Transcript Lecture7 RADIOLOGICAL EXAMINATION OF THE

RADIOLOGICAL
EXAMINATION OF THE
CARDIOVASCULAR SYSTEM
DEPARTMENT OF ONCOLOGY AND
RADIOLOGY
PREPARED BY I.M.LESKIV
METODS OF EXAMINATION
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Echocardiography, radionuclide examinations and plain films are the
standard non-invasive imaging investigations used in cardiac disease.
Echocardiography has now become a particularly important imaging
technique that provides morphological as well as functional information. It
is excellent for looking at the heart valves, assessing chamber morphology
and volume, determining the thickness of the ventricular wall and
diagnosing intraluminal masses. Doppler ultrasound is an extremely useful
tool for determining the velocity and direction of blood flow through the
heart valves and within cardiac chambers. Radionuclide examinations
reflect physiological parameters such as myocardial blood flow and
ventricular contractility but provide little anatomical detail, whereas plain
radiographs are useful for looking at the effects of cardiac disease on the
lungs and pleural cavities, but provide only limited information about the
heart itself. MRI provides both functional and anatomical information but
is only available in specialized centres and is used only for specific reasons.
ROENTGENOGRAPHY
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A complete roentgen study of the heart usually requires a minimum of four
projections: posteroanterior, left anterior oblique at approximately 60°,
right anterior oblique at approximately 45°, and lateral. The films are
exposed at a 6-foot distance, with the patient in the upright position and in
moderately deep inspiration. Magnification resulting from divergent
distortion is minimized by obtaining posteroanterior and anterior oblique
views to place the heart closer to the film (the anterior chest is adjacent to
film). A left lateral view (with the left side adjacent to film) also tends to
minimize magnification. To outline the esophagus, we use a barium
suspension as an aid in determining position and size of the aortic arch. In
addition, alteration in esophageal contour may reflect changes in the leftsided chambers. The use of ultrasound in determining cardiac chamber size
has decreased the use of the oblique projections, so that frequently the
cardiac examination is restricted to PA and lateral projections, usually
without barium in the esophagus.
FLUOROSCOPY
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Cardiovascular fluoroscopy no longer has widespread use and in our
institution is largely limited to the evaluation of specific questions: i.e., the
presence of large pericardial effusions and the evaluation of aortic arch
anomalies. Generally, calcium is better seen on fluoroscopy then on plain
films and these observations may be made at the time of cardiac
catheterization. Minor amounts of calcification are best seen on CT. The
use of fluoroscopy has virtually disappeared in the study of congenital heart
disease because in general the patients require more definitive studies such
as cardiac catheterization, angiocardiography, ultrasonography, and MRI.
There are several disadvantages in cardiac fluoroscopy, one of the most
important of which is the amount of radiation to which the patient is
exposed.
The second disadvantage is distortion. Because the distance between the
target of the x-ray tube and the patient is short, there is considerable
enlargement of the cardiac silhouette and distortion of other thoracic
structures. This can be decreased by using longer distances between target
and the patient, and by using a small shutter opening, producing the central
beam effect. The third disadvantage is lack of permanent record. This is
obviated to a certain extent by the use of cine or videotape recording and
by roentgenograms obtained before the procedure.
ANGIOCARDIOGRAPHY
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This method of contrast cardiac visualization has
been used widely for examination of patients
with all types of cardiac and pulmonary
diseases. The method is used in the diagnosis of
congenital and acquired cardiac disease.
Selective angiocardiography in which a small
amount of opaque medium (an organic iodide) is
injected into a specific chamber or vessel during
cardiac catheterization is used almost
exclusively.
CORONARY ARTERIOGRAPHY
AORTOGRAPHY
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CORONARY ARTERIOGRAPHY
Selective catheterization of the coronary arteries followed by injection of a
contrast medium (one of the organic iodides) is used in combination with
cineradiography rapid serial filming or videotaping to study the coronary
arteries. Details of technique are beyond the scope of this discussion.
AORTOGRAPHY
This examination consists of the injection of one of the organic iodides into
the aorta through a catheter introduced into one of its major branches and
placed into a desired position in the aorta. The examination has a place in
the investigation of patients with congenital and acquired problems of the
aortic arch. It is used in infants with congestive heart failure in whom there
is evidence of a left to right shunt and in whom patent ductus arteriosus is
suspected. Coarctation of the aorta in infants may also cause congestive
heart failure. The lesion can be defined by aortography. In adults,
aortography is used to define anomalies of the aortic arch and its branches
as well as in the study of the aortic valve and the coronary arteries. It is also
useful in patients with masses adjacent to the aorta in whom aneurysm is a
possibility and in patients suspected of having dissecting hematoma, and
traumatic or other aneurysms.
