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Transcript
Document downloaded from http://www.elsevier.es, day 27/04/2015. This copy is for personal use. Any transmission of this document by any media or format is strictly prohibited.
Radiología. 2013;55(1):24---36
www.elsevier.es/rx
UPDATE IN RADIOLOGY
Cardiac computed tomography for valve disease夽
H. Cuéllar a,∗ , A. Roque a , V. Pineda a , J. Rodríguez b
a
b
Instituto de Diagnóstico por la Imagen (IDI), Servicio de Radiología, Hospital de la Vall d’Hebron, Barcelona, Spain
Laboratorio de Ecocardiografía, Servicio de Cardiología, Hospital de la Vall d’Hebron, Barcelona, Spain
Received 28 September 2011; accepted 11 May 2012
KEYWORDS
Volumetric computed
tomography;
Coronary heart
disease;
Angiography;
Heart valve disease
Abstract Heart valve disease and coronary heart disease are very prevalent in the general
population and often coincide in the same patient. Cardiac computed tomography (CT) makes it
possible to noninvasively rule out coronary disease before valve surgery and to potentially avoid
invasive heart catheterization in 66---75% of patients. The same imaging test provides abundant
anatomic and functional information that complements the information from echocardiography,
making it possible to characterize the etiology of the valve disease and its repercussions on the
heart and aorta, as well as to quantify the severity of disease affecting the valves of the left
side of the heart.
In this article, we describe the anatomy of the heart valves and the technical requisites of
cardiac CT for the study of the valves. We go on to explore the usefulness of CT in the preoperative study of the coronary arteries and in the morphological and functional characterization
of valve disease, with special emphasize on the valves of the left side of the heart.
© 2011 SERAM. Published by Elsevier España, S.L. All rights reserved.
PALABRAS CLAVE
La tomografía computarizada cardiaca en la afección valvular
Tomografía
computarizada
volumétrica;
Enfermedad cardiaca
coronaria;
Arteriografía;
Enfermedades de las
válvulas cardiacas
Resumen La patología valvular cardiaca y la enfermedad coronaria son muy prevalentes en la
población general y frecuentemente coinciden en el mismo paciente. La TC cardiaca permite
descartar la enfermedad coronaria antes de la cirugía valvular de forma no invasiva y evitar
potencialmente un 66-75% de las coronariografías invasivas. La misma prueba aporta abundante
información anatómica y funcional complementaria a la ecocardiografía, que permite caracterizar la etiología de las valvulopatías, así como su repercusión en el corazón y la aorta y, en
el caso de las válvulas izquierdas, cuantificar su gravedad.
夽 Please cite this article: Cuéllar H, et al. La tomografía computarizada cardiaca en la afección valvular. Radiología. 2012.
http://dx.doi.org/10.1016/j.rx.2012.05.006.
∗ Corresponding author.
E-mail address: [email protected] (H. Cuéllar).
2173-5107/$ – see front matter © 2011 SERAM. Published by Elsevier España, S.L. All rights reserved.
Document downloaded from http://www.elsevier.es, day 27/04/2015. This copy is for personal use. Any transmission of this document by any media or format is strictly prohibited.
Cardiac computed tomography for valve disease
25
En este trabajo se describe la anatomía valvular cardiaca y los requisitos técnicos de
la TC cardiaca para el estudio valvular, para profundizar posteriormente en el valor de la
coronariografía prequirúrgica y la caracterización morfo-funcional de la patología valvular
mediante TC, haciendo hincapié en las válvulas izquierdas.
© 2011 SERAM. Publicado por Elsevier España, S.L. Todos los derechos reservados.
Introduction
Valvular heart disease, both congenital and acquired, is
a common heart condition with an estimated prevalence
of 2.5% in the general population in the United States.
Close clinical follow-up is required and very often patients
with valvular heart disease end up requiring surgery.1 Valve
surgery represents approximately 20% of all cardiac procedures, with an increase of 4---7% per year. Repeat surgery
accounts for one third of procedures.
Degenerative disease is responsible for 63% of cases
of valvular disease, with patients >65 years having higher
incidence. Valvular disease reaches pandemic levels in
developed countries due to long life expectancy.2 In these
patients, degenerative aortic valve stenosis is the most common valvular disease. Sclerosis and calcification of aortic
leaflets are accompanied by a progressive reduction in the
aortic valve area, eventually leading to clinically significant stenosis. In our setting, the progressive increase of
degenerative valvular diseases has been accompanied by
a decrease in rheumatic heart disease incidence, which
currently accounts for approximately 22% of all valvular diseases.2 Prevalence of rheumatic heart disease is
higher among the elderly and immigrants from developing
countries, where it is the most common cause of valvular disease. The pathologic spectrum also includes infective
(endocarditis), congenital, inflammatory, radiation- and
drug-induced valvular diseases2 (Table 1).
