Value of the ventilation / perfusion scan in acute pulmonary ...

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scans were obtained with 1.5 x 10" Bq of , technetium Tc 99m macroaggregated albumin that contained 100 000 to Requests for Lung Scans 700 000 particles using a 20% symmetric 5587 window set over the 140-keV energy peak. Particles were injected into an I I antecubital vein over 5 to 10 respiratory cycles, with the patient supine or at Scan Requests Cancelled. most semierect. The perfusion images Scans Requested for Research Purposes. El19lbl~abents consisted of anterior, posterior, both I Diagnoses Other Than Acute 6 posterior oblique, and both anterior Pulmonary Embolism, oblique views, with 750 000 counts per Patients In Whom Angiography .. Contraindicated. and Other Reasons Consent Consent l~age for each. Fo~ the lateral vIew , ( for Ineligibility According to Given Refused W1t~ the best perfusIon, 500 000 counts Study Design 1493 1523 per Image were collected: the other lat- ~ 2571 eral view was obtained for the same length of time. Scintillation cameras f Random Sample with a wide field of view (38.1 cm in ; -diameter) were used with parallel-hole, ; I low-energy, all-purpose collimators. t Not Selected for Selected for Perfus~on scans were sat~sfa~tory or f Sensitivity and Sensitivity and better In 96% of cas.es, ventilation scans ! Specificity Analyses SpeCIficity Analyses adequate or better In 95%. ( 560 933 ( I Angiography i I The femoral-vein Seldinger tech- I Inlerpretable Scan Scan nique with a multiple side-holed, 6F to Not Compleled Completed 8F pi gtai l catheter was used Small 2 931 .. I: amounts of contrast matenal (5 to 8 mI,.) '; were injected by hand, to check the pa- I tency of the inferior vena cava by fluo- ! roscopy. The catheter was directed into Angiogram I Angiogram I the main pulmonary artery of the lung Completed Not Completed with the greatest V/Q scan abnormali- 755 176 ty. I mtla .. 1 fil mlng .. was In t h e antero- I posterior projection. Seventy-six per- I cent iodinated contrast material was Pulmonary Embolism Pulmonary Embolism Pulmonary ~rnbolism injec~d at a rate of 20 to 35 mL/s for a Present Absent Uncer1ain total of 40 to 50 mL (2-second injection). 251 480 24 Film ra~s were three per second for 3 seconds, followed by one per second for 4 to 6 seconds. Depending on the size of i .the lungs, filming was not magnified or :' Flow char1 illustrating the numbers of r1!Quests for lung scans. recruitment of patients, completion of lung given a low magnification of 1.4. A 12:1 scans. and results of angiography in the Prospectiw InvestigatIOn of Pulmonary Embolism Diagnosis. grid was used and roentgenographic factors were in the range of 70 to 80 kilovolts (peak) and 0.025 to 0.040 sec- ". onds at 1000 mA (large focal spot of 1.2 ...to 1.5 mm in diameter). If emboli were some patients could not be thoroughly Lung Scan :: not identified, injections were repeated evaluatedpriortocompletionoftheV/Q and magnification (1.8 to 2.0 times) scan, clinical investigators made every The protocol directed ventilation and oblique views were obtained of the ar- effort to record their individual clinical perfusion studies with the subject in the eas suspicious for pulmonary embolism. impressions as to the likelihood of pul- upright position, but other positions Films were obtained with an air-gap monary embolism prior to learning the were acceptable. VentilatiOn studies technique (ie, no grid used). Roent- i results of V/Q scans and angiography. were performed with 5.6 x 10' to genographic factors were in the range of : Impressions were based on an agreed on 11.1 x 10' Bq of xenon 133 using a 20% 78 to 88 kV(p) and 0.040 to 0.080 seconds ~ set of information-history, results of symmetric window set over the 8O-keV at 160 mA (small focal spot of 0.3 to 0.6 1 physical examination, arterial blood gas energy peak. They started with a mm in diameter). If no emboli were : analyses, chest roentgenograms, and 100 OOO-count, pos~rior-view, first- found in the first lung, or if bila~ral electrocardiograms-but without stan- breath image and then pos~rior equi- angiography in the clinical cen~r was dardized diagnostic algorithms. The librium (wash-in) images for two con- routine, identical techniques were used medical records of a random sample of secutive 120-second periods. Washout for the second lung. Angiography was patients who refused or were ineligible consisted of three serial 45-second pos- completed within 24 hours, and usually for study entry (refuser/ineligible pa- terior views, 45-second left and right within 12 hours of V/Q scans. Pulmo- '. -tients) were evaluated retrospectively pos~rior oblique views, and a final 45- .nary angiograms were adequate or bet- ,.