Imaging Pulmonary Embolism

Transcription

1 May 2001 Imaging Pulmonary Embolism New ways to look at a diagnostic dilemma Emily Willner,, HMS III Core Radiology Clerkship, BIDMC

2 New approaches to imaging PE: Agenda 1. Review two patients who had new diagnostic modalities used for diagnosing and/or treating PE 2. Review anatomy, differential diagnosis and menu of tests available for PE imaging. 3. Discuss algorithmic approach to use of imaging modalities, and the strengths and limitations of available tests. 2

3 Patient J.R.: A classic story 64 year old man with recent diagnosis of metastatic pancreatic CA. Known mets to the liver. Presents to the ED with acute onset of sharp, L-L sided pleuritic chest pain. Mild SOB for a few days. No cough or hemoptysis.. No fevers or chills. No leg symptoms PMHx: : Pancreatic CA. C4-5 5 ruptured disc. 3

4 J.R.: Physical Exam Vitals: Afebrile,, HR 72, BP 121/64, RR18, Sat 98% RA Thin man, mildly uncomfortable. Chest clear. Heart RRR, II/VI SEM, no rubs or gallops. Mild abdominal tenderness, + hepatomegaly Normal lower extremity exam 4

5 J.R.: Chest X-rayX Images from BIDMC PACS Poor inspiratory effort, but otherwise clear lungs. No pneumothorax,, no effusions. 5

6 J.R.: Ventilation/Perfusion Scan Ventilation Essentially normal RAO Ant LAO L Lat LPO Post RPO R Lat Perfusion Shows possible defect in LLL RAO Ant LAO L Lat LPO Post RPO R Lat Image from BIDMC PACS 6

7 J.R.: Chest CT Angiogram w/ contrast showing embolus Image from BIDMC PACS 7

8 Embolus easier to visualize scrolling through CT cuts Image from BIDMC PACS 8

9 Patient R.S.: An emergency on call 58 y.o.. man s/p cholecystectomy 2 weeks ago, re- hospitalized for mental status changes Abdominal/pelvic CT the day of admission incidentally showed L femoral and ileac DVT; heparin was started The following day, he became acutely SOB, O2 sat 88%, tachy to 146, EKG: S1, Q3, T3. Bedside echo: severe RV enlargement and hypokinesis 9

10 R.S.: CT on admission revealed DVT in left iliac v. Image from BIDMC PACS 10

11 R.S.: Chest X-ray while SOB Image from BIDMC PACS AP upright film: : Bilateral lower lung atelectasis.. Otherwise clear lungs. 11

12 R.S.: Large saddle embolus in L and R pulmonary arteries Image from BIDMC PACS 12

13 R.S.: Saddle embolus in R PA Image from BIDMC PACS 13

14 R.S.: Angiography and suction thrombectomy Pre-thrombectomy Post-thrombectomy Large filling defect. Virtually no flow to L lung. After suction thrombectomy, flow restored to L upper lung. Images from BIDMC PACS 14

15 Differential Diagnosis of chest pain with SOB Respiratory: : PE, pneumonia, pneumothorax, pulmonary edema, asthma/copd, bronchitis, lung CA Cardiac: Pericarditis, angina, MI, aortic dissection GI: : GERD, esophageal spasm, cholecystitis Musculoskeletal: Muscle spasm, pulled muscle, rib fracture, costochondritis Psychiatric: : Anxiety 15

16 Classic presentation of PE Risk factors Immobilization, surgery within 3 mo., trauma, malignancy, CHF, MI, h/o VTE, postpartum or hormone use Symptoms Pleuritic chest pain, dyspnea,, cough, hemoptysis, syncope Signs Tachypnea, rales,, tachycardia, S4, loud P2, fever <102 F 16

17 Lung Anatomy Arteries run with Bronchi Image from info.med.yale.edu/caim/ct/contents.html 17

18 Pulmonary vasculature and bronchi Bronchus Pulmonary trunk Image from Digital Anatomist, Pulmonary arterial anatomy Pulmonary trunk 2 Main pulmonary arteries Lobar arteries Segmental arteries Subsegmental arteries 18

19 CT correlation and cross- sectional anatomy T5-6 Aorta Pulmonary artery bifurcation Mainstem bronchus Aorta Pulmonary artery bifurcation Mainstem bronchus Aorta Image from Digital Anatomist, Pulmonary artery bifurcation Mainstem bronchus 19

20 Imaging tests in suspected PE Plain chest film: First test; r/o other etiology Ventilation/perfusion scanning Pulmonary angiography: the Gold Standard test Helical CT scan/ CT angiography MR imaging/ angiography Other: LE Venous duplex Doppler US, echocardiography 20

21 Chest X-ray findings in PE Most films (86%) are abnormal. Common findings are: atelectasis parenchymal opacity pleural effusion cardiomegaly hemidiaphragm elevation central pulmonary artery prominence Few show classic PE findings: Westermark s sign = loss of pulmonary vasculature distal to central embolus. Hampton s hump= = wedge- shaped, pleural based opacity representing infarct Fleischner's sign = regional oligemia in the presence of an ipsilateral enlarged pulmonary artery 21

22 Westermark sign Image from Virtual Hospital, 22

23 Hampton s Hump From ed/rad 23

24 Ventilation/perfusion scanning Nuclear medicine test, IV injection of 99Tc labeled to albumin maps perfusion Inhalation of radioactive tracer shows ventilation Read as high, intermediate, low probability, or normal Normal perfusion r/o embolus High prob scan, 42% have emboli; 96% if correlated with high clinical prob Intermediate and low prob scans = indeterminate 24

