29. Harris TR. Overholser KA, Stiles RG. Concurrent increases in resistance and transportafter coronary obstruction in dogs. Am .1 Phvsiol 198l;240(Heart Circ Phvsiol9):H262—H273.

30. Yipintsoi T, Dobbs WA Jr. Scanlon PD, Knopp Ti, Bassingthwaighte lB. Regionaldistribution of diffusible tracers and carbonized microspheres in the left ventricle ofisolated dog hearts. Circ Res 1973;33:573—587.

3 1. Goresky CA, Bach GG, Nadeau BE. Red cell carriage of label: its limiting effect onthe exchange of materials in the liver. Circ Res 1975;36:328—351.

32. Bergmann SR. Hack SN, Sobel BE. “Redistribution―of myocardial thallium-20lwithout reperfusion: Implications regarding absolute quantification of perfusion. Am JCardioll982;49:169l-1698.

33. Weich HF, Strauss 1-lW, Pitt B. The extraction of thallium-201 by the myocardium.Circulation1977;56:I88—191.

34. Martin P, Yudilevich DL. A theory for the quantification oftranscapillary exchange bytracer-dilution curves. Am J Phvsiol I964;207:l62—168.

35. Bassingthwaighte JB. Ackerman FH, Wood EH. Applications of the lagged normaldensity curve as a model for arterial dilution curves. Circ Rex 1966;18:398—4I5.

36. Chan IS, GoldsteinAA, BassingthwaitelB. SENSOP:a derivative-freesolverfornonlinear least squares with sensitivity scaling. Ann Biomed Eng I993;21:62I—631.

37. Curry FE. Michel CC. A fiber matrix model of capillary permeability. Microvasc Res1980;20:96—99.

38. L'Abbate A, Biagini A, Michelassi C, Maseri A. Myocardial kinetics ofthallium andpotassium in man. Circulation 1979;60:776—785.

39. Alvarez OA, Yudilevich DL. Heart capillary permeability to lipid-insoluble molecules.J Phvsiol l969;202:45—58.

40. DurãnWN, Yudilevich DL. Estimate of capillary permeability coefficients of canineheart to sodium and glucose. Microvasc Res l978;l5:195—205.

41. Roselli Ri, Harris TR. A four-phase model of capillary tracer exchange. Ann BiomedEng 1979;7:203—238.

42. Hille B. The permeability of the sodium channel to metal cations in myelinated nerve.J Gen Physiol 1972;59:637—658.

43. Hougen Ti, Smith TW. Inhibition ofmyocardial monovalent cation active transport bysubtoxic doses of ouabain in the dog. Circ Res 1978;42:856—863.

44. Hougen Ti, Lloyd BL, Smith TW. Effects of inotropic and arrhythmogenic digoxindoses and of digoxin-specificantibodyon myocardialmonovalentcationtransportinthe dog. Circ Res 1979;44:23—3l.

45. Winkler B, Schaper W. Tracer kinetics of thallium, a radionuclide used for cardiacimaging. In: Schaper W, ed. The pathophvsiology of myocardial perfusion. Amsterdam: ElsevierfNorth Holland: 1979:102—112.

46. Dani JA, Levitt DG. Water transport and ion-water interaction in the gramicidinchannel.Biophvsil981;35:501—508.

47. Reuter H, Stevens CF. Ion conductance and ion selectivity of potassium channels in

snail neurones. J Membrane Biol 1980;57:l03—l 18.48. wn,kler B, Schaper W. The role of radionuclides for cardiac research. In: Pabst HW,

Adam WE, ElI P. HörG, Kriegel H, eds. Handbook ofnuclear medicine, vol. 2: Heart.Stuttgart, New York: Gustav Fischer; 1992:390—407.

49. Krivokapich i, Watanabe CR, Shine K!. Effects of anoxia and ischemia on thalliumexchange in rabbit myocardium. Am J Pkvsiol l985;249:H620—H628.

50. Grunwald AM, Watson DD, Holzgrefe HH ir, Irving iF, BelIer GA. Myocardialthallium-201 kinetics in normal and ischemic myocardium. Circulation I981;64:610—618.

5 1. Budinger TF, Yano Y, Huesman RH, et al. Positron emission tomography ofthe heart.Physiologist l983;26:31—34.

52. Nielsen AP, Moms KG, Murdock R, Bruno FP,Cobb FR. Linear relationshipbetweenthe distribution of thallium-201 and blood flow in ischemic and nonischemicmyocardium during exercise. Circulation 1980:61:797—801.

53. Pohost GM, Okada RD, O'Keefe DD, et al. Thallium redistribution in dogs with severecoronary artery stenosis of fixed caliber. Circ Res l981;48:439—44.6.

54. Cousineau DF, Goresky CA, Rose CP. Simard A, Schwab AJ. Effects of flow,perfusion pressure, and oxygen consumption on cardiac capillary exchange. J App!Physioll995;78:1350—1359.

