Early clinical experience with color three-dimensional intravascular ultrasound in peripheral interventions.

PURPOSE: To report early clinical experiences with color 3-dimensional intravascular ultrasound (3-D IVUS) in assisting peripheral interventions. TECHNIQUE: A 3.5-F, 20-MHz IVUS catheter that utilizes ChromaFlo computer software to demonstrate blood flow in color was evaluated in over 100 peripheral interventions. ChromaFlo captures up to 30 conventional IVUS frames every second and generates "real-time" imaging. The software compares sequential axial IVUS images and interprets any differences in the position of echogenic blood particles, which are displayed as colorized flow in axial or 3-D renderings. CONCLUSIONS: ChromaFlo-enhanced IVUS demonstrates colorized blood flow inside the vessel lumen, which is helpful in distinguishing echolucent disease from luminal blood flow and can also be used to perform peripheral interventions in patients with renal failure or allergy, avoiding the use of contrast media.

Failed AAA endograft exclusion due to type II endoleak: explant analysis.

PURPOSE: To report the patient history and analysis of an explanted modular bifurcated endograft that was implanted to exclude an abdominal aortic aneurysm (AAA). CASE REPORT: An 80-year-old man with a 6-cm AAA underwent uneventful endovascular implantation of a bifurcated AneuRx stent-graft. His postprocedural clinical course was uneventful, although persistent contrast enhancement of the aneurysm remained via the inferior mesenteric artery (IMA). By 6 months, an endoleak connecting to the lumbar and mesenteric arteries became apparent. Over the ensuing 12 months, the endoleak and aneurysm enlarged; branch artery embolization was attempted in 4 percutaneous procedures. Despite successful IMA occlusion, the aneurysm continued to increase in diameter and volume, necessitating conversion to a conventional bypass at 20 months. Analysis of the explanted specimen revealed an intact endograft with fibrous incorporation of the stent framework at the proximal and distal fixation sites only; no incorporation of the endograft was noted within the aneurysm. The feeding channel for the endoleak was not identified. CONCLUSIONS: Serial imaging is a vital component of endograft surveillance, and persistent type II endoleaks that cannot be completely embolized endanger the longevity of the aneurysm exclusion. Explant analysis can play an important role in understanding the mechanisms of endograft failure.

Healing response of normal canine aorta and iliac artery to a nitinol stent encapsulated in carbon-lined ePTFE.

PURPOSE: To evaluate the healing response of normal canine arteries to a self-expanding nitinol stent encapsulated in carbon-lined expanded polytetrafluoroethylene (ePTFE). METHODS: Twenty-eight dogs were divided into aortic (n = 18) or iliac (n = 10) groups. In the latter, 2 animals were assigned to implantation intervals of 7, 30, and 90 days, respectively; 4 were designated for 180-day implantation. Half of the animals in each subgroup received a second overlapping stent-graft in one iliac artery. In the aortic cohort, 6 animals were assigned to the 180-day implantation group (2 with dual devices) and 3 to each of the others (1 dual implantation in each group). The devices were evaluated with angiography and intravascular ultrasound at implantation and explantation. After harvesting and gross examination, the specimens were examined microscopically and with scanning electron microscopy. RESULTS: The 49 implanted devices (24 aortic and 25 common iliac) were all widely patent at explantation, save for 2 iliac stents that had moderate (<40%) stenosis. No neointima was present at the 7-day interval. All stents were covered by thin neointima (<150 microm) at 30 days. At 180 days, an endothelial lining was present in the proximal and distal segments of all stents; in 4 of the 6 aortic stents, this endothelial lining was complete, whereas none of the iliac devices had endothelium in the midsegment at 180 days. At 1 year, 2 of the aortic specimens had an incomplete endothelial lining, whereas the lining was complete in the third. There was no evidence of stent-graft migration or inflammation associated with any device. CONCLUSIONS: The carbon-lined ePTFE-encapsulated stent is a novel approach to arterial stenting. The progressive endothelialization and lack of inflammatory reaction may provide improved long-term patency. Further study of this stent-graft design is warranted.

