidence of resting dyssynergy of the left ventricle as an indicator of retained contractile reserve and compared this with 99m Tc-labeled sestamibi uptake in the same regions.

Methods and Results

Twenty-seven patients with documented coronary artery disease and severe regional wall motion abnormalities underwent low-dose (5 to 15 μg/kg/min) dobutamine echocardiography and maximal (15 to 40 μg/kg/min) stress dobutamine ^99mTc-labeled sestamibi single-photon emission computed tomographic imaging. Separate-day rest ^99mTc-labeled sestamibi scanning was also performed. ^99mTc-labeled sestamibi uptake was assessed semiquantitatively from grades from 1 to 4, from normal to absent perfusion. Regions with grade 3 or less uptake were considered viable by ^99mTc-labeled sestamibi. Of the 34 regions with severe wall motion abnormalities by echocardiography, 32 showed improved wall thickening with low-dose dobutamine. Rest ^99mTc-labeled sestamibi detected retained myocardial viability in 29 of these regions (91%) that were deemed to have contractile reserve by echocardiography (concordance: 91% [K=0.53; p<0.001]). Furthermore, stress-rest ^99mTc-labeled sestamibi revealed completely reversible defects in five regions (16%), partially reversible defects in 24 regions (75%), and grade 4 uptake and fixed (nonviable) defects in three (9%) of these 32 regions with retained contractile reserve.

Conclusion

Uptake of ^99mTc-labeled sestamibi at rest accurately identifies regions of segmental dyssynergy in which recovery of function may be provoked by inotropic stimulation. Addition of stress dobutamine ^99mTc-labeled sestamibi provides further proof of retained myocardial viability in these dysfunctional segments.     

Improved detection of myocardial perfusion reversibility by rest-nitroglycerin Tc-99m-MIBI: Comparison with Tl-201 reinjection

BACKGROUND: The role of nitroglycerin (NTG) in Tc-99m-methoxyisobutil isonitrile (MIBI) studies to improve the assessment of myocardial viability in patients with coronary artery disease and its comparison with TI-201 reinjection has not yet been clarified. This study aimed to test whether sublingual administration of NTG could improve the capability of Tc-99m-MIBI to detect reversibility in exercise-induced perfusion defects and to compare it with the TI-201 stress-redistribution-reinjection protocol. METHODS AND RESULTS: Thirty-eight patients (33 men, 5 women; mean age 49.3 +/- 8.2 years with previous myocardial infarction [mean evolution 7.1 +/- 3.9 months]) underwent exercise, redistribution, and reinjection TI-201 imaging, as well as exercise, rest, and NTG MIBI myocardial scintigraphy (3-day protocol). A total of 494 myocardial segments were assessed by quantitative analysis. Of the 136 myocardial segments with fixed defects on exercise-rest sestamibi imaging, 109 (80%) did not change after NTG MIBI study, and 27 (20%) demonstrated enhanced uptake. In the 140 myocardial segments with fixed defects on exercise-redistribution thallium imaging, 112 (80%) did not improve after TI-201 reinjection study, and 28 (20%) showed increased activity. The observed agreement on reversibility detection between NTG MIBI and TI-201 reinjection, with the 210 segments with perfusion defects used for this analysis on both studies, was 78%, with a significant kappa = .56 +/- .07 SE. CONCLUSION: Our data suggest that the use of an NTG MIBI protocol results in an incremental improvement for detecting exercise-induced perfusion defect reversibility and achieves results similar to those from a TI-201 reinjection protocol.     

Comparison of reinjection thallium 201 and resting technetium 99m sestamibi tomographic images for the quantification of infarct size after acute myocardial infarction

Background

Both thallium 201 and technetium 99m sestamibi have been used to quantitate infarct size at rest. Exercise²⁰¹Tl scintigraphy has been shown to have powerful prognostic information after myocardial infarction. A single study using these agents that could provide data on infarct size and prognosis would be of value. The purpose of this study was to compare estimates of infarct size by use of²⁰¹Tl and^99mTc sestamibi and to correlate these measurements with left ventricular ejection fraction in patients after acute myocardial infarction.