Overall prevalence of significant coronary disease in
Mediterranean patients with valvular disease is estimated at
10---20%.1 Undiagnosed coronary disease is associated with a
worse intra- and postoperative outcome and it represents
a missed opportunity for performing coronary revascularization during the same surgical procedure. Spanish and
European guidelines recommend ruling out coronary disease
before heart surgery in patients with severe valvular disease, especially in patients with a previous history of the
disease, clinical suspicion of myocardial ischemia, evidence
of left ventricular systolic dysfunction, and as a rule in male
patients >40 years and postmenopausal women, and in the
presence of more than one coexiting risk factor for cardiovascular disease.1
In patients with valvular disease, coronary disease has
particularities relevant for the imaging techniques. First,
symptoms of ischemic heart disease are not specific of
coronary disease1 ; second, functional tests (myocardial
perfusion SPECT, stress echocardiography) are not able
to distinguish it from other conditions that may cause
similar symptoms.1 Last, risk factors for degenerative
aortic stenosis are similar to those of atherosclerosis and
coronary disease (age, male gender, smoking, arterial
hypertension, hypercholesterolemia), unlike what happens
in other etiologies.2
Invasive coronary angiography (cardiac catheterization)
is the technique of choice to rule out coronary disease before
valve surgery. Cardiac computed tomography (CCT) has
proven to accurately rule out significant coronary disease
in selected populations.3,4 Replacemen of catheterization
by non-invasive coronary angiography with CCT can reduce
morbidity and mortality providing a similar diagnostic accuracy. In addition, given the low overall prevalence of the
disease in this group of patients, only a few of them will
need additional catheterization to confirm, grade or treat
the coronary disease, which can eventually reduce costs.
Transthoracic and transesophageal echocardiographies
are the techniques of choice for non-invasive assessment of
heart valves, obviating the need for hemodynamic assessment by cardiac catheterization. If standard techniques
prove insufficient, current guidelines suggest that CCT is an
appropriate technique for the assessment of both native and
prosthetic valve dysfunction.4,5
In this article, we review the anatomy of the heart
valves and the technical requisites for their CT evaluation.
In addition, we examine in depth the usefulness of preoperative coronary angiography and the morphological and
functional characteristics of valvular disease at CCT, with
special emphasis on left heart valves.
Anatomy of the cardiac valves at computed
tomography
The semilunar valves have three leaflets and lie between
the ventricles and the major mediastinal arteries (the
aortic valve between the left ventricle and the aorta, and
the pulmonary valve between the right ventricle and the
pulmonary trunk). The atrioventricular valves are, on the
right side, the tricuspid valve with three leaflets and, on
the left side, the mitral valve that contains two leaflets.
Aortic valve
The three leaflets of the aortic valve are thin and redundant
and the line defined by their attachment points at the aortic
wall is a 3-pronged crown (Fig. 1). The virtual ring formed
by joining the basal attachment of the leaflets defines the
aortic surgical annulus.5,6 The superior part of each leaflet
attachment is parallel to that of the adjacent leaflet, forming three commissures (the crown’s prongs), which joined
by a virtual ring define the sinotubular junction. During ventricular diastole, the center of the ventricular surfaces of
the leaflets comes together as the valve closes, whereas
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26
Table 1
H. Cuéllar et al.
Etiology of left valvular diseases according to the Euro Heart Survey.
