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between precapillary pulmonary hypertension

(mean pulmonary arterial pressure > 25 mm

Hg, pulmonary capillary wedge pressure 15

mm Hg) and postcapillary pulmonary hyper-

tension (mean pulmonary arterial pressure > 25

mm Hg, pulmonary capillary wedge pressure >

15 mm Hg) may be more practical, particularly

for clinical use. Precapillary pulmonary hyper-

tension includes pulmonary arterial hyperten-

sion (WHO class 1), pulmonary hypertension

due to lung parenchymal disease (WHO class

3), chronic thromboembolic pulmonary hy-

pertension (WHO class 4), and miscellaneous

causes (WHO class 5). Postcapillary pulmo-

nary hypertension includes pulmonary venous

hypertension associated with left-heart disease

(WHO class 2).

The epidemiology, clinical presentation,

pathophysiologic mechanisms, and thera-

peutic strategies are discussed in detail else-

where. This focuses on the modern diagnos-

tic approach to pulmonary hypertension,

emphasizing the crucial role played by imag-

ing. The emerging role of noninvasive imag-

ing is discussed.

Role of Imaging in Diagnosis and

Management

Notwithstanding the vast number of condi-

tions that lead to pulmonary hypertension, the

clinical presentation is consistent: dyspnea, ini-

tially with exertion, with or without signs and

symptoms of the underlying condition. If pul-

monary hypertension is left untreated, the clini-

cal course is progressive nonlinear deterioration

Current Role of Imaging in theDiagnosis and Management ofPulmonary Hypertension

Eduardo Jose Mortani Barbosa, Jr.1

Narainder K. Gupta

Drew A. Torigian

Warren B. Gefter

Mortani Barbosa EJ Jr, Gupta NK, Torigian DA,

Gefter WB

1All authors: Department of Radiology, Hospital of the

University of Pennsylvania, 340 0 Spruce St, Philadelphia,

PA 19104. Address correspondence to E. J. Mortani

Barbosa Jr ([email protected]).

Cardiopulmonary Imaging Review

AJR2012; 198:13201331

0361803X/12/19861320

American Roentgen Ray Society

Classification

In its broadest sense, pulmonary hyperten-

sion is a pathophysiologic condition in which

the hemodynamics in the pulmonary circu-

lation are altered. An increase in pulmonary

vascular resistance increases mean pulmo-

nary arterial pressure to greater than 25 mm

Hg [1]. This definition encompasses several

distinct clinical entities with variable path-

ologic mechanisms and prognoses. Many

classification schemes have been devised

in an attempt to devise a conceptual frame-

work for clinical and research purposes. Ini-

tially, a division was made between primary

and secondary pulmonary hypertension [2].

The former comprised diseases that primar-

ily affect the pulmonary vasculature, and

the latter, diseases primarily involving the

heart and lung parenchyma. Improved un-

derstanding of molecular pathophysiologic

mechanisms led to more-detailed classifica-

tion schemes. A scheme that originated at the

second World Health Organization (WHO)

symposium [3] led to the current classifica-

tion, which was proposed at the third WHOsymposium in 2003 and modified in 2008 [4,

5]. The WHO classification divides pulmo-

nary hypertension into the five groups shown

in Appendix 1.

Because of the complex interplay between

the right heart, lungs, and left heart as a func-

tional cardiorespiratory unit, clinical diagno-

sis and classification according to the WHO

scheme can be challenging. From a diagnos-

tic standpoint, the hemodynamic distinction

Keywords:diagnosis, management, noninvasive imaging,

pulmonary hypertension

DOI:10.2214/AJR.11.7366

Received June 8, 2011; accepted after revisionOctober 18, 2011.

OBJECTIVE. The purpose of this review is to describe classification schemes and

imaging findings in the diagnosis and management of pulmonary hypertension.

CONCLUSION.Pulmonary hypertension is a complex pathophysiologic condition in

which several clinical entities increase pressure in the pulmonary circulation, progressively

impairing cardiopulmonary function and, if untreated, causing right ventricular failure. Cur-

rent classification schemes emphasize the necessity of an early, accurate etiologic diagnosis

for a tailored therapeutic approach. Imaging plays an increasingly important role in the diag-nosis and management of suspected pulmonary hypertension.

