Chronic PE

RadioGraphics 2009; 29:31–53

CT Diagnosis ofCT Diagnosis of Chronic Pulmonary Chronic Pulmonary ThromboembolismThromboembolism

Castañer et al :Castañer et al :Department of Radiology, Universitari Parc TaulDepartment of Radiology, Universitari Parc Taul ํํ-UAB, Barcelona-UAB, Barcelona

Present by Ekkasit S.

IntroductionIntroduction

• Chronic pulmonary thromboembolism is mainly a consequence of incomplete resolution of pulmonary thromboembolism.

• Increased vascular resistance due to obstruction of the vascular bed leads to chronic thromboembolic pulmonary hypertension.

IntroductionIntroduction

• The prevalence of chronic thromboembolic pulmonary hypertension in the general population has yet to be accurately determined and may have been significantly underestimated.

• Recent data : 4% after acute PE.

• Chronic thromboembolic pulmonary hypertension is clearly more common than previously was thought, and misdiagnosis is common because patients often present with nonspecific symptoms.

IntroductionIntroduction• Symptoms

– Nonspecific & related to the development of pulmonary hypertension.

– Symptoms worsen as the RV functional deteriorates.

– Chronic thromboembolic pulmonary hypertension often is identified during the diagnostic work-up in patients with unexplained pulmonary hypertension

radiologists must be aware of its radiologic manifestations because it is a treatable cause of pulmonary hypertension

in some patients

• Risk Factors and Clinical Manifestations

• Pathogenesis• CT Technique• CT Features of Chronic Pulmonary

Thromboembolism– Vascular Signs– Parenchymal Signs

• Differential Diagnosis• Diagnostic Evaluation• Treatment

Risk Factors & Clinical ManifestationsRisk Factors & Clinical Manifestations

Risk FactorsRisk Factors• Women ( slightly more frequently )• Underlying malignant, cardiovascular, or pulmonary

disease are at increased risk

• Other reported risk factors– Splenectomy– Ventriculoatrial shunts– Chronic inflammatory disorders– Myeloproliferative syndromes– Ethic (more prevalent in Asian patients)


Pengo V et al. Pengo V et al. (N Engl J Med 2004)(N Engl J Med 2004)“ “ Incidence of chronic thromboembolic pulmonary

hypertension after pulmonary embolism””

Factors associated with increased risk of chronic thromboembolic pulmonary hypertension

• Multiple episodes of pulmonary embolism• Larger perfusion defect• Younger age• Idiopathic manifestation of pulmonary thromboembolism


Chronic thromboembolic pulmonary Chronic thromboembolic pulmonary hypertensionhypertension

• Lupus anticoagulant is detected in approximately 10% of patients

• Plasma levels of factor VIII and antiphospholipid antibodies are elevated


• Symptoms are nonspecific and are related to the development of pulmonary hypertension.

• The extent of vascular obstruction is a major determinant of the severity of pulmonary hypertension.


Clinical Manifestations Of chronic Clinical Manifestations Of chronic thromboembolic pulmonary hypertensionthromboembolic pulmonary hypertension

May be asymptomatic for several years• Recurrent acute or progressive exertional dyspnea• Chronic nonproductive cough• Atypical chest pain• Tachycardia• Syncope• Cor pulmonale


Clinical Manifestations Of chronic Clinical Manifestations Of chronic thromboembolic pulmonary hypertensionthromboembolic pulmonary hypertension

• Pulmonary arterial pressure is elevated• Right atrial pressures are high• Cardiac output is reduced• Pulmonary capillary wedge pressures are normal




• Differential Diagnosis• Diagnostic Evaluation• Treatment• Conclusions

PathogenesisPathogenesis

“In more than 90% of patients includes total resolution or resolution with

minimal residual and restoration of normal pulmonary hemodynamics within

30 days after treatment”


• Early resolution of pulmonary vascular obstruction occurs by two mechanisms:

– Mechanical fragmentation. – Endogenous fibrinolysis.


• The pathogenesis of chronic thromboembolism is still unclear.

• Extensive analyses of plasma proteins in patients with chronic thromboembolic pulmonary hypertension have shown no abnormalities in fibrinolysis.