Etiology
Aortic stenosis (%)
Aortic insufficiency (%)
Mitral estenosis (%)
Mitral insufficiency (%)
Degenerative
Rheumatic
Endocarditis
Inflammatory
Congenital
Ischemic
Others
81.9
11.2
0.8
0.1
5.4
0.0
0.6
50.3
15.2
7.5
4.1
15.2
0.0
7.7
12.5
85.4
0.6
0.0
0.6
0.0
0.9
61.3
14.2
3.5
0.8
4.8
7.3
8.1
Source: Modified from Iung et al.2
during ventricular systole the normal aortic valve area is
2.5---4 cm2 .5
The aortic root comprises the structures located between
the ring and the sinotubular junction. The spaces
between the three bulges on the wall of the aortic
root and their respective leaflets are the coronary sinuses.6
In the most common configuration, the right and left
coronary sinuses give rise to the right coronary artery and
the common trunk, respectively. The third is a non-coronary
sinus, in a posterior location. The fibrous core of the aortic
root extends into the anterior mitral leaflet.6
Imperfect bicuspid aortic valves are charaterized by congenital fusion, complete or incomplete, of one commissure
known as ‘‘raphe’’. The presence of two leaflets with rectilinear overlapping is pathognomonic of perfect bicuspid
aortic valve. Both types of bicuspid valves are pathological
and the opening creates a ‘‘fish-mouth’’ appearance.6
with a crescent shape (Fig. 2). Each leaflet is divided into
3 scalops termed according to their proximity to the left
atrial appendage.5,7 The leaflets are anchored on the periphery of the mitral annulus. Annular calcification is a common
finding in the elderly, without implying leaflet dysfunction.
During ventricular diastole, the mitral valve area is typically
4---6 cm2 .5
The chordae tendineae are attached to the ventricular surface of the free margins of both leaflets and are
in continuity with the two papillary muscles, anterolateral and posteromedial, which attach to the non-compacted
myocardium of the left ventricle (Fig. 2). This subvalvular
apparatus supports the leaflets during ventricular contraction, preventing valve eversion and blood reflux into the
atrium (parachute appearance).7
Pulmonary valve
Mitral valve
The mitral valve has an anterior or aortic leaflet, with
a semicircular shape, and a posterior or mural leaflet,
A
The pulmonary valve is similar to the aortic valve, with thinner leaflets due to lower pressures, and it has no arteries
arising from its sinuses. During ventricular systole, the area
B
RCS
RCA
CT
NCS
LCS
Figure 1 Aortic valve anatomy. (A) Anterior projection volume reconstruction from cardiac computed tomography data shows
the external appearance of the aortic root. The red and the thing white line represent the attachments of aortic valve leaflets and
define the three-prong crown. The red points are the nadirs of the leaflets, which delimit the aortic surgical annulus (green). The
right coronary sinus gives rise to the right coronary artery (RCA) and the left sinus give rise to the common trunk (CT). Continuity
between the anterior mitral leaftlet and left coronary sinus (black arrows). (B) Planimetry of the aortic valve during diastole at sinus
level shows valve closure with complete apposition of the leaflets (yellow arrowheads). Each bulge on the root correspond to one
sinus: right (RCS), left (LCS), and non-coronary (NCS). The interleaflet triangles (red asteriks) are extensions of the left ventricle
that extend cranially toward the commissures and delimited by the inferior aspect of the aortic leaflets laterally.
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Cardiac computed tomography for valve disease
27
A
B
LCS
AML
tc
PML
PM
tc
Figure 2 Mitral valve anatomy. (A) Thick slab minimum-intensity projection in a dedicated three-chamber view shows the mitral
valve in mid-diastole. The anterior mitral leaflet (AML) is in continuity with the left coronary sinus (LCS). The posterior mitral
leaflet (PML) is independient. The tendinous chords (tc) connect the mitral leaflets to the papillary muscles (PM), which attach to
the trabeculated myocardium. (B) Inverted volume reconstruction shows an open mitral valve during mid-diastole viewed from the
ventricle, note the typical ‘‘smile’’ appearance.
of the normal pulmonary valve is approximately 2 cm2 /m2 of
body surface.5
Tricuspid valve
The subvalvular apparatus is similar to that of the mitral
valve, but it has three leaflets and three groups of chordae
tendineae and papillary muscles (septal, anterior and
posterior). The leaflets are thin and the annulus is more
apical than the mitral one.5
Technical considerations of cardiac computed
tomography in valvular disease
Coronary calcium score
Coronary artery calcifications, more common in elderly
patients with degenerative aortic stenosis, may hinder or
prevent the analysis of non-invasive coronary angiography.8
In this group of patients, an initial coronary calcium scoring
may help decide whether to perform a coronary angiography.
Medication used in coronary angiography
Artifacts caused by heart rate variability in mitral valve
disease and those caused by pulsatile movement in oartic
and mitral insufficiency can be partially reduced with beta
blockers, which reduce and stabilize heart rate.9 These
drugs may worsen the hemodynamic status in patients with
valve disease with impaired ventricular function or critical
valve stenosis and preserved function. Administration
should be based on heart rate, blood pressure, ECG and
echochardiographic findings. Drugs with short active life
(esmolol, atenolol) and patient monitoring during the
administration are recommended. These considerations are
applicable to the use of vasodilatadors (nitroglycerin).
