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1320 AJR:198 , June 2012
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
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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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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