(Circulation. 1998;97:2575-2576.)
© 1998 American Heart Association, Inc.
Images in Cardiovascular Medicine |
Simultaneous Morphological and Functional Assessment of a Renal Artery Stent Intervention With Intravascular Ultrasound
Stéphane G. Carlier, MD;
Wenguang Li, PhD;
E. Ignacio Céspedes, PhD;
Antonius F. W. van der Steen, PhD;
Jaap N. Hamburger, MD;
Nicolaas Bom, PhD;
; Patrick W. Serruys, MD, PhD
From Thoraxcentre Erasmus University Rotterdam, Netherlands (all
authors); Interuniversity Cardiology Institute of the Netherlands (W.L.,
A.F.W.v.d.S., N.B., P.W.S.); and Endosonics Corp, Rancho Cordova, Calif
(E.I.C.).
Correspondence to Stéphane G. Carlier, MD, Thoraxcentre Ee2302, Erasmus University Rotterdam, PO Box 1738, NL-3000 DR Rotterdam, Netherlands. E-mail carlier{at}tch.fgg.eur.nl
A 73-year-old woman with a history of high blood pressure
and hypercholesterolemia developed medically
uncontrolled hypertension (200/100 mm Hg). Serum
creatinine level was 145 µmol/L, and
creatinine clearance was 34 mL/min. Renal ultrasound
demonstrated a small right kidney (80 mm long) compared with the
left one (92 mm long). Left ventricular
hypertrophy was present on the ECG and was confirmed by
echocardiography. On isotope
radiography with
99mTc-mercaptoacetyltriglycine after oral intake of 25 mg
captopril, the right kidney was small, with delayed excretion and
impaired function (36%). Renal arteriography showed subocclusive
ostial stenosis of the right renal artery.
The lesion was related to a calcified plaque extending from the aortic
wall into the renal artery ostium (angiogram I in Figure 1
, arrow). After an unsuccessful angioplasty
attempt in the interventional radiology department (failure to cross
the stenosis), the patient was investigated in the cardiac
catheterization laboratory. The lesion was crossed with
a hydrophilic guidewire and predilated. A short (9-mm) stent was then
implanted by use of a 4.5-mm balloon inflated up to 18 atm for
postdilatation (angiogram II).
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Figure 1. Angiograms before (I), during (II), and after (III)
stent implantation in right renal artery. Tight stenosis is
indicated by arrow in angiogram I. Intravascular ultrasound (IVUS)
images (1 through 3) obtained after stenting at corresponding levels
indicated by arrows in angiogram III. Arrows in IVUS panel 2 show
well-apposed struts of stent, and in panel 3, calcified plaque at
junction with aorta (Ao).
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The immediate result of the intervention was assessed by both biplane
angiography (angiogram III, anteroposterior projection) and
intravascular ultrasound (IVUS). Distal to the stent, IVUS shows a
normal arterial wall (panel 1 in Figure 1
). A cross section
within the stent (panel 2) demonstrates good expansion and apposition
of the struts (arrows). The lumen area measured at this level was
18.9 mm2. The arrows in panel 3 demonstrate the highly
calcified plaque at the junction with the aorta.
The top of Figure 2 shows images
obtained with a newly developed method to quantify the blood flow with
an IVUS imaging catheter. They were recorded distally to the stent
at different times (a through e) during the cardiac cycle. This blood
flow measurement method has recently been validated and calibrated in
vitro against electromagnetic flowmeter data and in vivo in porcine
carotid arteries.1 The principle is based on the
analysis of decorrelation of the IVUS radiofrequency (RF)
signals. Red blood cells flowing in the ultrasound beam result in a
decorrelation of successively received RF signals. The rate of
decorrelation is proportional to the local blood flow
velocity.2 3 These are then converted into color maps
representing local instantaneous blood flow velocity in the
arterial cross section. The color scheme used goes from
dark red (10 cm/s) to yellow (100 cm/s). Flow velocities are measured
at 100 angular positions, with a depth resolution of 160 µm.
Cross sections with color flow data can be recorded during a
4-second period at 16 frames per second.
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Figure 2. Color mapping of blood flow velocity inside
arterial lumen after procedure, at different phases of
cardiac cycle (a through e), calculated from intravascular ultrasound
(IVUS) radiofrequency signal analysis. IVUS volume flow (green
trace) and Doppler-based volume flow (blue trace) with
corresponding ECG (black trace). Doppler-based volume flow is
calculated from depicted Doppler sonogram (range, 0 to 120 cm/s)
and diameter measured by quantitative coronary angiography on
angiogram III at level of tip of Doppler wire. IVUS volume flow is
calculated by integrating velocity components over arterial
lumen area. The two flow estimations are in good agreement.
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The moment of each IVUS image with flow information in the cardiac
cycle is indicated at the bottom right of Figure 2, showing flow traces
recorded simultaneously with the ECG. The instantaneous
flow calculated with the IVUS method is represented in
green and the flow derived from an intravascular Doppler wire in
blue. In panel a, very low blood flow velocities at end
diastole are not encoded, because they fall below the
sensitivity threshold level, which is 
10 cm/s. With increasing flow
in early systole (b), the color map shows homogeneous blood
flow velocities encoded in red. Maximal velocities are reached at peak
systole (c). The decrease in blood flow in diastole is seen
in panels d and e. Integration of the velocities over the lumen area
allows the computation of instantaneous volumetric blood flow (green
curve) during a 4-second period. The measurements are in agreement with
the blood flow simultaneously measured with the Doppler
wire (in blue: Doppler instantaneous peak velocity times the
cross-sectional vessel area at Doppler wire tip). The mean IVUS
flow was 238 mL/min, whereas the flow derived from the Doppler wire
measurements was 208 mL/min. This demonstrates the feasibility of
simultaneous assessment of morphological and
physiological parameters during
interventional procedures with an intravascular imaging catheter. The
method is presently being evaluated in coronary
arteries.
This patient was discharged 2 days after the procedure and is doing
well. Good early and long-term results of stenting ostial renal lesions
have been reported recently,4 with a restenosis
rate of 10%, making this procedure the best current therapy for
renovascular disease related to critical ostial stenoses.
Acknowledgments
The excellent technical support of J. Honkoop and F. Mastik was
of paramount importance for the realization of this work.
Footnotes
The editor of Images in Cardiovascular Medicine is Hugh A. McAllister, Jr, MD, Chief, Department of Pathology, St Luke's Episcopal Hospital and Texas Heart Institute, and Clinical Professor of Pathology, University of Texas Medical School and Baylor College of Medicine.
Circulation encourages readers to submit cardiovascular images to Dr Hugh A. McAllister, Jr, St Luke's Episcopal Hospital and Texas Heart Institute, 6720 Bertner Ave, MC1-267, Houston, TX 77030.
References
1.
Carlier S, Li W, Mastik F, Honkoop J, van der
Steen AFW, Lancée CT, de Zeeuw S, van Bremen R, Céspedes
EI, Serruys PW, Bom K. New intracoronary volumetric
blood flow measurement method with intravascular ultrasound: in-vitro
assessment and first in vivo results. Eur Heart
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2.
Li W, van der Steen AFW, Lancée CT,
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blood velocity and volume flow with intravascular ultrasound.
Ultrasound Med Biol. In press.
3.
Li W. Image and Signal Processing in
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4.
Blum U, Krumme B, Flügel P, Gabelmann A, Lehnert
T, Buitrago-Tellez C, Schollmeyer P, Langer M. Treatment of
ostial renal-artery stenoses with vascular endoprotheses after
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Med. 1997;336:459–465.[Abstract/Free Full Text]