Endovascular exclusion of descending thoracic aortic aneurysms and chronic dissections: Initial clinical results with the AneuRx device.

OBJECTIVE: The objective of this study was to analyze a single-center experience in which descending thoracic aortic aneurysms (TAAs) were treated with a new self-expanding endovascular prosthesis (Medtronic AVE). METHODS: Twenty-six patients (13 men, 13 women) with American Society of Anesthesiology grades II to IV and ages ranging from 53 to 92 years (average, 74 years) consented as part of a Phase I Food and Drug Administration-approved trial. Treated lesions included TAAs that were 5 to 10 cm in diameter, 12 diffuse dilations or fusiform aneurysms, and four saccular aneurysms. There were also nine chronic dissections (2 aneurysmal dilations and 7 symptomatic acute recurrent dissections). Three patients (2 with diffuse/fusiform and 1 with dissection) presented with hemothorax, contrast extravasation, or both. RESULTS: Twenty-five of the 26 patients who consented (96% technical success) were treated successfully with no surgical conversions. Eighteen patients have been followed up from 1 to 22 months (average, 9 months). One patient is lost to follow-up, and six patients have died (24%). One procedure-related death (4%) occurred within the 30-day postoperative period and was caused by diffuse embolization. There were no device-related deaths. Five additional patients (20%) have died during the study of comorbid conditions. Complications included one massive myocardial infarction 24 hours after the procedure requiring balloon counterpulsation and long-term dialysis, one cardiac tamponade resulting from central line placement before the procedure, one progression of aneurysm dilation proximal to the device at 1 year, and one bilateral lower extremity paralysis occurring 12 hours after successful deployment. Seven patients (5 women) had femoral artery reconstructions or iliac artery grafts to repair injuries during deployment catheter passage. Other significant parameters included average procedure time (2 hours 40 minutes; range, 1 hour 30 minutes to 5 hours 30 minutes), 450 cc average blood loss (n = 25; 100-3000 cc) being replaced by means of autotransfusion with only two patients receiving banked blood products, and an average 2 days to resumption of normal diet, 1 day in the intensive care unit, and 5 days' hospitalization postprocedure in uncomplicated cases (n = 22). One patient had an endoleak immediately after the procedure that sealed without treatment. Follow-up of all patients ranging from 1 to 22 months (average, 9 months; n = 18) demonstrates continued exclusion of the aneurysm with no endoleaks and either stable or decreasing aneurysm volume, except in one patient with volume increase and no obvious etiology who continues to be investigated. CONCLUSIONS: The study suggests that endovascular prosthesis exclusion of TAAs with an AneuRx self-expanding tubular device may be effective in many patients who are at significant risk for open surgical repair and substantiates further clinical investigation to confirm these findings.

Computed tomography assessment of abdominal aortic aneurysm morphology after endograft exclusion.