Contrast injection
The standard biphasic protocol (contrast injection with
saline flush) is sufficient for the study of the coronary
arteries and heart valves.9 For the study of the right valves,
however, a triphasic protocol is recommended where the
second phase is a contrast agent-saline mixture that pushes
the initial contrast bolus.5,9 This avoids artifacts caused
by the mixture of blood with and without contrast coming
from the cava veins, making the right ventricle to fill
homogeneously with contrast agent. If the dual-syringe
pump for simultaneos injection is not available, a similar
effect can be achieved by decreasing the saline flow rate.9
Acquisition and reconstruction of raw data
Techniques aimed at reducing the radiation dose, such
as prospective and retrospective acquisition with systolic
reduction, are not indicated for patients with fast or
irregular heart rate (atrial fibrillation), in whom ventricular
systole may be needed for the study of the coronary arteries.
Neither of these techniques is indicated for the assessment
of valve morphology during ventricular systole nor complex
valvular pathology (fistulas, endocarditis). The retrospectively acquired raw data are recontructed at 5---10% of the
R---R interval (10---20 images per cardiac cycle) in order to
detect the moments of best quality of the coronary artery
tree and valvular structures.10,11 A cine loop of these phases
allows qualitative assessment of the valvular function.
In general terms, the optimal phase of the cardiac cycle
for simultaneous assessment of coronary arteries and left
valves in most patients (Table 2) depends on the valve and
heart rate:
1) The area of the aortic opening is widest during midventricular diastole, 50---100 ms after the R wave peak,12
which corresponds to 20---30% of the R---R interval
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579 (est)
--0.15
--------133
Yes
64 detectors
0.4
0.55
0.5
0.85
0.69
0.73
0.62
0.33
0.42
0.2
0.26
0.19
0.3
0.96
0.98
1
1
0.99
0.98
0.67
0.58
0.55
0.82
0.66
0.84
0.78
0.95
0.8
0.92
0.89
0.94
0.92
0.81
1
1
0.95
0.95
40
35
55
70
237
106
No
Yes
No
No
Yes
Yes
0.68
1
1
0.44
0.68
0.62
Avoidable
catheterization
CD
prevalence
Negative
predictive
value
Positive
predictive
value
Specificity
2011
A number of studies published up to 2006 suggested that noninvasive coronary angiography was able to rule out coronary
disease before valve surgery with a sensitivity of 92---100%,
a specificity of 78---92%, positive predictive value of 55---82%,
and negative predictive value of 96---100% (Table 3).15---18
Nonetheless, these trials were based on small series of
patients whose only or predominant condition was aortic
stenosis. Patients with arrhythmias, fast heart rate and high
calcium levels (usually values >1000 Agatston units [AU])
16 detectors
16 detectors
16 detectors
32*2 detectors
32*2 detectors
16 detectors
Preoperative coronary angiography
with cardiac computed tomography
2006
2006
2006
2006
2009
2011
Parallel images, orthogonal to the left ventricular outflow
tract are recommended for the assessment of the aortic
valve and its area (aortic valve planimetry) (Fig. 4).12
For assessment of the mitral valve and its area, images
parallel to the mitral valve opening, including part of the
left atrium and ventricle, are recommended. They can be
obtained from a long axis image of the left ventricle (mitral
planimetry) (Fig. 4).10,13 For evaluation of mitral insufficiency, the three-chamber view is indicated with addition of
a series of radial images obtained from the mitral planimetry, starting from the center of the anterior mitral leaflet
and slicing perpendicularly through the line of apposition of
both leaflets (Fig. 4).13 For assessment of mitral valve prolapse, two- and three-chamber views are recommended.14
Reant et al.
Manghat et al.a
Gilard et al.
Meijiboom et al.
Bettencourt et al.
RodríguezPalomares
et al.
Catalán et al.b
Planes for the study of the heart valves
Total
Sensitivity
No. of
patients
depending on the heart rate and patient. In general, this
point coincides with the decrease in the T wave in the
electrocardiogram. Earlier reconstructions (0---50 ms)
keep this maximum area but with severe motion
artifacts.12
2) The optimal phase for evaluation of the closed mitral
valve during systole is at 5% of the R---R interval.13
3) For low heart rate (<65 bpm), the optimal phase to visualize the coronary arteries is ventricular mid-diastole,
at 60---75% of the R---R interval depending on the heart
rate and patient (Fig. 3).9 This point can be used to
assess the closed aortic valve and the mitral area.