Mortani Barbosa et al.Pulmonary Hypertension

Cardiopulmonary ImagingReview

AmericanJournalofRoentgenology2012.1

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Pulmonary Hypertension

resulting in severe right-heart dysfunction with

dyspnea at rest [6, 7]. The role of the clinician

is to make the diagnosis of pulmonary hyper-

tension as early as possible. It also is critical to

correctly classify the type of pulmonary hyper-

tension according to the modified WHO clas-

sification so that effective tailored therapy can

be instituted [5].

The definitive hemodynamic diagnosis of

pulmonary hypertension requires right-heart

catheterization [8, 9], an invasive diagnos-

tic procedure used for direct measurement

of right ventricular pressure and pulmonary

arterial pressure and indirect measurement

of pulmonary venous pressure through pul-

monary capillary wedge pressure through-

out the cardiac cycle [10]. Nonetheless, be-

cause of the costs and risks associated with

right-heart catheterization, this modality is

rarely used as a first-line test. Several ev-

idence-based diagnostic algorithms havebeen devised that emphasize judicious use of

invasive imaging and an initial approach that

combines noninvasive imaging, clinical as-

sessment, and nonimaging tests [1, 11].

The pivotal elements of the initial assess-

ment are history and physical examination,

chest radiography, ECG [12, 13], and trans-

thoracic echocardiography [1, 14]. The initial

goals are not only to establish a tentative diag-

nosis of pulmonary hypertension but also to

diagnose or exclude the most common causes

of pulmonary hypertension: left-heart failure

and lung parenchymal diseases that lead to hy-

poxemia (formerly categorized as secondarypulmonary hypertension) [1517]. Contingent

on the results of initial tests, additional, more

specific tests are ordered. For instance, abnor-

mal results of transthoracic echocardiography

would lead to transesophageal echocardiogra-

phy; abnormal findings at chest radiography

would lead to chest CT or ventilation-perfu-

sion (V/Q) scanning; and abnormal findings

at physical examination would lead to pulmo-

nary function testing.

If the diagnosis of left-heart failure or a

lung parenchymal disease that leads to hypox-

emia is confirmed and the degree of pulmo-

nary hypertension is deemed proportionate to

the severity of the underlying condition, the

diagnostic workup is terminated, and proper

treatment is instituted. If not, V/Q scanning

or contrast-enhanced chest CT should be per-

formed to evaluate for suspected thromboem-

bolic disease. If thromboembolic disease is

present, anticoagulation and other preventive

measures, such as placement of an inferior

vena caval filter, are instituted. If no pulmo-

nary arterial filling defects or other direct or

indirect findings suggesting pulmonary em-

bolism, either acute or chronic, are detected at

chest CT but segmental perfusion defects are

found at V/Q scanning, pulmonary venooc-

clusive disease and pulmonary capillary hem-

angiomatosis should be considered if other-

wise concordant chest CT findings are present

(see later). If no filling defects are seen in the

pulmonary arterial circulation at chest CT and

V/Q findings are normal, a tentative diagnosis

of pulmonary arterial hypertension (former-

ly categorized as primary pulmonary hyper-

tension) is made and confirmed with invasive

right ventricular catheterization. Additional

specific imaging and laboratory tests are per-

formed as needed to classify the condition

into one of the following groups: congenital

heart disease, connective tissue disease, HIV

infection, portal hypertension, chronic hemo-

lysis, drug toxicity, or idiopathic or familialdisorder [1, 11, 1821].

Imaging plays a crucial role throughout

the complex diagnostic algorithm. Every pa-

tient with suspected pulmonary hypertension

should generally undergo chest radiography

and transthoracic echocardiography. Chest

radiography is a universally available, safe,

and cost-effective study that can be used to

answer two fundamental questions: Does the

patient have substantial cardiomegaly (indi-

cating possible left-heart failure or congen-

ital heart disease)? Does the patient have

evidence of clinically significant chronic ob-

structive pulmonary disease (COPD) or in-terstitial lung disease (ILD)?

Chest Radiography

Chest radiography is not sensitive in the

detection of mild cardiomegaly, mild COPD,

or mild ILD, but the findings are almost nev-

er normal in the presence of moderate to se-

vere manifestations of any of these condi-

tions. If a finding is borderline normal or a

precise diagnosis is elusive, chest CT is the

recommended subsequent test because it is

more sensitive and specific than radiography.