25 Normal V/Q scan Ventilation RAO Ant LAO L Lat LPO Post RPO R Lat Perfusion RAO Ant LAO L Lat LPO Post RPO R Lat Image from BIDMC PACS 25

26 High Probability V/Q scan Ventilation Few small defects RAO Ant LAO L Lat LPO Post RPO R Lat Perfusion Multiple unmatched perfusion defects RAO LPO Ant Post LAO RPO L Lat R Lat Image from BIDMC PACS 26

27 Following up indeterminate V/Q 72% pts have indeterminate scan Emboli detected in 30% of intermediate scans and 14% of low prob scans THUS, PIOPED recommends f/u with PAgram in this group Only 5% in this group have pulmonary angiography!! Management is instead based on clinical judgment. 27

28 Diagnosing PE using V/Q scans: one algorithm V/Q Scan Normal perfusion Non-diagnostic HIgh probability No treatment Clinically stable Cinically unstable TREAT Eval bilateral lower extrem. Pulmonary angiography Nondiagnostic/ negative + DVT No PE PE present Serial leg studies v. angio TREAT No treatment TREAT Chart adapted from UpToDate,, ATS guidelines

29 Pulmonary Angiography The gold standard test for PE Trans-venous; mortality < 1%, morbidity 2-5% 2 Interobserver variability: PIOPED found a 92% concordance in PE cases Least sensitive for subsegmental emboli Diagnostic test can be combined with intervention (Greenfield (IVC) filter, thrombolysis, thrombectomy) 29

30 Normal Pulmonary Angiogram To RUL Left PA To LUL To RML To LLL To RLL Right PA Images from BIDMC PACS 30

31 CT angiography in PE diagnosis Helical CT with iodinated contrast bolus; sec. scan, may be done in 2 breath-holds holds Sensitivity: 86% for proximal vessels (main through segmental a.); % overall. Specificity: 93% for proximal vessels; % 100% overall. CT has similar sensitivity to V/Q scanning, but a negative CT is not as good as normal perfusion in r/o PE Should we re-think the algorithms? What is the role for CTA? 31

32 Diagnosing PE: an algorithm using helical CT as the initial test Supect PE Low clinical suspicion Intermediate or high clinical suspicion D-dimer CT angiography Normal Abnormal Other dx PE No PE PE excluded CT angiography Consider lower extremity evaluation Chart adapted from Ryu et. al., Consider V/Q scan if contraindication to IV contrast. V/Q has good utility as first test when patient has no pathology on CXR and no hx of cardiac or pulmonary disease 32

33 Normal CTA 33

34 Helical CT angio overview Plus Very fast Evolving technology faster scans and thinner slices May give alternate diagnosis if negative for PE 3-D D reconstructions Negative scan safe to withhold anticoagulation Minus Iodinated contrast (renal insufficiency) Radiation exposure Poor visualization of clots in subsegmental arteries and obliquely oriented vessels 34

35 3-D CT reconstruction: R.S. Image from BIDMC PACS 35

36 CT in diagnosis of DVT: One stop shopping? Recent data has suggested that CT of the lower extremities may be done at the same time as chest CTA to yield greater diagnostic accuracy One contrast bolus and one scan In future, possibly replace venous US in patient already undergoing CT? 36

37 Role of MRA in diagnosis of PE Plus Excellent images No iodinated contrast Sensitivity and specificity similar range to CTA Real-time reconstructions/ flow images Future:, ventilation scanning Minus Longer scan time (minutes v. seconds) Prolonged breath- holding (30+ sec.) Expensive Poor sensitivity in subsegmental a. clots 37

38 Gadolinium contrast MRA Normal MRA of a large embolus Image from www2.medical.philips.com/mri/applications/ Cardiac/Angiography.asp Image courtesy of Dr. Thomas Vrachliotis 38

39 Summary: Advances in imaging CXR remains the initial test of choice. V/Q scanning retains a role in healthier patients. Helical CT is sensitive, specific, fast, and gives alternate diagnoses. Potential for LE imaging. Needs more investigation to fully delineate role. Pulmonary angiography has a role especially in patients who will need interventions. MR is promising but currently scans too long and test too expensive. 39

40 References American Thoracic Society. The diagnostic approach to acute venous thromboembolism.. ATS guidelines. Am J Resp Critical Care Med 1999; 160: Goodman LR, Lipchik RJ, Kuzo RS. Subsequent pulmonary embolism. Risk after negative helical CT. Prospective comparison with scintigraphy. Radiology 2000; 215: 535. Kline JA, Johns KL, Colucciello SA, Israel EG. New diagnostic tests for pulmonary embolism. Ann Emerg Med 2000; 35(2): 343. Maki DD, Warren BG, Abass A. Emerging technology in clinical medicine: Recent advances in pulmonary imaging. Chest 1999; 116(5): PIOPED investigators. Value of ventilation/perfusion scan in acute pulmonary embolism. JAMA 1990; 263: Rathburn SW, Raskob GE, Whisett TL. Sensitivity and specificity of helical CT in the diagnosis of pulmonary embolism: a systematic review. Ann Int Med (3): 227. Ryu JH, Swensen SJ, Olson EJ, Pellikka PA. Diagnosis of pulmonary embolism with use of computed tomography. Thompson BT, Hales, CA. Clinical manifestations and diagnostic strategies s for acute pulmonary embolism. Up To Date

41 Acknowledgements Many thanks to Dr. Michelle Swire for her help with cases and images, Dr. Lieberman for her ideas and suggestions, and to Dr. Thomas Vrachliotis for his MR images. Thanks to my Radiology classmates who made doing this presentation much more fun. Thanks to Beverlee Turner for all her technical help. Special thanks to Larry Barbaras and Cara Lyn D amour, our WebMasters. 41