From the Society for Vascular Surgery

Contrast-enhanced Duplex surveillance afterendovascular abdominal aortic aneurysm repair:Improved efficacy using a continuousinfusion techniqueEsteban A. Henao, MD,a Megan D. Hodge, RN, RVT,b Deborah D. Felkai, RN, RVT,c

Charles H. McCollum, MD,a George P. Noon, MD,a Peter H. Lin, MD,a Alan B. Lumsden, MD, RVT,a

and Ruth L. Bush, MD, RVT,a Houston, Texas

Introduction: Currently, postoperative endoleak surveillance after endovascular aortic aneurysm repair (EVAR) isprimarily done by computed tomography (CT). The purpose of this study was to determine the efficacy of contrast-enhanced ultrasonography scans to detect endoleaks by using a novel infusion method and compare these findings withthose of CT angiography (CTA).Methods: Twenty male patients (mean age, 70.4 years) underwent surveillance utilizing both CTA and contrast-enhancedcolor Duplex imaging. One 3-mL vial of Optison (Perfluten Protein A microspheres for injection) and 57 mL normalsaline, for a total of 60 mL, were administered to each patient as a continuous infusion at 4 mL/min via a peripheral vein.Each study was optimized with harmonic imaging, and a reduced mechanical index of 0.4 to 0.5, compression of 1 to 3,and a focal zone below the aorta to minimize microsphere rupture. One minute was allowed from the time of infusion tothe appearance of contrast in the endograft. Flow was evaluated within the lumen of the graft and its components, as wasthe presence or absence of endoleaks. Findings were compared with standard color-flow Duplex imaging and CT utilizingCTA reconstruction protocols.Results: All patients evaluated had modular endografts implanted for elective aneurysm repair. Contrast-enhanced duplexscans identified nine endoleaks: one type I and eight type II. No additional endoleaks were seen on CTA. However, CTAfailed to recognize three type II endoleaks seen by contrast-enhanced ultrasound. The continuous infusion methodallowed for longer and more detailed imaging. An average of 46.8 mL of the contrast infusion solution was used perpatient.Conclusions: Contrast enhanced Duplex ultrasonography accurately demonstrates endoleaks after EVAR and may beconsidered as a primary surveillance modality. Continuous infusion permits longer imaging time. (J Vasc Surg 2006;43:

259-64.)

Although the benefits of less invasive surgery and shorterlength of stay are triumphs of endovascular aneurysm repair(EVAR), long-term surveillance is necessary to monitor forpersistent endoleaks, aneurysm growth, and potentially, rup-ture.1 Computed tomography (CT) is currently the standardmodality used for following patients after EVAR, 2 but theexposure to ionizing radiation and nephrotoxic contrastagents is also of concern. Financial issues of surveillance havealso been noted, with a recent study showing �65% of post-operative EVAR costs are due to CT scanning.3 For thesereasons, alterative surveillance methods such as duplex ultra-sound scans have been explored.

Color duplex ultrasound has been previously reportedas having lower sensitivity and positive predictive value in

From the Baylor College of Medicine,a the Methodist Hospital,b and theMichael E. DeBakey Veterans Affairs Medical Center.c

Competition of interest: none.Presented at the 59th Annual Meeting of the Society for Vascular Surgery,

Chicago, Il, June 16-19, 2005.Reprint requests: Esteban A Henao, MD, One Baylor Plaza #404D, c/o

Judy Corke Houston, TX 77030-3411 (e-mail: surgmax@hotmail.com).CME article0741-5214/$32.00Copyright © 2006 by The Society for Vascular Surgery.

doi:10.1016/j.jvs.2005.09.045

detecting endoleaks after EVAR compared with CT.4

However, the ultrasound contrast agents that have shownmarked benefit in echocardiography5-8 seem to increasesensitivity in ultrasound surveillance after EVAR by allow-ing improved blood flow echogenicity for better evalua-tion.9-12 For example, a recent study of patients with ab-dominal aortic aneurysm enlargement and no evidence ofcomplications were evaluated with contrast-enhanced ul-trasound (CEUS), which identified endoleaks, challengingthe existence of what has been defined as endotension.10

Similarly, another recent study characterized several en-doleaks found on CEUS not identified on CT as hypody-namic, or slow leaks.9

Our study prospectively evaluated the use of a contin-uous infusion method of ultrasound contrast in the surveil-lance of abdominal aortic endografts in detecting endoleakscompared with CT. Our hypothesis was that CEUS wasmore sensitive than CT for endoleak detection.