55. Okada an, Leppo JA, Strauss HW, Boucher CA, Pohost GM. Mechanisms and timecourse for the disappearance of thallium-201 defects at rest in dogs. Am J Cardioll982;49:699—706.

56. Okada RD, Jacobs ML, Daggeti WM, et al. Thaiiium-201 kinetics in nonisehemiccanine myocardium. Circulation 1982;65:70—77.

57. Leppo iA, MeerdinkDi. A comparisonof the myocardialuptakeof a technetiumlabeledisonitrileanalogandthallium.CircRes 1989;65:632—639.

58. Lcppo JA, Meerdink DJ. Comparative myocardial extraction of two technetium

labeled BATO derivatives (SQ30217, SQ32014) and thallium. J Nuc! Med 1990;31:67—74.

59. Maublant JC, Gachon P. Moms N. Hexakis (2-methoxy isobutylisonitrile) technetium99m and thallium-201-chlor,de: uptake and release in cultured myocardial cells. JNuc!Med 1988;29:48—54.

60. Marcus ML, Kerber RE, Erhardt iC, Falsetti HL, Davis DM, Abboud FM. Spatial andtemporal heterogeneity of left ventricular perfusion in awake dogs. Am Heart J1977;94:748—754.

61. King RB, Bassingthwaighte JB, Hales iRS, Rowell LB. Stability of heterogeneity ofmyocardial blood flow in normal awake baboons. Circ Res 1985;57:285—295.

62. Bassingthwaighte JB, Malone MA, Moffett TC, ci al. Molecular and particulatedepositions for regional myocardial flows in sheep. Circ Res 1990;66:I328-1344.

63. CrankJ. Themathematicsofd@ffrsion.Oxford:ClarendonPress;1956.64. Pollock F, Blum JJ. On the distribution of a permeable solute during Poiseuille flow

in capillary tubes. Biophys J l966;6: 19—29.65. Aroesty J, Gross iF. Convection and diffusion in the microcirculation. Microvasc Res

1970;2:247—267.66. Gonzalez-Femandez JM, Atta SE. Concentration of oxygen around capillaries in

polygonal regionsof supply.MathBiosci l972;13:55—69.

1.3 mm, Noflow60 = 8.9 ±2.8 mm). Late t1,@was significantlyshorter for Nofiow30(52.3±5.3 mm)and the Noflow60(50.9±4.3mm),compared to the Control hearts (74.1 ±6.6 mm, p < 0.05).One-hour fractional clearances were significantly greater for theNoflow3O and Noflow60 hearts (0.65 ±0.01 and 0.65 ±0.01,respectively)compared to the Controls (0.55 ±0.01, p < 0.05). Inhearts givenTritonX-100,there was a markedlyincreased fractionalclearance of 0.96 ±0.01 (p < 0.01 compared to Controls). Electronmicroscopy showed evidence of mild injury in the Noflow30 hearts,more extensivedamage inthe Noflow6ohearts and severe irreversible injuryin TritonX-100 hearts. Conclusion: Myocardial @Tcteboroxime uptake and clearance kinetics are significantly altered inmildlyand moderately injured reperfused myocardium. Technetium99m-teboroxime clearance is markedly accelerated in the sethng ofovert damage to cell and organelle membranes induced by TritonX-100.Key Words technetium-99m-teboroxime; kinetics; reperfused;nonviable; myocardium

J Nuci Med 1997;3&274'-279

This study evaluates @Tc-teboroximeuptake and clearance kinetics in reperfused infarcted myocardium. Methods In 47 isolatedbuffer perfused rat hearts, 17 had normal flow (Control), 13 had 30mm of no flow followed by reflow (Noflow30)and 11 had 60 mm ofno flow followed by reflow (Noflow6O).A 1-hr uptake phase wasbegun by normally perfusing all 41 hearts with @Tc-teboroximedoped buffer. After uptake, a 1-hr clearance phase was begun byswitching to a @“Tc-teboroxime-freebuffer. Technetium-99m activity was monitored with a Nal probe. Triton X-100, a membranedetergent, was given after tracer loading to six additional hearts.Results: Controland Noflow30hearts showed near linearand rapiduptake, while Noflow60 hearts showed curvilinear and significantlyless uptake than predk@ted. i@Jlthree of these groups showedbiexponential clearance. Early t1,@was not significantly different forthe three groups (Control = 6.3 ±1.9 sam mm, Noflow3o = 5.4 ±

Received Dec. 27, 1995; revision accepted June 13, 1996.For correspondence or reprints contact Gerald Johnson Ill,PhD, WilliamK Warren

Med@aIResearchInstitute,6465SouthYale,Suite1010,Tulsa,01<74136-7862.

