previous investigators reported that 201'fl redistributionwas observed in the resting state in regions with severecoronary artery stenosis (11, 12), suggesting that 201'flimaging would be useful for assessing viability. It is important to define regions with severe asynergy that willhave improved function after revascularization (13-16).Regional wall motion abnormality at rest may be due topersistently depressed blood flow or to prolonged myocardial cellular dysfunction following transient ischemia ormyocardial scarring(1 7-20). The different causes of severeasynergy may be differentiated by examining myocardialperfusion with rest-injected 2o―flimages.

In this study, we attempted to clarify the utility of therest-injected 2O1i@delayed image for distinguishing reversible asynergic regions from irreversible infarcted ones bycomparing regional wall motion before and after revascularization.

SUBJECTS AND METHODS

Subjects. The subjects were 17 (14 male, 3 female, median age62 ±9 yr) patients with anterior myocardial infarction and severestenosis of 90% or more in left anterior discending (LAD) artery.Patients were selected by identification of severe hypokinesis,

akinesis or dyskinesis in anterior, septal and apical regions, andno asynergy in other regions on 99mTcradionuclide ventriculography. No patient had suffered from acute myocardial infarctionfor the last 3 mo nor congestive heart failure. Two patients,however, complained of chest pain for a few minutes duringexercise. Coronary angiograms showed one lesion in ten patients,two lesions in three and three lesions in four. No patients had99% or more stenosis in other coronary arteries. Nine patientswere treated with percutaneous transluminal coronary angioplasty (PTCA), the result of which was successful in all lesions.In all patients,restenosisof the LADartery wasnot observedoncoronary angiography 5 mo after PTCA. Five patients underwent

coronary artery bypass graft (CABG) surgery. One patient had asingle graft, one patient had two grafts, and three patients hadthree grafts. Patency was confirmed in all grafts for LAD arterieson coronary angiography 1 mo after CABG surgery.

Methods. Resting 201Tl initial and delayed scans were performed about 1 wk before revascularization. The resting 2o1@flinitial image was taken 10 mm after intravenous injection of 111MBq2o1@fland the delayedimagewastaken 4 hr after injection.Thallium-20l imaging was performed in the anterior, 45°—60°left anterior oblique (LAO) views, which were the same views as

To evaluatethe utilityof rest-injected @°@T1initialand delayedimages for assessing the viabilityof severe asynergic regions,we studied17 patientswfth apparenttypnor infarctedmyocardium in combination wfth @Fcventhcukgraphy beforeand after revasculanzation. In 51 regions with severe asynergy, the percent 20111uptake was Calculatedas the ratio ofcounts on the segment with asynergy to the maximum countson the normal segment. Eleven of 14 regions with resting20111 redistribution (Group 1) had improved wall motion after

revasculanzation. However, 14 of 37 regions without redistribution also improved (Group 2). Twenty-three regions withoutredistribution or improved wall motion after revasculanzation(Group 3) had lower regional @°@T1uptake on their delayedimages than those in Groups 1 and 2. Moreover, the initialregional uptake of Group 2 was higher than that of Group 3.These results suggest that redistribution on rest-injected @°1TIscans indicates reversiblllty of severely asynergic myocardiumand that high 201@fluptake in regions without redistributionmaypredictimprovementin wall motionafter revasculanzation. We condude that @°i1uptake may be useful as a markerof viability of severe asynergic regions before revascularization.

J NucIMed 1991;32:1718-1724

n patients with apparently infarcted myocardium, differentiating viable but functionally impaired myocardiumfrom irreversibly infarcted myocardium is important ifrevascularization for myocardial salvage is contemplated.Stress 2o―flmyocardial imaging has been widely used forassessing myocardial viability (1-3). Recent studies havereported, however, that some persistent defects withoutredistribution may improve in regional perfusion andfunction after revascularization (3-5). To obviate possibleunderestimation ofviability on exercise 201'fl 4-hr delayedimages, some investigators have espoused the utility of 24-hr delayed images (5-7), 201'flreinjection images after a4-hr delayed image (8), and resting 201@flimages separatedby 1—2wk from the exercise 201'flimage (9, 10). However,

ReceivedNov.5, 1990;revisionacceptedMar.19,1991.Forreprintscontact:Forreprintscontact:TakaoMon.MD,Departmentof

cariiovascuiarSurgery,HyogoBrainandHeartCenterat Himeji,520Saishou,HimejiCity,HyogoPrefecture670.Japan.