METHODS

From July 2004 to May 2005, a prospective study,approved by the Institutional Review Board of Baylor Col-

lege of Medicine, was conducted to evaluate the effective-

259

JOURNAL OF VASCULAR SURGERYFebruary 2006260 Henao et al

ness of CEUS imaging to detect endoleaks in patients whounderwent endovascular treatment for an infrarenal ab-dominal aortic aneurysm. The standard for endoleak detec-tion in this study was CT with contrast. We defined en-doleak as the presence of persistent intrasac flow outside thestent-graft. The endoleaks were characterized in relation tothe endograft, aneurysm wall, and aortic side branches, andrecorded in accordance to the White-May classification aspreviously described.13,14

At our institution, patients are typically followed after asuccessful endovascular aneurysm repair at 1, 6, 12, and 24months, and annually thereafter. All men and postmeno-pausal women seen at these follow-up intervals were askedto participate unless there was a documented contraindica-tion to the use of ultrasound contrast, blood products, oralbumin. Participants received an information sheet ex-plaining the study and gave written informed consent onthe day of the scan. Exclusion criteria included patientswith a known endoleak from previous examinations, severeiodinated contrast allergy, or evidence of renal insufficiencymarked by a serum creatinine level � 1.5 mg/dL. Patientswere also excluded if there was evidence of a right-to-leftcardiac shunt or severe pulmonary or hepatic disease.

Optison (Perflutren Protein Type A Microspheres forInjection, Amersham Health, Princeton, NJ) is a Food andDrug Administration-approved injectable, sterile suspen-sion of human serum albumin and octafluoropropane gasmicrospheres used for contrast enhancement during echo-cardiography. It has a half-life reported by the manufac-turer of 1.3 � 0.69 minutes, and a benign toxicity profileshown to be free of nephrotoxicity.15 Contrast was pre-pared by using a single, 3-mL vial of Optison and 57 mLnormal saline combined in a sterile 60-mL syringe. Thesolution was placed on a syringe pump set to deliver acontinuous infusion at 4 mL/min, typically delivered via aright upper-extremity peripheral access (20-gauge angio-catheter). An assistant was available at each study to man-ually agitate the contrast to minimize microsphere precip-itation during the examination.

Four experienced vascular sonographers (M. H., D. P.,D. F., M. E.) performed all the ultrasound studies using a3.5-MHz probe on a Phillips iU22 unit (Phillips MedicalSystems, Bothell, Wash). Ultrasonographers were blindedto the results of previous angiographic or CT angiographic(CTA) results. Fasting patients were scanned with greyscale and color Duplex before the intravenous Optisonadministration. Measurements of the aneurysm were re-corded, and grey scale, color Duplex, and CEUS were usedto identify leaks.

Grey scale assessment protocols were performed, be-ginning at the level of the renal arteries and followed to theiliac bifurcation. Color Duplex was then performed, using acurved array 2- to 5-MHz probe. A mechanical index of atleast 1.2 was used. Special attention was directed to the areaof maximum dilatation of the aneurysm where both limbsof the endograft were visualized. A meticulous evaluationfor the presence of pulsatile color flow was performed at the

attachment sites proximally and distally as well as at the

junctional points of the modular grafts. Potential areas ofendoleak, such as the inferior mesenteric artery or lumbararteries were also inspected. The inspection was performedin both transverse and longitudinal orientations.

The CEUS protocol included specific settings to beused on each ultrasound machine to minimize microsphererupture. Harmonic imaging, a reduced mechanical index of0.4 to 0.5, compression of 1:3, and a focal zone positionedbelow the aorta allowed for the most efficient usage ofcontrast. Time from the beginning of contrast infusion toappearance in the endograft was recorded in all patients, aswell as the entire duration of the study, and the amount ofsolution used. The infrarenal aorta and native aneurysm sacwas scanned after Optison injection in a longitudinal andtransverse perspective from the renal to distal iliac arteries.Flow was evaluated within the lumen of the graft and itscomponents, as well as the presence or absence of en-doleaks. All procedures were recorded on standard VHSmedia for later evaluation and archiving purposes.