Various possible results of disturbed resolution of a thrombus


• The bronchial and nonbronchial systemic circulation is markedly increased.– To maintain pulmonary blood flow in the

presence of vessel obstruction





CT TechniqueCT Technique

Acute PEAcute PE• MDCT • Trigger threshold

– Main PA– 120 HU

• Contrast material– 100 mL (iopromide,

Ultravist 300)– 4 mL/sec

Chronic PEChronic PE• MDCT• Trigger threshold

– Main PA– 200 HU

• Contrast material– 100 mL (iopromide,

Ultravist 300)– 4 mL/sec

window width

window level

Lung window 1500 -600

Mediastinum window 350 40

Pulmonary thromboembolism-specific window

700 100

CT TechniqueCT Technique

CT TechniqueCT Technique• Multiplanar

reformatted images

• Maximum intensity projection images

- - 47Chronic pulmonary thromboembolism in a year old man. CoronalMIP iiiii





CT Features of ChronicCT Features of ChronicPulmonary ThromboembolismPulmonary Thromboembolism

• Vascular signsVascular signs– Direct pulmonary artery signs

– Signs due to pulmonary hypertension

– Signs due to systemiccollateral supply

• Parenchymal signsParenchymal signs– Scars

– A mosaic perfusion pattern

– Focal groundglass opacities

– Bronchial dilatation

Pulmonary Arterial SignsPulmonary Arterial Signs

• Complete ObstructionComplete Obstruction

– Abrupt decrease in vessel diameter – Absence of contrast material in the vessel segment

distal to the total obstruction

– Lung window : segmental and subsegmental vessels that are abnormally small in comparison with the accompanying bronchi.

Chronic pulmonary thromboembolism in a 65-year-old man with a history of multiple episodes of acute pulmonary thromboembolism.

(a) Axial contrast-enhanced CT, (b) Axial CT scan (lung window)

Pulmonary Arterial SignsPulmonary Arterial Signs

• Partial Filling DefectsPartial Filling Defects– Abrupt vessel narrowing.

• Recanalization• Organized thrombus

– Poststenotic dilatation or aneurysm. – Thrombus :

• Obtuse angles to arterial wall.• Band or web: most frequently in lobar or segmental arteries

, rarely in the main pulmonary artery.• Calcifications within chronic thrombi (in a small number of

patients)

Chronic pulmonary thromboembolism in a 47-year-old man.Coronal 10-mm-thick maximum intensity projection image.

Chronic pulmonary thromboembolism in an 80-year-old woman with a history of

acute pulmonary thromboembolism.Axial contrast-enhanced CT scan.


acute pulmonary thromboembolism.Axial contrast-enhanced CT scan.


acute pulmonary thromboembolism.Oblique coronal 30-mm-thick maximum intensity projection CT image.


acute pulmonary thromboembolism.Oblique coronal 10-mmthick maximum intensity projection CT image

Residual band from a pulmonary thrombus in an 83-year-old woman with dyspnea. Axial contrast-enhanced CT image .

Residual band from a pulmonary thrombus in an 83-year-old woman with dyspnea. Coronal 10-mm-thick maximum intensity projection CT image.

Chronic pulmonary thromboembolism in an 86-year-old woman. Axial contrast-enhanced CT scan, (width, 1100 HU; level, 100 HU)




– Signs due to systemiccollateral supply





Signs of pulmonary hypertension Signs of pulmonary hypertension

• Main pulmonary artery diameter more than 29 mm.• Diameter of MPA : Aorta > 1:1 = strong correlation

with elevated pulmonary artery pressure, especially in patients younger than 50 years.

• Central pulmonary arteries in patients with chronic thromboembolic pulmonary hypertension often are asymmetric in size.

• Atherosclerotic calcification of arterial wall.• Tortuous pulmonary vessels.

Main pulmonary artery diameter more than 29 mm

Chronic pulmonary thromboembolism and pulmonary hypertension in a 42-year-old man.Axial contrast-enhanced CT scan.


acute pulmonary thromboembolism.Oblique coronal 10-mmthick maximum intensity projection CT image

Signs of pulmonary hypertension Signs of pulmonary hypertension

• RV myocardial thickness greater than 4 mm.• RV dilatation : a ratio of more than 1:1 between the

RV:LV diameters. (At widest points)

• Mild pericardial thickening or a small pericardial effusion.

• May have enlarged lymph nodes.– At histologic examination of these enlarged nodes, a vascular

transformation of the lymph node sinus may be seen, often in association with sclerosis of varying degrees

Right heart abnormalities secondary to chronic thromboembolic pulmonary

hypertension in a 47-year-old man.Axial contrast-enhanced CT scan.

Right heart abnormalities secondary to chronic thromboembolic pulmonary

hypertension in a 47-year-old man.Axial contrast-enhanced CT scan.




– Signs due to systemic collateral supply





Collateral Systemic SupplyCollateral Systemic Supply

• Bronchial flow may represent almost 30% of the systemic blood flow ( Normal = 1-2%).

• Systemic-to-pulmonary arterial anastomoses develop beyond the level of obstruction.

• CT findings of bronchial artery hypervascularization.– Abnormal dilatation of the proximal portion of the bronchial

arteries (diameter of more than 2 mm) and arterial tortuosity.