4) For fast heart rate, the optimal phase to visualize the
coronary arteries is variable, from ventricular diastole
to ventricular mid-systole, which usually also is the best
phase to visualize the aortic valve.
Arrhythmias
The optimal points vary depending on the patient, heart rate and
equipment. For heart rate greater than 65 bpm with poor quality
of the diastolic series, acquisition of a series at end-systole is
recommended for assessment of the coronary arteries.
HR: heart rate; bpm: beats per minute.
AS
prevalence
60---75% if HR < 65 bpm
60---75% if HR < 65 bpm
CT equipment
20---30%
5%
Year
Aortic valve
Mitral valve
Authors
60---75% if HR < 65 bpm
Comparison of results reported by the main studies on non-invasive coronary angiography with CCT in patients with valvular disease.
20---30% if
HR > 65 bpm
Table 3
Coronary artery
Calcium
cutoff
Table 2 Indicative table of the optimal phases of the cardiac cycle to visualize the coronary arteries and left valves,
expressed as relative percentages of the R---R interval.
Quantitative values are expressed as percentages, with the exception of the number of patients, in nominal values, and the calcium cutoff recommended or used, expressed in Agatston
units.
AS: aortic stenosis; CD: coronary disease; (rec): cutoff value recommended and used in the inclusion criteria of the group; (est): recommended value estimated from the results of the
study.
a The study by Manghat et al. only provide values per segment; values in italics are the yield per segment, in contrast with the rest of the studies reporting values per patient.
b CD prevalence in the study by Catalán et al. is estimated from the positive results at CT that underwent invasive coronary angiography, and it is therefore an indicative value, shown
in italics.
H. Cuéllar et al.
--1000 (rec)
1000 (rec)
1000 (rec)
390 (est)
---
28
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Cardiac computed tomography for valve disease
RCA
29
ADA
CXA
Figure 3 Curve multiplanar images showing normal main coronary arteries in the preoperative study of a patient with aortic
insufficiency.
RCA: right coronary artery; ADA: anterior descending artery; CXA: circumflex artery.
Figure 4 Image acquisition using aortic planimetry (A---C), mitral planimetry (D---E), and mitral radial images (D---F). An oblique
parasagittal plane is created on a coronal image (A) parallel to the left ventricular outflow tract (yellow line). The resultant plane
(B), similar to the three-chamber view, allows the creation of a series of parallel planes, orthogonal to the left ventricular outflow
tract (yellow lines), which corresponds to the aortic planimetry (C). On the four-chamber view (D), planes are drawn parallel to
the mitral annulus and orifice (yellow line), and mitral planimetry is obtained (E). On the planimetry, a series of planes are drawn
from the center of the anterior mitral leaflet that slice perpendicularly the line of apposition of both leaflets (yellow lines), which
allow accurate evaluation of the mitral valve closure (F).
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30
were generally excluded. More recently, one Portuguese
trial19 and one Spanish trial20 have confirmed the excellent
yield of the technique in large series of patients (237 and
106, respectively) with different types of valve diseases.
In the Spanish trial, 38% of patients had a valve disease
different from degenerative oartic stenosis (Table 3).20 In
order to obtain homogeneous results that could be used
as a reference for the technique, a CT scanner with only
16-detectors was used throughout the study. Despite this,
catheterization could have been avoided in 64% of patients
(Fig. 3).20 At the same time, another Spanish group assessed
133 patients before non-coronary cardiac surgery, including patients with non-valvular conditions.21 The absence of
significant coronary artery disease at CCT was confirmed
by clinical follow-up of patients, and not by invasive coronary angiography, and none of the patients showed adverse
events that could be attributed to underdiagnosed coronary
artery disease after an average of 1000 days.21 Both Spanish trials included patients with arrhythmias controlled with
medication20,21 while maintaining a positive predictive value
of 99%20 without reducing the quality of the test.21
All the studies cited considered the presence of severe
coronary artery calcification to be the major obstacle to
interpreting a non-invasive coronary angiography. A number of studies15---18 have suggested that a calcium scoring
>1000 AU is more likely to result in an inconclusive or
non-diagnostic coronary angiography, thus forcing catheterization. In view of this situation, these studies recommended
discontinuing the use of non-invasive coronary angiography.