Computed tomography angiography was performed onthe same day (Lightspeed Ultra, GE Healthcare, Waukesha,Wisc) before CEUS. The protocol called for the intravenousinjection of 150 mL of a contrast agent at a rate of 2.5 mL/s.SmartPrep computer-automated scan technology (GEHealthcare) was used to optimize the injection phase. Thestandard scan delay for the arterial phase was 10 to 28seconds; the delayed phase was timed to commence 70seconds after the completion of the first scan, which took20 seconds on average. Tomograms were reconstructed byusing a 1.5-mm algorithm from celiac to iliac arteries.

RESULTS

Twenty men (mean age, 70.4 years) participated in ourstudy from July 2004 to May 2005. The mean height andweight of the group was 179 cm (range, 162 to 200 cm)and 91 kg (range, 61 to 137kg). Patients had a mean bodymass index (BMI), calculated as kg/m2, of 28.2. Meananeurysm size was 5.27 cm at the time of follow-up. Aver-age follow-up time was 8.7 months (range, 1 to 36months). The endografts had varying modular designs andhad been electively placed.

The average volume of ultrasound contrast solutionadministered to each study patient was 46.8 mL (range, 32to 60 mL). The mean time necessary to perform the con-trast enhanced portion of each exam was 11.8 minutes(range, 8 to 28 minutes). BMI was then compared withCEUS time, and a direct relationship was noted, with aPearson correlation coefficient of 0.47 (Fig 1). None of theCEUS scans done after all of the CTA studies appeared tohave been affected by the use of the standard iodinatedcontrast agents used in the CT scans. There were no adverseevents secondary to CEUS.

Contrast-enhanced ultrasound detected nine endoleaks(Table). Eight of the endoleaks were classified as type II (Fig2). Seven of the type II endoleaks were classified as lumbarin origin, and one was identified and confirmed on CTA asan inferior mesenteric arterial type II leak. A single type I

endoleak was noted on all modalities. This patient also

angiography of the same patient demonstrates no endoleak.

JOURNAL OF VASCULAR SURGERYVolume 43, Number 2 Henao et al 261

demonstrated a significant increase in aneurysm diameterthat led to a therapeutic intervention in which an endolu-minal extender cuff was successfully placed. Color Duplexultrasound scans identified four (44%) endoleaks, includingthe type I endoleak. Six (67%) endoleaks were also identi-fied with CTA. Three type II endoleaks found on CEUSwere not confirmed on CTA (Fig 3). No endoleaks wereseen on CTA that had not been found on CEUS.

DISCUSSION

Our study confirms previous observations that sug-gested the efficacy of CEUS vs CTA. Using a continuousinfusion technique, we were able to clearly visualize eighttype II endoleaks and one type I after EVAR, whereas CTA

CEUS Time Versus BMI

20

22

24

26

28

30

32

34

36

38

40

5 10 15 20 25 30

Time (minutes)

IM

B

P-Value = 0.037

Pearson correlation of Time and BMI =0.469

Fig 1. Relationship of contrast-enhanced ultrasound (CEUS)time with body mass index (BMI).

Table. Patient demographic data with endoleak typeidentified on contrast-enhanced ultrasound, color duplex,and computed tomography

Patient Age Leak typeConfirmed on

color USConfirmed on

CT

1 85 II Yes Yes2 78 None None None3 78 I, II Yes Yes4 71 II No No5 78 II No Yes6 79 II No No7 57 None None None8 70 None None None9 72 None None None

10 76 None None None11 56 II Yes Yes12 54 None None None13 57 None None None14 63 None None None15 65 II Yes No16 82 None None None17 80 II No Yes18 74 II No Yes19 62 None None None20 70 None None None

US, Ultrasound; CT, computed tomography.

identified five type II and one type I. The amount of time

Fig 2. A, Cross-sectional contrast-enhanced ultrasound image ofmain body of aortic endograft with a small type II endoleak(arrow). B, A cross-sectional color duplex ultrasound scan of samepatient shows no evidence of endoleak. C, Computed tomography

JOURNAL OF VASCULAR SURGERYFebruary 2006262 Henao et al

available to search for endoleaks was substantially greaterwith a continuous infusion. Thus, our continuous infusionmodality may have contributed to improved detectioncompared with previous reports of bolus contrast.