Collateral Systemic SupplyCollateral Systemic Supply

• Found more frequently in patients with chronic thromboembolic pulmonary hypertension (73%) than in patients with idiopathic pulmonary hypertension (14%).

• Lower mortality rate after pulmonary thromboendarterectomy.

• Development of systemic hypervascularization may also be responsible for hemoptysis in these patients

Chronic pulmonary thromboembolism in a 47-year-old man.Coronal 10-mm-thick maximum intensity projection image.


acute pulmonary thromboembolism Axial contrast-enhanced CT scan .


acute pulmonary thromboembolism Oblique coronal 20-mm-thick maximum intensity projection CT image

Chronic pulmonary thromboembolism in a 47-year-old man with multiple episodes of acute pulmonary thromboembolism.

Coronal 30-mm-thick maximum intensity projection CT image.









Parenchymal SignsParenchymal Signs

• Scars from prior pulmonary infarctions– May appear as parenchymal bands, wedge-shaped

opacities, peripheral nodules, cavities, or irregular peripheral linear opacities.

– Parenchymal scars often occur in multiples, generally are found in the lower lobes, and often are accompanied by pleural thickening.

Chronic pulmonary thromboembolism in an 85-year-old woman, 2 years after an episode of massive acute thromboembolism

CT scan (lung window)

Chronic pulmonary thromboembolism in a 65-year-old man with a history of multiple episodes of acute pulmonary thromboembolism.

Axial CT scan (lung window)

Chronic pulmonary thromboembolism in an 46-year-old man.CT scan (lung window)

Chronic pulmonary thromboembolism in a 65-year-old manCT scan (lung window)


• A mosaic pattern of perfusion – Sharply demarcated regions of decreased and increased

attenuation because of irregular perfusion.– Much more commonly in patients with chronic

thromboembolic pulmonary hypertension than in patients with idiopathic pulmonary hypertension

• Focal areas of ground-glass attenuation– Systemic perfusion of the peripheral pulmonary arterial bed

accounts for the presence of isolated focal areas of ground-glass attenuation.

Chronic pulmonary thromboembolism in an 85-year-old woman, 2 years after an episode of massive acute thromboembolism

CT scan (lung window)

Chronic pulmonary thromboembolism in a 65-year-old manCT scan (lung window)

Chronic pulmonary thromboembolism in an 80-year-old woman with a history of acute pulmonary thromboembolism

Coronal 20-mm-thick maximum intensity projection CT image.


• Air trapping – Arakawa et al : Significant associations between

• The appearance of air trapping and the presence of a proximal arterial stenosis or clot.

• The extent of air trapping and the degree of impairment of pulmonary function of the small airways.

– Seen in two thirds of patients with chronic thromboembolic pulmonary hypertension.

– Commonly seen in areas of hypoperfusion.

• Bronchial dilatation

Chronic pulmonary thromboembolism in an 82-year-old woman. Axial CT scan (lung window) (a) inspiration (b) expitation

Chronic pulmonary thromboembolism in an 82-year-old woman. (a) Axial CT scan (lung window) , (b) Axial contrast-enhanced CT scan













Differential DiagnosisDifferential Diagnosis

1. Idiopathic Pulmonary Hypertension.

2. Differentiation of Acute and Chronic Thromboembolism.

3. Proximal Interruption of the Pulmonary Artery.

4. Takayasu Arteritis.

5. Primary Sarcoma of the Pulmonary Artery.

6. Bronchial Abnormalities.

Differential DiagnosisDifferential Diagnosis• Idiopathic Pulmonary Idiopathic Pulmonary

Hypertension.Hypertension.– Enlargement of collateral arteries ( 73% in

chronic PE VS 14% in idiopathic pulmonary hypertension)

– Mosaic lung attenuation is seen frequently in patients with chronic thromboembolic pulmonary hypertension and is hardly ever seen in idiopathic pulmonary hypertension.

– Lung infarcts are rarely seen in patients with idiopathic pulmonary hypertension.

Differential DiagnosisDifferential Diagnosis• Differentiation of Acute and Differentiation of Acute and

Chronic Thromboembolism.Chronic Thromboembolism.– Acute and chronic thromboembolism commonly

coexist.

Differential DiagnosisDifferential DiagnosisAcute PEAcute PE Chronic PEChronic PE

Increased Diameter of pulmonary artery.

Decreased Diameter of pulmonary artery.

Nonobstructive eccentric filling defect forms acute angles with the vessel wall.

Nonobstructive eccentric filling defect forms obtuse angles with the vessel wall.

Dilated bronchial arteries.

Mean attenuation in chronic PE (87 HU ± 30) is higher than acute PE (33 HU ± 15).

