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342 AJR:186, February 2006

AJR2006; 186:342349

0361803X/06/1862342

American Roentgen Ray Society

M E D I C A L I M A G I N G

A C E N T U R Y

O F

t al.

f Aortic

fication

C a rd i ac I ma g in g O ri g in al R es e ar ch

Aortic Valve Calcification as an

Incidental Finding at CT of theElderly: Severity and Location asPredictors of Aortic Stenosis

Franklin Liu1

Courtney A. Coursey1

Cairistine Grahame-Clarke2

Robert R. Sciacca2

Anna Rozenshtein1

Shunichi Homma2

John H. M. Austin1

Liu F, Coursey CA, Grahame-Clarke C, et al.

Keywords:aortic valve, calcification, cardiovascular

disease, CT, heart, stenosis

DOI:10.2214/AJR.04.1366

Received August 31, 2004; accepted after revision

January 31, 2005.

1Department of Radiology, Columbia University Medical

Center, 630 W 168th St., New York, NY 10032. Address

correspondence to J. H. M. Austin.

2Department of Medicine, Columbia University Medical

Center, New York, NY 10032.

OBJECTIVE. The purpose of this study was to correlate the severity and location of aortic

valve calcifications, as an incidental finding at chest CT of elderly persons, with pressure gra-

dients across the valve.

MATERIALS AND METHODS. One hundred fifteen subjects who were 60 years old or

older and who showed aortic valve calcification on chest CT (5-mm reconstructed section

width, no IV contrast material) and who had also undergone transthoracic echocardiography

within 3 months of the CT examination were identified retrospectively. Aortic valve calcifica-

tion scores (Agatston and volumetric) and subjective calcification pattern scores (based on a 9-

point scale) were calculated and correlated with echocardiographic gradients.

RESULTS. Thirty patients (26%) (median age, 81 years) were identified who showed an in-

creased pressure gradient across the aortic valve at echocardiography. Eighty-five subjects (74%),

including 30 age-matched but otherwise randomly selected control subjects, showed no increase

in pressure gradient. The severity of aortic valve calcification was greater for the 30 subjects with

an increased gradient than for the control subjects (p < 0.0001). Increased mean and peak gradi-

ents across the aortic valve correlated with the subjective scores for aortic valve calcification

(r= 0.69 and 0.65, respectively;p < 0.0001), with Agatston scores (r= 0.76 and 0.70, respec-

tively;p < 0.0001), and with volumetric scores (r= 0.78 and 0.73, respectively;p < 0.0001). In

terms of specific commissures, the greatest correlation with mean and peak gradients was for pe-

ripheral left-posterior commissural calcification (r= 0.71 and 0.65, respectively;p < 0.0001) and

central rightleft commissural calcification (r= 0.69 and 0.66, respectively;p < 0.0001).

CONCLUSION. The severity of aortic valve calcifications on chest CT, as assessed eithersubjectively or objectively, correlated with increased pressure gradients across the aortic valve,

particularly for calcification of the peripheral left-posterior commissure and the central rightleft

commissure. These results indicate that the severity and location of aortic valve calcifications on

chest CT are associated with an increased pressure gradient across the aortic valve.

ortic stenosis is the most common

disease of a cardiac valve in in-

dustrialized countries and is mod-

erate to severe in 4.34.8% of per-

sons 75 years old or older [1]. It is the cause

of most surgical aortic valve replacements in

patients older than 75 years [2]. Over the past

60 years, the primary cause of aortic stenosis

has changed from rheumatic to senile degen-eration and calcification [2].

Patients suspected of having aortic stenosis

usually undergo Doppler echocardiography as

part of the evaluation [3, 4]. Doppler quantifica-

tion of the systolic pressure gradient and of the

aortic valve area is useful for management deci-

sions because aortic valve area and systolic pres-

sure gradients (mean and peak) across the aortic

valve are recognized predictors of outcome [4].

