Comparison of thallium redistribution with rest "reinjection" imaging for the detection of viable myocardium

To determine the incidence of incomplete redistribution on conventional delayed thallium images, 41 patients with persistent perfusion defects on myocardial images recorded 3 to 4 hours after thallium injection during exercise were studied. At the conclusion of their delayed images the patients were reinjected at rest with approximately 1 mCi of thallium-201 and a third set of images was recorded. The images were presented at random in pairs (initial:delayed, initial:reinjection) to 2 experienced observers for qualitative scoring of 9 segments/patient. Of the 360 segments analyzed, concordance between the delayed and reinjected images occurred in 307 (85%). Of 141 segments that demonstrated a persistent perfusion abnormality on 3- to 4-hour delayed images, 44 (31%) were reassigned to a redistribution score after reinjection. In 9 patients, reinjection images provided the only evidence of ischemia from the scintigraphic data. In 13 of 14 vascular territories that demonstrated redistribution after reinjection, intact perfusion (either anterograde or via collaterals) was detected at coronary angiography. These data suggest that rest reinjection imaging may provide a means of detecting viable myocardium in segments that demonstrate a fixed perfusion abnormality on conventional 3- to 4-hour delayed thallium images.     

Regional thallium uptake in irreversible defects. Magnitude of change in thallium activity after reinjection distinguishes viable from nonviable myocardium.

BACKGROUND. Thallium reinjection immediately after stress-redistribution imaging identifies ischemic but viable myocardium in as many as 50% of the regions characterized by conventional redistribution imaging as irreversibly injured. However, we have previously shown that some regions in which irreversible defects persist despite reinjection are metabolically active, and hence viable, by positron emission tomography. In the current study, we determined whether the severity of reduction in thallium activity within irreversible defects on redistribution images and the magnitude of change in regional thallium activity after reinjection can further discriminate viable from nonviable myocardium in such defects. METHODS AND RESULTS. We studied 150 patients with coronary artery disease by exercise thallium tomography using the rest-reinjection protocol. The three sets of images (stress, redistribution, and reinjection) were then analyzed quantitatively. The increase in regional thallium activity from redistribution to reinjection was computed, normalized to the increase observed in a normal region, and termed "differential uptake." Of the 175 myocardial regions designated to have irreversible thallium defects on conventional 3-4 hour redistribution images, 132 had only mild-to-moderate reduction in thallium activity (51-85% of normal activity), and 43 had severe reduction in thallium activity (less than or equal to 50% of normal activity). Thallium reinjection resulted in enhanced relative activity in 60 of 132 (45%) of the mild-to-moderate irreversible defects and 22 of 43 (51%) of the severe irreversible defects, leaving roughly half of these defects remaining irreversible after reinjection. However, in regions that appeared to remain irreversible despite reinjection, the magnitude of differential uptake differed between mild-to-moderate (74 +/- 14%) and severe (35 +/- 16%) irreversible defects (p less than 0.001). All regions with mild-to-moderate defects demonstrated greater than 50% differential uptake after reinjection. In contrast, all except two of the regions with severe irreversible defects demonstrated differential uptake of less than 50%. Fifteen patients also underwent positron emission tomography at rest with 18F-fluorodeoxyglucose (FDG) and 15O-water. FDG uptake was present in 91% of regions with mild-to-moderate reduction in thallium activity, and the results of differential uptake and FDG data were concordant in 81% of these regions. CONCLUSIONS. These data indicate that the magnitude of thallium uptake after reinjection differs between mild-to-moderate and severe irreversible defects on standard 3-4 hour redistribution images. The substantial differential uptake of thallium (greater than 50%) after reinjection in mild-to-moderate defects, even when relative thallium activity does not increase appreciably (and the defect appears to remain irreversible), coupled with preserved metabolic activity by positron emission tomography, supports the concept that such mild-to-moderate irreversible defects represent viable myocardium.     

Viable myocardium identified by reinjection thallium-201 imaging: comparison with regional wall motion and metabolic activity on FDG-PET.