~ for comparison with study patients. second pos~rior view. Then, perfusion ~r in ~5% of cases. ;~ jf 2754 JAMA. May 23/30. 1990-VoI263, No 20 Ventilation/Perfusion Scan-PIOPED Investigators~
. 'Pq of Central Scan and Table 1-PIOPED Central Scan Interpretation Categories and Criteria' 'gated )() ~o Angiogram Interpretations Two nuclear medicine readers, not c,,-~ ---~-~,,~ - High probability ;,,2 Large (> 750/0 of a segment) segmental perf1JSIOn defects WIthout corresponding ~ntilation or roenlgenonetric from the center that performed the graphIC abnom1alitles or substantially larger than eIther matching ventIlation or chest roentgenogram nergy Ito an ~ -atory or at llages ..abnom181ltles scan, mdepe?dently Interpreted the lung scans WIth chest roentgenograms accordl 'ng to preestabl ' h d t d .t IS e S u y cn e- ria (Table 1). Angiograms were likewise d I . d ..Bordertlne ran om y asslgne. .w pairs of angIo- ;,,2 Moderate segmental (;,,25% and ~75% of a segment) perf1JsK)n defects without matching ~ntilation or chest roentgenogram abnOm1alitles and 1 large mIsmatched segmental defect ;,,4 Moderate segmental perf1JsK)n defects without ventilation or chest roentgenogram abnom1alities IntermedIate probabIlity (Indetem1inate) Not lalling into nom1al. ve~low-. low-, or high-probability categories high or borderlIne low DIfficult to categonze as low or high both terior ts per VIeW ~ounts er latsame graphers from clInical centers other than the ori .nnatin g hos p ital The an- .e' .'. gIogram readers Interpreted the angIograms with lung scans as having acute uI b I ..Large p m.onary e~ 0 I.sm present-which required the IdentIfication of an embo- I b t t . I th tl ' f US 0 S ruc mg a vesse or e ou me 0 Low probability Nonsegmental perf1Jsion defects (~, ~ry small effusion causing blunting of the costophrenic angle. cardiomegaly. enlarged aorta. hIla. and medIastInum, and elevated dIaphragm) Single moderate mIsmatched segmental perfuSK)n defect with nom1al chest roentgenogram Any perf1JSlon defect with a substantially larger chest roentgenogram abnOm1ality or moderate segmental perf1JSIOn defects InvolvIng no more than 4 segments in 1 lung and no more than 3 segments In 1 lung regIOn with matching ~ntilation defects either equal to or larger In size and chest roentgenogram eIther nom1al or with abnom1alltles substantially smaller than perf1JSIOn defects >3 Small segmental perf1JsK)n defects «25% of a segment) with a nom1al chest roentgen.v.ram Very low probability .._" me~ cm m an embolus (filling deti ct) within a vesse I -a b sent, or uncert . m. If two read- ~3 Small segmental perf1Jsion defects with a nom1al chest roentgenogram Nom1al No perf1Jsion defects present l -hole, ers disagreed, the interpretations'were Perf1J$ion outlines exactly the shape of the lungs as seen on the chest roentgenogram (hilar and aortic impressions ators. adjudicated by readers who were se- may be si3en. chest roentgenogram and/or ventilation study may be abnom1al) ry or le~t~d randomly fro~ .the. remaining 'PIOPED indicates Prospectiw Investigation of Pulmonary Embolism Dia nosis scans clInical centers. If adJudIcatIng readers g did not agree with either of the first two readers, scans or angiograms went to panels of nuclear medicine or angiogra- Table 2 -Recruitment of Patients and Completion of Angiography' phy readers. The final adjudicated V IQ tech- scan readings consisted of four catego- 0/. of 6F to . h. h b b ' l ' . d .Eligible No. of PfOPEO P.tlent. With nes- Ig pro a Ilty, mterme late Patient. Lung Scan. Who Were Seiec1ed for Angiogram. Small probability (indeterminate), low proba- Clinical Center Recruited Anglographlc Pu..ult Obtained. No. ("!o} 8mL) bility, and low/very low probability ~ukeU~n~~ity 46 --137 1,15-'84)'-' le pa- through normal (near normal/normal). Henry ~ord Hos~it81 62 228 177 (78) .