is a third-year Radiology Resident at Stanford University Medical
Center, Stanford, CA. He completed his undergradulate and
master's training in Mechanical Engineering with research
interests in Biomechanics and Cardiovascular Function. He
completed the MD/PhD program at Temple University in
Philadelphia, PA. His thesis project addressed the progression of
cardiac dysfunction in the setting of functional mitral valve
Multidetector computed tomography (MDCT) imaging of the
cardiac valves has advanced significantly with the development of
16- and 64-detector scanners. Early MDCT imaging was primarily
used to assess valvular calcifications; however, with improved
temporal resolution, current scanners can visualize subtle
anatomy and can also evaluate valve function. With advancing
technology, the role of MDCT as a convenient and accurate imaging
modality is increasing in both preoperative assessment and the
evaluation of postsurgical patients with valvular disease.
Technologic advancements in computed tomography (CT) from the
early single-detector scanners presented by Ledley et at
in 1974 to current 64-detector scanners have resulted in temporal
and spatial resolutions capable of accurately evaluating cardiac
valvular anatomy and disease. Early attempts at cardiac imaging in
the late 1970s were limited by the poor temporal resolution of the
single-detector scanners that required at least 1 second to scan
each individual slice.
Throughout the 1980s and 1990s, development of the electron-beam CT
(EBCT) scanner resulted in marked improvement of spatial and
temporal resolution, which allowed accurate assessment of cardiac
motion and anatomy.
By the mid 1990s, development of helical and multislice scanners
began the technologic push toward 64-detector helical scanners with
spatial resolutions of 0.4 to 0.6 mm and temporal resolutions of 90
to 180 msec.
Aortic valve calcification and stenosis
Initial studies of multidetector CT (MDCT) to evaluate the
cardiac valves focused on valve calcification and its association
with aortic stenosis (AS).
The prevalence of nonrheumatic calcific AS in the elderly ranges
from 2% to 7%, which makes it the most common valvular heart
disease in patients 65 and older.
The imaging features of AS include left ventricular (LV)
hypertrophy, dilatation of the ascending aorta, and valvular
The pathology of AS is based upon one of two general categories:
congenital disease and acquired degenerative disease. The pattern
of calcification differs based upon the disease process. With
congenital aortic valve disease, calcification tends to deposit
along the commissural edges of the leaflets. In acquired
degenerative disease, calcification tends to be more severe and
develops within the annulus and leaflets.
Koos et al
evaluated the prevalence of aortic valve calcification that was
incidentally detected on MDCT scans. The study retrospectively
evaluated CT scans in 402 patients who also underwent
echocardiographic evaluations. The CT scans were performed on
4-detector (181 patients) and 16-detector (215 patients) scanners.
A total of 18% of patients had incidental calcifications of the
aortic valve, and the grade of calcification correlated with
echocardiographic measurements of mean and peak transvalvular
Previous studies have established the importance of aortic valve
calcification re porting moderate-to-severe calcification as a
strong, independent predictor of adverse clinical outcomes
as well as the correlation between severity of calcification and
the severity of AS.
Figure 1 illustrates the normal appearance of the aortic valve.
The aortic valve apparatus consists of the cusps, sinuses,
commissures, and coronary artery ostia. The sinuses include the
right coronary, left coronary, and posterior noncoronary sinus.
Figure 1A depicts a normal cadaveric specimen of the aortic valve
as viewed from the base of the heart. Figure 1B presents a
3-dimensional axial oblique representation of the aortic valve in
diastole imaged with a 64-detector CT scanner. Scan parameters
include 1-mm slice thickness with 10% reconstructions of the R-R
interval from 0% to 90%. Three-dimensional reconstructed images
were produced using commercially available software.
Previous studies of CT evaluation of the aortic valve have
reported a correlation between aortic valve calcification severity
and transvalvular gradients.
Liu et al
investigated the correlation between the severity and location of
aortic valve calcification with echocardiographicly determined
pressure gradients. This retrospective study evaluated 115 patients
with aortic valve calcification incidentally noted on chest CT
performed on 4 single-detector scanners and one 4-detector scanner.
All patients had also undergone transthoracic echocardiography
(TTE). The severity of valvular calcification correlated with both
increased mean and peak pressure gradients across the aortic valve
(r = 0.70 to 0.78).
Furthermore, this study found the highest correlation with
calcification of the peripheral left-posterior commissure and
central right-left commissure.
The progression of AS is faster in patients with severely
Previous studies have shown a correlation between the calcification
score and the rate of disease progression.
The extent and association of aortic valve calcification in
patients with AS was investigated by Cowell et al.
A total of 157 patients with known AS (that had been documented on
echocardiography) were evaluated using helical MDCT scans. The
calcium score, as determined with automated software, correlated
with the aortic postvalve velocity and peak gradient.
