ABSTRACTS

WEDNESDAY, APRIL 28, 1982 AM NUCLEAR CARDIOLOGY: NEW APPROACHES TO ASSESSMENT OF PERFUSION 8:30- 10:00

TIl.4LLIU’?I A”iD ,24DIOX”IVE MICROSPIIERY \iilli:un C. Eushong; ililli,un ?. ilcintrab, TX); Yonty 3. ~- Roden’wirner YD, FACC; S:rt,oshi Aklzuki, ITD; Vidya 7. &.nki, :%, PAX; Joi E. Agww-;l, W,, FACC; Xich,ird 11. H?lf:>ni., PTJj, FAX, Presbyterj ,za-Unlv. of pii. &d. Ct?., Phi1.r. , P;I.

Lba!uation of myocardi4 perfusion in p:tit,nt:: i:; current,ly limited to the use of 201-X. Dul? to the .superior irng:inC: properties of ‘Bm(?c) rewnl, efforts have bwn %Ld+ to :Il:velop :? 31 perfusion iwging +;ent.

technetiwn bwed myoc:ji-di- ?herefoi-e, the qanti t::-

tive blood flo;f ch:%r:icteristics of ‘1 %-diars complex wore investig-ited wing 18 open chest dogs, ,jnd corn- pwed to botli ‘3 ‘mnd r,jdiol:lbelled microspheres. In nine dogs, following pc:rtial coronary occlusion (5Cr.: of control flea;) microspheres wre given into the lzft L;trium ,uld ?s di:!rs WYS :jven intr‘ivznously. Does were minut_~r~ili~~d,,,J!~~ti~~jil. harts excised fifteen

;&: n I ‘y” . liultiple samples were: t&-

gl .to ~uari-ultit:itive comparison of myocardial *. Lin:>w regression .ul:ilysis be?vreen %-di,.irs :md

microspi?-r-s yield-d :A me:tn slope of 9.597 and XI r vr;lw of 0.91.: . In nine dogs microspheres were given five ?lin-utes cdter to%.l occlusion followed by simul- taneous intrivenous ‘Zc-di,Lrs ,uld 201 -‘X and sacrificed at 15 minutes. ?c-dizrs and 201-Y were compired to microspheres by lineer regression; wan slope 0.3?4 and r value 0.932 for ?c-diars, ;uld ‘llt?:a? slope O.?%Z ~I& me;>.? r v.&tue 0.944 for 201 ‘3 (X3). At 15 minutes g;;r o;n;;c~;; $ :s-d;yr;fi$md2 7, o,“looo;~;;$;; stmpled normal wocwrdium (NT;). There wzls no signifi- cant difference in blood level for ‘3 :uld “1 between IO ,rnd 15 minutes. 3 complexes G-W be comp;lr:ible to ‘X :ts myocardial blood flo? agents, and hold promise as imaging <cents due to thr superior rltdionuclide propertiw of tcch,nitiwn.

?fANGANESE-52m: A NEW MYOCARDIAL PERFUSION IMAGING AGENT FOR POSITRON EMISSION TOMOGRAPHY THAT DOES NOT REQUIRE AN ON-SITE CYCLOTRON Joann Llrquhart, MD;, Randolph E.Patterson, MD,FACC; Roger Aamodt, PhD; Edith Speir, BS; Robert Kessler, MD; NHLBI, Bethesda, Md.

The great potential of myocardial perfusion imaging (TIPI) by positron emission tomography (PET) has been limited by need for an on-site cyclotron to produce N-13 or by need for a special 'nigh speed PET system to image the ultra- short t /2 of Rb-82 (75sec). Our purpose was to test the physiological characteristics of Mn as an indicator of myocardial blood flow (MBF) and the speed of its clear- ance from blood to tissue by comparing Hn to other diffu- sible indicators. Nn-52m is available from algenerator (Fe-52) which fan be shipped conveniently (t /2=8hr) and Mn-521~ has a t /2 (20 min) which permits repeat imaging on the same day. We compared Mn,with Rb and Tl-201 in 5 dogs with acute coronary occlusion receiving isoproteren- 01 to produce a wide range of MBF (by Ce-141 micro- spheres) from 0.01 to 4.Cml/min/g. Dogs were sacrificed 4 min after simultaneous injection of all 4 indicators into the left atrium, reference arterial blood and myo- cardial samples were counted. The correlations in myo- cardial samples from each dog for Mn activity vs. MBF were as high (z-=.85 mean, and .69-.99 range) as between Tl(r=.90, .80-.98) or Rb(r=.89, . 77-.99) vs MBF. All di- ffusible indicators had-similar positive intercept values when MBF=O. In another dog the clearance from Plood to tissue of each indicator was similarly.rapid (t /2=25-40 set). We conclude that Mn-52m appears to be a promising radionuclide for MPI be ause of its availability from a generator, convenient t f 12, and rapid clearance from blood to tissue. Most important, Mn deposits in tissue as a linear function of blood flow as well as Tl-201 and Rb.