Aortic valve calcification can sometimes

be seen on chest radiography, and the pres-

ence of such calcificationsusually best seen

on the lateral radiographis a sensitive

marker for clinically significant aortic steno-

sis [5]. CT is a sensitive imaging tool for de-

tecting focal calcifications, and we have noted

subjectively that aortic valve calcifications

are often seen as incidental findings on CT ofelderly persons and that, moreover, these aor-

tic valve calcifications appear to show some

characteristic patterns. Recent studies have

shown correlations between CT measure-

ments of the severity of aortic valve calcifica-

tion and the severity of increased pressure

gradients across the valve [69]. Because the

severity and patterns of aortic valve calcifica-

tion offer the potential of aiding in presymp-

A

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CT of Aortic Valve Calcification

AJR:186, February 2006 343

tomatic detection of aortic valve stenosis, we

undertook this study.

Materials and Methods

A medical informatics-assisted search of com-

puterized medical records at Columbia University

Medical Center yielded 1,257 adult patients, 643 ofwhom were 60 years old or older and had under-

gone both chest CT and transthoracic echocardiog-

raphy within a 3-month interval between 1999 and

2002. Study subjects were then chosen from these

643 patients. Any patient who had a bicuspid aortic

valve, cardiac transplant, or previous aortic valve

surgery was excluded from the study. Patients se-

lected for study each showed aortic valve calcifica-

tion on CT, which was performed without IV con-

trast material and reconstructed at a width of 5 mm.

Rheumatic valve disease, poor left ventricular func-

tion, and coexisting aortic regurgitation were not

exclusion criteria. These criteria yielded a pool of

115 patients. Thirty (26%) of these patients (19women, 11 men; ages, 6192 years; mean, 79 9

[SD] years; median, 81 years) (study subjects)

showed evidence of an increased gradient across

the aortic valve at echocardiography, either as a

peak pressure gradient of 15 mm Hg or more, a

mean pressure gradient of 10 mm Hg or more, or

both. Among the 85 (74%) of these 115 patients

who showed aortic valve calcification on CT but no

evidence of an increase in pressure gradient across

the aortic valve at echocardiography (control sub-

jects), 30 age-matched control subjects (17 women,

13 men; 6391 years old; mean, 78 8 years; me-

dian, 80 years) were otherwise selected randomly.

Chest CT scans (0.75-sec scanning time per sec-tion, 120140 kVp, 200240 mA), each with the

patient in the supine position, were obtained on four

single-detector CT scanners (Somatom Plus-4, Sie-

mens Medical Solutions) using collimation of 5

mm, and on one 4-MDCT scanner (Siemens Vol-

ume Zoom) from August 1999 through December

2002. Images were reconstructed using a high-spa-

tial-frequency algorithm and reconstructed section

width of 5 mm. Each CT study was evaluated quan-

titatively for aortic valve calcification using Agat-

ston and volumetric calcification scores [10, 11]

(Vitrea 2 software, Vital Images) on a PACS

(Kodak) workstation. Pixels having a CT attenua-

tion of 130 H or greater were considered to beshowing calcification [10]. The calcifications as-

sessed were limited to the region of the aortic valve

and specifically excluded any arcuate or other focal

calcifications of atherosclerosis of the aortic root,

calcifications of atherosclerosis of the proximal

right and left coronary arteries, and calcification of

the superomedial aspect of the mitral annulus.

All chest CT studies were also reviewed indepen-

dently (at soft-tissue settings of 350-H width and 35-

Fig. 1Diagram showscommissures of aorticvalve as seen en face.Valve on CT of supinepatient is slightly obliqueto axial plane but issimilar in appearance tothis schematic depiction.

Ac = central right-posterior commissure,Ap = peripheral right-posterior commissure,Bc = central rightleftcommissure,Bp = peripheral rightleftcommissure,Cc = central left-posterior commissure,Cp = peripheral left-posterior commissure.