Reports concerning CEUS as a surveillance tool afterEVAR have all described the administration of contrastagents in the form of a bolus.9-12,16-18 The required oroptimal dosage for administration of contrast agents afterEVAR is not known, which has been the source of reporteddifficulties when using CEUS. Napoli et al10 were requiredto infuse multiple boluses in two patients because theycould not show any clear endoleak with the first dose.Bargellini et al9 found the need to increase the bolusamount from 1.5 mL to 2.4 mL for similar reasons. Afterthe administration of a contrast bolus, the time available tocomplete an enhanced scan was 3 to 11 minutes in previousreports.9-12,16

In our preliminary experience, the average learningcurve for using CEUS in those experienced with abdominalvascular screening was 10 to 15 studies. The initial difficultywas thought to be attributed to the pump setup and theneed for continuous agitation, as explained above. Thecontinuous infusion allowed for a longer study window,lasting as long as 28 minutes, and allowed for a moredeliberate search for small or slow endoleaks, potentiallyincreasing the sensitivity and ease of the study. It alsofacilitated scanning of the challenging patient with exces-sive bowel gas or large body habitus, using even unortho-dox views (ie, placing the patient in decubitus position)when necessary, without the worry of missing an endoleakbecause of limited contrast duration.

A weak correlation between BMI and the amount oftime it took to perform CEUS was noted. The true signif-icance of this is unknown because of the small sample size.

Ultrasonic contrast may minimize scanning hindrances,such as body habitus, while optimizing those features ofvascular blood flow.19 Enhanced ultrasound with harmonicimaging appears to diminish theses effects, as there were

Fig 3. A cross-sectional contrast-enhanced ultrasound image ofthe iliac limbs of an aortic stent demonstrates a type II endoleak(arrow) in the posterior sac.

more endoleaks identified than with color duplex imaging.

In our comparison of color duplex and CEUS, it was notedthat there was a tendency for more artifactual disturbanceswith color flow. This was despite the use of harmonics,compression, and adjustments in focal zone in both trans-verse and longitudinal views. Thus, there was a clear benefitin using contrast in that minimal-to-no change in ultrasonicgain was required to discriminate subtle type II endoleakswith contrast, whereas adjustments in the color modalitymay have led to artifacts. More CEUS observations areneeded to clarify this preliminary data trend.

In general, the cost of an ultrasound study may rangefrom $350 to $1000, and a vial of the Optison contrastagent is $140.40, according to the manufacturer. Severalpatients in our series required scanning periods well past themaximum duration reported in previous studies concerningbolus administration of contrast. If continuous infusionhad not been used, this may have led to additional contrastadministration as well as to increased cost.

Our study is limited by its small sample size. Morepatients are needed to accurately calculate the sensitivityand specificity of the technique. It could also benefit from atrue cost analysis20 to justify the relatively expensive pur-chase of contrast, syringe pump setup, and maintenance, aswell as the need for ancillary staff to monitor the contrastand provide continuous syringe agitation.

CONCLUSION

The potential for malignancy secondary to radiationexposure21 and the well-known complication of nephro-toxicity secondary to iodinated contrast agents drives thesearch for a better surveillance modality. While newer tech-nologies such as intrasac pressure sensors22 are currently indevelopment, a “perfect” surveillance tool does not yetexist. The need to characterize the dynamic flow of en-doleaks may be useful in the decision for therapy, andCEUS may be an excellent tool for this use. However, CTscanning remains the gold standard in the periodic moni-toring of aneurysm size, migration, and other physicalfactors such as changes in limb position and partial limbseparation and should continue to be a part of the standardfollow-up regimen in EVAR patients.