Methods and Results

The study group consisted of 20 patients who underwent low-level²⁰¹Tl stress studies with reinjection and^99mTc sestamibi resting studies within 4 days. Acute reperfusion was attempted in 18 of 20 patients. For^99mTc sestamibi tomographic imaging, infarct size was quantitated with 60% of maximal counts per slice for five short-axis slices as described in multiple previous studies. The postreinjection delayed²⁰¹Tl images acquired 4 hours after stress were quantitated according to the same threshold method.²⁰¹Tl patient images were also quantitated with a commercially available polar map program and compared with sex-matched control subjects. Ejection fraction was determined for each patient by radionuclide ventriculography 6 weeks later. Ejection fraction was well preserved for the group: mean 0.53±0.10. Infarct size with^99mTc sestamibi was 12%±13% of the left ventricle, which was significantly smaller than either method with²⁰¹Tl: threshold method, 29%±18% of left ventricle; polar map method, 25%±17% of left ventricle (both²⁰¹Tl estimates,p<0.0001 vs^99mTc sestamibi;²⁰¹Tl, 70% threshold vs²⁰¹Tl polar map,p=0.04). There was a significant correlation between infarct size with^99mTc sestamibi and that with²⁰¹Tl (r=0.72 to 0.73;p<0.001). Infarct size with^99mTc sestamibi, however, provided the closest correlation with ejection fraction (r=0.81;p<0.001), with the two²⁰¹Tl quantitative methods providing very similar correlations (r=0.69;p<0.001).

Conclusions

Infarct size with reinjection²⁰¹Tl imaging correlates significantly with resting infarct size with^99mTc sestamibi, although it provides significantly larger estimates. Although both approaches can be combined with a same-day exercise protocol, the closer correlation of infarct size with ejection fraction at 6 weeks suggests that resting infarct size with^99mTc sestamibi may be slightly more accurate.     

Dual-isotope myocardial imaging: feasibility,advantages and limitations

Two hundred and thirty-one patients underwent dual-isotope myocardial imaging (rest thallium-201 followed by stress technetium-99m sestamibi). The feasibility of the procedure was excellent: camera scheduling flexibility was improved and the duration of the procedure was less than that of a classical stress-redistribution procedure. Interpretation of defects due to image attenuation was facilitated by the different attenuation properties of ²⁰¹Tl and ^99mTc-sestamibi in 11 of 19 patients. ²¹⁰Tl cross-over on ^99mTc was found to be 15% ± 3% with doses of ²⁰¹Tl and ^99mTc-sestamibi of 3 and 10 mCi, respectively, and 7% ± 2% with doses of 3 and 20 mCi. This protocol should preferentially be reserved for patients with a history of myocardial infarction and/or a basal left ventricular dysfunction, in whom assessment of myocardial viability is of major interest. Extensive clinical validation of the dual-isotope procedure is required and optimal acquisition and reconstruction parameters should be established.     

Technetium-99m Q4: a prototype cationic perfusion radiotracer with myocardial washout

Technetium-99m Q4 is derived from an existing mixed ligand myocardial tracer (^99mTc-Q3) by the addition of an ester group to promote myocardial washout. Six subjects with single-vessel coronary disease documented by angiography and/or Q wave myocardial infarction documented by electrocardiography were studied with ^99mTc-Q4 injection during exercise and with comparative thallium-201 tomography. Six healthy volunteers were also studied with ^99mTc-Q4 imaging following injection at peak exercise. Tomographic images with ^99mTc-Q4 and ²⁰¹Tl each provided correct assessment of the presence or absence of coronary disease in 22 of 30 myocardial segments (73.3%). Six myocardial segments showed defect reversibility with ^99mTc-Q4, whereas 14 segments showed reversibility with ²⁰¹Tl, but the latter included three segments with no angiographic or electrocardiographic evidence of disease. In both normals and subjects with coronary artery disease, significant global washout of ^99mTc-Q4 was observed over 4 h. For five patients with angiographic evidence of unrevascularized coronary artery stenosis, the ischemic to normal zone count ratio increased from 0.782±0.107 at 45 min postexercise to 0.891±0.115 at 4 h postexercise (P = 0.016), suggesting occurrence of differential washout. It is concluded that addition of an ester group functionality to a previously studied mixed ligand cardiac tracer promotes global and regional myocardial tracer washout. Nevertheless, demonstration of perfusion defect reversibility with comparable frequency to that observed with ²⁰¹Tl stress and reinjection images, required separate injections of ^99mTc-Q4 at peak stress and at rest. Received 4 October and in revised form 19 December 1997     

