is a Resident and
is a Professor of Radiology and Medicine, Department of
Radiology, University of Vermont/Fletcher Allen Health Care,
The use of computed tomography (CT) has increased significantly
since its advent about 40 years ago with an estimated 62 million
scansperformed in the United States every year.
It is likely that a large portion of this increase is due to the
ability of CT angiography to detect pulmonary embolism and aortic
dissection. Standard chest CT has also revolutionized imaging of
the lungs with its ability to differentiate between many pulmonary
All too often, however, radiologists forget to analyze the heart
while interpreting these studies. With improved multislice scanners
and shortened imaging times, many cardiac abnormalities can be
detected even on an ungated study.
In many institutions CT for aortic disease is gated and, if slice
reconstruction is thin enough, important findings may become
CT findings in the heart may contribute additional information
to findings in the lungs, or may point to an entirely separate
disease process. In either case, they are likely to aid the
referring physician in appropriately treating the patient. It
therefore behooves the conscientious radiologist to evaluate the
heart and be able to recognize the more common abnormalities
encountered on a routine chest CT.
Coronary artery calcium
CT is extremely sensitive for detection of coronary artery
calcium. As atherosclerosis is the sole cause of calcium in the
coronary arteries, coronary calcium is specific for the presence of
Although one cannot infer the presence of significant
obstruction from the presence of calcium alone, it is still an
important observation and may be the first evidence of coronary
atherosclerosis. Soft plaque in the coronary arteries will almost
never be discernible on ungated studies, but may be visible on
gated aortic studies and it could provide an explanation for chest
pain in a patient thought to have a dissection.
Coronary aneurysms can frequently be identified on gated and
ungated studies, especially when calcified (Figure 2). They
typically result from atherosclerosis and rarely from Kawasaki's
Atherosclerotic aneurysms are a site for thrombosis or can be a
source of emboli to distal vessels.
In Kawasaki's disease the aneurysms are typically proximal and can
Calcium can also be seen in the regions of the mitral and aortic
Mitral annular calcium is common in elderly individuals, is a
degenerative phenomenon and is an incidental finding as there are
no symptoms or hemodynamic abnormalities usually associated with it
(Figure3). It is important not to confuse this with a calcified
mitral valve, which occurs in mitral stenosis due to rheumatic
heart disease (Figure 4) and which is quite rare in developed
Mitral annular and mitral valve calcium are readily distinguishable
as the former occurs in the atrioventricular groove around the
mitral valve and the latter in the valve at the midplane of the
left ventricle. A rare cause of calcium in the region of the mitral
valve is casseous necrosis of the mitral annulus (Figure 5).
Calcium in the aortic valve suggests aortic stenosis (Figure 6)
and the more heavily calcified the valve, the more likely a
significant obstruction is present.
Calcium occasionally occurs in the pulmonary valve after balloon
valvuloplasty for pulmonary valve stenosis.
Myocardial and pericardial calcium
Calcium in the myocardium of the left ventricle or in a
papillary muscle is indicative of a previous myocardial infarct
(Figure 7), but does not necessarily indicate an aneurysm or clot.
Calcium in the wall of the heart is usually curvilinear although it
can occasionally have anamorphous appearance.
The location of the calcified myocardium can be used to localize
the culprit lesion in a coronary artery.
For example, posterior wall calcification is compatible with a
right coronary artery territory infarct (Figure 8) whereas calcium
at the apex or in the ventricular septum usually results from an
anterior descending territory infarct (Figure 7). It is important
to distinguish myocardial calcium from pericardial calcium as it is
seen in patients with constrictive pericarditis.
Calcium in the pericardium usually extends onto the right heart
(Figure 9) whereas the right ventricular rarely, if ever, calcifies
Calcium in the atrioventricular groove is said to be nearly
pathognomonic of pericardial constriction.
CT can be useful for analyzing cardiac chambers to determine
their size, shape and thickness.
If the CT is gated, scans will usually be obtained during diastole.
With the proper views, one will be able to accurately measure
end-diastolic chamber dimensions and wall thickness. On nongated
studies the images may not reveal the true ventricular morphology
because the phase of the cardiac cycle is unknown and the imaging
plane will not likely be optimal.
Because the heart may be partially contracted, a cardiac chamber
will be at least as large as it appears, but it could be larger.
The ventricular wall, on the other hand, will be at least as thin
as it appears, but it could be thinner. Because of this, it is
possible to underestimate ventricular size and overestimate
ventricular wall thickness.
The normal left ventricle has a quasi-ellipsoidal shape. Using
echocardiographic measurements as a standard, in adults its normal
short axis dimension and wall thickness at end diastole should be
approximately 5.6 cm and 11 mm respectively (Figure 10). By the
same standards a normal left atrium should have an anteroposterior
dimension of approximately 4.5 cm
The right ventricle has a triangular shape with the ventricular
septum bulging into it. It has a thin wall measuring less than 4 mm
Right heart enlargement can be qualitatively assessed by comparing
its size to the corresponding left heart. At the midplane of the
left ventricle, the internal diameter of the right ventricle is
usually equal to or slightly less than that of the left ventricle
Aneurysms vs. pseudoaneurysms
The walls of the heart are normally smooth in contour. A focal
bulge in the ventricular wall frequently indicates an aneurysm.
As with any imaging modality, on CT a true aneurysm should have a
relatively wide mouth or neck (Figure 13). True left ventricular
aneurysms can be located anywhere. In contrast, a left ventricular
pseudoaneurysm is almost always located posteriorly or inferiorly.