More recent studies suggest lower score cutoffs of 579 AU21
and 390 AU.19 This latter value is partially explained by the
high prevalence of aortic estenosis and coronary artery disease of the series studied.
Current scientific evidence indicates that non-invasive
coronary angiography is an appropriate test to assess the
coronary tree before non-coronary surgery in patients with
intermediate risk of coronary artery disease, but its utility remains uncertain in low-risk patients.4 Similarly, there
is currently no consensus regarding the value of calcium
scores >400 AU to avoid non-invasive coronary angiography.4
We recommend assessment of calcium score images because
peripheral calcifications in proximal segments do not prevent evaluation of the coronary angiography in most cases.18
Assessment of aortic valve disease
An aortic valve area <1 cm2 is considered diagnostic for
severe aortic stenosis.1,5 The area can be measured by
transesophageal echocardiography as the geometric valve
area or by transthoracic echocardiography as effective
valve area, using the continuity equation. The geometric
area is greater than the effective area due to convergence
of the flow stream in the center of the orifice. However, the
continuity equation has limitations because it integrates
the velocity---time curves of the blood flow at the left
ventricular outflow tract and at the aortic valve during ventricular systole, which vary in relation to the hemodynamic
status of the patient.1 In addition, the measurements in
the outflow tract are calculated assuming a circular shape,
rather than elliptical.22,23 Leaflet calcification in aortic
stenosis may hinder the proper assessment of the orifice
H. Cuéllar et al.
Figure 5 Image of aortic planimetry during systole at the
level of the coronary sinuses shows critical degenarative aortic stenosis, with a maximum valve area <1 cm2 . The minimum
orifice delimited by the yellow dotted line is <1 cm2 . Note thickening and calcification of leaflets (white arrows), more marked
in the left leaftlet (red arrow).
with transesophageal echocardiography, but it does not
affect the quantitative analysis of aortic planimetry with
CCT (Fig. 5)24 or cardiac magnetic resonance (CMR). In fact,
the aortic valve calcium score is correlated with aortic
valve area and severity of aortic stenosis, having a proven
prognostic value for this condition.24---27
CCT allows 3D evaluation of the aortic valve providing better spatial resolution than CMR (voxels of 0.4 mm3
and 1.2 mm3 , respectively).5 However, 64-detector CT scanners do not provide optimal temporal resolution, although
dual-source scanners provide values close to those of CMR
(150---200 ms, 75 ms and 25---50 ms, respectively).5 Unlike
CMR, CCT can be used in patients with implanted pacemakers and defibrillators, but it does not provide information
about valve flow.
The geometric area measured by CCT has demonstrated
excellent correlation with the effective area measured by
transthoracic echocardiography, with a slight overestimation partially attributed to the methodological differences
between the two techniques.24 In one study, valve planimetry and measurement of geometric valve area by CCT were
feasible in all patients, but when using transesophageal
echocardiography they were feasible in only 78% and 58%
of patients, respectively.28 In the cases that could be
compared, for the detection of moderate to severe aortic estenosis with CCT, the sensitivity, specificity, positive
predictive value and negative predictive value were 98%,
92%, 98% and 92%, repectively, with excellent interobserver
agreement and between techniques.28
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Cardiac computed tomography for valve disease
31
Figure 6 Images of aortic planimetry during diastole show two different types of aortic insufficiency. (A) A patient with a double
degenerative valve lesion. Note thickening and calcification of the leaflets that result in retraction and the presence of a regurgitation
orifice. (B) The dilation of the aortic root prevents proper aortic leaflet closure. Note the large size of the coronary sinuses with
thin leaflets. Manual delimitation for the estimation of the valve area is shown in both cases.
In classic aortic insufficiency, the aortic leaflets fail
to close completely during ventricular diastole and blood
flows back through the orifice. This orifice can be visualized
by transesophageal or transthoracic echocardiography, CCT
and CMR (Fig. 6). Aortic insufficiency may occur alone or
associated with aortic stenosis (Table 1).2 In a series of
patients referred for non-invasive echocardiography who
also underwent transthoracic echocardiography, the sensitivity, specificity, positive and negative predictive value of
CCT for the detection and quantification of moderate and
severe aortic insufficiency was 95%, 100%, 100% and 98%,
respectively, with good correlation between area and retrograde flow at CCT and transthoracic echocardiography.29,30
However, a recent study using dual-source CT reported that
classification of aortic insufficiency based on the orifice area
was not accurate to differentiate mild and moderate aortic
insufficiency31 . This difficult evaluation of the mild forms of
aortic insufficiency could be explainced by the presence
of partial volume effect of calcium around a small regurgitation orifice and by the cases of bicuspid valves.30,31
Retrospective acquisition allows estimation of the aortic
regurgitation volume in the absence of other serious
valvular diseases by means of quantitative analysis of the
volumes and function of both ventricles,32 in a similar
fashion to MR imaging.
