Disclosures. CTA of Acute and Chronic Pulmonary Embolism. Background. Imaging. Which imaging test should be used to evaluate VTE? Objectives.

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1 CTA of Acute and Chronic Pulmonary Embolism None Disclosures Smita Patel, M.B.B.S., M.R.C.P., F.R.C.R. Professor, Cardiothoracic Radiology Department of Radiology University of Michigan Objectives To assess the role of CTA in the evaluation of Acute and Chronic Pulmonary Embolism To review the imaging findings that differentiate acute from chronic PE To review CT imaging findings indicative of poor outcomes in acute PE Background Incidence 600,000/year in the US Mortality 100, ,000 PE - asymptomatic in about 2/3 or may be incidentally detected Clinical S/Sx - non-specific Dyspnea, Pleuritic CP, hemoptysis, syncope, and a 1/4 th have leg swelling Scoring systems Wells, Geneva and D- dimer Imaging is key for diagnosis Which imaging test should be used to evaluate VTE? Suspected PE CXR V/Q Echo (TTE, TEE) Catheter pulmonary angiography CTPA MRA Imaging Suspected DVT US venography, Direct venography Indirect CTV MRV 1

2 CTPA CT has become the main diagnostic test for evaluating PE Management of Suspected Acute Pulmonary Embolism in the Era of CT Angiography: A Statement from the Fleischner Society Remy-Jardin et al, Radiology 2007; 245: Can CT Modify the Diagnostic Strategy for? Christopher Study (JAMA 2006) (dichotomized decision rule, D-dimer and CT) 3306 consecutive patients (82% - OP) 1/3 rd with unlikely clinical probability score and negative D-dimer 3 month VTE 0.5% = CTPA can be safely omitted In the remaining 2/3 rd CT reliably ruled out PE 3-month VTE = 1.3% Algorithm allowed Mx decision in 97.9% PIOPED II MDCT and NEJM 2006; 354: patients -23% diagnosed with PE CTPA alone CTPA/CTV Sensitivity 83% 90% Specificity 96% 95% PPV : High/low clin prob 96% Intermed clin prob 92% Predictive value of either depends on clinical probability Concordant with clinical probability: very accurate Discordant with clinical probability: requires additional testing PIOPED II Conclusions NEJM 2006; 354: Editorial: PIOPED II study convincingly established the diagnostic performance of MDCTPA, at least in outpatients and support the use of MDCTPA for suspected PE as a standalone imaging test. Clinicians should be wary of results that are discordant with their clinical judgment, especially in the rare cases of a patient with a high likelihood of PE and normal findings on CTA Scanner Type Optimize Technique Collimation (mm) Rotation (s) Scan duration (s,24 cm) (dyspnea) < DS < < < 4 Hartman EJR 2010; 74 2

3 Newer Scanners High pitch Low kv Iterative reconstruction Reduces radiation dose Also low volume of contrast with the high pitch low kv decreased contrast-induced nephropathy Patient Instruction Ultrashort scan times make optimization of contrast delivery more critical In co-operative pts, scan in inspiration during apnea at total lung capacity For longer breath-holds prior short hyperventilation is useful CTPA - Interpretation CT Findings of Acute Pulmonary Embolism Thrombus partially/completely occluding PA, +/- enlargement of artery Rim-sign Tram-track sign Vessel cut off Saddle Embolus 3

4 Occlusive PE Enlargement of vessels Rim - sign Tram-track sign Acute angle with vessel wall Vessel Cut-off Indirect Findings Pulmonary hemorrhage or infarct Pulmonary Infarct Oligemia of affected segment Mosaic perfusion Small pleural effusion Right ventricular strain pattern 4

5 Pathophysiology increases pulmonary vascular resistance and load on RV PA pressure does not rise till >30% of pulm circulation is obstructed Around this threshold, PE becomes hemodynamically significant As RV dilates, intramural pressure increases and intracoronary filling decreases Massive PE Systemic hypotension - Less than 90 mm Hg of a drop of 40 mm Hg for at least 15 minutes or Shock Mortality associated with systemic hypotension is substantial, and increases markedly in the presence of cardiogenic shock Hypoxemia of <90% is asso with >30- day mortality risk Massive and Submassive PE Submassive PE: Right heart strain, dilatation, dysfunction or ischemia Mortality 3% Massive PE: Sustained hypotesion -90 mm Hg of a drop of 40 mm Hg for at least 15 minutes requiring vasopressors - Mortality 25-65% RV Function : Echo RV dilation (RV/LV >1) CT or Echo Massive and Submassive PE Typically central (main or lobar) PE Acute Massive PE Saddle embolus Complete obstruction of one or partial obstruction of both R and L main pulmonary arteries Rt heart strain or hypotension Occlusive PE 5