274 THEJOURNALOFNUCLEARMEDICINE•Vol. 38 . No. 2 •February1997

Kinetic s of Technetium- 99m-Teboroxime inReperfused Nonviable MyocardiumRobert D. Okada, David K. Glover, Jeffrey D. Moffett, Delia Beju and Gerald Johnson IIIWilliam K. Warren Medical Research Institute, University of Oklahoma Health Sciences Center, Tulsa, Oklahoma

by on March 16, 2020. For personal use only. jnm.snmjournals.org Downloaded from

ISOLATEDHEART UT%@

a ii@m@i@ @s

. I, wSSN@@S NIlNS•@I@

[El'

Teciinetium-99m-teboroximeisamyocardia!imagingagentthat has 90% first-pass extraction (1), uptake that increaseslinearly with flow (2—4)and clearance that decreases withdecreased flow in viable myocardium (5—10).Because 99mTc@teboroxime is potentially a better flow marker than thallium orsestamibi, its use has been proposed to assess reperfusion afterthrombolytic therapy (2,11). However, the uptake and clearancekinetics of 9@Tc-teboroxime in reperfused nonviable myocardium have not been thoroughly reported. This study investigates these kinetics in a perfused rat heart model of acutemyocardial infarction followed by reperfusion and in a mode! ofcell !ysis induced by Triton X-lOO. We postulated that metabo!ic and structural abnormalities created by infarction andreperfusion injury would affect 9@Tc-teboroxime myocardialuptake and clearance kinetics despite normalization of flow.

MATERIALS AND METHODS

Isolated, Perfused Heart PreparationMale Sprague-Dawley rats (weighing 375 to 400 g) were

anesthetized with 65 mg intraperitoneal sodium pentobarbita!.After deep anesthesia was achieved, 400 units heparin wereadministered intravenously and the heart was removed through arapid parasternal thoracotomy. The heart was then immediatelyplaced in modified Krebs-Hense!eit buffer at 4°C.The aortic stumpwas then attached by suture to the cannula of the perfusionapparatus which is shown in Figure 1. A Masterfiex pump (ParmerInstruments, Burlington, IL) controlled the perfusion rate of thebuffer and removed sinus drainage. Flow was held constant at 12mi/mm without recirculation. Temperature of the perfusate wasmaintained at 37°Cby a water bath.

All hearts were retrogradely perfused using a modified KrebsHenseleit buffer containing (mmollliter): 1.25 KH2PO4, 0.56MgSO4, 1.51 CaC12, 4.88 KC!, 0.833 EDTA, 127 NaC!, 20NaHCO3 and 5.77 pyruvate. This buffer was continuously bubbledwith 95% O2/5%CO2 and maintained at pH 7.4 ±0.05 and 02>300% saturation. Triton X-lOO perfusate was prepared by adding100% Triton X-!00 to the Krebs-Hense!eit buffer to make a 0.5%solution of Triton X-100 by volume.

A small saline-filled, latex balloon-tipped catheter was passedthrough a slit in the left atrial appendage and into the left ventricle.The balloon was inflated to achieve a pressure of 100 mmHgthroughout the experiment. Pressure was measured by a Stathamp23d pressure transducer connected to the left ventricular catheter.All hearts were atrially paced (Model 5320, Medtronic, Minneapohs, MN) at 300 bpm. This constant work load preparation wasused since functional data was not felt to be relevant in this model.Temperature and oxygen saturation of the perfusate were monitored online by a probe. The pH was monitored by a separate inlineprobe. Left ventricular pressure, temperature, pH and oxygen levelswere continuously recorded on a physiological recorder.

As shown in Figure 1, two buffer storage tanks were filled with1 liter of the Krebs-Henseleit buffer. The uptake phase tank was

Isolation

Baseline

2Omim@es 60mñites 60mñ@es

No FlowIReflow

( Omkiiis. / Omims.)(3OmñmN160mñ@is)(60mñ@re160m1i@(0mñ@e. /OmIMss)

FIGURE2. Expetimentalprotocol.

doped with 500 @Ci @°‘Tc-teboroxime,whereas the clearance andcontrol tank was nonradioactive. The buffer storage and waste areawas shielded from the measurement area by lead walls. An IBMPC-AT computer was used to switch between the radioactiveuptake and the nonradioactive clearance buffers at the appropriatetime by controlling solenoid valves. The computer also controlledthe perfusion rate ofthe Masterfiex pump used to deliver the bufferand remove the sinus drainage. Myocardia! 99mTc..teboroximeactivity was monitored at 1-mm intervals using a lead collimatedsodium iodide scintillation detector placed in close proximity to theheart. Time-activity curves were recorded for each experiment.These curves were displayed on a computerized multichannelanalyzer. Myocardia! clearance curves were corrected for background and decay.

Technetium-99m-Teboroxime PreparationKits for the preparation of 99mTc..teboroximewere supplied in a

lyophilized form by Squibb Diagnostics, Princeton, NJ. A vial of99mTcteboroxime was reconstituted by addition of 25 mCi of99mTcpertec@etate The via! was then heated for 15 mm to 100°Cusing a heating block. After cooling to room temperature, paperchromatography was performed to determine the percentage ofsoluble contaminants and reduced hydrolyzed technetium. Whatman 31 ET chromatography strips (1.3 X 11 cm) and twoindividual mobile-phase solvent systems were used to determinethe radiochemical purity of the prepared product. The developedchromatographs were air-dried and counted. The results indicatedthat radiochemica! purity was 94.0 ±0.4%. The compound wasstored at room temperature until used, which was within 6 hr ofpreparation.