Chest radiographic findings may suggest the

presence of pulmonary hypertension, but

the sensitivity and specificity are not high

enough for a definitive diagnosis. The fol-

lowing chest radiographic findings may in-

dicate the presence of pulmonary hyperten-

sion: enlargement of the right and left main

pulmonary arteries; hilar enlargement; ta-

pering or pruning of peripheral pulmonary

arteries; enlargement of the right interlobar

artery (greater than 15-mm diameter on a

posteroanterior frontal radiograph); ri

atrial and right ventricular enlargement; a

areas of oligemia, which appear as increas

lucency and decreased vascularity [22, 2

(Figs. 15). Pulmonary venous pressure c

be measured as pulmonary capillary wed

pressure (PCWP), which reflects left atr

pressure and left ventricular diastolic fi

ing pressure. PCWP can be estimated by o

serving the vascular pattern and the presen

of interstitial or alveolar edema on chest

diographs. It has been suggested that PCW

greater than 13 but less than 18 mm Hg

dicates the presence of vascular redistrib

tion with relative hypervascularity of the u

per lung fields; 1825 mm Hg, interstit

pulmonary edema; and greater than 25 m

Hg, alveolar edema and, often, pleural ef

sions. If pulmonary hypertension is pres

in these clinical situations, strong consid

ation should be given to left ventricular faure as a causal factor [2426].

Transthoracic Echocardiography

Transthoracic echocardiography is a no

invasive, safe, and relatively readily ava

able modality that plays a major role in

evaluation of the heart, complementing ch

radiography. It yields semiquantitative fu

tional and anatomic information and is

invaluable tool for the diagnosis of syst

ic and diastolic dysfunction of the left a

right ventricles, of intracardiac shunt, and

valvular stenosis and regurgitation. Becau

assessment of right ventricular functionessential for determining prognosis and

sponse to therapy, transthoracic echocar

ography should be performed early in the

agnostic workup of pulmonary hypertensi

[27]. If there are limitations to the transth

racic approach, transesophageal echocar

ography should be considered.

Doppler Echocardiography

Echocardiography also can be used to

timate pulmonary arterial pressure, althou

precise measurement requires right ventricu

catheterization [1, 5, 11]. Pulmonary arte

pressure is estimated with Doppler sonograp

by measurement of the velocity of the regur

tant jet from the tricuspid valve during systo

Because pressure cannot be directly measu

with Doppler sonography, right atrial pr

sure must be assumed, usually to be 78 m

Hg. Central venous pressure is estimated

physical evaluation of neck vein distenti

[28]. Tissue Doppler imaging has been p

posed to better characterize right ventricu


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Mortani Barbosa et al.

performance in the presence of pulmonary hy-

pertension. It has been found that delayed con-

traction of the right ventricular free wall in rela-

tion to that of the interventricular septum (right

ventricular dyssynchrony) correlates with pul-

monary hypertension (delay > 25 milliseconds)

and with right ventricular dysfunction (delay >

37 milliseconds) [29]. Echocardiography is cur-

rently the chief noninvasive imaging modality

in clinical use for the assessment of WHO group

2 pulmonary hypertension (associated with left-heart disease) [30, 31].

Chest CT

Chest CT is an invaluable noninvasive im-

aging modality in the workup of pulmonary

hypertension. It is the reference standard for

noninvasive diagnosis of ILD, either idio-

pathic or secondary to connective tissue dis-

ease, and of COPD, particularly emphysema

predominant, in combination with pulmonary

function testing [3235]. Although the diag-

nosis of small airways diseasepredominant

COPD is challenging with standard chest CT,expiratory imaging coupled with quantitative

analysis of imaging metrics and volumes fa-

cilitates accurate diagnosis and quantifica-

tion of disease severity, there being a strong

correlation between the imaging findings and

key pulmonary function testing parameters

[36]. Normal chest CT findings in a patient

with pulmonary hypertension imply that it is

highly unlikely that ILD or emphysema is a

significant etiologic factor [3235]. There-fore, as the best method for evaluating the

A

Fig. 152-year-old woman with chronic dyspnea and smoking history.

Aand B,Posteroanterior (A) and lateral (B) chest radiographs show hyperinflation of lungs and enlargement ofcentral pulmonary arteries, representing pulmonary hypertension secondary to chronic obstructive pulmonarydisease, which is the second most common cause of pulmonary hypertension worldwide.