OBJECTIVES: Assessment of the long-term function of endografts to exclude abdominal aortic aneurysm (AAA) includes determination of aneurysm dimensions and morphologic changes that occur after implantation. This study reports the dimensional analysis of patients treated with AneuRx bifurcated endoprostheses with postintervention, 1-year (n = 51), 2-year (n = 28), and 3-year (n = 10) postimplantation contrast computed tomography data. METHODS: Maximal diameter (D) and cross-sectional area (CSA) of the AAA were measured from axial computed tomography images. Total volume, AAA thrombus volume (AAA volume minus the volume of the device and luminal blood flow), diameter of the aorta at the level of the renal arteries and within the device, distance from the renal arteries to the device, length of the device limbs, and the angle of the proximal neck were also determined at the same follow-up intervals after deployment with computed tomography angiograms reconstructed in an interactive environment. RESULTS: Fifty-one of 98 consecutively treated patients with the AneuRx bifurcated prosthesis (29 "stiff" and 22 "flexible" body devices) had complete data from the postprocedure and follow-up computed tomography studies available for analysis. Max D, CSA, total volume of the AAA, and AAA thrombus volume decreased sequentially from year to year compared with the postimplantation values. D and CSA decreased or were unchanged in all except four patients, two who had unrestricted enlargement of the aneurysm with eventual rupture and one who had surgical conversion for continued expansion despite four diagnostic angiograms and attempted embolizations. Total volume of the AAA increased in 11 of 51 patients at 1 year, eight of whom had endoleaks at some interval during the follow-up. Thrombus volume increased more than 5% in four of these patients, including the two with eventual rupture and the one conversion. Patients with endoleaks who had spontaneous thrombosis or were successfully treated either remained at the same volume or had decreased volume on subsequent examinations. D at the renal arteries increased an average of 0.9 mm during the first year, with a concomitant increase of 2.8 mm within the proximal end of the device related to the self-expanding nature of the Nitinol suprastructure. Subsequent enlargement of the proximal neck continued at a slow rate in some cases but never exceeded the diameter of the endoluminal device. The distance from the renal arteries to the device increased by an average of 3 mm over the first year, with the greatest increases occurring in patients with a "stiff" body device and those with rapid regression (>10% total volume) in 1 year. As regression of the AAA occurred, the angle of the proximal neck varied from -5 degrees to +25 degrees from the original alignment. Limb length varied from -8 mm to +10 mm, with no consistent pattern for the change, that is, ipsilateral or contralateral limb. CONCLUSION: Significant variation in the quantitation of aneurysm size occurs depending on the technique of computed tomography assessment used. In most patients diameter assessment is adequate, although volumetric analysis appears to be very helpful in certain patients who do not show aneurysm regression, or in whom the diameter increases or where endoleaks persist. Three-dimensional reconstruction and volumetric analysis are also useful to assess the mechanism by which the endovascular device accommodates to morphology changes and to determine criteria for reintervention.

The impact of intravascular ultrasound (IVUS) on endovascular interventions.

Intravascular ultrasound (IVUS) has undergone rapid evolution with the recent expansion of endovascular techniques and devices. This device can aid the surgeon, cardiologist, and interventional radiologist by increasing the accuracy of imaging and by adding important information to peripheral vascular and coronary interventions. Modern intravascular ultrasound provides a detailed view of the lumen, wall, and surrounding structures of blood vessels. Compared with other modalities, the diagnostic advantages of IVUS for examining arterial wall architecture and lesion morphology are evident. IVUS can determine lesion shape, length, and configuration, as well as identifying and examining the origins of branches and tributaries. Using this information, IVUS can guide the choice of appropriate angioplasty techniques, aid in the placement of endovascular devices, and assess and follow the efficacy of such interventions. IVUS helps reduce the use of radiation and contrast agents. Even though intravascular ultrasound requires additional equipment, personnel, and interpretative skills, it can be invaluable as a sensitive real-time imaging tool for complex endovascular interventions, therapeutic challenges, and diagnostic dilemmas.

The effect of angulation on intravascular ultrasound imaging observed in vascular phantoms.

PURPOSE: To quantify the error introduced by noncoaxial intravascular ultrasound (IVUS) imaging and to evaluate the use of a balloon-tipped catheter in compensating for intraluminal angulation and subsequent dimensional inaccuracy. METHODS: The effect of noncoaxial IVUS imaging was investigated in both a polyvinyl chloride phantom and an in vitro canine aorta using a calibrated setup to measure angulation off axis. Imaging was performed at increasing angulation (creating an elliptical image) in both phantoms, with the transducer centered and off center. Diameters were compared to the original coaxial diameter, as well as calculated diameters based on specific angles off axis. The percentage change (error) was also calculated at these angles. The measurements were repeated using a balloon-tipped catheter to center the transducer. RESULTS: The measured diameters and percentage changes compared closely with their calculated counterpart. Up to 25 degrees off axis, the apparent increase in diameter measurement was nearly 10%. Angulation from 30 degrees to 70 degrees resulted in an increase of 15% to 192%. Use of the centering balloon reduced the amount of error by 70% to 85% but was limited to angles < or = 25 degrees due to the design of the test apparatus. CONCLUSIONS: The error introduced by noncoaxial IVUS imaging can be significant and may be partially corrected by the use of a centering balloon. Further studies in the clinical application of a centering device are warranted.