Bp

Bc

Ap

Ac

Cc

Cp

H center, and bone settings of 1,500-H width and

300-H center) by two experienced thoracic radiolo-

gists who were blinded to all clinical data except

each patients age and sex, including blinding to each

patients echocardiographic data. Aortic valve calci-

fications were characterized subjectively by the fol-

lowing criteria: presence and location (central or pe-

ripheral half for each commissure [Fig. 1]);

subjective grade of severity (scale of 19), both over-

all and in each location (Fig. 1); and number of 5-

mm sections with calcification present. The 9-point

subjective scale of severity corresponded to the fol-lowing scores for calcification (see Fig. 2 for exam-

ples): 1 = judged absent, but mild calcification was

considered and rejected; 2 = judged mild, but ab-

sence of calcification was considered and rejected;

3 = judged unequivocally mild; 4 = judged mild, but

moderate calcification was considered and rejected;

5 = judged moderate, but mild calcification was con-

sidered and rejected; 6 = judged unequivocally mod-

erate; 7 = judged moderate, but severe calcification

was considered and rejected; 8 = judged severe, but

moderate calcification was considered and rejected;

and 9 = judged unequivocally severe. An average of

the subjective scores by the two radiologists for over-

all calcification of the aortic valve and for each re-gion of the aortic valve was used for statistical anal-

ysis. An average of the objective scores (Agatston

and volumetric) of the two radiologists for the quan-

tity of aortic valve calcification was also used for sta-

tistical analysis.

Transthoracic echocardiography reports were

obtained from the echocardiography database.

Echocardiography was performed by experienced

technicians using Agilent Sonos 4500 or 5500 ma-

chines. The echocardiographic scans were each in-

terpreted by various experienced cardiologists sub-

specializing in echocardiography, none of whom

was aware at the time of the reporting of the inclu-

sion of the subject in this study.

The peak instantaneous transvalvular aortic jet

velocity was determined using the modified Ber-

noulli equation. The valve was examined from mul-

tiple acoustic windows to obtain the highest peak

jet velocity. Mean Doppler velocities were calcu-

lated by averaging the instantaneous Doppler gra-

dients throughout the ejection period using an on-line quantification package. Three cardiac beats

were averaged and the spectral display velocity

curve was traced by hand. There were no cases of

additional subaortic or supraaortic stenosis. No aor-

tic valve gradients were unobtainable for technical

reasons (e.g., poor acoustic windows).

A retrospective chart review was conducted for

the 30 study and the 30 control subjects, document-

ing clinical variables that have been shown to be as-

sociated with aortic stenosis: history of cigarette

smoking [1, 1214], diabetes mellitus [13, 14], sys-

temic hypertension [1, 13] and coronary artery dis-

ease [15]. The presence of coronary artery disease

was based on the mention in the patients record ofcoronary artery disease, angina with positive

stress test, or myocardial infarction, but not

chest pain. Serum chemical tests that have been

associated with aortic stenosis were evaluated: se-

rum calcium [13,14], low-density and high-density

lipoprotein [13, 14], triglyceride [14], and creati-

nine [13, 16] levels were also recorded. Each labo-

ratory value recorded was the single data point clos-

est in time to the patients CT examination.

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Liu et al.


The relationships between pressure gradients

and CT aortic valve calcification data and clinical

variables were determined using the Spearmans

rank correlation. Differences in the presence and

distribution of aortic valve calcification between

patients and control subjects were tested using the

nonparametric rank-sum test. Differences in the

distribution of clinical factors between study and

control subjects were tested using the two-sided

Fishers exact test. Apvalue of less than 0.05 was

considered significant for analyses. This study was

approved by our institutional review board.

Results

Findings for study subjects and control

subjects are presented in Tables 1 and 2. The

average peak and mean gradients in the study

population were 42 31 [SD] mm Hg and

25 20 mm Hg, respectively; median scores

A B

C D

Fig. 2Aortic valve calcifications on CT (section thickness, 5 mm) in four elderly patients.A,Example of severe calcification (subjective grade, 8.5 on 9-point scale; peak gradient, 75 mm Hg; mean gradient, 49 mm Hg), both centrally and peripherally in valve,involving rightleft commissure (arrow) and left-posterior commissure (arrowhead). Patient is an 88-year-old woman.B,Example of moderate calcification (subjective grade, 6.5 on 9-point scale; peak gradient, 25 mm Hg; mean gradient, 19 mm Hg) involving center of valve and left-posteriorcommissure. Patient is an 86-year-old man.C,Example of moderate calcification (subjective grade, 5 on 9-point scale; peak gradient, 17 mm Hg; mean gradient, 10 mm Hg) involving mainly left-posterior commissureand rightleft commissure. Patient is an 84-year-old man.D,Example of mild calcification (subjective grade, 3 on 9-point scale; peak gradient, 18 mm Hg; mean gradient, 10 mm Hg) involving mainly right-posterior and rightleft

commissures centrally. Patient is a 74-year-old woman.