6 CT Features of Poor Outcome RV dilation RV/LV ratio greater than 1 made from axial images associated with a fold increase in short-term mortality Increase in RV afterload - RV dilatation, straightening/bowing of the interventricular septum, dilated IVC, SVC, azygous vein, reflux of contrast in IVC and hepatic veins Right Ventricular Dilatation Independent predictor for in-hosp death in hemodynamically stable patients RV Dilated RV with straightening of the IV septum RV:LV ratio >1 Lu MT et al, AJR 2012; 198: LV D/D Massive Central PE Massive (rare) Chronic thromboembolic disease Pulmonary Artery Sarcoma Tumor embolus Chronic Massive PE Malignancy/PA Sarcoma Internal heterogeneous enhancement Lobulated margins of embolus extending into the contrast column Lack of straight-line borders with contrast column Newer CT Techniques Dual energy/dual source Xenon ventilation CT with dual energy CT with perfusion imaging CAD CT Spectral CT reduces iodine load and radiation dose 6

7 CT Findings of Chronic Pulmonary Embolism Pathophysiology Most acute PE resolve with anticoag Rx Some PE do not resolve and become recanalised and endothelialised & can lead to CTEPH, in 5% of PE survivors CTED persistence of organized thrombi in lobar, segmental or subsegmental pulm arteries after 3 months of Rx CTED can occur with or without CTEPH Important to differentiate acute from chronic PE Chronic Thromboembolic PHT MPaP 25 PCWP < 15 Bronchial systemic blood flow markedly increases systemic to pulm anastomoses Increase pulm vasc resistance and pressures result in RV hypertrophy and ultimately RV dysfunction and failure Long term prognosis is poor 5-year survival 10% Chronic PE - Eccentric filling defects form obtuse angles with vessel wall ± wall thickening and intimal irregularity ± Ca Vessel narrowing/caliber change/beading/abrupt occlusion Webs/bands Increased number and size of bronchial arteries Enlarged central pulmonary arteries CTPA Findings of Chronic PE Obtuse angle, Irregular Interface PA 7

8 Webs and Small Sized Vessels CTPA of Chronic PE Postprocessing with MPR s or CMPR useful to demonstrate: Eccentric filling defects Abrupt narrowing of vessel Abrupt vessel occlusion Beading Chronic PE with dimunitive distal vessels Value of CTPA for Chronic PE Advantages: Sensitivity: %, Specificity: 96-98% More sensitive than cath PA for prox disease Pre/post appearance easier to compare Disadvantages: Axial plane decreased appreciation of beading, abrupt caliber change/occlusion Cardiac Findings of Chronic PE Right ventricular and right atrial enlargement and right ventricular hypertrophy Straightening +/- bowing of IV septum towards the LV Tricuspid Regurgitation (Dilated RA, retrograde flow of contrast into IVC & Hep V) Right ventricular function can be assessed with cardiac gating RA and RV Dilatation and Right Ventricular Hypertrophy and TR RA RA RV RV LV LV 8

9 Parenchymal Findings of Chronic PE Mosaic perfusion (70-100%) Subpleural bands Subpleural triangular opacities/scar or cavitation Bronchiectasis and air-trapping Mosaic Perfusion Worthy; Radiology 1997;205 Remy-Jardin; Radiology 1997;169 Arakawa JCAT 2003;27 Conclusion CTPA plays a key role in the diagnosis of both acute and chronic PE Imaging features of acute PE are easier to recognize Important to assess for the possibility of right heart strain with PTE particularly with submassive or massive PE CTPA findings of chronic PE may be subtle but have important prognostic implications References Ruggiero A, Screaton NJ. Imaging of acute and chronic thromboembolic disease: state of the art. Clinical Radiology 2017; 72: Wittram C et al. Acute and Chronic PE: Angiography-CT correlation. AJR 2006; S Castener E et al. CT diagnosis of chronic thromboembolism. Radiographics 2009; 29: Sista AK et al. Stratification Imaging and Management of Acute Massive and Submassive PE. Radiology 2017; 284 Thank You 9