Modular bifurcation endoprosthesis for treatment of abdominal aortic aneurysms.

OBJECTIVE: The authors analyzed a single group's experience treating abdominal aortic aneurysms (AAAs) with a new self-expanding, modular, bifurcated device. SUMMARY BACKGROUND DATA: Successful exclusion of AAAs by prototype devices has led to several controlled clinical trials evaluating prostheses designed and manufactured specifically for this application. METHODS: Sixteen patients (15 males, 1 female) of American Society of Anesthesiologists grade 2 through 4 and average age of 72 years had AAAs (average 57-mm diameter) treated as part of a phase I Food and Drug Administration-approved trial. RESULTS: All patients were treated successfully with no surgical conversions. No endoleaks or aneurysm enlargement was noted either predischarge by contrast computed tomography or on follow-up at 1 month by duplex ultrasound examination. At 6 months, 12 of 13 patients who were observed for this interval had no endoleaks, whereas one patient (patient 3) showed a small area of extravasation that appeared to arise from the device in an area that was traumatized at the time of deployment. One procedure-related mortality (6%) occurred in a patient who died of septic complications secondary to a gangrenous gallbladder diagnosed 1 day after the procedure. There were no device-related mortalities. Complications included two iliac artery dissections, two groin wound infections, and two transient elevations of serum creatinine. Other significant variables including median procedure length (5 hours), intensive care unit stay (1 day), hospitalization postprocedure (4.5 days), and blood loss (1100 mL) all decreased as the study progressed. Blood replacement in all but three patients was accomplished by autotransfusion or banked-autologous blood replacement. At 6-month follow-up in 13 patients, the maximum diameter of the aneurysm decreased by an average of 5.6 mm (range, 0-15 mm), and the maximal cross-sectional area decreased an average of 20.3% (range, 0-72%). CONCLUSIONS: This study suggests that endovascular prosthesis exclusion of AAAs using a self-expanding modular device may be effective in many patients who are otherwise surgical candidates for repair if further clinical studies confirm these observations.

Deployment and healing of an ePTFE encapsulated stent endograft in the canine aorta.

This study evaluated deployment mechanics and long-term healing of an endoluminally placed stent/graft in normal canine aortas. The endoluminal graft (ELG) consisted of a 8.5 cm segment of expanded polytetrafluoroethylene (ePTFE) graft material (Impra, Inc., Tempe, AZ) encapsulating a series of six Palmaz P-128 stents (Johnson & Johnson Interventional Incorporated, New Brunswick, NJ) along the length of the graft. The prostheses were deployed via the femoral artery using a 14Fr delivery system that contained a balloon catheter to expand the ELG in the infrarenal aorta. Twenty-one prostheses were deployed and evaluated at 1 week (n = 3), 1 month (n = 3), 3 months (n = 3), 6 months (n = 9), and 1 year (n = 3). Dimensions of the infrarenal aorta were determined with intravascular ultrasound (IVUS) and angiography prior to deployment of devices. Real-time fluoroscopy and IVUS were used to monitor device deployment with both imaging modalities repeated following implantation. Gross inspection and microscopic evaluation was performed on the explanted specimens following in vivo evaluation by CT scan, IVUS, and angiography prior to retrieval of the specimens. The prostheses were easily deployed from the femoral access site. Oversizing of the deployment balloon compared to the aortic diameter was necessary to accommodate the 10% device recoil observed following balloon deflation, however, all devices were seated against the aortic wall as evidenced by IVUS. At explant, all devices ware widely patent with limited luminal thrombosis observed in four specimens (19%). Devices were well-incorporated by cellular ingrowth into the ePTFE with the formation of neointima. No device migration or postdeployment recoil was observed. ePTFE graft material between stents protruded slightly into the vessel lumen accounting for a 10% luminal reduction. Fully supported ELG's consisting of balloon expandable stents encapsulated in ePTFE are easily deployed using a low-profile delivery system. Specimens demonstrated uniform long-term patency and healing up to 1 year in a canine aortic model. Those preliminary findings support further study of this fully supported prosthesis in the treatment of arterial disease.

