diagnostic imaging of pulmonary vasculature

ChestPulmonary Vasculature

Mohamed Zaitoun

Assistant Lecturer-Diagnostic Radiology Department , Zagazig University Hospitals

EgyptFINR (Fellowship of Interventional

Neuroradiology)-Switzerlandzaitoun82@gmail.com

Knowing as much as possible about your enemy precedes successful battle

and learning about the disease process precedes successful management

Pulmonary Vasculaturea) Pulmonary Artery Hypertensionb) Pulmonary Edemac) Pulmonary Embolismd) Venous Abnormalities

a) Pulmonary Artery Hypertension :1-Definition2-Etiology3-Classification4-Radiographic Findings

1-Definition :-PAH is defined as P-systolic > 30 mm Hg or P-

mean > 25 mm Hg-Normal pulmonary artery pressures in adults :P-systolic = 20 mm HgP-diastolic = 10 mm HgP-mean = 14 mm HgCapillary wedge pressure = 5 mm Hg

2-Etiology :a) Primary PAH (females 10-40 years , rare)b) Secondary PAH (more common) :1-Eisenmenger's syndrome2-Chronic PE3-Emphysema , pulmonary fibrosis4-Schistosomiasis (most common cause

worldwide)

3-Classification :a) Precapillary Hypertension :1-Vascular :-Increased flow : L-R shunts-Chronic PE-Vasculitis-Drugs-Idiopathic2-Pulmonary :-Emphysema-Interstitial Fibrosis-Fibrothorax , chest wall deformities-Alveolar hypoventilation

b) Postcapillary Hypertension :1-Cardiac :-LV failure-Mitral stenosis-Atrial Tumor2-Pulmonary Venous :-Idiopathic venocclusive disease-Thrombosis

4-Radiographic Findings :a) Plain Radiographyb) CTc) MRI

a) Plain Radiography :-The classic radiographic findings of pulmonary

hypertension are evident only late in the disease process :

1-Central pulmonary arterial dilatation2-Cardiomegaly (enlarged right ventricle & atrium)3-Calcification of the pulmonary arteries is

pathognomonic but occurs late in the disease

(a) Frontal chest radiograph shows a prominent main pulmonary artery (arrow) , dilated right interlobar artery (arrowhead) and pruning of peripheral pulmonary vascularity , (b) Lateral chest radiograph shows filling of the retrosternal airspace (arrow) a result of right ventricular dilatation , the right ventricle is in contact with more than one-third of the distance from the sternodiaphragmatic angle (black arrowhead) to the point where the trachea meets the sternum (white arrowhead)

 Yellow arrow shows enlarged right main pulmonary artery , red arrow shows the enlarged left pulmonary artery

b) CT :-Vascular , cardiac and parenchymal1-Vascular :-Enlarged main PA (diameter correlates with pressure) :

>29 mm is indicative of PAH-Rapid tapering of PA towards the periphery-If the ratio of pulmonary artery diameter to aortic diameter

is greater than 1 (rPA >1) by CT , there is a strong correlation with elevated mean PA pressure , particularly in patients <50 years of age

-Calcification of the pulmonary arteries is pathognomonic but occurs late in the disease

2-Cardiac :-Cardiomegaly (enlarged right ventricle &

atrium)-Dilatation of the inferior vena cava and

hepatic veins and pericardial effusion-Contrast material reflux into the inferior

vena cava and hepatic veins , a result of elevated right heart pressures also may be seen

3-Parenchymal :-Both primary and secondary forms of pulmonary

hypertension may produce a mosaic pattern of lung attenuation , a finding suggestive of regional variations in parenchymal perfusion , vascular cause for the mosaic pattern is suggested when areas of high attenuation contain larger-caliber vessels and areas of low attenuation contain vessels of diminished size

-Vascular signs of pulmonary hypertension

-Axial multidetector CT angiogram shows dilatation (29 mm or more) of the main pulmonary artery

-The ratio of the main pulmonary arterial diameter to that of the ascending aorta is also greater than or equal to 1, another useful sign of pulmonary hypertension

-(A) Markedly enlarged pulmonary arteries with tiny branching smaller vessels

-(B) Enlarged right ventricle and the smaller left ventricle , the septum is pushed towards the left ventricle due to very high pressure inside the right ventricle