Electron MicroscopyUltrastructural injury was assessed by transmission electron

microscopy. At the end of the experiment, two hearts from eachgroup were perfused with 2% glutaraldehyde in 0.1 M cacodylatebuffer at pH 7.4. The hearts were postfixed in 1% osmiumtetroxide, en bloc stained with 0.5% aqueous uranyl acetate,dehydrated in graded ethanol and embedded in PolyBed 8 12. Thinsections were obtained with MT-6000 and MT-2B ultramicrotomesequipped with diamond knives. The sections were contrasted withuranyl acetate and lead citrate and were examined in a Zeiss 109electron microscope operated at 80 kV.

Expe@mentaI Protoc@In 47 experiments, rat hearts were isolated, mounted on the

perfusion apparatus and perfused at 12 ml/min for 20 mm to ensurestabilization (Fig. 2). In 17 control hearts, normal flow rates werecontinued for an additional 30 mm; in 13 hearts, flow wascompletely shut off for 30 mm before resuming normal flow (30mm no flow/reflow group); and in I I hearts, flow was completelyFiGURE1. isolated bufferperfused rat heart apparatus.

TECHNETIUM-99m-TEBOROXIME KINETICS IN REPERFUSION •Okada et a!. 275

99mTc-Tthorexime

__L— __EM

@Tc@@

T@n@ U@ Clearance

I @I I

Tieatment Groups

c@30mktasflowh@flow60mm asflow/reflow

TritonX-lOO

by on March 16, 2020. For personal use only. jnm.snmjournals.org Downloaded from

FractionalUptakecurveGroupclearanceindex Earlyt1,@ Latet1,@

0.55 ±0.01 12 ±0.05 6.3 ±1.9 74.1 ±6.6

TABLE IMyocardial Teboroxime Uptake and Clearance Parameters

O@nl@onoIt@is Cure.mdix

u_ curesmdix . P@:::d

IPmm@d

Control(n=17)

Noflow3o(n=13)

Noflow60(n= 11)

ThtonX-100(n = 6)

0.65 ±O.O1@ 1.2 ±0.07 5.4 ±1.3 52.3 ±5•3*

0.65±O.O1@0.9±0.05* 8.9±2.8 50.9±43@

0.96 ±O.O1@ 1.2 ±0.05 2.0 ±0.2* 20.1 ±0.8*

Mean ±s.e.m.; *p < 0.05 compared to control; t1,@= time to reachone-halfinitialactivityearly= firstexponent inbiexponentialnonlinearcurvefit;late = second exponent inbiexponentialnonlinearcurve fit;Noflow30=30-mmno flow/reflowgroup NOflOW6O= 60-mmno flow/reflowgroup.

EthicsAll experimental animals were handled in accordance with the

Position of the American Heart Association on Research AnimalUse and the approval of the Institutional Animal Care and UseCommittee of the University of Oklahoma Health Sciences Center.

RESULTS

GenaralThe left ventricular balloon pressure was maintained at 100

mmHg, and the hearts were paced at 300 bpm throughout theexperiments. Visually, contractility ceased during no flow andresumed after reflow in all experiments.

Myocardial UptakeTable I lists the myocardial 9@Tc-teboroxime uptake curve

indices for the four groups. Normal control hearts demonstratednear linear and rapid myocardia! 9@Tc-teboroxime uptake,with a curve index near unity (1 .16 ±0.05). The 30-mm noflow/reflow group also demonstrated near linear and rapiduptake, with a curve index identical to control (1 .16 ±0.06,p = ns). However, the 60-mm no flow/reflow group demonstrated a curvilinear uptake, with a curve index of 0.90 ±0.05(p < 0.05 compared to control and 30 mm no flow/reflow). TheTriton X-lOO hearts demonstrated a curve index similar to thecontrol group, since 99mTc..teboroxime was administered to thegroup during control conditions.

Figure 4 demonstrates the group mean myocardia! uptakecurves for the first 5 mm after the onset of the infusion. Thesefirst 5 mm were felt to be most relevant to a bolus injection inpatients. At 5 mm, uptake was significantly greater for thecontrol and the 30 mm no flow/reflow group compared to the 60mm no flow/reflow group (p < 0.05). Triton X-lOO heartsdemonstrate an uptake curve similar to that of controls.

Myocardial ClearanceFigure 5 demonstrates the mean myocardia! 9@Tc

teboroxime clearance curves for the control, 30-mm no flow/reflow, 60-ruin no flow/reflow and Triton X-100 groups. Allfour groups demonstrated a biphasic clearance pattern. Myocardial retention was less for the 30-mm no flow/reflow and the60-min no flow/reflow groups compared to control at everytime point (j < 0.01). The Triton X-lOO hearts demonstrated aneven lower retention at every time point compared to the otherthree groups (j < 0.01).