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were 30 and 17 mm Hg, respectively

(Table 1). Severity scores for aortic valve cal-cification (9-point scale) between the two ra-

diologists agreed within 1 point for 71.9% of

the assessments and within 2 points for 84.4%

of the assessments.

Agatston scores and volumetric scores for

severity of aortic valve calcification both dif-

fered significantly between study and control

subjects (p < 0.0001) (Table 3). The number

of 5-mm-thick sections showing aortic valve

calcification differed significantly between

study and control subjects (p = 0.0004)(Table 3). In addition, study and control sub-

jects differed significantly in the overall sub-

jective calcification grade (p < 0.0001), in-

cluding at each of the six designated locations

of valve calcification (p < 0.01) (Table 3). Di-

abetes mellitus was documented in 13 (43%)

of the control subjects and in four (13%) of

the study subjects, but information concern-

ing diabetes mellitus was not available for 11

TABLE 1: Aortic Valve Calcifications at CT: Increased EchocardiographicGradients for 30 Study Patients

PatientNo. Sex Age (yr)

Calcification ScoreEchocardiographicGradients (mm Hg)

Subjectivea Agatston Volumetr ic

No. of 5-mmSectionsInvolved Peak Mean

1 F 61 4.5 1,092 1,026 4 38 17

2 M 64 8.5 4,645 3,856 5 75 49

3 F 65 2 33 39 1 18 10

4 M 66 6 1,345 1,108 4 34 21

5 F 67 2 50 78 3 19 10

6 M 68 7 2,867 2,294 4 24 21

7 F 70 7 695 611 4 71 49

8 F 71 3 150 266 2 45 23

9 F 74 3 192 190 2 18 10

10 F 76 2.5 222 249 2 24 15

11 F 77 6.5 607 609 3 40 22

12 F 78 4.5 669 617 3 30 2013 F 78 3 15 31 2 15 9

14 M 79 4.5 533 447 3 80 52

15 F 81 3 121 199 3 32 17

16 F 81 3 50 76 2 18 10

17 M 82 3 113 99 2 19 10

18 M 82 3.5 172 313 3 44 23

19 M 84 5 459 422 2 17 10

20 F 84 5 390 386 3 18 9

21 F 84 8.5 2,744 2,152 4 125 75

22 F 85 8.5 2,672 2,066 4 61 34

23 M 86 6.5 1,219 982 4 25 15

24 F 87 5.5 90 94 2 30 1525 F 88 8 6,286 4,868 7 85 55

26 M 88 3 348 374 3 28 15

27 M 89 7 1,454 1,112 3 50 35

28 F 89 8.5 4,727 3,624 4 128 86

29 M 91 4.5 97 158 3 21 11

30 F 92 4 115 106 2 20 11

Median 81 4.5 424.5 404 3 30 17

aOn a scale ranging from 1, absent, to 9, severe.

(37%) of the 30 control subjects or for three

(10%) of the 30 study subjects (Table 4).

The Agatston and volumetric calcium

scores were each found in the 30 study sub-

jects to correlate positively with mean

(r= 0.76 and 0.78, respectively;p < 0.0001)

and peak (r= 0.70 and 0.73, respectively;p < 0.0001) gradients at echocardiography

(Table 3). The number of 5-mm-thick sec-

tions showing calcification also correlated

positively with mean and peak gradients

(r= 0.56 and 0.53, respectively; p < 0.003)

(Table 3). The subjective calcification grade

in five of the six designated commissural re-

gions of the aortic valve correlated positively

with peak and mean gradients (r= 0.480.71

and r= 0.470.66, respectively; p < 0.01),

except for the peripheral right-posterior com-

missure, which showed no significant corre-

lation (Table 3). The highest CTechocardio-

graphic correlations were found forperipheral left-posterior commissural calcifi-

cation (mean, r= 0.71; peak, r= 0.65; each

p < 0.0001) and central rightleft commis-

sural calcification (mean, r= 0.69; peak,

r= 0.66; eachp < 0.0001) (Table 3). None of

the serum chemical or clinical variables cor-

related significantly with mean or peak gradi-

ents (Table 4).