Diagnostic utility of tomographic myocardial perfusion imaging with technetium 99m furifosmin (Q12) compared with thallium 201: Results of a phase III multicenter trial

Background  

Based on physical properties, ^99mTc-labeled perfusion agents offer several advantages over ²⁰¹Tl for myocardial perfusion imaging. The results of in vivo and experimental studies, along with preliminary experience in human subjects, have shown ^99mTc-labeled furifosmin to be a promising new perfusion tracer. The purpose of this study was to evaluate the safety of a new myocardial perfusion agent, ^99mTc-labeled furifosmin (Q12), and determine the concordance of furifosmin perfusion scintigraphy to ²⁰¹Tl imaging. In addition, we sought to determine the normalcy rate of myocardial scintigraphy with furifosmin.     

Reduced variability of interpretation and improved image quality with a technetium 99m myocardial perfusion agent: Comparison of thallium 201 and technetium 99m-labeled tetrofosmin

Background  

The purpose of this study was to determine the relative image quality and interobserver variability among four readers for²⁰¹Tl and^99mTc-labeled tetrofosmin myocardial perfusion images.^99mTc-labeled perfusion agents, with near-optimal physical characteristics for gamma camera imaging, may allow for superior image quality and improved consistency of interpretation. However, most studies to date have demonstrated only similarity in the diagnostic accuracy between technetium agents and thallium. Tetrofosmin is a recently developed^99mTc-labeled agent that has shown promising results in early clinical trials.     

Comparison of exercise-rest-reinjection Tl-201 imaging and rest sublingual isosorbide dinitrate Tc-99m MIBI imaging for the assessment of myocardial viability

Purpose  Nitrate administration has been proposed to enhance the detection of myocardial viability when performing myocardial perfusion imaging. In this study, we aimed to compare Tl-201 exercise-rest-reinjection protocol with rest isosorbide dinitrate (ISDN)-Tc99m MIBI study in the same population examined for the myocardial viability. Methods  Twenty-six patients with coronary artery disease who had fixed segmental defects on exercise-rest-Tl-201 imaging were studied. All of them underwent Tl-201 reinjection study. Within 1 week of Tl-201 imaging, rest-Tc99m MIBI imaging was performed after sublingual 5 mg ISDN administration (2-day protocol). For each study, tomograms were divided into 20 segments based on three short-axis slices, one vertical long-axis representing the totality of the left ventricle and regional tracer uptake was quantitatively analyzed. Regional tracer uptake was evaluated in 20 myocardial segments for all patients. Viability was defined as presence of tracer uptake ≥50% of peak activity on each study. A total 520 myocardial segments were assessed by semi quantitative analysis. Result  On the baseline rest Tl-201 studies, 211 segments of the 520 segments that were analyzed had <50% of peak activity. Of these segments, 42 (20%) showed reversibility after reinjection Tl-201 imaging and 55 segments (27%) described as viable on the rest ISDN-Tc99m MIBI imaging. There was 89% concordance between the ISDN-Tc99m MIBI study and Tl-201 reinjection study regarding viable myocardial segments. Of the 23 segments with discordant results, 18 were irreversible on Tl-201 reinjection study, but showed ≥50% uptake on ISDN-Tc99m MIBI. Conclusion  Observation of good agreement between Tl-201 reinjection and ISDN-Tc99m MIBI study studies led us to suggest the use of ISDN enhanced imaging in the evaluation of myocardial viability.     