1718 The Journal of Nudear Medicine •Vol. 32 •No. 9 •September 1991

Rest-Injected Thaffium-20 1 Imaging for AssessingViability of Severe Asynergic RegionsTakao Mori, Katsumi Minamiji, Hiroyuki Kurogane, Kyoichi Ogawa, and Yutaka Yoshida

Department ofCardiology, Department ofCardiovascular Surgery, Hyogo Brain and Heart Center at Himeji, Himeji City,Japan

Resting thaHium-201 imgs Tchn.tium-99m v•ntriculo9raphy

ANT L.S@ LAT ANT LaO

c@@2 6b@@@7t) 9@@@

36@@A 11 12@ 6©7

\@@91 a 7a io(p@ ‘J't \

A

Anteriorregion93.7±5.5Septalregion90.2 ±4.4Apicalregion90.1 ±6.0

in 99mTcradionuclide ventriculography, and the left lateral viewusing a single crystal gamma scintillation camera (GCA-40l,Toshiba) equipped with a middle-energy parallel-hole collimator.A 20% energywindowcenteredat 80 keY was selected.Imageswereexposedin a 64 x 64 matrixformatfor 6 mm foreachview.Each view was divided into five segments for a total of 15segments (Fig. 1). Small-size (4 x 4 pixels) regions of interest(ROIs) were placed within these 15 segments by operators (Fig.2) and %20―fluptake was calculated from the formula:

TI counts in segments with asynergy%Tluptake= . . x100.

maximal TI counts in normal segments

In Figure 1, asynergic regions consisted of the anterior region ofsegments 2 and 9, the septal region of 6a and 6b, and the apicalregion of 3 and 10. The ROI size was appropriate for assessing201'riuptakewithintheleftventricularmyocardiumasshowninFigure 2. The mean counts per pixel in ROIs ranged from 218 to1028 in the normal segments and from 147 to 645 in segmentswith asynergy. Regional 20―fluptake in the anterior region wasdetermined by the average of % uptake in segments 2 and 9.Septal 20―fluptake was an average of those in segments 6a and6b and apical uptake was an average of those in segments 3 and10. Redistribution was present when the regional 20'fl uptakeincreased on the delayed image compared with the initial imagemore than 1 s.d. of regional 201Tluptake calculated from 12normal subjects (Table 1).

Technetium-99m radionuclide ventriculography was performed 1 wk before and 1.5 mo after revascularization. Redblood cells were labeled in vivo after intravenous injection ofabout 740 MBq of@mTc.Multiple-gated blood-pool scintigraphywas performed using the same gamma camera-collimator systemasdescribedfor 201'flscintigraphyandastandarddigital computersystem (Shimadzu Scintipac 700). Data acquisition was made inan anterior view and a 45°—60°LAO view to provide optimalseparation of left and right ventricles. A 20% window was usedaround the 140 keY gamma peak and a total of 5 to 8 million

counts was exposed in a 64 x 64 matrix format with a l.4xzoom. A commercially available automated variable edge detection program was used for the determination of left ventricularejection fraction (LVEF). Segmental wall motion was interpretedby two experienced observers without knowledge of the clinicaland angiographic findings by one display analysis. The anteriorview was divided into the same five segments as those ofthe 201Tl

FIGURE1. Schematicrepresentationof leftventricularsegments of @°‘Tlimage and @“Tcradionuclideventriculography.ANT=anteriorview, LAO= left anterioroblique,LAT= lateralview. Segments:1 = basalanterior,2 = anterior,3 = apex, 4 =inferior, 5 = posterior, 6b = basal septum, 6a = apical septum,A = apical inferior, 7a = apical lateral, 7b = basal lateral, 8 =basal anterior, 9 = anterior, 10 = apex, 11 = inferior, 12 =posterior.