Regression of an abdominal aortic aneurysm after endograft exclusion.

We describe the regression of a 6.5 cm diameter abdominal aortic aneurysm in a 71-year-old patient within 1 year of aortic endograft placement. The aneurysm decreased in size to 4 cm at 3 months and was 3.3 cm at 8 months on duplex examination. By 1 year a spiral computed tomographic study confirmed complete regression of the aneurysm, with mild shortening and angulation of the unsupported body of the aortoiliac endoluminal prosthesis. The case demonstrates a potential of endograft treatment of aortic aneurysms and decribes the changes in prosthesis configuration and position that occurred after implantation.

Aortic aneurysm morphology for planning endovascular procedures.

Endovascular prosthesis repair of abdominal aortic aneurysms is based upon the development of low-profile devices that can be expediently deployed within the aneurysm, excluding it from intraluminal pressure. Many factors affect the treatment of patients in this manner, including the morphology of the proximal and distal fixation sites, the diameter and disease state of the access vessels, and the ability of the device to conform to the many anatomic variations of aneurysms. In addition, preliminary data suggest there is progressive shrinkage and morphologic change in the configuration of an aneurysm following exclusion, which not only affects the alignment of the device but may also influence its healing and stability. This paper reviews the morphologic parameters of aneurysms relevant to endovascular repair and describes the imaging technologies used to assess these parameters before, during, and after intervention.

Utility of intravascular ultrasound in peripheral interventions.

Endovascular imaging techniques encompass a variety of methods, including angiography, computed tomography, magnetic resonance imaging, angioscopy, and intravascular ultrasound. Each method provides unique information regarding the continuity of vascular structures and the morphology and distribution of lesions. Although arteriography has been the "gold standard" for imaging arterial anatomy, recent data have confirmed that even sophisticated arteriographic imaging substantially underestimates the degree of residual lesions, and that future observations and end-points for treatment will most likely be determined by data accumulated by computed tomography, magnetic resonance imaging, angioscopy, and intravascular ultrasound. Successful therapeutic applications of endovascular devices have developed because of improved patient selection using computed tomography, spiral computed tomography, magnetic resonance imaging, and computerized high-resolution angiography. Procedural success has been enhanced by improved mobile cinefluoroscopy, angioscopy, intraluminal ultrasound monitoring of angioplasty procedures, and the use of intravascular ultrasound for stent and stent-graft sizing and deployment. Newly developed methods and low-profile delivery systems enabling deployment and fixation of vascular prostheses by an endoluminal approach have heightened the interest of many interventionalists, particularly surgeons, in the use of endovascular surgical techniques. The evolution of this method promises to add a new dimension to the treatment of vascular lesions and relies heavily on the incorporation of miniaturized imaging systems, such as intravascular ultrasound, as a means to provide precise placement of devices.

Endograft repair of an aortic pseudoaneurysm following gunshot wound injury: impact of imaging on diagnosis and planning of intervention.

PURPOSE: To describe the endovascular treatment of a gunshot injury to the visceral aorta and the role of various imaging modalities in the staging and planning of the endograft procedure. METHODS AND RESULTS: The bullet entered the aorta posteriorly beneath the origin of the superior mesenteric artery and traversed the wall in a tangential manner entering the lumen proximal to the renal arteries. Intravascular ultrasound (IVUS) imaging and spiral computed tomography (CT) identified the injury that the initial angiograms failed to demonstrate. Combined use of IVUS and CT imaging enabled observation of the evolution of a pseudoaneurysm until an interval when endograft exclusion was possible. A stent-graft was customized based on precise IVUS and CT dimensional data and implanted successfully through an arteriotomy in the common femoral artery 3 weeks after the initial injury. Three-month follow-up imaging demonstrated continued exclusion of the pseudoaneurysm, and the patient remains well at 16 months. CONCLUSIONS: IVUS and spiral CT scans were instrumental in identifying an arteriographically undetected aortic injury. The combined imaging modalities also helped determine the timing for the endovascular procedure and provided the precise measurements for device fabrication and deployment.