Diagnostic accuracy of dipyridamole technetium 99m-labeled sestamibi myocardial tomography for detection of coronary artery disease

Background

The diagnostic accuracy of exercise ^99mTc-labeled sestamibi and intravenous dipyridamole ²⁰¹Tl-labeled myocardial tomography is established. The accuracy of dipyridamole stress ^99mTc-labeled sestamibi myocardial tomography for the detection of coronary artery disease has not been reported.

Methods and Results

Our purpose was to determine the diagnostic accuracy of same-day, rest-dipyridamole stress ^99mTc-labeled sestamibi myocardial single-photon emission computed tomography (SPECT) compared with coronary angiography. Two hundred forty-four patients who were unable to exercise adequately underwent both dipyridamole ^99mTc-labeled sestamibi SPECT and coronary angiography within 6 months. Dipyridamole was administered intravenously in a standard dose of 0.56 mg/kg for 4 minutes. Cardiac and noncardiac side effects were recorded. The presence of coronary stenoses of 50% or greater diameter reduction in each of the major coronary arteries was compared with imaging data in corresponding myocardial perfusion beds. The patient population was predominately (98.8%) male with a mean age of 63±9 years (range 33 to 83 years). The majority of patients had stable angina (88%). Eighty-four patients (35%) gave a prior history of myocardial infarction; 44 patients (18%) had a history of congestire heart failure. The principal limitation to exercise stress was peripheral vascular disease in 62 patients (26%). No serious side effects occurred during dipyridamole stress; 14% of patients had chest pain and 8% of patients had 1 mm or greater ST segment depression. Of the 204 patients with documented coronary stenoses, 43 (21%) had single-vessel disease and 161 (79%) had multivessel disease. The sensitivity was 93% (40/43 in patients with single-vessel disease) and 91% (146/161 in patients with multivessel disease). Overall sensitivity was 91%. The specificity was 28% (11/40) in this population with a high prestest probability of coronary artery disease and posttest referral for cardiac catheterization.

Conclusion

^99mTc-labeled sestamibi myocardial tomography in conjunction with intravenous dipyridamole stress is a safe and sensitive method for the detection of coronary artery disease. The diagnostic accuracy of dipyridamole stress ^99mTc-labeled sestamibi SPECT for the detection of coronary artery disease is similar to that reported for exercise stress ^99mTc-labeled sestamibi tomography, making this a suitable alternative for the evaluation of patients who are unable to exercise adequately.     

Attenuation-corrected rest thallium-201/stress technetium 99m sestamibi myocardial SPECT in normals

Background  Rest thallium-201/stress technetium 99m sestamibi protocol is widely used in the clinical setting. Although attenuation correction (AC) represents an important recent development in cardiac single photon emission computed tomography (SPECT) imaging, adjacent extracardiac activity can affect the myocardial count density distribution on AC images, particularly with ²⁰¹Tl. The aims of this study were to compare normal distribution between AC rest ²⁰¹Tl and stress ^99mTc-sestamibi SPECT images as well as to evaluate the effect of extracardiac activity on AC SPECT images with ^99mTc and ²⁰¹Tl. Methods and Results  A phantom measurement and a study of 21 patients with low likelihood of coronary artery disease were performed with a triple-head SPECT system equipped with a americium 241 line source. In the phantom study, the presence of extracardiac activity increased the inferior-to-anterior ratios, particularly with ²⁰¹Tl (1.01 to 1.32). In the clinical data, reduced count density with ²⁰¹Tl compared to ^99mTc-sestamibi was observed in most of the noninferior segments. On an individual segment basis, 37 (20%) of 189 segments from 11 (52%) of 21 subjects showed reduced count density on the ²⁰¹Tl image compared to ^99mTc-sestamibi by >10% of peak activity. Conclusions  There is a significant difference in myocardial count density distribution between ^99mTc-sestamibi and ²⁰¹Tl on AC SPECT images, indicating that a careful image interpretation that considers the different normal count density distribution between the tracers and/or a tracer specific normal database is necessary, especially when defect reversibility is of concern. Further work should aim for the incorporation of scatter correction combined with attenuation correction. Supported by Mitsubishi Research Institute, Japan.     