Fig. 264-year-old man with ST-segment elevationmyocardial infarction and progressive respiratory

failure. Anteroposterior chest radiograph showstypical appearance of pulmonary alveolar edemasecondary to left ventricular congestive failurewith postcapillary pulmonary hypertension. Leftventricular failure is the most common cause ofpulmonary hypertension worldwide.

B

A

Fig. 333-year-old man with mild dyspnea on exertion.Aand B,Posteroanterior (A) and lateral (B) chest radiographs show moderate pulmonary arterial dilatation in association with known pulmonary hypertensionsecondary to left to right shunt due to longstanding atrial septal defect (ASD).C,Axial balanced steady-state free precession gradient-recalled echo cardiac MR image shows secundum ASD (arrow).

CB


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pulmonary parenchyma, chest CT is the best

diagnostic modality for diagnosis of WHO

group 3 pulmonary hypertension, which is

caused by hypoxic vasoconstriction second-

ary to parenchymal lung disease.

Contrast-enhanced chest CT performed with

MDCT scanners that generate isotropic volu-

metric datasets is the reference standard for the

diagnosis of acute and chronic thromboembol-

ic disease [3740]. Chest CT has intrinsic ad-

vantages over V/Q scanning in that it is tomo-

graphic (rather than planar), has submillimeter

spatial resolution, and, on high-quality imag-

es, depicts thrombotic and embolic filling de-

fects in the pulmonary arterial tree from the

level of the main pulmonary artery (MPA) to

the level of the subsegmental arteries [4143].

V/Q scanning plays a role in the diagnosis of

microvascular disease that manifests itself as

perfusion defects on a perfusion scan but is not

associated with directly detectable abnormali-

ties on chest CT images [44, 45] (Fig. 6).

On the one hand, because of the immense

functional reserve of the normal pulmonary

vasculature, it is uncommon for acute pul-

monary embolism to cause pulmonary hy-

pertension or right ventricular dysfunction

[4648]. Poor clinical outcome after acute

pulmonary embolism is nonetheless associ-

ated with right ventricular dysfunction and

large embolic burden, as measured with an

obstruction index of the pulmonary arterial

circulation of 40% or greater at helical chest

CT [49]. This situation generally occurs

only with massive saddle emboli in the large

proximal pulmonary arteries or with a large

number of relatively small emboli occluding

the more distal segmental or subsegmental

arteries [50, 51] (Fig. 7). On the other hand,

chronic pulmonary thromboembolism is far

more prone to be associated with pulmonary

hypertension, even in the absence of a sub-

stantial thromboembolic burden, because of

molecular adaptation mechanisms that lead

to remodeling of the pulmonary vasculatu

with medial hypertrophy and in situ sma

vessel thrombosis [37, 52, 53] (Fig. 8).

Acute and chronic pulmonary thromb

embolic disease can be differentiated on i

ages by the morphologic features of the p

monary arterial filling defects (usually clo

to central in location and occlusive if acu

likely eccentric in location, nonocclusive, a

sometimes calcified if chronic) and by the c

iber and distribution of the pulmonary arte

al branches (normal if acute, usually dila

centrally and pruned peripherally if chroni

The nonopacified pulmonary arterial bran

es tend to be dilated in acute thromboembo

disease but are generally smaller than adjac

patent vessels in chronic thromboembolic d

ease. Moreover, chronic thromboembolic d

ease tends to be associated with dilated c

tral pulmonary arteries, indicating pulmon

hypertension. Acute thromboembolic disea

however, generally presents with normal-c

A

A

Fig. 457-year-old woman with progressive dyspnea on exertion.Aand B,Posteroanterior (A) and lateral (B) chest radiographs show marked pulmonary arterial dilatation representing longstanding severe pulmonary hypertension d

to known patent ductus arteriosus and Eisenmenger physiology. Pulmonary arterial calcifications (arrow,B) are typical of chronic, severe pulmonary hypertension.C,Axial contrast-enhanced chest CT image confirms marked enlargement of central pulmonary arteries and mediastinal and chest wall edema suggesting rightventricular failure. Pulmonary artery catheter (Swan-Ganz) has been placed.

Fig. 546-year-old man with holodiastolic murmuAand B,Arterial (A) and venous (B) phase pulmonangiograms show postcapillary pulmonaryhypertension secondary to mitral stenosis. Massivleft atrial enlargement is evident.

B

B


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iber central pulmonary arteries unless there is

preexisting pulmonary hypertension. Other

findings suggesting chronic thromboembolic

disease include a mosaic perfusion pattern and

the presence of dilated bronchial or other sys-

temic collateral vessels [53, 54].