Reinjection thallium-201 scans were performed in 68 patients with coronary artery disease after the routine stress-delayed scans for more accurate identification of new fill-in. Following the stress and 3 hour delayed thallium-201 SPECT scans, 40 MBq (1.1 mCi) was injected at rest, and 10 min later, the reinjection SPECT scan was obtained. To determine whether the reinjection method can aid in identifying ischemic but viable myocardium, the thallium-201 findings were compared with regional wall motion on radionuclide ventriculography in 61 patients and with metabolic activity on positron emission tomography (PET) using F-18 fluorodeoxyglucose (FDG) in 18 patients. The reinjection scan identified new fill-in which had not been shown on the stress-delayed scans in 6 of the 22 patients (27%) or in 29 of the 105 segments (28%). Regional wall motion was preserved more in the segments that exhibited new fill-in after reinjection (wall motion score = 1.64 +/- 1.29) than in those without new fill-in (score = 2.72 +/- 1.04) (p < 0.01). In the comparative study with FDG-PET, persistent FDG uptake was observed in all segments with new fill-in (20/20 segments: 100%); whereas, it was seen in only 7 of the 28 segments (25%) without new fill-in after reinjection (p < 0.05). We concluded that the segments having new fill-in after reinjection may represent ischemic but viable myocardium. Thus, the reinjection thallium-201 scan should be performed to identify ischemic myocardium which occasionally cannot be detected by the routine stress-delayed thallium-201 scans.     

Differential uptake and apparent 201Tl washout after thallium reinjection. Options regarding early redistribution imaging before reinjection or late redistribution imaging after reinjection.

BACKGROUND. Because thallium reinjection enhances the identification of viable myocardium, many laboratories have adopted the routine practice of performing reinjection imaging instead of 3-4-hour redistribution imaging. This approach assumes that the stress-reinjection protocol provides the necessary information regarding both exercise-induced ischemia and myocardial viability. Because apparent "washout" of thallium may occur between redistribution and reinjection studies, we examined the limitations created by eliminating 3-4-hour redistribution images. METHODS AND RESULTS. We studied 50 patients with chronic stable coronary artery disease by exercise thallium tomography, radionuclide angiography, and coronary arteriography. Immediately after the 3-4-hour redistribution images, 1 mCi thallium was injected at rest, and images were reacquired both 10 minutes and 24 hours after reinjection. The stress, redistribution, reinjection, and 24-hour images were then analyzed quantitatively, and the magnitude of change in regional thallium activity after reinjection was termed "differential uptake." Of the 127 abnormal myocardial regions on the stress images, 55 (43%) demonstrated either complete or partial reversibility on 3-4-hour redistribution images. After reinjection, 14 of these regions (25%) demonstrated apparent thallium washout due to low differential uptake of thallium, which was only 46 +/- 20% of that observed in normal regions. As a result, the relative thallium activity, which was 55 +/- 13% during stress (relative to normal regions) and increased significantly to 75 +/- 13% on 3-4-hour redistribution studies (p less than 0.001), decreased to only 58 +/- 13% after thallium reinjection. At 24 hours, redistribution again developed in all 14 regions, resulting in a relative thallium activity of 71 +/- 16% (p less than 0.03), which was similar to that achieved on 3-4-hour redistribution images. Twelve of the 14 regions (86%) exhibiting apparent washout after reinjection were supplied by a totally occluded coronary artery, of which eight (67%) had normal wall motion at rest. In contrast, only 41% of the regions with either improved or unchanged thallium uptake after reinjection were supplied by a totally occluded coronary artery (p less than 0.05). CONCLUSIONS. These data indicate that regions with thallium defects that are reversible on 3-4-hour redistribution images may demonstrate apparent washout of thallium after reinjection due to low differential uptake. Although this occurs in only a small fraction of regions (8%) identified as abnormal on exercise images, these regions represent approximately 25% of regions showing redistribution. Such defects would appear irreversible if redistribution imaging is not performed before reinjection. However, these same myocardial regions also redistribute further after reinjection and are identified as reversible on 24-hour images. Thus, one of two imaging options, either stress-redistribution-reinjection imaging or stress-reinjection-24-hour imaging, may be used for a comprehensive assessment of myocardial ischemia and viability.     