~uo- The near-normal/normal category in- ~assachus~~ ~eneral Hospjtal 33 140 120 (86) d Into cludes readings of very low probability University of Michigan 52 102 65 (64) ~ lun~ by one reader and low probability by the University 01 Pennsylvania 70 168 134 (80) ~all- other, very low probability by both, ~aleuniversity 43 156 144 (92) 1tero- very low probability by one and normal Total 50 931 755 (81) per- by the other, and normal by both. Re- , 1 was fu I. I.. bl t ' ts' PIOPED Indicates Prospective Investigation of Pulmonary Embolism Diagnosis ser me IgI e pa Ien scans were . ~or a read in each clinical center by the clini- 'tlon). cal center's PIOPED nuclear medicine for 3 reader(s) and not reread. 1d for F II d lants and in whom no outcome event 900 to 1000 patients in the random sam- :ze of 0 ow-up an ..suggested pulmonary embolism. Pul- pie for PIOPED angiography was d or Outcome ClassIfication monary embolism status could be deter- planned to obtain estimates of sensitiv- 12:1 Patients were contacted by telephone mined as positive or negative for 902 ityand specificity with 95% CIs no wid- 1hic at I, 3, 6, and 12 months after study patients. A clinical assessment of the er than == 8%. To determine the sensi- ; 80 entry. Deaths, new studies for pulmo- likelihood of pulmonary embolism was tivity and specificity of V IQ lung scans ,ec- nary embolism, and major bleeding available for 887 (98%) of these patients. without the biases associated with hap- 1.2 complications were reviewed by an out- hazard patierlt selection (ie, conveere come classification committee using all Statistical Methods nience sampling).8.t a 933-patient sam- lted available information. Only 23 (2.5%) of Probability values for the comparison pie of the 1493 patients who consented mes) the 931 patients had incomplete (16) or of percentages and proportions and 95% to PIOPED participation was selected \e ar- no (7) follow-up. Angiograms, follow-up confidence intervals (CIs) were calcu- according to random sampling sched- \lism, data, and outcome classifications were lated using standard: tests.' A ~ test ules created separately by the data and r-gap used to determine pulmonary embolism for homogeneity of proportions was coordinating center for each clinical cenoent- status as positive for patients with an- used to compare distributions.' Sensi- ter, The PIOPED protocol required 1ge of giograms that showed pulmonary em- tivity is defined as the proportion of these 933 patients to undergo angiogra- :onds boli and for patients for whom outcome cases of pulmonary embolism correctly phy if their scans were abnormal, Of the :00.6 review established the presence of pul- diagnosed and specificity as the pro- 933 patients selected for angiography, 1 were monary emboli at the time of PIOPED portion of diagnoses that pulmonary patient died before the V/Q scan could lteral recruitment. Pulmonary embolism sta- embolism is absent for patients without be completed and 1 other patient's V/Q .was tus was determined as negative for pa- pulmonary embolism. Sensitivity, spe- scan was determined to be uninterpreused tients with angiograms that did not cificity, and percent agreement have table. These 2 patients are not further .was show pulmonary emboli and no contrary been calculated according to standard reported herein. ually outcome review and for patients who methods for proportion8,' Analyses .lImo- lacked a definitive angiogram reading were performed with the Statistical RESULTS .bet- who were discharged from the hospital Package for the Social Sciences statisti- Of the 3016 patients eligible for without a prescription for anticoagu- cal software package.' Recruitment of PIOPED, 1493 (50%) gave consent to gators JAMA. May 23/30. 1990-VoI263, No 20 Ventilation/Perfusion Scan-PIOPED Investigators 2755 ~~- "';::: -I .
Page 1: t' , ~. ..Original Contributions (\
Page 5 and 6: ~ Table 6 -Pulmonary Embolism (PE)
Page 7 and 8: ~ j Clinical Centers University of
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