Scintigraphic quantification of myocardial ischemia: a new approach.

Thisstudy was undertaken todevelop a quantitative scintigraphic measurementof ischemia. We recorded 201TI scintigrams bytheseven-pinhole tomographic technique immediately after exercise and3hrlater in15normal subjects with alowlikelihood ofcoronarydisease andin55 catheterized patients withchest pain. Circumferential profiles oftheinitial and3hrtracer distribution andofthe3hrclearance rate weregenerated foreachofthree left ventricular sections. Acircumferen- tial profile ofthe3hrclearance rate(initial countsminus3hrcountsdivided byinitial counts, expressed aspercent) was alsogenerated foreachofthese sections. A scintigraphic ischemic score (SIS) was thenderived bysummingforthethree sections thearea(inarbitrary units) between the exercise and3hrprofiles andtheareabywhichtheclearance profile fell belowthelower limits of normal forclearance derived fromthenormal subj'ects. Thissummedareawas thennormalized forthe level ofstress bydividing bytheproduct oftheexercise duration (inminutes) andthefraction ofage- predicted maximumheart rateachieved. ThisSISwas above the95%confidence limits derived from thenormal subjects in44of46(96%)patients withthesignificant coronarydisease andinonly one of ninewith lessthan a50%obstruction. TheSISwas 52+ 58,233+ 220, 427 325,and826 551 U (mean SD)forpatients without coronarydisease andforthose with one-,two-,and' three-vessel disease, respectively. Theintergroup differences werestatistically significant, butthere was consider- ableoverlap among individual patients. Moreimportantly, theSIScorrelated significantly with a coronaryarteriography scoredesigned toreflect thepotential forischemia based on thecoronary anatomy(r= .78, p < .001) andwith anindex ofischemia generated fromtheexercise electrocardio- gram(r= .72, p< .001). Thesefindings suggest that acontinuous andquantitative scintigraphic index ofmyocardial ischemia canbederived fromanalysis ofthepostexercise distribution andclearance of 201T1. Suchanindex should bevaluable indetermining prognosis andchoosing therapy forpatients with coronaryartery disease andinassessing their responsetotherapeutic interventions. Circulation 68,No.4,747-755, 1983. THALLIUM-201 (207T1) scintigraphy iswidely used to detect coronary disease, usually'in conjunction with exercise testing. Inaddition, manygroups haveevalu- ateditsability tolocalize obstructed vessels andto estimate theextent ofanatomic involvement.24 Unfor- tunately, thescintigraphic results withthese latter ap- plications haveoften beendisappointing, atleast in partbecause oftherelative nature oftheconventional interpretation criteria, whichoccasionally makeitdif-