Improved diagnostic accuracy of planar imaging with technetium 99m-labeled tetrofosmin compared with thallium-201 for the detection of coronary artery disease

Background

Receiver operating characteristic (ROC) curve analysis provides detailed information about the performance of a diagnostic test.

Methods and Results

As part of a multicenter phase III trial, 160 patients with known or suspected coronary artery disease underwent planar stress-rest^99mTc-labeled tetrofosmin and stress-redistribution²⁰¹Tl imaging within 14 days of each other, to compare the diagnostic accuracy of these imaging modalities by ROC curve analysis. Coronary arteriography was used as the reference standard and greater than 70% stenosis was considered significant. ROC curve analysis showed improved detection of coronary artery disease with^99mTc-labeled tetrofosmin compared with²⁰¹Tl, with ROC curve areas of 0.765 versus 0.644, respectively (p=0.02).^99mTc-labeled tetrofosmin also better identified single-vessel disease in those without previous myocardial infarction (ROC curve areas of 0.684 vs 0.510 for^99mTc-labeled tetrofosmin and²⁰¹Tl, respectively;p=0.04) and enhanced the detection of multivessel disease in those with previous myocardial infarction (ROC curve areas of 0.764 vs 0.638, respectively;p=0.02).

Conclusions

Detailed assessment of diagnostic performance by ROC curve analysis shows that, for planar imaging,^99mTc-labeled tetrofosmin enhances the detection of coronary artery disease compared with²⁰¹Tl.     

Comparison of cationic myocardial perfusion agents: Characteristics of accumulation in cultured smooth muscle cells

The uptake and washout kinetics of two cationic lipophilic^99mTc-labeled myocardial perfusion agents,^99mTc-methoxyisobutylisonitrile (^99mTc-MIBI) and^99mTc-l,2-bis[bis-(2-ethoxyethyl)-phosphino]ethane (^99mTc-Tetrofosmin), were studied in cultured smooth muscle cells and compared to the conventional myocardial perfusion agent,²⁰¹Tl. Both^99mTc-MIBI and^99mTc-Tetrofosmin had a 4-fold greater uptake than²⁰¹Tl, and they were washed out of cells through similar kinetics which had slower rates than²⁰¹T1. Incubation with metabolism inhibitors had a modest influence on the uptake of these two^99mTc-labeled agents, although their extent and inhibited sites were slightly different. Ion transport inhibitors did not affect the uptake of^99mTc-MIBI, although the^99mTc-Tetrofosmin uptake was slightly inhibited when the Ca²⁺ channel was blocked. Our studies indicate that^99mTc-MIBI and^99mTc-Tetrofosmin were taken up by smooth muscle cells in similar pharmacokinetic patterns, but their accumulation reflected a different meaning for cell viability.     

Myocardial uptake of thallium 201 and technetium 99m-labeled sestamibi after ischemia and reperfusion: Comparison by quantitative dual-tracer autoradiography in rabbits

Background  

Myocardial scintigraphy with^99mTc-labeled sestamibi (^99mTc-sestamibi) or²⁰¹Tl is used to assess regional perfusion in acute coronary syndromes associated with metabolic or functional abnormalities, such as acute coronary thrombosis with reperfusion and ischemia at rest. However, the initial uptake of these agents may be affected by a recent ischemic insult because the myocardial retention of these tracers depends on cellular metabolism.     