Evolution of chronic occlusive pulmonary thromboembolism from acute embolism in a 40-year-old man. (a) Axial contrast-enhanced CT scan shows acute embolism in the left lower lobe, with increased arterial

diameters (arrows) due to impacted thrombi. (b) Axial contrast-enhanced CT scan obtained at the same level as a, 1 year later, when the patient presented

with dyspnea, shows a permanent reduction in the diameters of the left lower lobe arteries (arrows) because of thrombus organization and retraction, findings indicative of chronic thromboembolism.

Differential DiagnosisDifferential Diagnosis• Proximal Interruption of the Proximal Interruption of the

Pulmonary ArteryPulmonary Artery– smooth, abrupt tapering of the pulmonary artery,

without endoluminal changes.– Only 3% presence multiple bilateral arterial

abnormalities.

Unilateral proximal interruption of the right pulmonary artery in a 52-year-old woman with progressive dyspnea.

Axial contrast-enhanced CT scan .

Differential DiagnosisDifferential Diagnosis• Takayasu ArteritisTakayasu Arteritis

– Frequently affects the aorta and its major branches.– Pulmonary artery involvement occurs in 50%–80% of

patients and is a manifestation of late-stage disease.

– Findings of wall thickening in the aorta and aortic branches – Stenosis and occlusion, mainly involve segmental and

subsegmental a. ,less involve lobar or main pulmonary a.

Late-stage Takayasu arteritis with right pulmonary artery involvement in a 63-year-old woman. (a) Axial contrast-enhanced CT scan (b) at the level of the supra-aortic trunks

Differential DiagnosisDifferential Diagnosis• Primary Sarcoma of the Pulmonary Primary Sarcoma of the Pulmonary

a.a.– Rare.– Most invole: The main or proximal pulmonary a.

– Filling defect frequently spans the entire luminal diameter of the artery.

– Extension into the lung parenchyma or mediastinum – Delayed enhancement

– Chong et al reported : positive uptake of fluorine 18 fluorodeoxyglucose at PET CT

Pulmonary artery sarcoma in a 70-yearold man with dyspnea. Axial contrast-enhanced CT

Differential DiagnosisDifferential Diagnosis• Bronchial AbnormalitiesBronchial Abnormalities

– Bronchial dilatation is a well-known hallmark of chronic obstructive pulmonary disease (COPD).

– Mucus-filled dilated bronchi, pulmonary infiltrates, or both are usually present.





Diagnostic EvaluationDiagnostic Evaluation

• Transthoracic echocardiographyTransthoracic echocardiography– Diagnosis of pulmonary hypertension.– Exclude other cardiac causes of pulmonary

hypertension.


• Ventilation-Perfusion ScintigraphyVentilation-Perfusion Scintigraphy– Tunariu et al : V/Q scintigraphy has a higher

sensitivity than CTPA.– Not determination of the magnitude, location or

extent of disease.– Cannot predict its surgical operability. – Not help identify other causes of pulmonary

hypertension


• Right Heart Catheterization and Right Heart Catheterization and Pulmonary AngiographyPulmonary Angiography

– Standard for diagnosis chronic thromboembolic pulmonary hypertension.

– Determination of the postoperative prognosis.– Gives an indication of surgical operability.

– However, in the future, pulmonary angiography probably will be performed only when an adequate surgical roadmap has not been provided by CT and MRI

Diagnostic EvaluationDiagnostic Evaluation• CT AngiographyCT Angiography

– Diagnosing chronic thromboembolic pulmonary hypertension

– Determining surgical operability

– More sensitive than conventional angiography in depicting the central thrombotic disease.

– Equally sensitive to MRA in depicting the disease at the segmental level

– Superior to MRA for the depiction of patent subsegmental a. and intraluminal webs and for the direct demonstration of thrombotic wall thickening

Diagnostic EvaluationDiagnostic Evaluation• MR ImagingMR Imaging

– Characterization of the impairment of function in the right side of the heart.

– Estimation of flow in the bronchial arteries.– It also may play an important role in postoperative follow-

up

– Cannot take the place of conventional angiography and right heart catheterization for the preoperative determination of pulmonary vascular resistance and mean pulmonary artery pressure





TreatmentTreatment• The primary treatment for chronic thromboembolic pulmonary

hypertension is surgical pulmonary thromboendarterectomy.– Hemodynamic or ventilatory impairment at rest or exercise.

– Marked pulmonary hypertension develops during exercise.

• CTA features predictive of a good response.– Evidence of extensive central vessel disease and limited small-

vessel involvement .

– Dilated bronchial arteries.

• Placement of a filter in the inferior vena cava is recommended.• Lifelong anticoagulant therapy

Education

Chronic PE