Identification of viable myocardium in patients with chronic coronary artery disease and left ventricular dysfunction. Comparison of thallium scintigraphy with reinjection and PET imaging with 18F-fluorodeoxyglucose

In patients with chronic coronary artery disease and left ventricular dysfunction, the distinction between ventricular dysfunction arising from myocardial fibrosis and ischemic, but viable, myocardium has important clinical implications. By positron emission tomography (PET), enhanced fluorine-18-labeled fluorodeoxyglucose (FDG) uptake in myocardial segments with impaired function and reduced blood flow is evidence of myocardial viability. Reinjection of thallium-201 at rest immediately after stress-redistribution imaging may also provide evidence of myocardial viability by demonstrating thallium uptake in regions with apparently "irreversible" defects. To compare these two methods, we studied 16 patients with chronic coronary artery disease and left ventricular dysfunction (ejection fraction, 27 +/- 9%), all of whom had irreversible defects on standard exercise-redistribution thallium single-photon emission computed tomography (SPECT) imaging. Thallium was reinjected immediately after the redistribution study, and SPECT images were reacquired. The patients also underwent PET imaging with FDG and oxygen-15-labeled water. A total of 432 myocardial segments were analyzed from comparable transaxial tomograms, of which 166 (38%) had irreversible thallium defects on redistribution images before reinjection. FDG uptake was demonstrated in 121 (73%) of these irreversible defects. Irreversible defects were then subgrouped according to the degree of thallium activity, relative to peak activity in normal regions. Irreversible defects with only mild (60-85% of peak activity) or moderate (50-59% of peak) reduction in thallium activity were considered viable on the basis of FDG uptake in 91% and 84% of these segments, respectively. In contrast, in irreversible defects with severe reduction in thallium activity (less than 50% of peak), FDG uptake was present in 51% of segments. In such severe defects, an identical number of segments (51%) demonstrated enhanced uptake of thallium after reinjection. In these severe "irreversible" defects, data on myocardial viability were concordant by the two techniques in 88% of segments, with 45% identified as viable and 43% identified as scar on both PET and thallium reinjection studies. These observations suggest that thallium imaging can be used to identify viable myocardium in patients with chronic coronary artery disease and left ventricular dysfunction. Most irreversible defects with only mild or moderate reduction in thallium activity represent viable myocardium as confirmed by FDG uptake.(ABSTRACT TRUNCATED AT 400 WORDS)     

再注射201铊心肌显像检测冬眠心肌的价值

目的探讨再注射２０１铊（Ｔｌ）心肌单光子发射计算机断层显像检测冬眠心肌的价值。方法对２２例冠心病心肌梗塞患者进行了运动再分布再注射２０１Ｔｌ心肌显像、心血池显像、冠状动脉（冠脉）造影及冠脉血运重建术，术后复查心血池及运动再分布２０１Ｔｌ心肌显像。结果１８个（４５％）在运动再分布影像上呈不可逆缺损节段在再注射影像上有再分布。再注射２０１Ｔｌ心肌显像预测冬眠心肌血运重建术后血流灌注与功能改善的阳性预测值为８８．９％和８３．３％，阴性预测值为７７．３％和８１８％，两者符合率为８４８％。术后患者运动耐量及左室射血分数改善。结论再注射２０１Ｔｌ心肌显像是检测冬眠心肌较可靠和实用的方法     

Noninvasive identification of collateralized myocardium by 201 thallium tomography in vasodilation and redistribution

Coronary arteriolar vasodilatation may provoke the redistribution of flow to collateral-dependent jeopardized myocardium. To assess the physiologic significance of collateral channels, 80 consecutive postinfarction patients (aged: 58 +/- 8 years) underwent vasodilatation/redistribution thallium-201 tomographic (SPECT) imaging using 0.56 mg dipyridamole/kg body weight. Circumferential profile analysis of redistribution and slow washout in representative left ventricular tomograms provided quantitative evaluation of transient and persistent defects and a separation between a periinfarctional and distant inducible hypoperfusion. Tomographic perfusion data were correlated to subsequent cineangiographic analysis of wall motion and to the extent of collateral circulation between two distinct anatomic perfusion areas, one of which involved the infarct zone. Patients were grouped according to the presence (59%) or absence (41%) of angiographically visible collateral channels to the jeopardized myocardium. In the presence of collaterals, distant reversible defects were larger than in the absence of collaterals (p less than 0.05); the extent of combined periinfarctional and distant redistribution was also larger in collateralized patients (p less than 0.025), whereas the size of the persistent perfusion defect was similar in both groups. In a prospective analysis, the tomographic perfusion pattern of combined periinfarctional and distant ischemia revealed a sensitivity of 85% and a specificity of 78% for the detection of significant collateral circulation in this group of patients. Thus, using the limited collateral flow reserve as a diagnostic tool, vasodilatation/redistribution thallium-201 tomography has some potential for identifying and quantifying collateral-dependent myocardium and may guide diagnostic and therapeutic decision-making.     