All patients with severe AS had calcium scores >3700 AU. Figure
2 presents a contrast-enhanced, electrocardiographic (ECG)-gated,
64-detector CT evaluation of a patient with aortic valve
calcification incidentally noted on a coronary examination. Axial
and sagittal oblique images reveal valvular calcification primarily
along the commissures.
The use of intravenous contrast for the evaluation of valve
morphology and calcification is debated. Most authors agree that
the use of contrast is beneficial for the evaluation of valve
However, there is debate regarding the use of contrast in assessing
aortic valve calcification. Mühlenbruch et al
found that the quantification of aortic valve calcification was not
reliable with the use of intravenous contrast because contrast
material can simulate calcium. In a small cohort of patients,
Willmann et al
reported no significant difference between the accuracy of calcium
assessment using nonenhanced and contrast-enhanced studies as
compared with assessment at the time of surgery.
Gated MDCT has been shown to provide an accurate assessment of
valvular calcification compared with the quantity of calcium in the
The accuracy of CT quantification of valvular calcium was
investigated in vitro by Boughner et al.
A total of 24 human aortic valve cusps were obtained from autopsy
specimens and were scanned in multiple projections with a
quantitative computed microtomograph. The findings were compared
with a densitometry scan and standard control specimens. The study
reported an excellent correlation between the 2 quantitative
measurements (R2 = 0.94) with a total calcium content ranging from
0 to 15 mg.
Recent studies have investigated the use of 64-detector CT
scanners to analyze aortic valve anatomy and pathology. Pannu et al
retrospectively evaluated 4-dimensional images of the aortic valve
in 20 patients to assess valve visibility, number of leaflets,
valve motion, and calcification. The parameters used were 0.6-mm
detector collimation, 0.75-mm-thick slices, and 0.4-mm intervals
with 80 mL of nonionic isosmolar contrast on a 64-detector CT
scanner. Images were reconstructed at 10% segments of the R-R
interval. This study found excellent valve visualization in all 20
patients during systolic and diastolic phases of the cardiac cycle
with 3 valve leaflets present in all pa-tients.
Valve motion was also evaluated because of the increased temporal
resolution of the 64-detector CT scanner. The findings suggest that
MDCT is a potential alternative to echocardiography for the
assessment of the valve orifice area; however, radiation dose
(approximately 12 mSv) is a limitation of the study.
Congenital aortic valve anomalies
Bicuspid aortic valve is the most common congenital cardiac
anomaly and occurs in 1% to 2% of the general population.
The patient may be asymptomatic for many years and present later in
life with degenerative fibrosis and calcification that results in
AS. Patients with bicuspid valves present earlier than patients
with degenerative tricuspid aortic valves. The bicuspid valve cusps
are usually symmetric in size, often with a ridge across 1 cusp,
which represents a false commissure. Figure 3 presents several
images of patients with congenital bicuspid aortic valves with a
64-detector CT scanner. Figure 3A is an axial view of the bicuspid
aortic valve from a 67-year-old patient with a sinus of Valsalva
aneurysm. There is calcification along the valve commissures and
annulus. Figure 3B depicts a bicuspid aortic valve with fusion of
the right and left coronary cusps. There is a prominent calcified
ridge (a false commissure) in the area where the commissure should
have formed. Figures 3C and 3D are volume-rendered images of a
bicuspid valve in diastole and systole. In the systolic phase
(Figure 3D), the valve orifice assumes an ellipsoid configuration
with marked narrowing resulting in moderate-to-severe stenosis in
this patient. When evaluating a bicuspid aortic valve for potential
surgical planning, it is important to assess the degree of
calcification and the presence of sinus of Valsalva aneurysms. With
significant valve calcifications, root replacement and coronary
reimplantation may be required.
In addition to congenital bicuspid aortic valves, there may also
be unicuspid or quadricuspid valves. These types of anomalies are
much less common than bicuspid valves. The literature reports the
incidence of a quadricuspid aortic valve (QAV) in the range of
0.003% to 0.043%.
In contrast to the stenotic bicuspid aortic valve, the most common
physiologic abnormality in a QAV is valvular incompetence.
Jacobs et al
presented a case report on QAV imaging using a 64-detector CT
scanner with correlation of echocardiographic imaging. This report
presented excellent visualization and characterization of the valve
anomalies using a contrast-enhanced protocol with a slice thickness
of 0.75 mm and a reconstruction interval of 0.5 mm. The authors
described an incompetent QAV with mildly thickened leaflets and
Findings were confirmed by a previous TTE.
Aortic valve regurgitation
Assessment of aortic valve insufficiency is based on secondary
findings of incomplete valve coaptation in the diastolic phase,
LV dilatation, and aortic dilation.