Discussion

These results indicate that the severity of

aortic valve calcifications, as assessed subjec-

tively on routine chest CT of subjects 60 years

old or older, correlated with increased meanand peak pressure gradients across the aortic

valve and was significantly greater in patients

with an increased gradient across the valve

than in patients with a normal gradient across

the valve. Furthermore, the location of aortic

valve calcifications proved to be of interest:

increased mean and peak pressure gradients

correlated most strongly with the severity of

commissural calcifications in the central half

of the rightleft commissure and in the pe-

ripheral half of the left-posterior commissure.

The incidental finding of aortic valve calcifi-

cations on routine chest CT examinations has

been described previously, yet few studies haveexamined its clinical relevance. In an early ret-

rospective study of 100 patients (40 years or

older) who underwent chest CT examination

(1.0-cm collimation), Woodring and West [17]

identified five patients with aortic valve calcifi-

cation, three of whom had echocardiograms

showing a significantly increased gradient

across the aortic valve. Lippert et al. [18], in a

retrospective study of 109 patients (mean age,

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Liu et al.


TABLE 2: Aortic Valve Calcifications at CT for 30 Control Subjects with NormalAortic Valve Echocardiographic Gradients

Patient No. Sex Age (yr)

Calcification Score No. of 5-mmSectionsInvolvedOverall Subjectivea Agatston Volumetric

1 M 63 1.5 0 0 1

2 M 65 4.5 71 129 33 F 65 2 13 32 2

4 F 67 2.5 77 77 1

5 M 66 2.5 21 43 2

6 M 68 2.5 76 84 1

7 F 71 2 146 174 3

8 F 72 1.5 0 0 0

9 F 72 2 136 119 1

10 M 73 1.5 0 0 0

11 F 74 3.5 87 110 2

12 F 77 3 37 56 1

13 F 79 1 26 39 1

14 M 80 1.5 18 55 1

15 F 80 3 62 88 3

16 F 80 1 0 0 3

17 F 80 2 27 47 3

18 F 81 3 42 69 1

19 F 82 2.5 5 16 2

20 F 82 1 14 25 2

21 M 82 3 259 288 3

22 M 82 2.5 189 181 2

23 M 83 1 4 12 1

24 F 84 9 2,487 1,955 5

25 F 85 2 16 48 3

26 M 86 2 0 0 0

27 F 89 1 78 98 4

28 M 87 6 964 779 4

29 M 88 1 2 6 1

30 M 91 3 530 462 4

Median 80 2 32 55.5 2

aOn a scale ranging from 1, absent, to 9, severe.

60 years) who underwent both chest CT (0.5- to

1.0-cm collimation) and echocardiography

over a 2-year period, found aortic valve calcifi-cation in 30% of their patients, and five patients

showed a hemodynamically significantly in-

creased gradient, defined as a peak gradient of

25 mm Hg or greater. They concluded that aor-

tic valve calcification detected on CT is a com-

mon finding that is usually clinically insignifi-

cant; however, they noted that calcification was

seen in all cases of a hemodynamically signifi-

cantly increased gradient across the valve.

Our study confirms the results of four re-

cent studies that the echocardiographic as-

sessment of the severity of aortic stenosis cor-relates well with CT Agatston- and