Evaluation of a modular endovascular bifurcation prosthesis in a canine aortic aneurysm model.

PURPOSE: The study evaluated the deployment and healing of a novel self-expanding modular bifurcation endovascular prosthesis in a canine abdominal aortic aneurysm model. The endoluminal prosthesis consists of self-expanding nitinol stents lined by a synthetic prosthesis. One component of the device is a bifurcated body with a 12- to 14-mm diameter aortic segment and an integral 7- to 8-mm diameter iliac limb. The bifurcated body also has a stent-reinforced opening (pant-leg) for subsequent insertion of a contralateral 7- to 8-mm diameter iliac limb component. METHODS: Seventeen bifurcated prosthesis were placed; 7 were inserted through the left common carotid artery and 10 from the femoral arteries. With either route of access the 16F or 17F aortoiliac limb and the 13F iliac limb delivery catheters enabled easy passage and secure positioning of the bifurcated prostheses. Predeployment and postdeployment inspection of the dimensions and continuity of the aortoiliac prosthetic components were evaluated by cinefluoroscopy and intravascular ultrasonography (IVUS). RESULTS: After deployment was done, interval patency was assessed with angiography, IVUS, and contrast-enhanced computed tomography with the prostheses removed for analysis at 1 week (n = 4), 1 month (n = 3), 3 months (n = 4), and 6 months (n = 6). Five of the first seven implanted prostheses had occlusion of segments of the device. In two dogs the bifurcated body and both legs were occluded. In the other three the nonoccluded leg and bifurcation body were fully patent. In the first seven animals IVUS at implantation showed compression of an iliac leg by the orifice of the contralateral iliac component. After concentric fixation of the flow divider was performed, only one additional iliac limb occlusion occurred in the next 10 animals. Cinefluoroscopy, computed tomography, IVUS imaging, and histologic analysis of retrieved specimens demonstrated healing of the aortoiliac prostheses without evidence of perigraft leaks. CONCLUSIONS: This feasibility study demonstrates the ability to deploy and maintain acceptable patency of a self-expanding endoluminal, modular bifurcation prosthesis in a canine aortic model. Clinical evaluation of the device is planned for the near future.

Preliminary clinical outcome and imaging criterion for endovascular prosthesis development in high-risk patients who have aortoiliac and traumatic arterial lesions.

PURPOSE: This report reviews our preliminary experience of prospective treatment of arterial lesions with endoluminal grafts in a Food and Drug Administration (FDA)-approved, investigator-sponsored Investigation Device Exemptions study. The utility and accuracy of various imaging methods, including angiography, cinefluoroscopy, computed tomography (CT), intravascular ultrasonography (IVUS), and duplex scanning, in performing the procedures was also assessed. METHODS: Thirty-one patients were evaluated; 17 patients were treated, including 11 with abdominal aortic aneurysms, one with an aortic occlusive lesion, two with iliac artery aneurysms, and three with traumatic arteriovenous fistulas. Twelve of the 14 patients who had aorta and iliac artery lesions were high-risk. The mean follow-up of patients treated was 9 months (range, 6 to 15 months). RESULTS: Aortoaortic endoluminal interposition procedures were not successful for treating abdominal aortic aneurysms early in the study (n = 3). Aortoiliac endoluminal bypass, contralateral iliac artery occlusion, and femorofemoral bypass procedures were successful in seven of eight subsequent cases (88%), with no incidence of endoleaks at either the proximal or distal fixation sites using the deployment methods described in this report. The 30-day operative mortality rate on follow-up evaluations for patients who underwent aortoiliac procedures was 14% (two of 14). Other major complications included transient renal failure in three patients that required short-term (two to eight times) dialysis, one arterial perforation and one dissection, and one prolonged intubation. No myocardial infarctions or strokes occurred. After major complications or identification of limitations in the study, the protocol was modified with the approval of the FDA to help avoid the recurrence of the same problems. There were no deaths or complications in the trauma cases. CONCLUSIONS: Contrast-enhanced CT (axial images and spiral reconstructions) was the most accurate method to determine candidacy for aortoiliac procedures and to choose the site for deployment of the devices. Angiographic scans were misleading in several patients regarding the critical determinants of patient candidacy and device deployment, particularly regarding the presence of a distal aortic neck. Cinefluoroscopy was used in all patient and was particularly useful for determining the continuity of vascular structures and the anatomy of branch arteries and for enabling precise positioning of stent devices. Determination of fixation sites and assessing dimensional information by cinefluoroscopy and angiography were limited by inaccuracies produced by image magnification, parallax, and uniplanar views. IVUS was used to determine the morphologic features of vascular structures (i.e., calcium, thrombus), to perform real-time observation of the expansion of devices, and to assure firm fixation of balloon-expanded stents before the procedures were completed. Duplex scanning was very helpful in assessing and identifying precisely the location of arteriovenous fistulas before intervention and provided assessment at follow-up intervals. Three-dimensional reconstruction imaging technologies such as spiral CT were particularly helpful for assessing the morphologic features of vascular anatomy before the intervention and at follow-up intervals, whereas 3-D IVUS provided a similar real-time perspective during the procedure.