ULTRASONIC INVESTIGATION
OF THE HEART
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The use of ultrasound in examination of the heart has increased greatly in
the past 20 years, and it is now well established and a widely used
diagnostic tool. Ultrasonic investigation is a noninvasive, safe, and
comfortable study that will demonstrate valve and chamber motion wall
thickness and size. Doppler examination allows determination of the cross
sectional area of a valve as well as quantification of gradients that may be
present. It is of value in the study of the hypertrophic cardiomyopathies
both with and without associated subaortic stenosis and in the study of the
congestive type in which there is chamber dilatation. With ultrasound, left
ventricular diameter and outflow configuration can be determined;
qualitative assessment of right and left ventricular size is possible, also. The
size of the left atrium can be measured accurately and left atrial myxomas
or other intraatrial tumors can be detected. Ultrasound is also useful in the
investigation of congenital heart disease, particularly in patients with
hypoplastic left-heart syndrome, double-outlet right ventricle, and right
ventricular volume overload. In addition, it is the most sensitive method for
determining the presence of pericardial effusion.
DETERMINATION OF CARDIAC SIZE
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The most commonly used are (1) measurement of transverse diameters; (2)
measurement of surface area; and (3) cardio-thoracic ratio. The transverse
diameter of the heart is the sum of the maximum projections of the heart to
the right and to the left of the midline; the measurement should be made so
as not to include epicardial fat or other noncardiac structures. The diameter
can then be compared with the theoretic transverse diameter of the heart for
various and weights. Surface area estimations based on artificial
construction of the base of the heart and of the diaphragmatic contour of
the heart. The cardiothoracic ratio is the ratio between the transverse
cardiac diameter and the greatest internal diameter of the thorax, measured
on the frontal teleroentgenogram. This is the easiest and quickest method of
measurement of cardiac size; an adult heart that measures more than one
half of the internal diameter of the chest is considered enlarged. The
method is gross, because the cardiothoracic ratio varies widely with
variations in body habitus. It can be useful, however, as a rough estimate of
cardiac size. The cardiothoracic ratio is most useful in assessing changes in
heart size or monitoring progression of disease, or as a response to therapy.
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Measurement of heart size. The transverse diameter of the heart is the distance
between the two vertical tangents to the heart outline. When the cardiothoracic
ratio (CTR) is calculated, the transverse diameter of the heart (B) is divided by
the maximum internal diameter of the chest (A)
THE ADULT HEART
Position of oesophagus (not
opacified in this instance)
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Left ventricular enlargment
in a patient with aortic
incompetence. The cardiac
apex is displaced downwards
and to the left. Note also that
the ascending aorta causes a
bulge of the right mediastinal
border - a feature that is
almost always seen in
significant
aortic
valve
disease.
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Right ventricular
enlargement in an adult
with primary pulmonary
hypertension. The heart is
enlarged with the apex of
the heart somewhat lifted
off the diaphragm. Note
also the features of
pulmonary arterial
hypertension enlargement of the main
pulmonary artery and
hilar arteries with normal
vessels within the lungs.
Left atrial enlargement in a
patient with mitral valve
disease showing the 'double
contour sign' (the left atrial
border has been drawn in)
and dilatation of the left
atrial appendage (LAA)
(arrow). The enlarged LAA
should not be confused with
dilatation of the main
pulmonary artery. The main
pulmonary artery is the
segment immediately below
the aortic knuckle. The
LAA is separated from the
aortic knuckle by the main
pulmonary artery
Pericardial disease
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Echocardiography is ideally suited to detect pericardial fluid. Since patients are examined
supine, fluid in the pericardial space tends to flow behind the left ventricle and is recognized as
an echo-free space between the wall of the left ventricle and the pericardium. A smaller amount
of fluid can usually be seen anterior to the right ventricle. Even quantities as small as 20-50 ml
of pericardial fluid can be diagnosed by ultrasound. The nature of the fluid cannot usually be
ascertained, and needle aspiration of the fluid may be necessary; such aspiration is best
performed under ultrasound control. Pericardial effusion can also be recognized at CT and
MRI, although they are rarely performed primarily for this purpose. Computed tomography
and MRI are particularly useful for assessing thickening of the pericardium, whereas
echocardiography is poor in this regard.
It is unusual to be able to diagnose a pericardial effusion from the plain chest radiograph.