FIGURE2. Placementof ROlswithinleftventricularmyocardiumon 201flimage.ROIs(4 x 4 pixels)were placedwithineachsegment.

image, and the LAO view was divided into segments 6, A, and 7as shown in Figure 1. Segments 2, 3, and 6 correspond to anterior,apical, and septal regions, respectively. Left ventricular wall motion before revascularization was evaluated into five grades: normokinesis, hypokinesis, severe hypokinesis, akinesis, and dyskinesis. Change in regional wall motion was assessed by simultaneously viewing radionuclide ventriculography images before and

after revascularization without knowing which study was postrevascularization. After assessing change in wall motion, regionalwallmotion afterrevascularizationwasclassifiedinto fivegrades.

Coronary arteriography was performed by the Judkins technique. The severity ofa coronary artery stenosis was expressed asa percentage based on the American Heart Association classification (21).

Classification of SubjectsOnly six patients had more than 5% improvement in global

LVEF 1.5 mo after revascularization. Twenty-five regions, however, had improved wall motion. On the basis of resting @°‘T1scintigraphy and the change in asynergy, regions were dividedinto three groups. Group 1 consisted of 14 regions that exhibitedresting 2o1@flredistribution. Thirty-seven regions without redistribution constituted Groups 2 and 3. Group 2 consisted of 14regions in which wall motion abnormalities improved after revascularization. On the other hand, Group 3 consisted of 23regions that had no improvement in wall motion abnormality inspite of revascularization.

Statistical AnalysisAll data were expressed as the mean ±standard deviation. The

non-paired Student's t-test and F-test were used to compare dataamong the groups. The paired t-test was performed to determinethe statistical significance from the paired data. The chi-squaretest was used to determine the significance of the difference inthe rate of occurrence. A probability (p) value of less than 0.05was considered to be significant. Interobserver variability of re

TABLE 1Mean and Standard Deviation of Regional 201TlUptake in

Twelve Normal Subjects

Mean±s.d.

1719RestingThallium-201Scanfor Viability•Monet al

50 60 70 90(%) 100

First examination

Regionalthallium-201uptake

80

50 60 70Obwver-1

Regional thalllum-201 uptake

80

gional 2o1@fluptake was calculated for 24 regions. The reproducibility of 201'fluptake was determined by re-scoring the thalliumscansfor 18regionsin three patients.

RESULTS

ObserverVariabilityand Reproducibilityof Regional20111 Uptake

The interobserver variability ofregional 201Tluptake foranalysis of 24 regions from four patients was excellent(interobserver variability r = 0.874, y = 0.97x + 0.98, Fig.3). Studies of the reproducibility of regional 201T1uptakewas performed in three patients within a 3-mo interval.Figure 4 demonstrated that determination ofregional 201T1uptake in the same patient was reproducible (r = 0.834,y = O.99x —0.31).

Changein LVEFand Hemodynamics

Six patients had improved global LVEF after revascularization (before: 41.3% ±6.3% versus after 53.8% ±6.4%; p < 0.01). Four of the six patients had the regionswith resting 201T1redistribution (Fig. 5). The LVEF of theother eleven patients did not improve significantly afterrevascularization (before: 34.6% ± 6.9% versus after:34. 1% ±8.6%: n.s.). Three of these eleven patients hadregions with resting 2OVflredistribution and improved wallmotion after revascularization. Systemic blood pressureand heart rate did not change in patients with and withoutimproved ejection fraction (Table 2).

FIGURE3. Interobsevervariabilityinregional@°@Tluptakefromfour patients. These data representthe result of analysisof 24regions.

100

(%)

90

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E@ 70

@0Cg60

(I)

50

4040

n=18y = - 0.31 + O.99xr =0.834

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FIGURE4. Reproducibilityinregional201Tluptakefromthreepatients. Each was restudied twice within 3 mo. These datarepresent the result of analysis of 18 regions.

Changein RegionalWall Motion

Figure 6 shows changes in regional wall motion of thethree groups. Eleven patients (78.6%) of Group 1 hadimproved wall motion after revasculanzation. As definedin classification of the groups, regional wall motion ofGroup 2 improved after revascularization, and that ofGroup 3 did not improve. The grade of wall motionabnormality before revascularization is shown in Table 3.The occurrence ofdyskinesis or akinesis was more frequentin Group 3 than in the other two groups (p < 0.05). Mostregions of Group 1 exhibited severe hypokinesis.