Recent studies evaluating aortic and mitral valve (MV)
regurgitation describe the methodology of quantifying the
regurgitant volume for single-valve disease based on the difference
in stroke volume between the regurgitant ventricle and the normal
This methodology is inaccurate with multivalve disease.
Mitral valve morphology
The MV apparatus consists of the mitral annulus, the posterior
and anterior cusps, chordae tendineae, and the LV papillary
muscles. With improved surgical techniques, the importance of early
identification of MV disease is increasing. Few studies have been
published investigating the MDCT characteristics of MV disease. A
study by Willmann et al
evaluated MV morphology using a retrospectively ECG-gated
4-detector CT scanner; however, the technique was somewhat limited,
as it provided only 2-dimensional static images of the MV
apparatus. A more recent study by Alkadhi et al
evaluated the MV apparatus in 37 patients with normal valve anatomy
as shown on transesophageal echocardiographic (TEE) studies. The
authors retrospectively used data obtained from contrast-enhanced
16-detector CT that was being performed for coronary artery
disease. CT images were reconstructed using a slice thickness of 1
mm at an increment of 0.5 mm at 5% increments of the RR interval.
The images were independently reviewed by 2 observers and offered
excellent visualization of the leaflets, zone of apposition,
commissures, annulus, chordae tendineae, and papillary muscles
during all phases of the cardiac cycle. Superior visualization was
seen in the perpendicular long axis compared with the parallel
Figure 4 illustrates the normal MV apparatus obtained from a
ECG-gated 64-detector CT scanned with intravenous contrast and
reconstructed at 1-mm-thick sections. The anterior and posterior
leaflets are visualized in the systolic phase of the cardiac cycle
(Figure 4A). In the coronal plane, Figure 4B, the papillary muscles
and chordae tendineae are seen with the normal attachments to the
Mitral valve calcification and stenosis
Mitral valve stenosis is most commonly results from degenerative
changes of rheumatic heart disease. Chronic, progressive fibrosis
results in leaflet thickening, calcification, and fusion.
Eval- uation of MV calcification uses identical methodology as the
aortic valve assessments. Similarly, evaluation of MV stenosis is
based upon measurements of the maximal orifice in the diastolic
phase of the cardiac cycle. Cardiac changes related to chronic MV
stenosis include left atrial enlargement with a morphologically
normal LV. Secondary findings may include pulmonary vein
dilatation, pulmonary hypertension, and right ventricular
hypertrophy. Budoff et al
investigated the reproducibility of CT mea- surements of mitral
annulus calcification and measurements of aortic calcification. The
study data was collected using 2 CT scans performed on either an
EBCT or 4-detector CT scanner at the same appointment for the
evaluation of coronary artery calcification. A total of 100
patients were included in the analysis, 99 of whom had 2 scans
successfully performed. The study reported excellent intra-reader
and inter-reader variability for the evaluation of mitral annulus
calcification. However, the interscan variability was somewhat
higher (28% to 33%); this was suggested to be secondary to valve
Mitral valve regurgitation
Findings in MV regurgitation (MVR) vary depending upon the
chronicity and etiology.
Acute MVR may demonstrate only left atrial hypertension and
interstitial pulmonary edema with incomplete coaptation of the
valve leaflets on CT.
With chronic MVR there is enlargement of the left atrium and LV
with associated myocardial thickening.
Initial studies on MVR quantification that used CT used EBCT
In a study of 43 patients using EBCT, compared with TTE, Lembcke et
reported good agreement in measurements of total LV stroke volume,
antegrade stroke volume, mitral regurgitation volume, and
regurgitant fraction. In 2004, Lembcke et al
again confirmed the accuracy of EBCT in quantifying MVR when
compared with LV catheterization in a study of 50 patients.
Historically, MDCT evaluation of MVR has been limited by poor
temporal and spatial resolution as compared with EBCT and magnetic
resonance imaging (MRI). Alkadhi et al
used an ECG-gated 16-detector CT to quantify MVR in a study of 44
patients. A total of 19 patients with MVR and 25 without MVR based
on TEE and ventriculography were imaged prospectively using a
contrast-enhanced protocol with images reconstructed at 5%
increments of the R-R interval and a slice thickness of 1 mm, with
an increment of 0.5 mm. Two experienced readers assessed the images
blindly and measured the maximal regurgitant orifice area of the
MV. Assessment of the MV apparatus was also noted with the
evaluation of annulus calcification, leaflet thickening and
calcification, valve prolapse, and rupture or thickening of the
chordae tendineae and papillary muscles. The results of the study
indicated a significant correlation between the regurgitation
orifice area measured by CT with findings from TEE and
ventriculography (r = 0.807 and 0.922, respectively).
Furthermore, there were no false-positive or -negative findings of
MVR in this limited study group. There was excellent agreement in
the morphologic features of the MV apparatus between the imaging
modalities, suggesting that MDCT is an accurate alternative to TEE
in the evaluation of MV disease.