Indeed, a patient may have sufficient pericardial fluid to cause life-threatening tamponade, but
only have mild cardiac enlargement with an otherwise normal contour. A marked increase or
decrease in the transverse cardiac diameter within a week or two, particularly if no pulmonary
oedema occurs, is virtually diagnostic of the condition. Pericardial effusion should also be
considered when the heart is greatly enlarged and there are no features to suggest specific
chamber enlargement . Pericardial calcification is seen in up to 50 % of patients with
constrictive pericarditis. Calcific constrictive pericarditis is usually postinfective in aetiology,
tuberculosis and Coxsackie infections being the common known causes. In many cases no
infecting agent can be identified. The calcification occurs patchily in the pericardium, even
though the pericardium is thickened and rigid all over the heart. It may be difficult or even
impossible to see the calcification on the frontal view. On the lateral film, it is usually maximal
along the anterior and inferior pericardial borders. Widespread pericardial calcification is an
important sign, because it makes the diagnosis of constrictive pericarditis certain.
Large pericardial effusion on an apical fourchamber view echocardiogram. (b). CT scan
showing fluid density (arrows) in pericardium.
LA, left atrium; LV, left ventricle; RA, right
atrium; RV, right ventricle.
Pericardial effusion. The heart is
greatly enlarged. (Three weeks
before, the heart had been normal in
shape and size.) The outline is well
defined and the shape globular. The
lungs are normal. The cause in this
case was a viral pericarditis. This
appearance of the heart, though
highly suggestive of, is not specific to
pericardial effusion. (Compare with
(b).) (b) Congestive cardiomyopathy
causing
generalized
cardiac
dilatation. This appearance can easily
be confused radiologically with a
pericardial effusion.
A
B
Pericardial calcification in a patient with severe constrictive
pericarditis. The distribution of the calcification is typical. It
follows the contour of the heart and is maximal anteriorly and
inferiorly. As always, it is more difficult to see the calcification
on the PA film. (This patient also had pneumonia in the right
lower lobe.)
Pulmonary vessels
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The plain chest film provides a simple method of assessing the pulmonary
vasculature. Even though it is not possible to measure the true diameter of
the main pulmonary artery on plain film, there are degrees of bulging that
permit one to say that it is indeed enlarged. Conversely, the pulmonary
artery may be recognizably small. The assessment of the hilar vessels can
be more objective since the diameter of the right lower lobe artery can be
measured: the diameter at its midpoint is normally between 9 and 16 mm.
The size of the vessels within the lungs reflects pulmonary blood flow.
There are no generally accepted measurements of normality, so the
diagnosis is based on experience with normal films. By observing the size
of these various vessels it may be possible to diagnose one of the following
haemodynamic patterns.
Increased pulmonary blood flow: Atrial septal defect, ventricular septal
defect and patent ductus arteriosus are the common anomalies in which
there is shunting of blood from the systemic to the pulmonary circuits (socalled left to right shunts), thereby increasing pulmonary blood flow. The
severity of the shunt varies greatly. In patients with a haemodynamically
significant left to right shunt (2:1 or more), all the vessels from the main
pulmonary artery to the periphery of the lungs are large. This radiographic
appearance is sometimes called pulmonary plethora. There is reasonably
good correlation between the size of the vessels on the chest film and the
degree of shunting.
Decreased pulmonary blood flow: To be recognizable radiologically, the reduction in
pulmonary blood flow must be substantial. The pulmonary vessels are all small, an
appearance known as pulmonary oligaemia. The commonest cause is the tetralogy of Fallot,
where there is obstruction to the right ventricular outflow and a ventricular septal defect
which allows right to left shunting of the blood. Pulmonary valve stenosis only causes
oligaemia in extremely severe cases in babies and very young children.
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Pulmonary arterial hypertension: The pressure in the pulmonary artery is dependent on
cardiac output and pulmonary vascular resistance. The con ditions that cause significant
pulmonary arterial hypertension all increase the resistance of blood flow through the
lungs. There are many such conditions including:
various lung diseases (cor pulmonale);
pulmonary emboli;
pulmonary arterial narrowing in response to mitral valve disease or left to right shunts;
idiopathic pulmonary hypertension.
Pulmonary arterial hypertension has to be severe before it can be diagnosed on plain
films and it is difficult to quantify in most cases. The plain chest film features are
enlargement of the pulmonary artery and hilar arteries, the vessels within the lung
being normal or small. When the pulmonary hypertension is part of Eisenmenger's
syndrome (greatly raised pulmonary arterial resistance in association with atrial septal
defect, ventricular septal defect or patent ductus arteriosus, leading to reversal of the
shunt so that it becomes right to left), the vessels within the lungs may also be large, but
there is still disproportionate enlargement of the central vessels.The reason for
pulmonary arterial hypertension may be visible on the chest film; in cor pulmonale the
lung disease is often radiologically obvious, and in mitral valve disease and other.