Dual-energy CT angiography has been pro-

posed as a method of assessing both vascu-

lar anatomy and quantitative perfusion in the

presence of chronic thromboembolic pulmo-

nary embolism. The correlation between per-

fusion parameters derived with dual-energy

CT and subjective assessment of mosaic atten-

uation pattern was strong (r> 0.6,p< 0.006),

but there was no statistically significant cor-

relation with vascular obstructive index, mean

pulmonary artery pressure, or pulmonary vas-

cular resistance [55]. Consequently, contrast-

enhanced chest CT is the most useful diag-

nostic modality for WHO group 4 pulmonary

hypertension (associated with acute and chron-

ic thromboembolic disease) (Figs. 912).

Other diseases that involve the pulmo-

nary microvasculature, such as pulmonary

venoocclusive disease and pulmonary capil-

lary hemangiomatosis (WHO group 1), and

miscellaneous causes, such as sarcoidosis,

hematologic disorders, neoplastic obstruc-

tion, fibrosing mediastinitis, and pulmonary

Langerhans cell histiocytosis (WHO group

5), can also be diagnosed with chest CT, fur-

ther augmenting the importance of this im-

aging modality in the diagnostic workup ofpulmonary hypertension [5659]. Chest CT

is also an important ancillary modality for

patients with WHO group 2 pulmonary hy-

pertension (associated with left-heart dis-

ease) because it depicts pulmonary inter-

stitial and alveolar edema, indicating the

presence of congestive heart failure and pul-

monary venous hypertension.

In addition to its dominant role in evalua-

tion of the lung parenchyma and pulmonary

thromboembolic disease, chest CT is useful

for direct assessment of the pulmonary arteries

Fig. 637-year-old man with ventilation-perfusion (V/Q) scan findings of chronic pulmonary

thromboembolism and pulmonary arterialhypertension. Planar ventilation images (top tworows) and planar perfusion images in differentprojections (bottom two rows) show multiple bilateralmismatched segmental perfusion defects. Diagnosisof pulmonary hypertension cannot be establishedwith V/Q scan alone, nor can this method be used

to differentiate acute from chronic pulmonarythromboembolism.

Fig. 750-year-old woman with acute dyspnea.Pulmonary angiogram shows extensive filling defectsin right interlobar artery and its right lower andmiddle lobe branches, indicating acute pulmonary

thromboembolism (PTE). Acute PTE is uncommonlyassociated with pulmonary hypertension, exceptif massive, in which case right ventr icular failuregenerally ensues with worse prognosis. Caliber ofpulmonary arterial tree is normal.

Fig. 854-year-old woman with recurrent pulmonarythromboembolism (PTE). Pulmonary angiogram showsdilatation and poor opacification of segmental andsubsegmental arteries without occlusive filling defects,indicating presence of chronic PTE, which is commonlyassociated with pulmonary hypertension. Markedenlargement of central pulmonary arteries is evident,as are pacemaker leads and cardiomegaly. Measuredmean pulmonary arterial pressure is 76 mm Hg.

Fig. 949-year-old man with chronic dyspnea onexertion. Axial contrast-enhanced chest CT imageshows chronic pulmonary thromboembolism,eccentric filling defect in right pulmonary artery(arrow), and marked enlargement of main pulmonaryartery to 4.9 cm, suggesting presence of pulmonaryhypertension.


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when pulmonary arterial hypertension is s

pected. It has been reported [60] that the fin

ing of MPA caliber greater than 29 mm m

sured 2 cm from the pulmonary valve has 84

sensitivity, 75% specificity, and 97% posit

predictive value for the presence of pulm

nary arterial hypertension, as confirmed w

invasive imaging. Moreover, if the MPA h

a maximum transverse diameter greater th

that of the proximal ascending thoracic ao

sensitivity is 70%, specificity 92%, and p

itive predictive value 96% for the presen

of pulmonary arterial hypertension [60]. O

should be mindful to first determine that

ascending aorta is not aneurysmal when p

forming these measurements.