When modeled, all four groups demonstrated a biexponentialclearance (Table 1). Early t112was not significantly different for

FIGUREa Schematic diagram ofmethodforcalculatinguptakecurveindex.

shut off for 60 mm before resuming normal flow (60 mm noflow/reflow group). Next, a I-hr @‘@Tc-teboroximeuptake phasewas begun by switching to the radioactive buffer tank perfused at12 ml/min for 60 mm. At the end of the 60-mm uptake phase, a1-hr clearance phase was begun by switching to the nonradioactivebuffer at 12 mI/mm. Technetium-99m-teboroxime activity wasmonitored throughout the 120-mm period after tracer administration.

In six additional hearts given Triton X-l00, a protocol similar tothe control hearts was used. Triton X-lOO is a nonionic detergentwhich lyses cell membranes. Technetium-99m-teboroxime wasadministered during control conditions, since little uptake wouldhave occurred after Triton X- 100 treatment. However, during theclearance phase, hearts were perfused with Krebs-Henseleit buffercontaining 0.5% Triton X-lOO at 12 ml/min.

Data AnalysisFor each individual heart, background counts taken for 5 mm

before the 99mTcteboroxime uptake phase were averaged andsubtracted from the activity recorded on the multichannel analyzerfor each minute of clearance. The background-subtracted countswere then corrected for @“@Tcdecay. The background-subtracted,decay-corrected counts were then used to calculate fractional99mTcteboroxime washout. Time-activity curves were normalizedas a percentage of peak uptake. Data from individual experimentsalso were averaged to obtain mean curves for each group.

To quantitatively compare the shape of the @Tc-teboroximeuptake curves, an uptake curve index was calculated (Fig. 3). Theuptake curve index was the ratio between the actual peak myocardial uptake and the peak myocardial uptake predicted from linearregression analysis of the uptake curve. Thus, an uptake curveindex less than 1.0 would indicate a plateauing ofthe uptake curve.

Curve-Fithng TechniqueNonlinear regression analysis was used to fit clearance curve

data by means of automated curve-fitting software using a Levenburg-Marquardt least squares algorithm (Tab!eCurve 2D, JandelScientific, San Rafael, CA). The best fit statistic used was the r@value.

S@caI AnalysisOne-way analysis of variance (ANOVA) procedure (Crunch

Statistical Software, San Diego, CA) was used to analyze groupdifferences. When the assumption of homogeneity of varianceamong groups was violated, the equivalent nonparametric(Kruskal-Wallis) analysis was used. Tests of mean differenceswere conducted by analysis with t-tests using the Bonferronicorrection for multiple tests. A difference was considered to bestatistically significant if p < 0.05. Data were reported as mean ±s.e.m.

@ms(m@se)

276 THEJOURNALOFNUCLEARMEDICINE. Vol. 38 •No. 2 â€F̃ebruary1997

by on March 16, 2020. For personal use only. jnm.snmjournals.org Downloaded from

0 1 2 3 4 S

4.

*

1@

0 10 20 30 40 50 50

40ce

t3000

1000@

FiGURE6@Representativeelectronmk@rographfroma controlheart.S

controls (0.55 ±0.01, p < 0.05). Triton X-lOO hearts demonstrated an even greater fractional clearance (0.96 ±0.01, p <0.05) compared to the other groups.

Electron MicroscopyFigures 6, 7, 8 and 9 represent electron micrographs from

control, 30-mm no flow/reflow, 60-mm no flow/reflow andTriton X-lOO hearts, respectively. Control hearts demonstratednormal appearance ofmitochondria and myofibrils (Fig. 6). Thefew minor abnormalities noted in the control hearts were mostlikely due to processing of the tissues for observation. The30-mm no flow/reflow hearts demonstrated normal appearancein most areas as shown in Figure 7. However, some evidence ofinjury to mitochondria was demonstrated by swelling of themitochondrial matrix and presence of relatively small intramitochondrial amorphous densities. Some evidence of cell swelling and bleb formation was also noted. The 60-mm no fowlreflow hearts, while having patches of normal-appearingmyocardium, had substantially more injured tissue that provided evidence of more severe injury (Fig. 8). Variations inmitochondrial size indicative of swelling were noted along withclearing of the mitochondrial matrix. Large electron-denseinclusions were present in many mitochondria. Disruptions inthe sarcoplasmic reticulum were observed along with irregularZ bands in some areas. Triton X-l00 hearts demonstrated

FIGURE7. Representabveelectronmicrographfroma 30-mmnoflow/reflowhead

FIGURE4. Meandecay and background-corrected @c-teborodmemyocardialuptake curves for the four groups. *p< 0.05 from NOflOW6O.

the control (6.3 ±1.9 mm.), 30-mm no flow/reflow (5.4 ±1.3min) and 60-mm no flow/reflow groups (8.9 ±2.8 mm., p =ns). Triton X-l00 hearts, however, demonstrated a significantlyshorter early ti,2 (2.0 ± 0.2 min, p < 0.05) compared tocontrols. Late t112was significantly shorter for the 30-mm noflow/reflow group (52.3 ± 5.3 mm.) and the 60-mm noflow/reflow group (50.9 ± 4.3 mm.) compared to controls(74.1 ±6.6 mm., p < 0.05). Triton X-lOO hearts demonstratedan even shorter late t112(20. 1 ±0.8 mm., p < 0.05) comparedto other groups.

