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Conventional angiography has generally been considered the
gold standard in vivo method for assessing luminal diameter.
luminal area and extent or severity of atherosclerotic
disease. However. the accur.tcy of visual assessments of the
physiologic significance of stenosis has been recently qucstioned (1). Even angiographic
determination
of left main
coronary artery stenosis is subject to considerable error
when compared with histologic deter ination (2). Although
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From the Department of Medicine. Divihiun ofCardiology. Duke !_lni&~
sily Medical Center. Durham. North C;mGx~. Thk study wit\ pre\entcd in
part at the 39th Annual Scientific Sesion of the American College 01
Cardiology. New Orleans. Louisiana. March IYYO. II WB\ cupported in part hy
Na~ionaB Research Service Award Grant 5T37HL tJ71111fr~~rn the N;ttional
Heart. Lung. and Blood Institute. National Institute\ of Health. Ht~the~da.
Mar?/hnd.
anuscripl received December !I. 19x9: revkd
manuxript
received
March 7. 1990. accepted March 26. IYYO.
Address forrenrints: Charles 9. Davidson. MD. Duke UntverGty Medical
Center. Deparlmenl
of Medicine.
Diwsion of Cxdiolop.
Box 31195.
Durham. North Carolinlr 27710.
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_
~~t~tomated q~aatitative angiography overcomes so
limitations of visual assessment of coronary stenosis 63.4).
its ability to define vessel morphology is limited.
The feasibility of intravascular u~t~aso~o~raphy to provide real-time two-dimensional
images of arteries and veins
has recently been demonstrated in vitro and in vivo 6-9).
Catheter-based
ultrasonography is able to define intraluminal morphology including delineation of plaque characteristics. To date, this imaging approach has been shown to
provide data regarding luminal diameter and area that are
similar to those from pathologic sections of arterial Wall.
animal
models indicate that go
ssel diameter and area by ultras
compared with c~~~iper~de~iv
tative ci~lea~~jo~raphy (101. owever. few data exist from
humans in vivo.
The purposes of this hu an in viva study were to
graphic and digital subcompare catheter-based
ultt
ts of arterial lumen size
traction angiographic measu
634
DAVIDSON ET AL.
C’LTRASONOGRAPHY
VERSUS
ANGIOGRAPHY
and to contrast the ability of the two techniques
!esion morphology.
to define
Study patients. Twenty-one patients undergoing diagnostic cardiac catheterization were enrolled in the study according to a protocol that had been previously approved by the
Institutional
Review Board. There were I3 men and 8
women whose mean age was 55 + I9 years (range 24 to 83).
Indication for catheterization
was chest pain in 9 patients
and valvular heart disease in 12. Ultrasound and digital
subtraction images were obtained in 86 arterial segments that
included 49 femoral, 3 renal, 5 iliac, 7 pulmonary and 22
aortic sites.
Ultrasound images. The ultrasound transducer was a 20
MHz, 1.75 mm aperture, single piezoelectric crystal transducer bonded to a guide wire and housed within a 6F
blunt-tipped or an 8F monorail over-the-wire catheter sheath
(Boston Scientific CorporationlDiasonics).
The transducer
was mechanically rotated within the catheter at 1,800 rpm to
provide cross-sectional
images and was connected to an
ultrasourrd diagnostic imaging console specifically designed
for display of the two-dimensional
images. The ultrasound
beam was em:rted at a IO” forward look angle. The framing
rate was I5 frames/s and the images were displayed on a
video monitor on a 512 x 512 pixel matrix that discriminated
64 shades of gray.
All images were recorded on 0.5 in. (I 27 cm) high fidelity
videotape for subsequent off-line analysis. In vitro testing in
our laboratory indicated that axial resolution and lateral
resolution at a distance of 5 mm from the transducer tip were
0.39 and I .30 mm. respectively.
Digital subtraction images. Images were recorded with an
ADAC 4100-C digital radiography system interfaced to a
General Electric-MPX
L/U X-ray unit. Single plane anteriorposterior view images were acquired with use of a 9 in.
(22.86 cm) image intensifier and fed into a 512 x 512 x 8
pixel matrix at 30 frames/s. All vessels of interest were
centered to avoid pin-cushion distortion.
R-wave-gated
masked mode subtraction was performed after the procedure. All images were acquired and stored in digital format.
TO ensure that ultrasound and digital images were acquired from the same arterial segment, a radiopaque graphic
marker was placed on the patient at the point of ultrasound
image acquisition. Subsequent quantitative and qrditative
angiographic analyses were then performed at the corresponding marked segment.
Hand injection of nonionic contrast medium was utilized
for femoral and iliac artery radiographic images. Power
hh3iOn Of 40 ml of nonionic contrast medium at 15 to
30 d/S was made for central aorta and pulmonary artery
image acquisition.
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Quantitative data analysis. Ultrasound data analysis was
performed by digitizing i
computer and software
titative measurements wer:: made for
eter. Cross-sectional area ii~i%Sobtaine
image displaying maximal arterial diameter ita the horizontal
plane and maximal cross-sectional area was used for measurement. Diameter intraobserver variability for 10 i
was r = 0.99. SFE = 0.03 mm and interobserver correlation
was r = 0.99, sGk -; O.Gj
server and int~r~~se~ver
cm” and 0.99, SEE :- 0.08
Digital slrbtrcrctiott i’ng
with a previously validat&, commercially available software
program (I I, 12). A grid placed at the level of the artery was
used for calibration. Absolute luminal diameter and crosssectional area were determined for the same seg
artery that was imaged with intravascular ultrason
QMalitat~ve analysis. Ultrasound
images we
tively evaluated by consensus agreement of tw
for vessel morphology with use of a met
suggested by Gussenhoven
et al. (5).
defined as intimal thickening with bright
distal acoustic shadowing consistent with calcium, or
Soft plaque lacked these characteristics and was repres
as less dense echoes of thickened arterial wall.