Pulmonary oedema: The common cardiac conditions causing pulmonary oedema are left ventricular
failure and mitral stenosis. Cardiogenic pulmonary oedema occurs when the pulmonary venous
pressure rises above 24-25 mmHg (the osmotic pressure of plasma). Initially, the oedema is confined to
the interstitial tissues of the lung, but if it becomes more severe fluid will also collect in the alveoli. Both
interstitial and alveolar pulmonary oedema are recognizable on plain chest films.
Interstitial oedema: There are many septa in the lungs
which are invisible on the normal chest film because 
they consist of little more than a sheet of connective
tissue containing very small blood and lymph vessels.
When thickened by oedema, the peripherally located
septa may be seen as line shadows. These lines, known
as Kerley В lines, named after the radiologist who
first described them, are horizontal lines never more
than 2 cm long seen laterally in the lower zones. They
reach the lung edge and are therefore readily
distinguished from blood vessels, which never extend
into the outer centimetre of the lung. Other septa
radiate towards the hila in the mid and upper zones
(Kerley A lines). These are much thinner than the
adjacent blood vessels and are 3-1 cm in length.
Another sign of interstitial oedema is that the outline
of the blood vessels may become indistinct owing to
oedema collecting around them. This loss of clarity is
a difficult sign to evaluate and it may only be
recognized by looking at follow-up films after the
oedema has cleared. Fissures may appear thickened
because oedema may collect against them.
Alveolar oedema: Alveolar
oedema is a more severe
form of oedema in which
the fluid collects in the
alveoli. It is almost always
bilateral, involving all the
lobes. The pulmonary
shadowing is usually
maximal close to the hila
and fades out peripherally
leaving a relatively clear
zone that may contain
septal lines, around the
edge of the lobes. This
pattern of oedema is
sometimes referred to as
the 'butterfly' or 'bat's
wing' pattern.
Septal lines in interstitial pulmonary oedema, (a) Left upper zone showing the septal lines
known as Kerley A lines (arrowed) in a patient with acute left ventricular failure following a
myocardial infarction. Note that these lines are narrower and sharper than the adjacent
blood vessels, (b) Right costophrenic angle showing the septal lines known as Kerley В lines
in a patient with mitral stenosis. Note that these oedematous septa are horizontal nonbranching lines which reach the pleura. One such line is arrowed.
B
Alveolar oedema in a patient with acute left ventricular failure following a myocardial
infarction. The oedema fluid is concentrated in the more central portion of the lungs leaving a
relatively clear zone peripherally. Note that all the lobes are fairly equally involved.
Aorta
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With increasing age the aorta elongates. Elongation necessarily involves unfolding,
because the aorta is fixed at the aortic valve and at the diaphragm. This unfolding
results in the ascending aorta deviating to the right and the descending aorta to the left.
Aortic unfolding can easily be confused with aortic dilatation.
 True dilatation of the ascending aorta may be due to aneurysm formation or secondary
to aortic regurgitation, aortic stenosis or systemic hypertension.
 The two common causes of aneurysm of the descending aorta are atheroma and aortic
dissection. A rarer cause is previous trauma, usually following a severe deceleration
injury. The diagnosis of aortic aneurysm may be obvious on plain film but substantial
dilatation is needed before a bulge of the right mediastinal border can be recognized.
Atheromatous aneurysms invariably show calcification in their walls and this
calcification is usually recognizable on plain film. Computed tomography with
intravenous contrast enhancement is very useful when aortic aneurysms are assessed. It
is important to know the extent of aortic dissections as those involving the ascending
aorta are treated surgically while those confined to the descending aorta are usually
treated conservatively with hypotensive drugs. Standard echocardiography shows
dissection of the aortic root but transoesophageal echocardiography shows dissections
distal to the aortic root and in the descending aorta as well. Dissecting aneurysms can
also be shown with CT and MRI and these non-invasive techniques have largely
replaced aortography, which is only performed in selected cases.
 Two congenital anomalies of the aorta may be visible on plain films of the chest:
coarctation and right-sided aortic arch, a condition that is sometimes seen in association
with intracardiac malformations, notably tetralogy of Fallot, pulmonary atresia and
truncus arteriosus. It can also be an isolated and clinically insignificant abnormality. In
right aortic arch, the soft tissue shadow of the arch is seen to the right, instead of to the
left, of the lower trachea.
Aortic dissection, (a) Transoesophageal echocardiogram
showing the true (T) and false (F) lumina in the
descending aorta. CT scan showing the displaced intima
(arrows) separating the true and false lumina in the
ascending and descending aorta. MRI scan showing the
displaced intima in the ascending and descending aorta
(arrows). AAo, ascending aorta; DAo, descending aorta;
PA, pulmonary artery.