CCT is highly accurate for the identification of naturally
perfect bicuspid aortic valves during ventricular diastole,33
but for imperfect valves, the ‘‘fish-mouth’’ appearance has
to be visualized during ventricular systole (Fig. 7). In these
cases, the thoracic aorta should be included in the study
to rule out dilation or coarctation of the ascending aorta,
usually associated to bicuspid valve (Fig. 7).
CCT complements the findings of transesophageal
echocardiography in endocarditis with paravalvular involvement, as it allows an accurate 3D evaluation of abscessses,
pseudoaneurysms and fistulas (Fig. 8).34 In addition, noninvasive coronary angiography is particularly important in
patients with endocarditis because catheterization poses a
high risk of embolization of vegetations or perforation of
abscesses.34
CCT provides additional information regarding the origin
and functional repercussion of aortic valve disease. Diffuse
thickening of the left ventricular myocardium and dilation
of the ascending aorta at CCT are indirect findings suggestive of aortic stenosis, while left ventricular dilation
associated with these findings is more characteristic of aortic insufficiency.5 Proper closure of the aortic valve should
be routinely assessed on CCT images regardless of the initial
suspected diagnosis.
Calcifications of aortic valve are incidentally detected
in 13---30% of patients referred for non-invasive coronary
angiography.27 These calcifications must be reported and
in case of retrospective acquisition, the aortic valve area
must be measured. An echocardiography is recommended in
patients with areas <2---3 cm2 .5
Assessment of mitral valve disease
Rheumatic disease is the most common cause of mitral
stenosis in our setting. Mitral stenosis may occur alone
or in association with mitral insufficiency or other valve
diseases.2 CCT can detect the morphological changes typical of mitral stenosis such as thickening and calcification
of leaflets with margin fusion and simultaneous subvalvular involvement with retraction of chordae tendineae and
papillary muscles (Fig. 9). This results in a ‘‘fish-mouth’’
appearance on short-axis images, while the open anterior
leaflet shows a ‘‘hockey-stick’’ appearance on threechamber images (Fig. 9).5,35
The mitral valve area determined by mitral planimetry with CCT is systematically larger than that determined
by transesophageal echocardiography and catheterization,
but it does not prevent discrimination between grades of
MS.11 In a series of 28 patients with MS, values of mitral
valve area <1.7 cm2 allowed detection of moderate to severe
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32
H. Cuéllar et al.
A
B
sist
Figure 7 Image of aortic planimetry during systole at the level of the coronary sinuses (A) shows critical degenerative stenosis
of a naturally perfect (with two sinuses) aortic valve, with a maximum valve area <1 cm2 . The maximum intensity projection (MIP)
in the oblique parasagittal plane (B) during diastole allows accurate evaluation of the aneurysm in the ascending aorta associated
with the bicuspid valve.
MS with a sensitivity, specificity, positive predictive value,
and negative predictive value of 73%, 88%, 80% and 83%,
respectively.11
Chronic mitral insufficiency is more common and has a
multiple etiology. The acute form is rare and is caused by
ischemic rupture of the chords. In a series of 44 patients with
and without mitral insufficiency, CCT correctly detected
all the cases of insufficiency diagnosed with transthoracic
echocardiography.10 Similarly, there was good correlation
between the regurgitant orifice area measured by CCT,
transesophageal echocardiography and ventriculography.10
Mitral valve prolapse, defined as a displacement of mitral
Figure 8 Two cases of aortic valve endocarditis. Image of aortic planimetry at the level of the coronary sinuses showing an
abscess of the aortic root secondary to endocarditis on a biological valve prosthesis (A). The yellow arrows delimit the outer
margin of the abscess that corresponds to the hypondense wall thickening. Anterior projection of a volume reconstruction showing
a pseudoaneurysm of the aortic root secondary to endocarditis on a biological prosthesis (B). The yellow arrows delimit the outer
margin of the pseudoaneurysm. Note the involvement of the common trunk in (A) and the cranial displacement of the proximal
right coronary artery in (B) (white stars).