CONTINUOUS MYOCARDIAL BLOODFLOW DISTRIBUTION IMAGING IN MAN WITH KRYPTON 81 m INTRACORONARY. Correlation with myocardial lactate metabolism during single and repetitive periods of myocardial ischemia. Willem 3 Remme,MD;Peter Cox,PhD;X.Hanno Krauss,MD. Dept. of Cardiology,Zuiderziekenhuis,Rotterdam,The Netherlands.

Lactate production(L prod)when determined directly after pacing,is far more sensitive and indicative of myocardial ischemia than other parameters,including angina1 pain. Kr8lm is an inert,freely diffusable radionuclide with a nalflife of 13 set permitting repetitive bloodflow distribution measurements at short intervals.In 10 pts with left-CAD 10 areas with 90% and 4 areas with 70% stenosis were present.During atria1 pacing L extraction (%)and Kr8lm measurements were performed at control,100 b/min,lZO b/min,anginal pain or block and 15 sec,l and 2 min post-pacing(P-P).KrBlm distribution decreased early during pacing in all 90% and variably in 70% areas with early rises in normal areas.Though L prod was found in all pts(maxima1 L prod-21% at 15 set P-P)KrBlm distribution decreased long before L prod in 8/10 pts and occurred in 2,‘lO pts simultaneously.No correlation betwem L prod levels and size of the ischemic area was found.In both normal and stenotic areas Kr8lm changes were only slowly restoredcup to 5 min)with actual on-going flow reduction in pts with severe lesions.In 4 pts a second pacetest was performed after 15 min;Kr8lm distribution was not reproducible;a greater reduction was found in the second test with diminished L prod in 3/4 pts.lt is concluded that in l-CAD pts continuous Kr8lm intracoronary demonstrates early myocardial bloodflow changes before abnormal L metabolism occurs and indicates localization and size of ischemic areas.The slow return to control values after pacing excludes a correlation between high L efflux and flow changes immediately after pacing.

ABNORMAL THALLIUM 201 SCINTIGRAPHY DURING VASOPRESSIN INFUSION Richard Davison, MD, FACC; Kerry Kaplan, MD, FACC; Ann Bines,RN; StewaxSF, MD; Mike Reed, Pharm. D., Northwestern University Medical School, Chicago, Ill.

Vasopressin (V) infusions are widely used for the control of gastrointestinal bleeding. Cardiovascular complications during its administration are not uncommon and are mainly due to peripheral and coronary artery vasoconstriction. Serial ECGs are considered mandatory during V infusions. In 8 patients (pt) without prior history of heart disease, Thallium 201 (TI) scintigrams and ECGs were obtained during V infusions at 0.1 units/min and 2-3 hrs after discontinuation of the V. V was infused via a peripheral vein in 6 pts and via a celiac artery catheter in 2 pt. No pt complained of chest pain or had serious arrhythmias during the V infusion. While on V, 6 of the 8 pts had a clear-cut area of diminished TI uptake which resolved after V was stopped. Five of the 6 pts with positive TI scans had normal ECGs during and after V. The remaining pt developed heart failure shortly after V was started but did not show ECG changes until 4 days later. Both the heart failure and ECG changes subsided after V was stopped. Therefore: 1) clinically silent reductions in myocardial perfusion are common during low-dose V infusions; 2) ECG monitoring is an insensitive method for their detection; 3) the cardiac effects of V infusions are more accurately detected with TI scinti- graphy.

March 1982 The American Journal of CARDIOLOGY Volume 49 979