Another chest CT finding suggestive

pulmonary arterial hypertension is enlar

ment of the segmental arteries greater th

1.25 times the caliber of the adjacent bro

chus. A combination of positive findings creases diagnostic confidence. For instan

the finding of an enlarged MPA (> 29 m

and concomitant enlargement of three

four segmental arteries (arterial-to-bronc

al diameter ratio, > 1.25) has 100% specifi

ity for the diagnosis of pulmonary arter

hypertension [60]. If pulmonary fibrosis

emphysema is present, however, the cor

lation between pulmonary artery dimensi

and severity of pulmonary hypertension

substantially weaker [61]. In the latter cl

ical situations, a combination of findings

warranted to suggest the diagnosis.

A prospective study [62] in which the sujects were 134 patients who underwent rig

heart catheterization and chest CT within

hours of each other showed that CT-deriv

measurement of the MPA diameter has stro

ger correlation with the presence of pulmon

hypertension in patients without ILD (M

diameter > 31.6 mm had a positive predict

value of 90.0% and a negative predictive va

of 58.3%) than in patients with ILD (MPA

ameter > 25 mm had a positive predictive v

ue of 46.3% and a negative predictive value

83.8%). In both groups, however, the MPA

ameter was significantly greater in patients w

pulmonary hypertension than in those witho

One conclusion is that pulmonary hypert

sion is more likely to be present even with n

mal-caliber pulmonary arteries if the under

ing diagnosis is ILD [62]. The presence

bronchial artery hypertrophy greater than

mm has also been implicated in pulmonary

terial hypertension, although this sign is pro

ably far more common in chronic pulmon

thromboembolic disease [63].

A B

Fig. 1064-year-old man with recurrent deep venous thrombosis.Aand B,Axial (A) and coronal maximum-intensity-projection (B) contrast-enhanced chest CT images showchronic pulmonary thromboembolism, eccentric filling defect in right pulmonary artery ( arrows, A), andmarked enlargement of central pulmonary arteries. Small loculated right pleural effusion and hypertrophy ofextrapleural fat on left also are evident.

A

Fig. 1171-year-old man with chronic exertional dyspnea.A,Axial contrast-enhanced chest CT image shows semiocclusive filling defect and intravascular web (arrow) inright lower lobe proximal lobar artery characteristic of chronic pulmonary thromboembolism.B,Coronal maximum-intensity-projection image shows variable caliber of lobar, segmental, and subsegmentalarteries in different lobes. Dilated branches are evident in right upper lobe and mid left upper lobe. Narrowedbranches are present in apical left upper lobe, another finding that is commonly seen in chronic pulmonary

thromboembolism.C,Axial chest CT image shows mosaic perfusion pattern secondary to chronic pulmonary thromboembolism.

C

B


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Several pulmonary parenchymal findings

are associated with pulmonary arterial hy-

pertension, though individually they are not

sensitive or specific enough to warrant the

diagnosis [58]. These findings include mosa-

ic attenuation (more commonly seen in pul-

monary hypertension due to chronic pulmo-

nary thromboembolic disease but also seen

in small airways disease without pulmonary

hypertension, among other possibilities)

and widespread tiny centrilobular ground-glass nodules (similar to those observed in

hypersensitivity pneumonitis but pathologi-

cally deemed to represent cholesterol gran-

ulomas or large plexogenic arterial lesions),

which have been described in 747% of pa-

tients with pulmonary arterial hypertension.

In a patient with pulmonary hypertension,

the presence of widespread tiny centrilobu-

lar ground-glass nodules or interlobular sep-

tal thickening should suggest the presence

of pulmonary capillary hemangiomatosis or

pulmonary venoocclusive disease, respec-

tively [6470] (Figs. 1315).

Direct evaluation of the heart is a relative-

ly new capability with ECG-gated MDCT,

which has high temporal and spatial resolu-

tion for 3D anatomic assessment of the heart

combined with 4D cardiac functional assess-

ment [71]. Several cardiac findings of pul-

monary hypertension can be present even atroutine nonECG-gated chest CT, includ-

ing right ventricular enlargement, flattening

or leftward convexity of the interventricu-

lar septum, and reflux of IV contrast mate-

rial from the right atrium into the inferior

vena cava. In addition to dilation of the main,

right, and left pulmonary arteries, quantita-

tive measurements of the heart obtained at

nonECG-gated chest CT have been found

predictive of pulmonary hypertension in hos-

pitalized patients as estimated with Doppler

echocardiography. In particular, right ven-

tricular free wall thickness of 6 mm or great-

er (odds ratio, 30.5), right ventricular wall

toleft ventricular wall thickness ratio of 0.32

or greater (odds ratio, 8.8), right ventricular

toleft ventricular luminal diameter ratio of

1.28 or greater (odds ratio, 28.8), and main

pulmonary arterytoascending aorta diam-

eter ratio of 0.84 or greater (odds ratio, 6.0)have been associated with increased odds of

pulmonary hypertension [72]. Calcifications

may be present in the walls of the central pul-

monary arteries, pathologically representing

atheromatous plaques. However, this finding

is usually seen only in late stage, severe pul-

monary hypertension.