Cardiac features of pulmonary hypertension. (a) CTA shows that the right ventricular myocardium (white arrow) is more than 4 mm thick , a finding consistent with right ventricular hypertrophy. Straightening of the interventricular septum (black arrow) also is seen. (b) CTA shows right ventricular dilatation which is defined as a diameter ratio (the ratio of the right ventricular diameter [black arrow] to the left ventricular diameter [white arrow]) greater than 1:1 at the midventricular level , Leftward bowing of the interventricular septum also is seen. (c) CTA shows reflux of contrast material into the inferior vena cava which is dilated and hepatic veins (arrow)

c) MRI :-Morphologic cardiac changes include right

ventricular dilatation and hypertrophy , right atrial enlargement , flattening of the interventricular septum or leftward bowing & tricuspid regurgitation

-Decreased velocity of pulmonary flow by MRA

b) Pulmonary Edema :1-Etiology2-Radiographic Features

1-Etiology :1-Cardiogenic : (any cause of impaired left ventricular function)-LVF , MR2-Renal :-RF , volume overload3-Lung Injury :-Septic shock , neurogenic shock-Fat embolism-Aspiration , drowning4-Cerebral Diseases :-Cerebrovascular accident , head injury or raised intracranial pressure5-Radiotherapy6-Liver diseases and other causes of hypoproteinemia7-Drug induced 8-Poisons9-Mediastinal Tumors (producing venous or lymphatic obstruction)10-ARDS11-High altitude

-N.B. :Unilateral pulmonary edema :a) Pulmonary edema on the same side as a pre-

existing abnormality :1-Prolonged lateral decubitus position2-Unilateral aspiration3-Pulmonary contusion4-Rapid thoracocentesis of air or fluid5-Bronchial obstruction6-Systemic artery to pulmonary artery shunts

b) Pulmonary edema on the opposite side to a pre-existing abnormality :

1-Congenital absence or hypoplasia of a pulmonary artery

2-McLeod syndrome3-Thromboembolism4-Unilateral emphysema5-Lobectomy6-Pleural disease

2-Radiographic Features :-Cardiac size / cardio-thoracic ratio (LT sided

cardiac ++) : useful for assessing for an underlying cardiogenic cause or association

-Bat wing pulmonary opacities (centrally located lesion) , i.e. enlarged hazy hilar shadows

-Distended upper lobe vessels -Septal lines , Kerley lines-Thickened interlobar fissures-Pleural effusions (right sided , if bilateral it will be

more at the RT side)-Presence of peribronchial cuffing-Patient is almost in the ICU with ECG leads

appearing in the film

c) Pulmonary Embolism :1-Definition2-Types3-Risk Factors4-Clinical Picture5-Radiographic Findings

1-Definition :-Embolic occlusion of the pulmonary arterial

system

2-Types :a) Incomplete Infarct :-Hemorrhagic pulmonary edema without tissue

necrosis , resolution within daysb) Complete Infarct :-Tissue necrosis , healing by scar formation

3-Risk Factors :a) Immobilization >72 hours (55% of patients with

proven PE have this risk factor)b) Recent hip surgery , 40%c) Cardiac disease , 30%d) Malignancy , 20%e) Estrogen use (prostate cancer ,

contraceptives) , 6%f) Prior deep vein thrombosis (DVT) , 20%

4-Clinical Picture :-Chest pain , 90%-Tachypnea (>16 breaths/min) , 90%-Dyspnea , 85%-Rales , 60%-Cough , 55%

5-Radiographic Findings :a) Plain Radiographyb) CTAc) Nuclear Medicine

a) Plain Radiography :1-Fleishner sign : enlarged pulmonary artery

(20%)2-Hampton hump : peripheral wedge of

airspace opacity and implies lung infarction (20%)

3-Westermark's sign : regional oligaemia (10%)

4-Pleural effusion (35%)

Fleishner Sign

Hampton Hump

-Westermark's Sign-A chest x-ray showed an

elevated left hemidiaphragm and an area of focal oligemia (Westermark's sign) in the right lung (area between white arrowheads) with a prominent right descending pulmonary artery

b) CTA :1-Acute PE :-Filling defects within the pulmonary vasculature-Polo mint sign : when observed in the axial plane ,

the central filling defect from the thrombus is surrounded by a thin rim of contrast appearing like the popular sweet , the polo mint