冠状动脉闭塞血运重建术后存活心肌对心功能的影响

目的观测冠状动脉闭塞血运重建术后存活心肌的情况,分析其对心功能恢复的影响。方法选择30例冠状动脉闭塞的患者,分别于血运重建术前、术后6月行99mTc-M IB I结合18F-FDG心肌代谢的双核素心肌灌注显像方法检测存活心肌;根据灌注代谢情况来评价存活心肌的程度,术前心肌灌注代谢均减低者为无存活心肌（A组,n=12）,心肌灌注减低而代谢正常者为有存活心肌（B组,n=18）,通过超声心动图观察两组心功能的变化,并且对比评价术前、术后运动耐量的变化特点。结果血运重建术后存活的心肌增加至180个节段;B组血运重建术后6月心功能恢复显著,左心室射血分数（LVEF）为（52±4）%vs（64±4）%（P<0.01）;心肌显像缺血程度较术前有明显改善,血运重建术后运动时间延长,运动距离增加;A组变化不明显。结论冠状动脉闭塞血运重建术后存活心肌的数量与心功能的恢复密切相关。     

Concordance between dobutamine Doppler tissue imaging echocardiography and rest reinjection thallium-201 tomography in dysfunctional hypoperfused myocardium

OBJECTIVE—To evaluate the efficiency of the new technique colour Doppler tissue imaging (DTI) by studying the concordance between dobutamine DTI, standard grey scale echocardiography (SE), and rest-reinjection TI-201 tomography (TI) in dysfunctional myocardium.
PATIENTS—23 patients with chronic wall motion abnormalities and proven coronary artery disease (> 70% diameter stenosis of at least one major coronary artery at angiogram).
METHODS—The contractile reserve and the resting perfusion characteristics of dysfunctional myocardial segments were assessed with low dose dobutamine SE and/or DTI (2.5 up to 20 γ/kg/min) and TI on a semiquantitative basis. The DTI or SE data were separately compared with TI, on the basis of a 13 segment ventricular model. The resulting score of combined DTI and SE was also compared with TI. Finally the results obtained from DTI were compared with SE.
RESULTS—A total of 142 severely hypokinetic or akinetic segments were visualised. The viability study was feasible in 127 (89%) and 121 (85%) segments with DTI and SE, respectively. TI detected viability more frequently than DTI (84 v 61, p < 0.001) and SE (80 v 50, p < 0.001). However, as many viable segments were detected with combined DTI and SE as with TI (78 v 84, NS). The κ values between TI and SE, DTI or combined SE and DTI were 0.38, 0.45, and 0.57, respectively, and increased to 0.52 and 0.76, respectively, for SE and DTI versus TI when mid-anterior and mid-inferior segments only were considered. The κ value between SE and DTI was 0.34.
CONCLUSIONS—DTI is a helpful adjunct to SE, when using low dose dobutamine. This combination revealed as many viable segments as TI and showed a better agreement than DTI or SE alone for the assessment of myocardial viable segments evidenced by TI.


Keywords: colour Doppler tissue imaging; hibernating myocardium; thallium 201 single photon emission computed tomography; stress echocardiography     

CARTO电压标测识别猪急性心肌梗死模型中存活心肌的研究

目的 研究应用CARTO电压标测的方法识别猪急性心肌梗死模型中存活心肌的准确性和实用性.方法 用普通家猪13头,麻醉气管插管后行冠状动脉造影术,置入经皮腔内冠状动脉成形术球囊至冠状动脉左前降支远端,堵闭血流60～90 min,建立家猪心肌梗死模型.采用CARTO电压标测系统构建左心室,通过电压标测识别存活心肌.处死试验动物取出心脏,将心肌组织切成薄片后采用氯化三苯基四氮唑(TTC)染色法识别存活心肌.CARTO电压标测识别存活心肌的标准为0.5～1.5 mV为存活心肌,TTC染色存活心肌呈淡红色.将CARTO电压标测的结果与TTC染色结果进行对比.结果 所有猪均完成冠状动脉左前降支远端的封堵,2头分别在堵闭45和65 min时因心室颤动死亡.存活11头猪成功地建立急性心肌梗死模型.将猪的左心室分为16个节段,11头共176个节段,分别通过CARTO电压标测与TTC染色法对各节段心肌进行识别并评价两种方法的一致性,两者的一致性较好(Kappa=0.816,P＜0.001).以TTC染色检测出的存活心肌为标准,CARTO电压标测检测存活心肌的敏感度为71.8%,特异度为96.5%;准确度为90.9%.结论 运用经皮腔内冠状动脉成形术球囊封堵冠状动脉可成功建立猪急性心肌梗死模型.通过CARTO电压标测系统能够识别出模型中的存活心肌,为检测存活心肌提供了一个新的方法.     