For evaluation of subtle cardiac findings as-

sociated with the diagnosis of mild to moderate

A

A

B

B

Fig. 1249-year-old man with long-standingpulmonary hypertension.Aand B,Unenhanced axial chest CT images showmarked enlargement of central pulmonary arteries(A) and hypodense eccentric thrombus in dilatedright pulmonary artery (short arrow) with linear wallcalcifications (longarrow) (B). Linear calcificationsin pulmonary arterial walls represent atheromatousplaques, which can be seen in severe longstanding

pulmonary hypertension.

Fig. 1358-year-old woman with chronic cough and progressive dyspnea.A,Unenhanced axial chest CT image shows enlargement of main pulmonary artery to 3.8 cm.B,Unenhanced coronal chest CT image shows severe interstitial lung disease. Patient underwent bilateral

lung transplant, and clinical and pathologic findings confirmed pulmonary hypertension secondary to chronichypersensitivity pneumonitis.

Fig. 1463-year-old woman with pulmonaryhypertension. Unenhanced coronal chest CTimage shows widespread centrilobular andperibronchovascular ground-glass opacities.

Diagnosis of pulmonary capillary hemangiomatosiswas confirmed with bronchoscopic biopsy.


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pulmonary hypertension, ECG gating is nec-

essary. Intracardiac shunts such as atrial sep-

tal defect causing left to right shunting can be

diagnosed, as can details on the specific type

of defect (sinus venosus, ostium primum, osti-

um secundum). Ventricular septal defect is less

common in adults but when present can cause

substantial left to right shunting. In an adult ad-

mitted to the hospital with a diagnosis of septal

defect, the presence of a ventricular septal de-

fect and pulmonary hypertension is associated

with higher mortality than atrial septal defect

[73]. Partial and total anomalous pulmonary

venous return can cause marked left to right

shunting that leads to right-heart volume over-

load and eventually pulmonary hypertension

and right-heart failure, particularly if the left to

right shunt fraction is greater than 2 [74, 75].

Patent ductus arteriosus is another poten-

tial cause of left to right shunting that can

lead to severe pulmonary hypertension if un-corrected [76]. Regardless of the actual an-

atomic abnormality involved, any sustain

clinically significant left to right shunti

overloads the right-heart circulation, a

molecular and cellular adaptation mech

nisms lead to chronic right ventricular h

pertrophy and dilation and pulmonary arte

al hypertension [7782]. If the patient is n

treated, the arterial pressure in the right-s

circulation can rise above the systemic ar

rial pressure, effectively reversing the dir

tion of shunting (Eisenmenger physiolog

worsening the prognosis. Complex conge

tal cardiomyopathy and valvular disease c

also be diagnosed with ECG-gated chest C

but cardiac MRI is the preferred diagnos

modality for these conditions. Because

the absence of cardiac motion artifacts,

transverse diameter of the central arter

can be more accurately measured with EC

gated than with nongated chest CT [83, 84

Right and left ventricular function cbe quantitatively assessed with ECG-ga

A

D

B

E

Fig. 1634-year-old woman with idiopathicpulmonary arterial hypertension.Aand B,Balanced steady-state free precessiongradient-recalled echo right ventricular outflow

tract (A) and axial (B) cardiac MR images showenlargement of central pulmonary arteries.C,Midsystolic short-axis MR image shows leftwardeviation with flattening of interventricular septumdue to increased right ventricular pressure.Dand E,Velocity-encoded phase-contrast magnit(D) and phase (E) MR images can be used to measu

the velocity in main pulmonary artery (arrow,E),which correlates with pulmonary arterial pressure

Fig. 1544-year-old woman with pulmonaryhypertension who underwent bone marrow transplant5 years previously. Unenhanced coronal reformationchest CT image shows peripheral faint intralobularand interlobular septal thickening and associatedheterogeneous attenuat ion of lung parenchymadue to mosaic perfusion. Diagnosis of pulmonary

venoocclusive disease was proposed on the basisof clinical, imaging, and bronchoscopic findings.