Table 1 demonstrates the 1-hr fractional myocardial 9@'Tcteboroxime clearances for the control, 30-min and 60-ruin noflow/reflow groups. Fractional clearances were significantlygreater for the 30-mm and 60-mm no flow/reflow groups(0.65 ± 0.01 and 0.65 ± 0.01, respectively) compared to

F1GURE5. Mean decay and background-corrected @c-teboroxImemyocardial clearance curves for Control, 30-mm no flow/reflow,60-mm noflow/reflowand TritonX-100-treatedhearts. *p< 0.01 compared to control.

100

go

so

70

so

so

40

30

20

10

0

I ‘a

¶urns (minuts.)

TECIn@Enui@t-99m-TEBoRoxIMEKINETICSm@REPERFUSION•Okada et a!. 277

by on March 16, 2020. For personal use only. jnm.snmjournals.org Downloaded from

I

@_@@

- .@@

j@a@

. . @@:v@@ .,@@

@@ ,=@-@@ $@@ @‘

.. *@p ,@• ‘

@ ‘. .@@@sR@S ;•... ,

a5

the mildly injured group and a reduced volume ofdistribution inthe severely injured group. The first 5 mm of uptake wereanalyzed separately, since it was felt that this portion of thecurve was most relevant to bolus administration in patients.This analysis also demonstrated reduced uptake in the Noflow60 group compared to both control and Noflow30 groups.

Regarding myocardial uptake kinetics, Maublant et a!. (14)have reported an uptake half-time of less than 2 min for

@Tc-teboroxime in cultures of normal-beating newborn ratmyocardial cells. Smith et al. (4) fitted @Tc-teboroximetime-activity uptake curves from a canine coronary occlusionmodel to a two-compartment, first-order kinetics mode!. Theyfound that the washin parameter k21 decreased significantlywhen flow decreased. Abraham et a!. (15) used a 60-mmocclusion followed by reperfusion swine model and found thatinfarct/normal zone @Tc-teboroxime ratios were lower thancorresponding blood flow ratios after 60 mm of reperfusion.They concluded that @Tc-teboroximerequires viable myocardium for retention and is not exclusively a tracer of blood flowwhen imaged 5—7mm after injection.

The effects of metabolic factors on 9@Tc-teboroxime myocardial uptake has been studied in mono!ayers of contractileheart cells. Kronauge et al. (16) found that incubation withcationic membrane transport inhibitors had little effect onuptake; however, metabolic inhibitors had a modest influence.Maublant et al. (1 7) found that 9@'Tc-teboroxime uptake wasdecreased at low temperature, while metabolic inhibition had noeffect. They also found that osmotic cell lysis had no definiteeffect on tracer uptake. This is somewhat in contrast to thecurrent study that demonstrates markedly reduced 9@Tcteboroxime retention after Triton X-lOO, a membrane detergent.However, the differences between these two studies include thefacts that the Maublant model had no flow during the entirestudy and that osmotic lysis does leave myocardia! membranefragments intact.

Myocardlel QearanceThe current study demonstrates that normal myocardium has

a biexponentia! 9@°Tc-teboroximeclearance curve with a fastfollowed by slow component. This is in agreement withprevious reports (1, 16). Previously, however, the clearancekinetics in reperfused infarcted myocardium have not been wellstudied. In the current study, we found that mildly and severelyinjured myocardium demonstrates biexponentia! and increased60-mm fractional clearance compared to controls. The fasterclearance was found to be due to the differences in the late slowcomponent rather than the early fast clearance component. Pienet a!. have reported slightly faster clearance from myocardiumsubjected to 45 min of coronary occlusion followed by 30—45mm of reperfusion (12). However, the presence or absence ofinfarction was not mentioned.

Differential myocardial @Tc-teboroxime clearance kineticspreviously have been reported in noninfarcted viable tissue.Myocardial clearance from noninfarcted viable tissue is relatedto blood flow and is increasedwith higher than normal flowrates and decreased with lower than normal flow rates(3,5,6,9,10,18). This change in clearance rate has been attributed to changes in the early t112by some investigators (7) and tochanges in the late t112by others (1). The change in clearancerate in low flow states has been shown to be due to acombination of hypoxia and reduced flow per se (8).

This study demonstrates markedly accelerated 9@Tcteboroxime clearance after exposure to Triton X-lOO, a membrane detergent. This agent induced a rapid and irreversiblesevere injury to sarcolemmal and organel!e membranes. Thus,

,,.