Tricuspid and pulmonary valve disease
Since current MDCT contrast protocols are based on the
evaluation of coronary artery disease, limited information is
available on right-heart valve disease. With the current use of
saline chaser techniques, the contrast becomes diluted in the right
heart with limited visualization of the tricuspid and pulmonary
valves. If known right-sided valve disease is to be evaluated, a
mixture of contrast and saline could be used or a slow infusion of
contrast can be used following the initial bolus.
One of the more common valvular abnormalities of the right heart is
tricuspid valve regurgitation (TVR) caused by pulmonary
hypertension resulting in right ventricular hypertrophy and
dilation. Additional abnormalities of the tricuspid valve that may
be evaluated using MDCT include Ebstein's anomaly and changes
related to Marfan's syndrome.
With Ebstein's anomaly, there is downward displacement of the valve
leaflets that results in TVR and atrialization of a portion of the
right ventricle. In Marfan's syndrome, numerous valvular anomalies
may be present; involvement of the tricuspid valve results in
floppy redundant leaflets with valve incompetence. Diseases of the
pulmonic valve are less common than aortic and MV disease. Most
etiologies of pulmonary valve disease are congenital in nature
including congenital pulmonic stenosis in the setting of tetralogy
Acute infections of the cardiac valves caused by
or fungi may rapidly progress, resulting in diffuse valve
destruction. Less virulent infections by
result in a slower progressive clinical decline. Large vegetations
may result in functional stenosis of the valve, whereas valve
deformation and destruction may cause valve incompetence. Patients
classically present with congestive heart failure, fever, and
Figure 5 presents a 64-detector CT image of vegetation on the
noncoronary cusp of the aortic valve. CT findings are consistent
with a soft tissue mass involving the valve apparatus with
secondary findings of stenosis or regurgitation. Gilkeson et al
published an update of MDCT imaging of aortic valve disease with
several representative images of patients with valve vegetations
secondary to previous valve replacement and systemic lupus
Postsurgical cardiac valves
With improved surgical techniques, advanced age is no longer an
absolute contraindication to valve replacement surgery. Results of
a study of 105 patients by Morgan-Hughes et al
indicated excellent long-term postoperative survival and quality of
life in patients ranging from 75 to 89 years of age who underwent
valve replacement surgery. Increasing numbers of patients with
valvular replacements will require imaging assessment to determine
postsurgical planning and to assess valve function. Improved
imaging characteristics have resulted in excellent postoperative
visualization of valve prostheses
with decreased metallic artifacts. Figure 6 presents several
postoperative images obtained on a 64-detector CT scanner. Figure
6A is an 3-mm reconstructed short-axis image of a prosthetic MV
showing the open valve leaflets during diastole. Figures 6B and 6C
illustrate 2-mm-thick sections of a bioprosthetic tricuspid valve
replacement showing the metallic leaflet supports with minimal
streak artifact. Figure 6D and 6E are 2 images of a patient with a
prosthetic mitral and aortic valve with a bioprosthetic tricuspid
valve in the diastolic phase of the cardiac cycle.
Postsurgical complications of valvular repair and replacement
can also be evaluated using MDCT. A case report by Ghersin et al
described pseudoaneurysm formation following aortic valve
replacement. In this patient, images obtained throughout the
cardiac cycle allowed dynamic evaluation of the lumen with
expansion during systole and complete collapse in diastole.
Figure 7 depicts pseudoaneurysm formation following prosthetic
aortic valve replacement. CT allows accurate assessment of the
3-dimensional orientation of the collection as well as the dynamic
changes during the cardiac cycle. Additional roles of MDCT in
postsurgical patients include the evaluation of abscess formation
and valve dehiscence, providing both anatomic and dynamic
information important to surgical planning.
Technologic advancements over the past 3 decades have resulted
in markedly improved imaging of the cardiac valves. Current
temporal resolutions of 90 to 180 msec with a spatial resolution of
0.4 to 0.6 mm result in accurate as-sessment of valve morphology
and function. Compared with MRI, MDCT has a significantly higher
spatial resolution, which provides excellent visualization of the
delicate valve anatomy. In addition, fast scan times (approximately
10 seconds) make MDCT a much more readily available modality for
imaging the growing population of patients with valvular disease.
The primary limitation of current MDCT scanners is the radiation
dose (approximately 13 to 21 mSv).
Current contrast-bolus techniques for coronary artery imaging
limits visualization of the right-heart structures; however, this
can be overcome with a dedicated scan of the right-heart valves or
using a mixed or slow contrast infusion. MDCT offers excellent
visualization of the postoperative valve prosthesis with minimal
artifact using current imaging technique. With excellent image
quality and speed of image acquisition, MDCT is a potential
alternative to invasive TEE studies and the limited spatial
resolution of MRI.