-Expanded unopacified vessel-Eccentric filling defect-Peripheral wedge shaped consolidation-Pleural effusion

Impacted thrombus distal to point of occlusion (arrow) that expands vessel diameter

Eccentric filling defect within pulmonary artery (arrow)

With lung infarction

Saddle shaped thrombus

2-Chronic PE :-Webs or bands , intimal irregularities-Abrupt narrowing or complete obstruction of

the pulmonary arteries-Pouching defects which are defined as

chronic thromboemboli organized in a concave shape that points toward the vessel lumen

Band or web (arrow)

Multiple intimal irregularities (straight arrows). , poststenotic dilatation (arrowhead) is shown affecting posterior segment of right upper lobe , also noted within right lower lobe is tortuous vessel (curved arrow)

Organized thrombus (arrows) as cause of intimal irregularities , in addition , poststenotic dilatation (arrowhead) is shown affecting posterior segmental artery , again shown within right lower lobe is tortuous vessel (curved arrow)

Pouch defect of anterior basal segment of right lower lobe (arrow) , contracted artery (arrowheads) is smaller than adjacent bronchus

c) Nuclear Medicine : V/Q scan-Show ventilation-perfusion mismatches

-N.B. :Differential Diagnosis of non-thrombotic pulmonary

emboli :1-Septic embolism (venous catheters , tricuspid valve

endocarditis & peripheral septic thrombophlebitis)2-Catheter embolism3-Fat embolism4-Venous air embolism 5-Amniotic fluid embolism6-Tumor embolism7-Talc embolism (in i.v. drug abusers)8-Iodinated oil embolism (following contrast

lymphangiography)9-Cotton embolism10-Hydatid embolism

d) Venous Abnormalities :1-Pulmonary AVM2-Pulmonary Varices3-Aortic Nipple4-Pulmonary Venoocclusive Disease

1-Pulmonary AVM :a) Definitionb) Typesc) Locationd) Radiographic Features

a) Definition :-Abnormal communication between

pulmonary artery and veins -They can be multiple in 1/3 of cases

b) Types :1-Congenital : 60 %-Osler Weber Rendu Disease (Hereditary

Hemorrhagic Telangiectasia “HHT”)2-Acquired :-Iatrogenic-Infection-Tumor

c) Location :-Lower lobes , 70% > middle lobe > upper

lobes

d) Radiographic Features :1-Plain Radiography2-CT

1-Plain Radiography :- A common radiographic finding is a round

or oval mass of uniform opacity-The opacity may have sharply defined

borders with occasional lobulation-The mass is usually 1-5 cm and linear

shadows are adjacent to the opacity , these are the feeding vessels

Multiple PAVM

2-CT :-The characteristic presentation of a PAVM on

non-contrast CT is a homogeneous well-circumscribed non-calcified nodule up to several centimeters in diameter or the presence of a serpiginous mass connected with blood vessels

-Contrast injection shows enhancement of the feeding artery , the aneurysmal part and the draining vein on early phase sequences

NECT

2-Pulmonary Varices :a) Definitionb) Radiographic Features

a) Definition :-Localized aneurysmal dilatation of a

pulmonary vein -Uncommon lesions that are typically

asymptomatic and do not require treatment , usually discovered incidentally

1-Root of aorta2-Pulmonary outflow3-Left atrium4-Left pulmonary vein5-Superior vena cava6-Descending aorta

b) Radiographic Features :-Dilated vein-Usually near left atrium

Dilatation of right upper pulmonary vein adjacent to left atrium

3-Aortic Nipple :-Normal variant (10% of population) caused

by the left superior intercostal vein seen adjacent to the aortic arch

-Maximum diameter of vein : 4 mm

-Left superior intercotal vein , curvilinear contrast filled vessel along the left lateral border of the aorta (white arrow) that can be traced from the left brachiocephalic vein (red arrow) to the region of the accessory hemiazygous vein (blue arrow)

4-Pulmonary Venoocclusive Disease :-Occlusion of small pulmonary veins-The proposed initial insult in PVOD is

venous thrombosis , possibly initiated by infection , toxic exposure or immune complex deposition