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Cardiac computed tomography for valve disease
33
Figure 9 Images parallel to the three-chamber plane during diastole show one case of severe mitral stenosis of rheumatic origin
(A---D). Note shortening and thickening of papillary chords (red arrows) and retraction of leaflets that appear diffusely thickened
and calcified. Visualization of a small valve orifice in this plane (white star) and fusion of commissures (yellow arrows) suggest
stenosis. Note the associated atrial dilation and the ‘‘hockey-stick’’ opening (white arrow) of the anterior mitral leaflet, typical of
rheumatic disease.
valve leaflets toward the left atrium ≥2 mm below the
mitral annulus, is one of the causes of mitral insufficiency
that can be identified with CCT (Fig. 10).5,14 The combined use of two- and three-chamber views at CCT yields
an accuracy of 95% for the diagnosis of mitral valve prolapse with respect to transesophageal echocardiography.14
In the absence of other valve diseases, CCT allows quantitative assessment of the severity of mitral insufficiency
Figure 10 Mitral insufficiency in three-chamber (A) and two-chamber (B) views in diastole show a closure defect of the mitral
valve (white arrow), with partial prolapse of the anterior leaflet toward the right atrium (yellow arrow). The linear hypondense
image corresponds to a fragment of ruptured tendinous chord dragged by retrograde flow. Note dilation of left atrium and right
chambers secondary to increased retrograde pressure.
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34
by calculating the regurgitant volume and regurgitant
fraction.35
Echocardiography and CMR imaging are usually sufficient
for the evaluation of mitral pathology, consigning CCT to a
secondary role except for the evaluation of calcified lesions,
such as the caseous calcification of the mitral annulus.36
Left atrial dilation with wall calcification or thrombus in
the atrial appendage, left ventricular dilation, signs of
congestion in the lung parenchyma and right ventricular
hypertrophy are indirect sign that, when found on a CT study,
will force the evaluation of the mitral valve.5
Assessment of right valve diseases
CCT is not appropriate for assessment of right valves because
of their characteristically thin leaflets and because homogeneous opacification of the right cavities is difficult to
achieve. Nonetheless, a large number of findings of right
valve disease can be identified using CCT.5
H. Cuéllar et al.
Confidentiality of data. The authors declare that no data
from patients are shown in this article.
Right to privacy and informed consent. The authors
declare that no data from patients are shown in this article.
Authorship
1.
2.
3.
4.
5.
6.
7.
8.
9.
Responsible for the integrity of the study: HC.
Conception of the study: HC and VP.
Design of the study: HC and VP.
Acquisition of data: HC and AR.
Analysis and interpretation of data: HC, AR and JR.
Statistical analysis: N/A.
Bibliographic search: HC.
Writing of the paper: HC.
Critical review with intellectually relevant contributions: HC, AR, VP and JR.
10. Approval of the final version: HC, AR, VP and JR.
Conflicts of interest
Postoperative evaluation of heart valves
Artifacts induced by prosthetic valves and surgical material
do not prevent the acquisition of a CT with diagnostic quality, which is a good complement to echocardiography.4,37
In case of suspected bileaflet mechanical valve dysfunction, CCT allows the detection and quantification of
leaflet restriction,38---40 as well as thrombus and pannus
formation.41,42 In valve bioprosthesis, CCT allows the detection of leaftlet degeneration with calcification.41 In the
absence of these morphological abnormalities, the dysfunction may be attributed to patient-prosthesis mismatch.41
Finally, CCT provides the surgeon with relevant information before reoperative cardiac surgery, including the state
of previous coronary shunts and the degree of mediastinal fibrosis, and it can help plan the clamping of ascending
aorta.43---45
Conclusion
CCT allows evaluation of the coronary tree before heart
valve surgery, and qualitative and quantitative assessment
of aortic and mitral valve pathology, which is useful in
patients with poor image quality at echocardiography. In
addition, CCT is an excellent technique for the evaluation
of patients after valve surgery or before reoperative cardiac
procedures.
The heart valves should be routinely assessed on CCT
images, regardless of the initial suspected diagnosis, and
any pathologic findings should be included in the radiological
report.
Ethical responsibilities
Protection of humans and animal subjects. The authors
declare that no experiments involving animals or humans
have been carried out for this study.
The authors declare not having any conflicts of interest.
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