volumetric-based scoring of aortic valve cal-

cification [69]. Two of these studies used an

MDCT scanner (2.7-mm collimation [6] and

2.5-mm collimation [7], the latter study ECG-

gated) and two of the studies used ECG-gated

electron beam tomography (EBT) (3-mm col-

limation) [8, 9]. The validity of EBT in quan-

tifying aortic valve calcification has been

confirmed in a recent histomorphometric an-

alysis [19]. However, our study did not use

ECG gating or an EBT scanner. Rather, it ex-

tends the original results of the four earlier

studies [69] to the arena of clinical radiology

practice using subjective assessment of aortic

valve calcification.Furthermore, MDCT has recently been

shown to be comparable to EBT for assessing

aortic valve calcification, although low levels

of aortic valve calcification tended to show

higher levels of interscan variability than

moderate to high levels, despite ECG gating

[7]. Multidetector, ECG-gated CT has also re-

cently been shown to have good agreement of

the assessment of aortic valve calcification

with the quantity of calcium in the aortic

valve in surgical specimens [20]. The results

of our study suggest that ECG gating may not

be necessary for clinically useful assessment

on CT of aortic valve calcification [6].The predictive value of commissural pat-

terns of aortic valve calcification has not, to

our knowledge, been evaluated previously. In

an autopsy study of elderly patients with se-

vere aortic stenosis, nodular calcific deposits

were found on the aortic aspects of the valve

cusps adjacent to commissures, which were

mostly unfused [21]. Two major patterns of

aortic valve calcification have been described

previously in pathology specimens: first, a

coaptation pattern in which calcifications oc-

cur as two spokes, parallel and immediately

adjacent to each other on each side of the line

of cusp coaptation [22]; and second, a radialpattern in which calcifications occur as mul-

tiple spokes radiating from the cusp attach-

ment toward the center of the cusp [22]. To

our knowledge, the observation that the cen-

tral rightleft commissure and the peripheral

left-posterior commissure are the sites of the

strongest correlations between the severity of

aortic valve calcifications and transvalvular

gradients has not previously been reported.

Two mechanisms appear likely to explain

these associations. One is that these two

specific regions may represent the sites of

greatest mechanical stress for the stenotic

aortic valve [22], probably in associationwith decreased compliance of the sinuses of

Valsalva [23]. Another possibility is that the

left aortic cusp, which forms the posterior

aspect of the rightleft commissure and the

left aspect of the left-posterior commissure,

tends to be the largest of the three cusps [24]

and perhaps is thus the cusp most associated

with the stresses that lead to calcific depos-

its. However, Cujec and Pollick [25] have

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reported that the cusp most likely to be in-

volved in isolated aortic valve thickening is

most commonly the noncoronary cusp, fol-

lowed by the right and then the left. A defi-

nite mechanism for preferential correlation

of calcification of the central rightleft

commissure and of the peripheral left-pos-

terior commissure and increased pressure

gradients across the aortic valve remains to

be elucidated. A limitation of the present

study is that the aortic valve is slightly ob-

lique to the axial projection of CT, so the

three commissures do project slightly ob-

liquely with respect to the plane of a section

through the valve.

TABLE 3: Indices of Aortic Valve Calcifications at CT and Correlations with Echocardiographic Gradients

Index Study Subjects Control Subjects paMean Gradient

Correlation pbPeak Gradient

Correlation pc

Agatston score 1,139 1,622 180 477 < 0.0001 0.76 < 0.0001 0.70 < 0.0001

Volumetric score 948 1,253 166 374 < 0.0001 0.78 < 0.0001 0.73 < 0.0001

Number of sections showing calcification 3.1 1.1 2.0 1.2 0.0004 0.56 0.0012 0.53 0.0027

Subjective scored

Overall grade 5.0 2.1 2.5 1.7 < 0.0001 0.69 < 0.0001 0.65 < 0.0001

Ac (central right-posterior commissure) 2.4 0.7 1.2 1.7 0.0012 0.52 0.0033 0.47 0.0090

Ap (peripheral right-posterior commissure) 1.4 1.5 0.4 1.1 0.0019 0.08 0.68 0.12 0.52

Bc (central rightleft commissure) 3.2 2.5 0.9 1.9 < 0.0001 0.69 < 0.0001 0.66 < 0.0001

Bp (peripheral rightleft commissure) 3.2 2.5 1.5 2.9 < 0.0001 0.48 0.0072 0.51 0.0037

Cc (central left-posterior commissure) 3.7 2.9 1.5 1.9 0.0056 0.55 0.0017 0.49 0.0062