__I_ ---‘ _L ..1

FIGURE5. LVEFbeforeandafterrevascularization.Sixpatients revealedimprovedejectionfractionmorethan5%asshowninleftside.

100

C,')

90

80

70

60

n=24y=O.@+O.97xF = 0.874

(%)60c,l

I-

0

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S

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0 50

f@f40

30

20

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@eT0re AlterPtswlthimprovedEF

@erore AlterPtswlthoutimprovedEF

1720 TheJournalof NuclearMedicine•Vol.32 •No.9 •September1991

NumberSystolic pressureDiastolicpressureHeartratePatients

with improvedEF6BeforeAfter1

32 ±15134 ±2185

± 570 ± 976

± 779 ±11Patients

withoutimprovedEF1 1BeforeAfter1

28 ±14125 ±1677

±1080 ±1075

± 778 ± 8

Wall MotionGradeTABLE3

Abnormality Before RevasEach Patient Groupcularization

inSevereTotalhypokinesis

AkinesisDyskinesisGroup

11 49 (64.3%) 5 (35.7%)0(0%)Group2145 (35.7%) 9 (64.3%)0(0%)Group3233 (11.5%) 16 (69.6%)4(17.4%)p.cz

0.05

TABLE 2Hemodynamics Before and After Revascularization

Severityof CoronaryArteryStenosisand CollateralFlow

Table 4 shows the severity ofcoronary artery stenosis ofthe involved vessel and occurrence of collateral flow ineach region. The severity of coronary artery stenosis wasnot different between the three groups. In addition, theoccurrence of collateral flow did not differ between thethree groups.

Comparison of Regional @°@TlUptake

Table 5 shows regional 20Tl uptake on resting 201T1initial and delayed images in the three groups. Only inGroup 1 did regional 2OVfluptake increase from the initialto the delayed image (p < 0.001). The regional 201T1uptakeon the delayed image was higher not only in Group 1 butalso in Group 2 than in Group 3 (p < 0.001). Moreover,it is noteworthy that even on the initial image the regional201T1uptake of both Group 1 and Group 2 was higherthan that of Group 3 (p < 0.05). Interestingly, the initialregional 201T1uptake was highest in Group 2.

Case Presentation

A 70-yr-old man who suffered from acute myocardialinfarction on April 4, 1989 came to our hospital for cardiacexamination in November 1989. He did not complain of

FIGURE 6. Comparisonof segmentalwallmotionabnormalitybefore and after revascularizationbetween the three groups.N = normal wall motion, H = hypokinesis, SH = severe hypokinesis,A = akinesis,and D = dyskinesis.

chest pain after his acute infarction. Electrocardiogramrevealed poor R-wave progression on leads Vl , V2 andV3. The treadmill test provoked significant ST depressionon leads V4, VS and V6, although he did not complain ofchest pain. A rest-injected 201Tlscan on February 3, 1990revealed a perfusion defect on anteroseptal segments withincomplete redistribution (Fig. 7). On radionuclide yentriculography, segments 2, 3, and 6 exhibited severe hypokinesis and LVEF was 41 %. Coronary arteriography onFebruary 13, 1990 revealed complete obstruction of theLAD with collateral flow from the right coronary artery,which was treated successfully to 0% with PTCA. Theradionuclide ventriculography 1.5 mo after PTCA showedimproved wall motion and ejection fraction was 48% (Fig.8).

DISCUSSIONInitial myocardial uptake of 201T1is known to depend

on blood flow and myocardial extraction fraction, whichwas defined under physiologic conditions (22-24). Therefore, the initial uptake of 201Tlis proportional to myocardial blood flow. In this study, patients with 99% or morestenosis of other coronary arteries were excluded. Theintracellular accumulation of 201T1is caused by a passivetransport mechanism by the transmembrane electropotential gradient (25). Consequently, myocardial uptake of201T1is considered to mean the presence of viable muscle.