AUTHOR CONTRIBUTIONS

Conception and design: EAH, MDH, DDF, CH.M, GPN,PHL, ABL, RLB

Analysis and interpretation: EAH, MDH, DDF, RLBData collection: EAH, MDH, DDF, RLBWriting the article: EAH, RLBCritical revision of the article: EAH, MDH, DDF, CHM,

GPN, PHL, ABL, RLBFinal approval of the article: EAH, MDH, DDF, CHM,

GPN, PHL, ABL, RLBStatistical analysis: EAH, RLBObtained funding: CHM, GPN, PHL, ABL, RLB

Overall responsibility: EAH

JOURNAL OF VASCULAR SURGERYVolume 43, Number 2 Henao et al 263

REFERENCES

1. Veith FJ, Baum RA, Ohki T, Amor M, Adiseshiah M, Blankensteijn JD,et al. Nature and significance of endoleaks and endotension: summary ofopinions expressed at an international conference. J Vasc Surg 2002;35:1029-35.

2. Golzarian, J., Dussaussois L, Abada HT, Gevenois PA, Van GansbekeD, Ferreira J, et al. Helical CT of aorta after endoluminal stent-grafttherapy: value of biphasic acquisition. AJR Am J Roentgenol 1998171:329-31.

3. Prinssen, M, Wixon CL, Buskens E, Blankensteijn JD. Surveillance afterendovascular aneurysm repair: diagnostics, complications, and associ-ated costs. Ann Vasc Surg 2004;18:421-7.

4. Raman KG, Missig-Carroll N, Richardson T, Muluk SC, Makaroun MS.Color-flow duplex ultrasound scan versus computed tomographic scanin the surveillance of endovascular aneurysm repair. J Vasc Surg 2003;38:645-51.

5. Firschke C, Koberl B, von Bibra H, Horcher J, Schomig A. Combineduse of contrast-enhanced 2-dimensional and color Doppler echocardi-ography for improved left ventricular endocardial border delineationusing Levovist, a new venous echocardiographic contrast agent. IntJ Card Imaging 1997;13:137-44.

6. Lindner JR, Firschke C, Wei K, Goodman NC, Skyba DM, Kaul S.Myocardial perfusion characteristics and hemodynamic profile of MRX-115, a venous echocardiographic contrast agent, during acute myocardialinfarction. J Am Soc Echocardiogr 1998;11:36-46.

7. Porter TR, Xie F. Transient myocardial contrast after initial exposure todiagnostic ultrasound pressures with minute doses of intravenouslyinjected microbubbles. Demonstration and potential mechanisms. Cir-culation 1995;92:2391-5.

8. Mulvagh SL, Foley DA, Aeschbacher BC, Klarich KK, Seward JB.Second harmonic imaging of an intravenously administered echocardio-graphic contrast agent: visualization of coronary arteries and measure-ment of coronary blood flow. J Am Coll Cardiol 1996;27:1519-25.

9. Bargellini I, Napoli V, Petruzzi P, Cioni R, Vignali C, Sardella SG, et al.Type II lumbar endoleaks: hemodynamic differentiation by contrast-enhanced ultrasound scanning and influence on aneurysm enlargementafter endovascular aneurysm repair. J Vasc Surg 2005;41:10-8.

10. Napoli V Bargellini I, Sardella SG, Petruzzi P, Cioni R, Vignali C, et al.Abdominal aortic aneurysm: contrast-enhanced US for missed en-

doleaks after endoluminal repair. Radiology 2004;233:217-25.

approved for echocardiography only.

11. Giannoni MF, Palombo G, Sbarigia E, Speziale F, Zaccaria A, Fiorani P.Contrast-enhanced ultrasound imaging for aortic stent-graft surveil-lance. J Endovasc Ther 2003;10:208-17.

12. Bendick PJ, Bove PG, Long GW, Zelenock GB, Brown OW, ShanleyCJ. Efficacy of ultrasound scan contrast agents in the noninvasivefollow-up of aortic stent grafts. J Vasc Surg 2003;37:381-5.

13. White GH, May J, Waugh RC, Yu W. Type I and type II endoleaks: amore useful classification for reporting results of endoluminal AAArepair. J Endovasc Surg 1998;5:189-91.

14. White GH, May J, Waugh RC, Chaufour X, Yu W. Type III and type IVendoleak: toward a complete definition of blood flow in the sac afterendoluminal AAA repair. J Endovasc Surg 1998;5:305-9.