Data andysis. The correlation between angiographic an
intravascular ultra nographic images was calculated wit
linear regression.
ata are expressed as mean values 2
SEE. Categoric data were analyzed with the chi-square test.
Qime~siu~a~ correlates. The absolute luminal diameters
for all (n = 86) arterial segments acquired by digital subtraction angiography and intravascular
ultrasonography
were
closely related (r = 0.97, SEE = 1.83 mm). The linear
correlation is described by the equation y = 0.85x + 2.7 (Fig.
I). The correlation for arterial segments C IO mm in diameter
(n = 53) was 0.87. SEE = I.25 mm, and for those IO to 40
mm (n = 32) it was 0.93, SEE = 2.40 mm.
The arterial cross-sectional areas as visualized by both
tcchniqaes were also closely related (r = 0.95, SEE = 0.65
cm’) and the correlation is described by the linear regression
of y = 0.87x + 0.32 (Fig. 2). Angiographically
determined
cross-sectional
area <I cm2 demonstrated
a correlation
coefficient of 0.93. SEE = 0. I4 cm’ and areas >1 cm*
ex
ted a correlation coefficient of 0.92, SEE =
que correlates and lesion morphology (Table
vascular ultrasonography identified 24 sites in which athemsclerotic plaque was present. In II (46%) of these 24
segments, the arterial lumen appeared to be ang~ogra~~ically
normal. A representative
example of a “normal”
angiographic segment that demonstrated plaque on ultrasonogra-
JACC Vol. 16. No. 3
September ~99~:~33-~
ihd
Linear correlations of i~nii~~~
titative digital subtraction angiography
M~trasono~~pby WM.
~travasc~iar
The cot-t-elation
of eecettrtic
fo
imeter derived by qwrn(DSAI
and intravascular
ared normal by intravascular
ultrasonogra
for detennittadotl
of l~ttnit~~tl
was simita
arterial segments fr = 0.96, SEE = 0.82
). The correlation toe
graphically derived cross-sectional a
tric plaque (n = 24) was 0.93, SEE
regions
excellent
~l~~i4e
ia
that for normal
versus r = 0.96.
subtraction angiography of femoral
corresponding arterial
right pranei = position T
tally
Figure 2. Linear correlation of luminal cross-sectional area derived
by digital subtraction angiography (DSAI and intravascular ultrasonography (IVUS).
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“silent”
plaque is indicated by arrows.
636
DAVIDSON ET AL.
ULTRASONOGRAPHY
JACC Vol. 16, No. 3
September 1990:hJ3-6
VERSUS ANGlOGRAPHY
these data without
the potential confounding effects Of
vasodilation inherent in the use of contrast agents. Thus. this
new technique may more accurately determine arterial dimensions either during or after interventional therapy.
Delineation of atherosclerotic plaque and vessel morphology. The two techniques were discordant in their ability to
delineate the presence of atherosclerotic
plaque. Although
quantitative determinations were close@ related, on several
occasions digital subtraction angiography failed to reveal
focal areas of stenosis that were consistent with plaque by
intravascular ultrasonography.
It appears that intravascular
ultrasonography may thus provide additional data regarding
atherckclerotic
plaque within arterial segments that are
angiographically
“silent.”
In vitro studies utilizing intravascular
ultrasonography
indicate that plaque composition may be ascertained (5).
Potential differentiation of cross-sectional lesion pathology
such as thrombus, vasculitis or atheroma has important
therapeutic implications. The potential advantages of this
added delineation of vessel morphology are numerous in the
setting of interventional
therapy including angioplasty,
atherectomy,
stents or laser surgery. This morphologic
definition may assist in selecting the most appropriate intervention based on lesion characteristics and guide additional
treatment in complicated interventions where contrast angiography yields equivocal information.
Although digital subtraction images were acquired with
use of a single plane projection, the correlation between
angiography and ultrasonography for eccentric lesions appeared similar to the correlation for insignificantly narrowed
normal arterial segments with regard to absolute vessel
diameter and cross-sectional area. This was also true in
segments of calcific plaque, although there were only I I
segments in which this type of plaque was identified by
ultrasonography.
It has recently been suggested that single
plane angiography of the “worst view” is adequate in the
vast majority of cases for evaluation of minimal lesion
diameter and for measurement of percent area stenosis (13).
These data are further supported by the ultrasound data
provided in the current study.
Because of potential arterial injury, catheter advancement into severe:y tortuous segments of arterial anatomy
was not attempted. Although diameter and area correlation
should b? similar in tortuous segments, eccentric catheter
position within a large vessel couldadverselyaffectfar-field
image quality and morphologic assessment.
conclusions. Accurate determination of vessel diameter
and area are readily obtainable by intravascular ultrasonog-
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raphy. However, ultrasound provides additional deformation
because vessel anatomy and plaque morphology
are not
adequately visualized by silhouette contrast a~g~og~a~~y.
This imaging technique appears to be a useful adjunct to
contrast angiography in diagnostic and i~te~ve~tio~a~ therapy of both peripheral arterial disease and coronary artery
disease.
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MR. Collins SM.
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