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Emily Willner, Willner, HMS III Gillian Lieberman, MD May 2001 Imaging Pulmonary Embolism New ways to look at a diagnostic dilemma Emily Willner, HMS III Gillian Lieberman, MD Core Radiology Clerkship, BIDMC Emily Willner, Willner, HMS III Gillian Lieberman, MD New approaches to imaging PE: Agenda 1. 2. 3. Review two patients who had new diagnostic modalities used for diagnosing and/or treating PE Review anatomy, differential diagnosis and menu of tests available for PE imaging. Discuss algorithmic approach to use of imaging modalities, and the strengths and limitations of available tests. 2 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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, Lsided 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 ruptured disc. 3 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD J.R.: Chest X-ray Images from BIDMC PACS Poor inspiratory effort, but otherwise clear lungs. No pneumothorax, no effusions. 5 Emily Willner, Willner, HMS III Gillian Lieberman, MD J.R.: Ventilation/Perfusion Scan Ventilation •Essentially normal RAO LPO Ant Post LAO RPO L Lat R Lat Perfusion • Shows possible defect in LLL RAO LPO Ant Post LAO RPO L Lat R Lat Image from BIDMC PACS 6 Emily Willner, Willner, HMS III Gillian Lieberman, MD J.R.: Chest CT Angiogram w/ contrast showing embolus 7 Image from BIDMC PACS Emily Willner, Willner, HMS III Gillian Lieberman, MD Embolus easier to visualize scrolling through CT cuts 8 Image from BIDMC PACS Emily Willner, Willner, HMS III Gillian Lieberman, MD Patient R.S.: An emergency on call 58 y.o. man s/p cholecystectomy 2 weeks ago, rehospitalized 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD R.S.: CT on admission revealed DVT in left iliac v. 10 Image from BIDMC PACS Emily Willner, Willner, HMS III Gillian Lieberman, MD R.S.: Chest X-ray while SOB Image from BIDMC PACS AP upright film: Bilateral lower lung atelectasis. Otherwise clear lungs. 11 Emily Willner, Willner, HMS III Gillian Lieberman, MD R.S.: Large saddle embolus in L and R pulmonary arteries 12 Image from BIDMC PACS Emily Willner, Willner, HMS III Gillian Lieberman, MD R.S.: Saddle embolus in R PA 13 Image from BIDMC PACS Emily Willner, Willner, HMS III Gillian Lieberman, MD R.S.: Angiography and suction thrombectomy Pre-thrombectomy Large filling defect. Virtually no flow to L lung. Post-thrombectomy After suction thrombectomy, flow restored to L upper lung. Images from BIDMC PACS 14 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD Lung Anatomy Arteries run with Bronchi Image from info.med.yale.edu/caim/ct/contents.html 17 Emily Willner, Willner, HMS III Gillian Lieberman, MD Pulmonary vasculature and bronchi Bronchus Pulmonary trunk Pulmonary arterial anatomy Pulmonary trunk Æ 2 Main pulmonary arteries Æ Lobar arteries Æ Segmental arteries ÆSubsegmental arteries Image from Digital Anatomist, http://www9.biostr.washington.edu/da.html 18 Emily Willner, Willner, HMS III Gillian Lieberman, MD CT correlation and crosssectional anatomy T5-6 Aorta Pulmonary artery bifurcation Mainstem bronchus Pulmonary artery bifurcation Aorta Mainstem bronchus Pulmonary artery bifurcation Aorta Image from Digital Anatomist, http://www9.biostr.washington.edu/da.html Mainstem bronchus 19 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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= wedgeshaped, pleural based opacity representing infarct Fleischner's sign = regional oligemia in the presence of an ipsilateral enlarged pulmonary artery 21 Emily Willner, Willner, HMS III Gillian Lieberman, MD Westermark sign Image from Virtual Hospital, www.vh.org 22 Emily Willner, Willner, HMS III Gillian Lieberman, MD Hampton’s Hump From www.med.virgina.edu/medwww.med.virgina.edu/med-ed/rad 23 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD Normal V/Q scan Ventilation RAO LPO Ant Post LAO RPO L Lat R Lat Perfusion RAO LPO Ant Post LAO RPO L Lat R Lat Image from BIDMC PACS 25 Emily Willner, Willner, HMS III Gillian Lieberman, MD High Probability V/Q scan Ventilation •Few small defects RAO LPO Perfusion • Multiple RAO Ant Post Ant LAO RPO LAO L Lat R Lat L Lat unmatched perfusion defects LPO Post RPO R Lat Image from BIDMC PACS 26 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD Diagnosing PE using V/Q scans: one algorithm V/Q Scan Normal perfusion No treatment Non-diagnostic HIgh probability Clinically stable Cinically unstable Eval bilateral lower extrem. Pulmonary angiography Nondiagnostic/ negative + DVT No PE PE present Serial leg studies v. angio TREAT No treatment TREAT TREAT Chart adapted from UpToDate, ATS guidelines 1999. 28 Emily Willner, Willner, HMS III Gillian Lieberman, MD Pulmonary Angiography The “gold standard” test for PE Trans-venous; mortality < 1%, morbidity 2-5% 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD Normal Pulmonary Angiogram To RUL Left PA To LUL To RML To LLL To RLL Right PA Images from BIDMC PACS 30 Emily Willner, Willner, HMS III Gillian Lieberman, MD CT angiography in PE diagnosis Helical CT with iodinated contrast bolus; 20-30 sec. scan, may be done in 2 breath-holds Sensitivity: 86% for proximal vessels (main through segmental a.); 53-100% overall. Specificity: 93% for proximal vessels; 81-100% 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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 PE excluded CT angiography Other dx PE No PE Consider lower extremity evaluation Chart adapted from Ryu et. al., 2001. • 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD Normal CTA 33 Images from BIDMC PACS Emily Willner, Willner, HMS III Gillian Lieberman, MD Helical CT angio overview Plus Very fast Evolving technology Æfaster scans and thinner slices May give alternate diagnosis if negative for PE 3-D reconstructions Negative scanÆ safe to withhold anticoagulation Minus Iodinated contrast (renal insufficiency) Radiation exposure Poor visualization of clots in subsegmental arteries and obliquely oriented vessels 34 Emily Willner, Willner, HMS III Gillian Lieberman, MD 3-D CT reconstruction: R.S. Image from BIDMC PACS 35 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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 breathholding (30+ sec.) Expensive Poor sensitivity in subsegmental a. clots 37 Emily Willner, Willner, HMS III Gillian Lieberman, MD Gadolinium contrast MRA Normal Image from www2.medical.philips.com/mri/Applications/ Cardiac/Angiography.asp Cardiac/Angiography.asp MRA of a large embolus Image courtesy of Dr. Thomas Vrachliotis 38 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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 Emily Willner, Willner, HMS III Gillian Lieberman, MD References American Thoracic Society. The diagnostic approach to acute venous thromboembolism. ATS guidelines. Am J Resp Critical Care Med 1999; 160: 1043. 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): 1388. PIOPED investigators. Value of ventilation/perfusion scan in acute pulmonary embolism. JAMA 1990; 263: 2753. Rathburn SW, Raskob GE, Whisett TL. Sensitivity and specificity of helical CT in the diagnosis of pulmonary embolism: a systematic review. Ann Int Med 2000. 132(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 for acute pulmonary embolism. Up To Date 2001. 40 Emily Willner, Willner, HMS III Gillian Lieberman, MD 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