A comparison of resting images from two myocardial perfusion tracers

We have compared stress-redistribution and delayed rest thallium-201 with rest technetium-99m methoxyisobutylisonitrile (MIBI) tomograms in order to compare the tracers for the assessment of myocardial viability and to validate a rapid protocol combining the two tracers. We studied 30 consecutive patients with known or suspected coronary artery disease [group 1: 16 with normal left ventricular function, mean left ventricular ejection fraction (LVEF) 55%, SD 6%; group 2: 14 with abnormal function, mean LVEF 28%, SD 8%].²⁰¹Tl was injected during infusion of adenosine followed by acquisition of conventional stress and redistribution tomograms. On a separate day,²⁰¹Tl was injected at rest with imaging 4 h later.^99mTc-MIBI was then given at rest and imaging was performed. Three images were compared: redistribution²⁰¹Tl, rest²⁰¹Tl, and rest^99mTc-MIBI. Tracer activity was classified visually and quantitatively in nine segments and segments with>50% activity were defined as containing clinically significant viable myocardium. Mean (±SD) global tracer uptake as a percentage of maximum was similar in group 1 (rest²⁰¹Tl 69%±12%, redistribution²⁰¹Tl 69%±15%, rest^99mTc-MIBI 70%±13%, ANOVAP>0.05), but in group 2 mean tracer uptake was significantly greater in the rest²⁰¹Tl images (59%±16%) than in redistribution²⁰¹Tl images (53%±17%) or rest^99mTc-MIBI images (53%±19%) (ANOVAP=0.02). Overall agreement for regional uptake score was excellent ( from 0.79 to 0.84), although there were a significant number of segments with less uptake shown by redistribution²⁰¹Tl and by rest^99mTc-MIBI than by rest²⁰¹Tl in group 2 (P<0.001). The number of segments with significant viable myocardium in group 1 was very similar between the three images (P>0.05) but in group 2 rest²⁰¹Tl identified significantly more segments as viable than the other images (McNemarP<0.001). Thus²⁰¹Tl and^99mTc-MIBI provide similar information in patients without prior infarction and with normal left ventricular function (group 1), and a rapid protocol with stress²⁰¹Tl injection and imaging followed immediately by rest^99mTc-MIBI injection and imaging is feasible. In patients with abnormal left ventricular function and prior infarction (group 2),^99mTc-MIBI may underestimate the extent of clinically significant viable myocardium.     

Accuracy of detection of myocardial viability and residual infarct vessel stenoses with rest Tl-201 and adenosine Tc-99m sestamibi imaging after coronary reperfusion in dogs with experimental acute myocardial infarction

BACKGROUND: We sought to determine whether a dual-isotope imaging strategy (rest thallium 201/stress technetium 99m sestamibi) might be useful for assessing myocardial viability and residual ischemia in the infarct zone very early after reperfusion. METHODS AND RESULTS: Fifteen open-chest dogs had left anterior descending coronary artery occlusion for 60 minutes, followed by full reperfusion (group 1, n = 8) or reperfusion through a residual critical stenosis (group 2, n = 7). Tl-201 was injected at rest 45 minutes after reperfusion, and initial and 2-hour redistribution images were acquired. Tc-99m sestamibi was then injected during vasodilator stress, followed by imaging. Infarct size was similar in both groups (risk area, 21% +/- 4% vs 22% +/- 3%). Rest Tl-201 defect count ratios (left anterior descending coronary artery/left circumflex artery) were comparable (0.71 +/- 0.03 vs 0.74 +/- 0.02) and reflected infarct size. With vasodilation, Tc-99m sestamibi defect count ratio in group 1 (0.71 +/- 0.02) was comparable to rest Tl-201 and was significantly greater than in group 2 (0.62 +/- 0.02) with residual stenoses (P <.01). Although vasodilator Tc-99m sestamibi imaging unmasked the presence of residual stenoses, Tc-99m sestamibi uptake underestimated their functional severity (flow ratio, 0.38 +/- 0.03). CONCLUSIONS: Dual-isotope imaging very early after reperfusion may have limited utility for detecting residual stenoses in the infarct zone. Underestimation of the flow disparity by Tc-99m sestamibi may make the detection of stenoses more difficult, and impaired flow reserve after ischemic insult may complicate the detection of fully reperfused segments.