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chest CT. The distensibility of the right pul-

monary artery has the strongest correlation

with mean pulmonary arterial pressure [85].

It is superior to right ventricular outflow tract

wall thickness and systolic diameter, indicat-

ing that functional measurements obtained

with ECG-gated chest CT add value to ana-tomic assessment of pulmonary arterial cali-

ber in the diagnosis and management of pul-

monary hypertension.

MRI

MRI is a powerful, noninvasive, flexible

modality that has several advantages over

CT and echocardiography in evaluation of

the heart. The absence of ionizing radiation

allows repeated examinations when neces-

sary without accumulative radiation expo-

sure. MRI has superior soft-tissue contrast

resolution and spatial resolution compared

with echocardiography and is operator inde-

pendent because it is not limited by acous-

tic windows and large habitus. MRI also can

be tailored for assessment of the heart (car-

diac MRI) and great vessels (MR angiogra-

phy of the chest) to generate both structural

and functional information. The usefulness

of MRI in assessing the pulmonary paren-

chyma, however, is substantially inferior to

that of CT [8692].

MRI is the reference standard for assess-

ment of congenital heart disease because it

accurately delineates structural changes,

cardiac situs, intracardiac shunts, atrioven-

tricular and ventriculoarterial relations, vas-

cular dimensions, and wall motion and val-

vular abnormalities [93]. MRI also is the

most useful modality for assessing right ven-

tricular anatomy and function, which is crit-

ical in the prognosis of pulmonary hyper-

tension [94, 95]. Contrast-enhanced MRI is

unique in depicting the presence and extent

of myocardial scarring related to previous

infarction, myocarditis, and infiltrative dis-

ease of the myocardium through depiction of

delayed enhancement, findings that can be

associated with left ventricular dysfunction

and pulmonary venous hypertension [96].

MRI, like Doppler echocardiography, can

be used to quantify flow velocity with phase-

contrast imaging, allowing estimation of ar-terial and intracardiac pressures. A major

strength of MRI compared with echocardi-

ography is that arbitrary planes can be set

without limitation by available acoustic win-

dows, leading to greater accuracy and repro-

ducibility in comparison with Doppler echo-

cardiography [97]. Further developments in

MRI techniques will increase the clinical

usefulness of this modality. It is conceiv-

able that the combination of advanced CT

and MRI techniques will effect thorough

anatomic and functional assessment of the

heart-lung unit in patients with suspected

pulmonary hypertension, obviating invasiveright-heart catheterization in selected pa-

tients. The introduction of PET/MRI systems

may contribute further to noninvasive diag-

nostic imaging through the acquisition of an-

atomic, physiologic, and metabolic data in a

single examination.

MRI is useful for comprehensive assess-

ment of the right ventricle. The complex 3D

structure of this chamber can be directly as-

sessed with MRI to measure right ventricu-

lar systolic and diastolic volumes and mass.

Four-dimensional functional assessment fa-

cilitates accurate evaluation of right ventricu-

lar ejection fraction, as well as detection and

quantification of global and regional wall

motion abnormalities. Moreover, the abili-

ty to repeat the study as often as clinically

indicated can be invaluable in patient care.

For example, a trial of a pulmonary vasodi-

lator drug can be instituted, and MRI can be

performed at sequential time points to assess

for an objective response in right ventricular

volume and mass because right ventricular

end-diastolic volume is a strong predictor of

mortality in pulmonary arterial hypertension

[94, 95]. Moreover, if severe dilation of the

right ventricle with increased pressure caus-

ing leftward bowing of the interventricular

septum has occurred, left ventricular func-

tion may be compromised owing to impaired

early diastolic filling. This finding can be ac-

curately evaluated with cardiac MRI and has

prognostic implications [86, 89, 90].

Phase-contrast MRI is increasingly used

to measure flow velocity in any major artery

because pulmonary arterial pressure can be

estimated from pulmonary artery flow ve-

locity. A study in which the subjects were

42 patients with pulmonary artery hyper-

tension confirmed with right-heart catheter-

ization [98] showed good correlation of av-

erage pulmonary artery velocity and mean

pulmonary arterial pressure, systolic pulmo-

nary arterial pressure, and pulmonary vas-cular resistance index, the correlation coef-

ficients being 0.73, 0.76, and 0.86 (p

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