15. Cosgrove DO, Kiely P, Williamson R, Blomley MJ, Eckersley RJ.Ultrasonographic contrast media in the urinary tract. BJU Int 2000;86Suppl 1:11-7.

16. McWilliams RG, Martin J, White D, Gould DA, Rowlands PC, HaycoxA, et al. Detection of endoleak with enhanced ultrasound imaging:comparison with biphasic computed tomography. J Endovasc Ther2002;9:170-9.

17. McWilliams RG, Martin J, White D, Gould DA, Harris PL, Fear SC, etal. Use of contrast-enhanced ultrasound in follow-up after endovascularaortic aneurysm repair. J Vasc Interv Radiol 1999;10:1107-14.

18. Heilberger P, Schunn C, Ritter W, Weber S, Raithel D, et al. Postop-erative color flow duplex scanning in aortic endografting. J EndovascSurg 1997;4:262-71.

19. Melany ML, Grant EG, Farooki S, McElroy D, Kimme-Smith C, et al.Effect of US contrast agents on spectral velocities: in vitro evaluation.Radiology 1999;211:427-31.

20. Bendick PJ, Zelenock GB, Bove PG, Long GW, Shanley CJ, BrownOW. Duplex ultrasound imaging with an ultrasound contrast agent: theeconomic alternative to CT angiography for aortic stent graft surveil-lance. Vasc Endovascular Surg 2003;37:165-70.

21. Diederich S, Lenzen H. Radiation exposure associated with imaging ofthe chest: comparison of different radiographic and computed tomog-raphy techniques. Cancer 2000;89(11 Suppl):2457-60.

22. Ellozy SH, Carroccio A, Lookstein RA, Minor ME, Sheahan CM, JutaJ, et al. First experience in human beings with a permanently implant-able intrasac pressure transducer for monitoring endovascular repair ofabdominal aortic aneurysms. J Vasc Surg 2004;40:405-12.

Submitted Jun 28, 2005; accepted Sep 26, 2005.

DISCUSSION

Dr K. Craig Kent (New York, NY). You said that there ispotential for decreased cost. Do you have any idea of what the costof the agent is? Can you compare this to the cost of a CT scan?

Dr Esteban A. Henao. There was a study in 2003 by Bendick,which used a different contrast agent, demonstrating the cost effec-tiveness of CEUS. A figure that I can give you is $140 per US contrastvial used in our study. And the average cost for a follow-up US scan isanywhere from $150 to $400, depending on the area and the hospital.Compare that to CT scan, which can range from $1,500 to $4,000.

Dr Ali AbuRahma (Charleston, WV). Did you follow yourpatients who had CT scans by delayed imaging, which may haveshown leaks that were missed?

Second question, for patients who had duplex ultrasoundwithout contrast, were the leaks type I or type II, which may haveclinical significance?

When do you see this agent becoming commercially available,since we still don’t have it here in the United States?

Dr Henao. To answer your first question, this study used abiphasic CT scan, so there was an arterial phase and a delayedphase.

In terms of duplex without contrast, the grey scale view wasdone as part of our general evaluation, but it wasn’t used to lookfor endoleaks.

Lastly, the contrast used in our study is currently FDA-

Dr Munier Nazzal (Toledo, Ohio). What is the gold standardhere? How do you know that what you are diagnosing is not anartifact leading to overdiagnosis of endoleak?

Dr Henao. That is a good question. And I don’t know if thereare any hard data that says what is the gold standard. Right now CTis what we use.

Yesterday Dr Ohki gave an excellent presentation on pressuremonitoring of the sac. That may actually be the new gold standard,depending on how that comes out.

The truth of the matter is that there is no one perfect study. Ithink even if we do implement a device that evaluates pressuremeasurements, we are still going to want to look at the integrity of thedevice, we are still going to want to see blood flow around theendograft. So inevitably, we are going to integrate all these differentmodalities and come up with a unified way to follow these grafts.

Dr Kent (New York, NY). You may have told us the answer tothis question, but what are the next steps? How long until we havethis available in clinical practice, and what other evaluations have tobe conducted before we get to that stage?