Belier et al. explained that 201Tl redistribution in fixedcoronary artery stenosis is the result of the slower intrinsicwashout rate at a reduced perfusion level (26, 27). Bergeret al. reported that resting 201T1redistribution was observedin regions with decreased blood flow at rest (12). Inpartially infarcted regions, however, 201T1 redistributionmay be related not only to the severity of coronary artery

N

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D

Before AfterGroup I

Before After Before AfterGroup2 Group3

1721Resting Thallium-201 Scan for Viability •Mori et al

i@0,@:4j@0?@

TABLE4Severity of Coronary Artery Stenosis and Occurrence of

Collateral Flow in Each Patient Group

Coronaryarterystenosis

Is

Groupi1476107Group214471211Group3237114119n.s.

TABLE 5Comparison of Regional 20111Uptake Between theThreeGroupsInitial

imageDelayedimageGroup

1 77.1% ±7@/*85.1% ±6@4%*tGroup2 83.5%±7@9%fl82.3% ±7.1%@Group3

71.8%±6.2%71.2%±7.0%*

Versus Group 3, p

rest-injected 201T1redistribution, which had a higher 201T1uptake, exhibited improved myocardial function after revascularization. Tamaki et al. reported that in areas witha 20tTlpersistentdefect,areaswithan increasein ‘8F-2-fluoro-deoxyglucose (FDG) uptake exhibited a milder decrease in ‘3N-ammoniaperfusion and milder wall motionabnormality than did areas without an increase in FDGuptake (31). The ‘3N-ammoniadistribution was proportional to myocardial perfusion (32). Therefore, the higher201T1uptake in regions with improved wall motion withoutredistribution may indicate that their blood supply wasnot low enough to cause tissue necrosis. Accordingly, theseregions may also represent hibernating myocardium. Failure of201Tl redistribution to occur in Group 2 may reflectthe fact that perfusion defects were not as severe as thosein Group 1. The prevalence of akinesis was, however,more frequent in Group 2 than in Group 1, suggestingthat severe myocardial dysfunction in Group 2 mightresult from more viable muscle loss.

The prevalence of akinesis or dyskinesis was frequentand the regional 201Tluptake was lower in Group 3, whichdid not demonstrate any improvement. These findingsindicate that regions in Group 3 had the most markedviable muscle loss. The standard deviation in the regional2OPfl uptake was, however, large in all three groups and

overlap in the distribution was great. First, it may be oneof the reasons that left ventricular dysfunction due tohibernating myocardium with or without stunning maypersist for a longer period than 1.5 mo when perfusion isrestored. Second, it may be due in part to the resolutionlimits of201Tlimaging. Interobserver variability and reproducibility of regional 201Tluptake in our study was goodbut not perfect. However, this limitation may also reflecta general limitation of imaging that examines perfusionalone, and suggests the need for evaluating myocardialmetabolism (33,34).

Clinical Implications

Myocardial function in regions with severe asynergymay revert in the affected territory when perfusion isrestored. Our results indicate that rest-injected 201Tlredistribution suggests the reversibility of severely asynergicmyocardium, and that high 2o'@fluptake in regions withoutredistribution may predict improvement in myocardialdysfunction after revascularization.

ACKNOWLEDGMENTSThe authors are grateful to Seiji Wake and Torn Kida for their

technical assistance.

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1723Resting Thallium-201Scan for Viability•Monet al

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(continuedfrom page 5A)

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Anterior

Posterior

1724 The Journalof NuclearMedicine•Vol. 32 •No. 9 •September1991

FIRST IMPRESSIONSPURPOSE:This 20-yr-old male patient was referred for bone scanevaluation of left ankle pain. Three-hour delayed images following intravenous injection of 20 mCi of99mTcMDP revealed serendipitous pectoralis muscleuptake of nuclide. Two days prior to imaging the patient experienced mild chest pain after bench pressing200 lb for the first time following a long hiatus fromthe sport.

TRACER:99mTc..MDP

ROUTE OF ADMINISTRATION:Intraveneously

TIME AFTER INJECTION:Three hours

INSTRUMENTATION:Gamma camera

CONTRIBUTORS:Max Rosen, MD and Rachel Powsner, MD

INSTITUTION:Department of Radiology and Department ofNuclear Medicine, University Hospital,Boston, Massachusetts