Role of myocardium scintigraphy with thallium dipyridamole in the evaluation of arterial disease of the legs

Thirty-eight consecutive patients with severe arterial disease of the lower extremities benefited from an exploration of the coronary reserve by myocardial scintigraphy with thallium dipyridamole. With this examination, it has been possible to screen 20 p. cent of asymptomatic patients and at least modify the perioperative treatment or even the very indication for surgery.     

Quantification of viable myocardium in multivessel coronary disease: Effects of the redistribution time after reinjection of thallium-201 and comparison with postrevascularization defect size

Reinjection of²⁰¹Tl is used for improved detection of viable myocardium. Prospectively the effect of the redistribution time after injection for the quantification of the definitive perfusion defect size in multivessel coronary heart disease and severely impaired left ventricular function was examined. Thirty patients were included preoperatively before CABG. The study was performed with 80–90 MBq²⁰¹Tl-Cl and reinjection (40–50 MBq). Imaging was performed after an exercise test and 3 hours afterwards. Thereafter, the reinjection dose was given and repeated studies were performed 10 minutes, 2 hours, and 20 hours later. Defect sizes were compared with the 3-hour rest-study without reinjection. Imaging studies were repeated postoperatively. The defect size was expressed as % of left ventricular total myocardium. Perfusion defect sizes were as follows: post-stress study (27%), 3 hour rest-study (17%), post-reinjection-10 min (12%), 2 hours (9%), and 20 hours (7%). Compared with the 3 hour rest-study, the perfusion defect was reduced only in 7/30 patients in the study immediately after reinjection. In the delayed studies, defect sizes were markedly smaller (p<0.05) both in studies 2 hours and 20 hours after reinjection. In 15/30 patients there was a marked reduction of 50% of defect sizes in the study 2 hours post-reinjection vs the 3 hour rest-study. The residual defects at 2 hours after reinjection were identical to the postoperative defect sizes (10%). Further prolongation of the redistribution time to 20 horus caused an additional small reduction in defect size only in two patients compared with the 2-hour post-reinjection images (n.s.). Using a marker as²⁰¹Tl with redistribution characteristics, the redistribution time after reinjection is of utmost importance to correctly identify the definitive size of the perfusion defect vs viable myocardium in patients with multivessel disease. A delay of 2 hours for redistribution after the reinjection most correctly corresponds to the postop defect size; a longer redistribution time did not provide additional advantages.Presented in part at the 39th Annual World Congress, International College of Angiology, Istanbul, Turkey, June 1997     

Defect reversibility using thallium-201 reinjection

Immediate poststress thallium-201 reinjection followed by imaging one hour later has been proposed as an alternative reinjection protocol. This procedure is patient-convenient and time-saving as it shortens the investigation time to maximally 2.5 hours. The efficacy of the immediate thallium-201 reinjection protocol was assessed in 305 patients with stress perfusion defects in whom we compared the scintigraphic findings of 210 consecutive patients who underwent the standard thallium-201 stress/redistribution/reinjection protocol (Group I), with 95 consective patients who subsequently underwent the thallium-201 stress/immediate reinjection protocol (Group II). In all patients three-view planar images were visually and quantitatively analyzed. In Group I, defect reversibility was observed in 433 of 622 (70%) stress perfusion defects compared to 220 of 320 (69%) segments in Group II (p=NS). With respect to Q-wave related segments, defect reversibility was seen in 102 of 172 (59%) segments in Group I compared to 34 of 63 (54%) in Group II (p=NS). Based on defect reversibility, the diagnosis of myocardial ischemia was made in 184 of 210 (88%) patients Group I compared to 86 of 95 (91%) patients in Group II (p=NS).These findings indicate that immediate thallium-201 reinjection imaging provides at least similar data on defect reversibility as the standard thallium-201 stress/redistribution/reinjection approach. In practical terms, the stress/immediate reinjection approach seems advantageous as it reduces imaging time, enhances patient throughout and can be considered as one comprehensive imaging procedure.