Vascular imaging before, during, and after endovascular repair.

Endovascular techniques for repair of vascular lesions are developing rapidly. Imaging modalities are critical in this evolution from several perspectives. Device development and evaluation rely on precise imaging to ensure fixation of devices, isolation of lesions, and assessment of healing at various intervals. Clinical implementation of endovascular techniques requires a spectrum of imaging methods to choose patients appropriately for procedures, to deploy devices expediently and precisely, and to evaluate long-term efficacy in a minimally invasive manner. This paper reviews the utility of available imaging methods for performing these assessments.

The ideal guidance imaging system for endovascular interventions.

Endovascular interventions enable a minimally invasive approach to a variety of cardiovascular lesions. Small catheter-based delivery systems have rapidly evolved, diversifying endovascular therapeutic options. Coronary and peripheral vascular occlusive lesions may be amenable to angioplasty dilatation, intravascular stenting and ablation with mechanical atherectomy devices or lasers. New experimental transluminally placed endovascular stented grafts (TPEGs) have demonstrated feasibility for treating aneurysmal arteries, arteriovenous fistulas, and atherosclerotic occlusions. Improvements in imaging systems have provided better resolution of lesions, have improved patient selection and interventional strategy, and are invaluable for precise performance of procedures. The ideal guidance system should provide realtime imaging by a combination of complimentary modalities. These include cinefluoroscopy and contrast angiography, catheter-based intravascular ultrasound and angioscopy.

Utility of intravascular ultrasound in carotid stenting.

PURPOSE: To illustrate the utility of intravascular ultrasound (IVUS) imaging during endoluminal interventions in the carotid artery. METHODS AND RESULTS: A patient with symptomatic internal carotid artery occlusive disease was treated with balloon angioplasty and evaluated with both angiography (interpreted as a widely patent outcome) and IVUS, which identified a residual 70% cross-sectional area stenosis. A stent was placed across the lesion, producing a 70% increase in the lumen as documented by IVUS in comparison to the cross-sectional area of the reference vessel. Postprocedural angiography of the stented segment showed only an approximate 20% increase in diameter. CONCLUSIONS: This study highlights the utility of IVUS for accurate assessment of angioplasty outcome and for quantitative assessment of luminal volume following intervention and stent placement. The case emphasizes the need for IVUS as an integral part of the procedure to ensure adequate treatment and to accurately document the residual lesion for assessment of recurrence phenomena at follow-up.

Optimal imaging for endovascular procedures: redefining the gold standard.

Minimally invasive techniques have been gaining popularity in all fields of surgery. Their application to vascular surgery has spawned advances in endovascular treatment of aneurysmal and atherosclerotic arterial disease. These procedures are dependent on various imaging modalities, including angiogra- phy, intravascular ultrasound, and computerized tomography scanning to choose appropriate candidates and devices, and to assure precise en doluminal treatment. No single imaging method is adequate for all aspects of endovascular surgery; however, an algorithmic approach may judiciously reduce the inherent inaccuracy and morbidity associated with current methods.