Cp (peripheral left-posterior commissure) 3.8 2.7 1.5 2.0 0.0005 0.71 < 0.0001 0.65 < 0.0001

Central commissure 4.8 2.4 2.4 1.9 < 0.0001 0.76 < 0.0001 0.71 < 0.0001

Peripheral commissure 4.7 2.2 2.0 1.9 < 0.0001 0.76 < 0.0001 0.72 < 0.0001

A (right-posterior commissure) 3.2 2.5 1.4 1.8 0.0004 0.44 0.016 0.41 0.023

B (rightleft commissure) 3.9 2.4 1.1 1.9 < 0.0001 0.69 < 0.0001 0.65 0.0001

C (left-posterior commissure) 4.4 2.7 2.0 1.9 0.0004 0.63 0.0002 0.58 0.0008

NoteResults for study subjects and control subjects are expressed as mean SD. Values for pwere derived using chi-square test.aFor study subjects vs control subjects.bFor correlation among study subjects.cFor correlation among study subjects.dOn a scale ranging from 1, absent, to 9, severe.

TABLE 4: Clinical Data and Correlations with Echocardiographic Gradients

Clinical Data Study Subjects Control Subjects paMean Gradient

Correlation pbPeak Gradient

Correlation pc

Serum data

Low-density lipoprotein (mg/dL) 97 44 106 37 0.57 0.03 0.89 0.06 0.81

High-density lipoprotein (mg/dL) 45 19 44 13 0.92 0.21 0.37 0.26 0.26

Triglyceride (mg/dL) 121 52 128 78 0.91 0.06 0.80 0.08 0.72

Corrected calcium (mg/dL) 8.9 0.5 8.8 0.6 0.76 0.01 0.98 0.04 0.85

Creatinine (U/L) 1.4 1.0 1.2 0.9 0.43 0.17 0.39 0.17 0.38

Erythrocyte sedimentation rate (mm/hr) 42 22 38 36 0.32 0.23 0.36 0.18 0.48

Additional clinical data

Coronary artery disease 13 / 29 9 / 19 1

Hypertension 21 / 29 12 / 19 0.54

Cigarette smoking 15 / 27 14 / 19 0.24

Diabetes mellitus 13 / 27 4 / 19 0.07

NoteResults for serum chemical data are expressed as mean SD. Results for additional clinical data are expressed as numbers of patients with positive findings dividedby numbers of patients for whom relevant data were available. Values for pwere derived from two-sided Fischers exact test.

aFor study subjects vs control subjects.bFor correlation among study subjects.cFor correlation among study subjects.

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Although the severity of aortic valve calci-

fication did correlate in our study with gradi-

ents across the aortic valve, the association

was an imperfect predictor: as false-nega-

tives, two (6.7%) of 30 subjects with an in-

creased gradient had subjective calcification

scores of 2 or less on our 9-point subjectivescale, and four (13.3%) of these 30 subjects

had an Agatston score of 50 or less (Table 1).

As false-positives, two (6.7%) of the 30 con-

trol subjects had a subjective severity score of

6 or more on the 9-point scale, and four

(13.3%) of these 30 control subjects had an

Agatston score of 200 or more (Table 2). Nev-

ertheless, these percentages are sufficiently

low to support strongly the clinical precept

that more than minimal aortic valve calcifica-

tion of an elderly person on CT is an indica-

tion for echocardiographic evaluation.

The quantity of aortic valve calcification at

the time of diagnosis of aortic stenosis ap-pears to be of prognostic import: the greater

the quantity of calcification, the more rapid

will be the loss of valve area [4, 16, 26, 27].

Moreover, the smaller the valve area, the

greater the rate of progression of aortic steno-

sis, according to two studies [4, 26], although

not according to a third study [28]. The rate of

progression is variable [4, 26, 28], but the

mean rate of progression of calcific aortic

stenosis has been described as in the range of

a loss of valve area of approximately 0.1 cm2

per year [4, 26, 28] and as a mean increase of

mean gradient of 67 mm Hg per year [4, 28],

at least as long as cardiac failure does not su-pervene [4, 29]. None of the patients in our se-

ries was in a state of cardiac failure. Five-year

event-free survival after the diagnosis of an

increased aortic valve gradient in asympto-

matic subjects, defining an event as either

death or aortic valve replacement, has been

reported as only 26% 10% [4]. In another

series of 128 consecutive asymptomatic per-

sons with severe aortic stenosis, 4-year event-

free survival was only 20% 5% [27].