Dr Henao. I am not sure what the answer is. I think we aremaking headway. This is going to be the sixth preliminary study. Ithink if we have more patients, we can present that to the FDA andget this thing underway, because the proof is in the pudding. Onecan see endoleaks and there is definitely evidence of ruptures

despite negative CT findings. So if we are missing potential disas-

JOURNAL OF VASCULAR SURGERYFebruary 2006264 Forbes

ters with computed tomography, it is imperative that we find abetter modality.

Dr Kent. One last question. Do you sense that there has to beany special expertise in your ultrasound lab to use this technique, ordoes this diminish the need for special expertise?

Dr Henao. I think one of the criticisms of ultrasound in thefollow-up of EVAR is that it is operator-dependent. But withthe use of the contrast agent, there were many times that I feltthat I could probably do the scan myself, and I am by no meansa certified technologist. The clarity of blood flow makes the scan

substantially easier. However, it is still a very labor-intensive

dalities offer extensive detail about endograft integrity, aneurysm

scan. I don’t know if any of you have ever seen an ultrasound ofan EVAR follow-up, but it is very hard on the technician, and Ithink using the contrast helps to speed up the process signifi-cantly.

Dr Julie Ann Freischlag (Baltimore, Md). Have you used thistechnique in other arteries besides the aorta looking for endoleaks,such as the carotid?

Dr. Henao. We have, but it is anecdotal at this stage, lookingat SFA, a string sign of the carotid, but we don’t really have ahard-and-fast experience to comment on at this point, but it seems

to be very useful.

INVITED COMMENTARY

Thomas L. Forbes, MD, London, Ontario, Canada

After endovascular repair of an aortic aneurysm, the infrarenalaorta continues to demonstrate characteristic changes duringfollow-up. Even in the successfully excluded aorta, there re-mains a remodeling process reflected in changes in aortic neck,aneurysm, and iliac artery geometry. With aneurysm sac pressur-ization these changes are exacerbated and unpredictable, reinforc-ing the need for long-term surveillance. Until fairly recently, manycenters have used static computed tomography (CT) images astheir surveillance modality of this dynamic remodeling. Althoughquite capable of identifying significant endograft migration,contrast-enhanced CT scans are less than perfect in identifyingthe source of some endoleaks, predicting their physiologic ramifi-cations, and in planning endoleak directed therapies.

In the present study, the Baylor group is to be commended forfurther refining a contrast-enhanced ultrasound protocol for en-dograft follow-up. They used a continuous infusion technique ofan albumin and microsphere suspension-based agent previouslyused with contrast echocardiography. It proved more accuratethan CT imaging in the identification and classification of en-doleaks and allowed for longer periods of monitoring comparedwith ultrasound scans using boluses of contrast. The findings ofthis 20-patient study certainly suggest further examination of thistechnique is warranted. This may also prove to be a more cost-effective method of surveillance.

Although static (CT) and dynamic (ultrasound) imaging mo-

geometry, and endoleak identification and classification, they areincapable of predicting the ramifications of these changes. Thisrequires a measure of aneurysm pressurization, of which aneurysmdiameter, volume, and endoleak identification are but a surro-gate. A noninvasive method of sac pressure measurement hasrecently been developed that offers the possibility of determin-ing which aneurysms required reintervention based on physio-logic parameters.1

As the authors suggest, the perfect surveillance tool afterendovascular repair undoubtedly involves an algorithm rather thana single imaging modality. This includes static imaging techniques(plain radiographs, CT, magnetic resonance) to monitor endograftintegrity and aneurysm remodeling, dynamic imaging (ultrasound)to accurately identify and classify endoleaks, and physiologic mon-itoring (intrasac pressure transducer) to determine the need forreintervention. As this surveillance algorithm is elucidated further,it is likely that follow-up regimens will become patient specific, asall aneurysms will not require all surveillance modalities. Thiscontinues to be an important and evolving area of endovascularsurgery that all vascular surgeons are encouraged to follow closely.

REFERENCE

1. Ellozy SH, Carroccio A, Lookstein RA, Minor ME, Sheahan CM, Juta J,et al. First experience in human beings with a permanently implantableintrasac pressure transducer for monitoring endovascular repair of ab-

dominal aortic aneurysms. J Vasc Surg 2004;40:405-12.