I-V

4,,.@

.,;,fr @..

.@. V.. :@

FiGUREa. Representath,eelectronmk@rographfroma 60-mmnoflow/reflowhead

extensive alterations as seen in Figure 9. Many mitochondriademonstrated marked disruption, reduced numbers or absenceof cristae and a lucent matrix. Large amorphous densities wereoften observed as were irregular Z bands. The most significantchanges were the severe sarcolemmal and mitochondrial disruption. These alterations to cell membranes and mitochondriawere consistent with severe irreversible cell injury.

DISCUSSION

Technetium-99m-Teboroxime UptakeTechnetium-99m-teboroxime has been shown to be taken up

by viable myocardium with uptake related to blood flow(2,3, 12). Leppo and associates have shown that peak 9@Tcteboroxime extraction determined by paired indicator dilutiontechnique also correlated with blood flow (13). However, thekinetics of 99mTcte@roxime uptake in normal and nonviablemyocardium have not been well studied.

The current study demonstrated that 9@Tc-teboroxime myocardia! uptake was taken up with a nearly linear shape and anuptake curve index near unity for control and 30-mm noflow/reflow hearts. However, the more severely injured 60-mmno flow/reflow hearts demonstrated curvilinear uptake with asignificantly reduced curve index compared to the other twogroups. This would suggest a normal volume of distribution in

FIGURE9. Representabveelectronmicrographfroma TritonX-100-treatedhead

•‘@@:‘ @•@ ?@@

p •

:,@@ . @- ‘•@-@-@.

@‘i; @:@ ‘a

@‘

@ 4.@,e

, J_ ‘@

.‘-@

..

.@ ,\@.@@

278 THEJOURNALOFNUCLEARMEDICINE•Vol. 38 •No. 2 •February1997

•øi@@'@'@-41 ‘@@*@‘

v.@@ @‘@ ,@r \

@At.:a@::@ im1@#@f;

@‘@‘

*@

by on March 16, 2020. For personal use only. jnm.snmjournals.org Downloaded from

99mTcteboroxime retention appears to be highly dependentupon sarcolemma! integrity.

PotentialStudyUmitationsThe current study used Krebs-Hense!eit buffer perfusion.

Dahlberg et a!. (19) and Rumsey et a!. (20) have shown that9@Tc-teboroxime binds to blood components. This bindingcauses reduced 9@Tc-teboroxime extraction and increases theapparent rate of overall cardiac clearance. In pilot studies, wehave also observed faster overall clearance in red blood cellperfused hearts. Furthermore, the faster clearance from infarcted reperfused myocardium compared to controls is againobserved.

CONCLUSIONNormal and mildly injured reperfused myocardium demon

strates near linear and rapid 99mTc@teboroxime uptake with acurve index near unity. Severely injured reperfused myocardium demonstrates a curvilinear uptake, with a reduced curveindex. Myocardia! 99mTc@teboroxime clearance is biexponentia!from infarcted reperfused myocardium, with significantlyshorter late t112in infarcted reperfused myocardium comparedto normal. This results in significant increases in 60-mmfractional clearance in infarcted reperfused myocardium. Technetium-99m-teboroxime myocardial clearance is greatly accelerated after Triton X-lOO, indicating that @Tc-teboroximeretention is highly dependent upon sarco!emmal integrity.

ACKNOWLEDGMENTSWe thank Dr. William Eckelman and Squibb Diagnostics for

their continued support of this investigation and Andrea Lightfootfor her excellent administrative assistance. This study is dedicatedto the William K. Warren Family and Foundation for theircontinued support of medical research.

REFERENCES1. Stewart RE, Schwaiger M, Hutchins GD, Ct al. Myocardial clearance kinetics of

technetium-99m-5Q30217: a marker of regional myocardial blood flow. J Nuc! Med19031:1183—1190.

2. DiRoccoRi, RumseyWL,KuczynskiBL,LinderKE,PirroJP,NarraRK,NunnAD.Measurement ofmyocardial blood flow using a co-injection technique for technetium99m-teboroxime, technetium-96-sestamibi and thallium-201. J Nuci Med 1992;33:I152—1159.

3. BeanlandsR,Muzik0, NguyenN, PetryN, SchwaigerM. Therelationshipbetweenmyocardial retention oftechnetium-99m-teboroxime and myocardial blood flow. JAmCoilCardiol199220:712—719.

4. Smith AM, Gullberg GT, Christian PE, Datz FL. Kinetic modeling of teboroximeusing dynamic SPECT imaging of a canine model. J Nuci Med 1994;35:484—495.

5. StewartRE,Heyl B, O'RourkeRA, BlumhardtR, MillerDD. Demonstrationofdifferential post-stenotic myocardial technetium-99m-teboroxime clearance kinetics after experimental ischemia and hyperemic stress. J Nuci Med 1991;32:2000—2008.