Because a pseudoaneurysm is the result of a contained myocardial
rupture, it is characterized by a narrow mouth or neck
On contrast-enhanced studies, cardiac thrombus can usually be
readily identified as a filling defect (Figure 13B) and is
sometimes visible as an area of decreased attenuation on
In patients with ischemic heart disease, it is more commonly
located in the left ventricle than the right ventricle.
Thrombus in the apex is sometimes mimicked by fat in the
myocardium, another sign of infarction (Figure 15).
Right ventricular and right atrial clots are usually either a
tumor thrombus or a migrated clot from the lower extremities
(Figure 16). A left atrial clot may be difficult to distinguish
from an atrial tumor. Most atrial clots are plastered against the
atrial wall in an enlarged atrium or in the atrial appendage
(Figure 17). A filling defect is less likely to be a clot and more
likely to be tumor if the atrium is not enlarged (Figure 18).
The majority of cardiac tumors are metastases, which are 20 to
40 times more common than primary cardiac tumors.
The visceral pericardium is involved in about 90% of patients who
have metastases to the heart (Figure 19). Lung, breast and lymphoma
are the most commonly encountered metastases in the heart due to
their high prevalence and in the case of lung cancer, its close
Melanomaand lymphoma have the highest proclivity to metastasize to
Of the primary benign cardiac tumors, myxoma is the most common.
These are intracavitary, are usually located in the left atrium
(Figure18) and are attached to the atrial septum.
They can occur in any chamber, however, and are sometimes multiple.
Rhabdomyoma is a tumor of the myocardial wall (Figure 20) and is
associated with tuberous sclerosis.
Other benign primarycardiac tumors include lipomas, fibromas and
The most common primary malignant tumors are angiosarcoma in
adults and rhabdomyosarcoma in children.
These tumors are rare and usually cannot reliably be differentiated
from metastases by CT or magnetic resonance imaging (Figure
Chest CT can also assess abnormalities in pulmonary vascularity.
Clinically pulmonary venous hypertension is diagnosed by an
elevated pulmonary capillary wedge pressure greater than 14 mmHg.
CT findings include redistribution of pulmonary blood flow to
thenondependant lung zones, thickening of the fissures (subpleural
edema), ground glass opacities, air space consolidations and
Pulmonary arterial or precapillary pulmonary hypertension is
caused by increased pulmonary resistance. The key finding on CT is
an enlarged pulmonary trunk with normal to diminished peripheral
(Figure 23). For patients younger than 50, apulmonary trunk to
aortic ratio >1 is a reliable indicator of precapillary
hypertension in patients without overcirculation.
For patients older than 50, because the aorta dilates, this is less
reliable and using a measurement of the pulmonary artery short axis
>3.5cm is a better indicator.
These criteria are fairly specific but they have only moderate
In contrast to pulmonary arterial hypertension, all of the
pulmonary vessels are enlarged in pulmonary overcirculation.
The two main diseases causing pulmonary overcirculation are
left-to-right shunts and chronic systemic volume overload.
In the former case, either anatrial septal defect (Figure 24) or
partial anomalous pulmonary venous return is the most likely cause
in an adult. Severe, chronic anemia and pregnancy can also give the
appearance of pulmonary overcirculation.
The postoperative heart
Detecting signs of prior cardiac surgery on a chest CT is
usually simple due to the presence of synthetic material and
More detailed interpretation of postoperative findings can be
challenging without prior knowledge and experience. Following a few
basic principles, any radiologist will be able to analyze the
common postoperative findings from prior coronary artery bypass
grafts or valve repair.
Coronary artery bypass grafts
The origins of common coronary artery grafts can usually be
readily identified. A vein graft to the left anterior descending
(LAD) usually originates from the anterior aorta several
centimeters above the aortic valve
(Figure 25A). A graft to an obtuse marginal branch of the left
circumflex usually arises from the anterior aorta slightly above
the origin of the LAD graft (Figure 25B).
Right coronary artery grafts usually arise just above the sinus
of the Valsalva and course to the right side of the heart. A left
internal mammary graft to the left anterior descending is usually
visible in the anterior mediastinal fat (Figure 26) and is
frequently accompanied by multiple surgical clips.
Visible contrast within a graft indicates patency, but does not
guarantee a lack of stenosis.
Occluded grafts may be visible when surrounded by mediastinal
fat, but will have soft tissue attenuation. Saphenous vein grafts
can develop atherosclerotic aneurysms in the same fashion as native
They can be distinguished from native coronary aneurysms by
location (Figure 27). Mycotic aneurysms can also form in coronary
Two of the most widely used prosthetic valves are the St. Jude
Medical and Carpentier-Edwards bovine pericardial valves. The St.
Jude valve is a mechanical valve with 2 half-moon shaped leaflets.
When the valve is open, the leaflets are oriented parallel to the
direction of blood flow; when the valve is closed, the leaflets are
oriented horizontally to each other
(Figure 29). The Carpentier-Edwards bovine pericardial valve has a
distinct appearance on CT. In cross section, its 3 metallic struts
appear as 3 crosses that are oriented in the shape of a triangle.
When viewed in profile, the struts have an elongated narrow U shape
(Figure 30). Mitral anuloplasty rings come in many shapes, but
similar to mitral annular calcium, are readily recognized by their
characteristic location and lack of leaflets
(Figure 31). Tricuspid annuloplasty rings and valves are similar in
appearance to their mitral counterparts, but on the other side of
A large number of cardiac abnormalities may be visible on
standard thoracic CT. A conscientious effort in evaluating the
heart and applying these principles may provide important
information for the clinician caring for the patient and, as a side
benefit, enhance your credibility to your local cardiologist.