Serum chemical values showed no signifi-

cant differences between study and control

subjects in our study (Table 4). Although

prior studies have implicated elevated serumcholesterol [1, 12, 13], creatinine [1, 30, 16],

and calcium [30] levels as risk factors for pro-

gression of aortic stenosis, our results, based

on a single serum test, support no such asso-

ciations. The progression of aortic stenosis

does appear to be multifaceted, including cur-

rent cigarette smoking as a major risk factor

for rapid progression [1, 27], and having an

association with coronary artery atheroscle-

rotic disease that may respond to serum lipid-

lowering therapy [12]. We did not assess ther-

apeutic interventions in this study.

Advanced age is not necessarily a contrain-

dication to aortic valve replacement for aortic

stenosis. Long-term postoperative survival

and quality of life were termed excellent in arecent series of 105 subjects 7589 years old

(mean, 79 years) [7]. Detecting aortic valve

stenosis in this age group, in candidates ap-

propriate for aortic valve replacement, may

be clinically beneficial.

A limitation of our study is that the aortic

valve was assessed on echocardiography only

by Doppler gradients and not by assessment

of the continuity equation [31]. Had the con-

tinuity equation been used, it would have al-

lowed the aortic valve area to be determined

and would thereby have lessened the possibil-

ities of either overcalculation or undercalcu-

lation of aortic valve stenosis because of co-existing aortic regurgitation or poor function

of the left ventricle, respectively [31]. During

the time of our study, our echocardiography

laboratory did not routinely use the continuity

equation, which involves time-consuming

measurement of the outflow tract diameter of

the left ventricle.

EBT scans have been shown to yield excel-

lent reliability for Agatston and volumetric

assessment of aortic valve calcification in a

context of ECG gating [32]. Shavelle et al. [8]

have suggested that aortic valve calcification

at EBT showing Agatston scores in excess of

a certain level (e.g., 150) warrant echocardio-graphic assessment [8].

Two other limitations of this study are that

it excluded subjects with a bicuspid aortic

valve [33] and also excluded subjects younger

than 60 years. Aortic valve calcification is

well recognized as occasionally occurring in

subjects younger than 60 years, especially in

those with a bicuspid aortic valve or in those

who had rheumatic fever in childhood. How-

ever, we chose to limit our study to subjects

with a tricuspid aortic valve and 60 years old

or older because this population is at major

risk for the underdiagnosis of senile degener-

ation of the aortic valve before clinically sig-nificant stenosis of the valve develops [2].

Another limitation of our study is that it was

retrospective and used a rather small sample

(30 subjects with aortic valve stenosis). We

suggest that a prospective study of a larger se-

ries, including subjects younger than 60 years,

would be advisable for further understanding

the clinical importance of CT detection of un-

anticipated aortic valve calcification.

Both a limitation and a strength of our study

is that the CT examinations did not use the

most sensitive of modern CT technologic ap-

proaches (we used mostly single-detector ex-

aminations, slice thickness was 0.5 cm, scan-

ning time was 0.75 sec, and ECG gating was

not used). In assessing coronary artery calcifi-cations on CT, sections thinner than 0.5 cm and

scanning times shorter than 0.75 sec, in a con-

text of ECG gating, produce more accurate cal-

cium scoring than the techniques of our study

[10, 34]; presumably, the same observation

also holds for the calcified aortic valve [35].

However, aortic valve calcification at MDCT

has been shown, using 2.7-mm collimation and

no ECG gating, to correlate closely with the se-

verity of aortic stenosis [6]. Correspondingly,

the strength of our study is that, because no

ECG gating was used, our positive results offer

a clinically practical guideline: if the subjective

rating of aortic valve calcifications is greaterthan mild, especially for the central rightleft

commissure and the peripheral left-posterior

commissure, then echocardiographic evalua-

tion may be indicated.

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