6. Gray WA, Gewirtz H. Compaiison of@'Tc-tebomxime with thallium for myocardialimaging in the presence ofa coronary artery stenosis. Circulation l991;84:l796—l807.

7. JohnsonG, GloverDK, HebertCB, OkadaRD. Earlymyocardialclearancekineticsoftechnetium-99m-teboroxime differentiate normal and flow-restricted canine myocardium at rest. J Nuci Med 1993;34:630—636.

8. JohnsonG, OkadaRD. Glover DK, HebertCB. A combinationof hypoxiaand lowflow reduce myocardial Cardiolec clearance in ischemic myocardium. In: SchmidtHAE, Hofer R, eds. Nuclear medicine: nuclear medicine in research and practice.

Vienna: Schattauer 1991:171—174.9. Johnson G, Glover DK, Hebert CB, Okada RD. Myocardial technetium-99m-labeled

teboroxime clearance derived from canine scans differentiates severity ofstenosis afterdipyridamole. J Nuci Cardiol 1994;1:338—350.

10. Johnson0, Glover DK, Hebert CB, Okada RD Myocardial clearancekinetics ofTc-99m-teboroxime following dipyridamole: differentiation of stenosis seventy incanine myocardium. J Nuci Med 1995;36:l 11—119.

1 1. Heller LI, Villegas Bi, Weiner BH, McSherry BA, Dalhberg 51, Leppo JA. Use of

sequential teboroxime imaging for the detection of coronaiy artery occlusion andreperfusion in ischemic and infarcted myocardium. Am Heart J l994;127:779—785.

12.PieriP, YasudaT, FischmanAJ,AhmadM, MooreR, YaoitaH, 5traussHW.Myocardial accumulation and clearance oftechnetium-99m-teboroxime at l00%, 75%,50%andzerocomnaiy blood flow in dogs.Eur J NucI Med 1991;l8:725—731.

13. Leppo JA, Meerdink DJ. Comparative myocardial extraction of two technetiumlabeled BATO derivatives 17, 5Q32014) and thallium. J NucI Med 1990;3 I:67—74.

14. MaublantJC, MomsN, GachonP. Uptakeand releaseof two new Tc-99m-labeledmyocardial blood flow imaging agents in cultured cardiac cells. Eur J Nuci Med1989;15:l80—182.

15. Abraham 5A, Mirecki FN, Levine D, Nunn A, Strauss HW, Gewirtz H. Myocardialtechnetium-99m-teboroxime activity in acute coronary artery occlusion and reperfusion: relation to myocardial blood flow and viability. JNuc!Med 1995;36:1062—l068.

16. KronaugeSF,ChiuML, Cone iS, Davison A, HolmanBL, JonesAG, Piwnica-WormsD. Comparisonof neutralandcationic myocardialperfusionagents:characteristicsofaccumulation in cultured cells. Nucl Med Biol 1992;l9:14l—148.

17. Maublant JC, Moms N, Gachon P, Renoux M, Zhang Z, Veyre A. Uptake oftechnetium-99m-tebomxime in cultured myocardial cells: comparison with thallium201andtechnetium-99m-sestamibi.J Nuci Med 1993;34:255—259.

18. Marshall RC, Leidholdt EM, 7,hangD-Y, BarneS CA. The effect of flow ontechnetium-99m-teboroxime (5Q30217) and thallium-201 extraction and retention inrabbitheart.JNuciMed l991;32:l979—1988.

19. Dahlberg ST. Gilmore MP, Leppo JA. Interactionof technetium-99m-labeledteboroxime with red blood cells reduces the compound's extraction and increasesapparent cardiac washout. J NucI Cardiol l994;l:270—279.

20. RumseyWL, RosenspireKC, NunnAD. Myocardialextractionofteboroxime: effectsof teboroxime interaction with blood. J Nuci Med l992;33:94—l0l.

KINETICSn@iREPERFUSION•Okada et a!. 279

by on March 16, 2020. For personal use only. jnm.snmjournals.org Downloaded from

1997;38:274-279.J Nucl Med.   Robert D. Okada, David K. Glover, Jeffrey D. Moffett, Delia Beju and Gerald Johnson III  Kinetics of Technetium-99m-Teboroxime in Reperfused Nonviable Myocardium

http://jnm.snmjournals.org/content/38/2/274This article and updated information are available at:

  http://jnm.snmjournals.org/site/subscriptions/online.xhtml

Information about subscriptions to JNM can be found at:  

http://jnm.snmjournals.org/site/misc/permission.xhtmlInformation about reproducing figures, tables, or other portions of this article can be found online at:

(Print ISSN: 0161-5505, Online ISSN: 2159-662X)1850 Samuel Morse Drive, Reston, VA 20190.SNMMI | Society of Nuclear Medicine and Molecular Imaging

is published monthly.The Journal of Nuclear Medicine

© Copyright 1997 SNMMI; all rights reserved.

by on March 16, 2020. For personal use only. jnm.snmjournals.org Downloaded from